Bio

Academic Appointments


Administrative Appointments


  • Chief of Audiology, Stanford Dept of Otolaryngology (2005 - Present)
  • Co-Director, Stanford Balance Center (2009 - Present)
  • Faculty Affiliate, Stanford Bio-X (2007 - Present)
  • Member of Executive Board, Johnson Center for Pregnancy and Neonatal Services, Lucile Packard Children's Hospital (2008 - 2010)

Honors & Awards


  • Fellow, American Speech-Language-Hearing Association (1987)
  • Knud Terkildsen Research Fellowship, University of Copenhagen (1992)
  • Silver Certificate, Acoustical Society of America (1997)
  • Special Citation, Association for Research in Otolaryngology (2000)
  • Fellow, American Academy of Audiology (2004)
  • Certificate of Appreciation for Founding JARO, Association for Research in Otolaryngology (2007)

Boards, Advisory Committees, Professional Organizations


  • Faculty Advisor, Stanford Center on Longevity (2012 - Present)
  • Board Member, Baker Institute for Hearing Impaired Children (2008 - Present)

Professional Education


  • BA, Kent State University, Experimental Psychology (1968)
  • MA, Kent State University, Audiology (1970)
  • PhD, University of Wisconsin, Communication Sciences (1974)
  • PostDoc, UCLA, Otolaryngology (1978)

Community and International Work


  • Board Member, Baker Institute for Hearing Impaired Children

    Topic

    Childhood Hearing Impairment

    Populations Served

    Hearing Impaired Children

    Location

    International

    Ongoing Project

    Yes

    Opportunities for Student Involvement

    Yes

Research & Scholarship

Current Research and Scholarly Interests


Accurate measurement of auditory function in small mammals is necessary for research focussed on regenerating auditory function. My current work involves development of new stimulus probes, new measurement probes, related digital signal processing, and automated measurement systems necessary for comprehensive measures of auditory function in common research animals such as mice and guinea pigs, particularly for frequencies up to 100,000 Hz.

Accurate measurement of auditory function in humans is necessary for research focussed mathematical modeling of middle ear structures and for accurately measuring the toxic effects of various antibiotics and pharmaceuticals used for cancer treatment. My current work involves development of transducers for bone conduction signals up to 20,000 Hz in humans.

New digital devices with enhanced high-frequency output require new assessment methods. My current work involves understanding and developing assessment techniques for new digital devices with high frequency capability up to 20,000 Hz.

Neonatal bilirubin exposure can be neurotoxic. My current work involves quantifying neurotoxic effects of hyperbilirubinemia with precise non-invasive auditory neural measures in neonates.

Publications

Journal Articles


  • Preliminary comparison of bone-anchored hearing instruments and a dental device as treatments for unilateral hearing loss INTERNATIONAL JOURNAL OF AUDIOLOGY Moore, B. C., Popelka, G. R. 2013; 52 (10): 678-686

    Abstract

    Objective: To compare the effectiveness of two types of treatment for unilateral hearing loss (UHL), bone-anchored hearing instruments (BAHI) and a dental device (SoundBite). Design: Either BAHI or SoundBite were worn for 30 days, and then the devices were swapped and the second device was worn for 30 days. Measures included unaided and aided sound-field thresholds, sound localization, and perception of speech in babble. The APHAB questionnaire was administered for each trial period. Study sample: Nine adult BAHI wearers with UHL. Results: Mid-frequency aided thresholds were lower for SoundBite than for BAHI. Both devices gave benefits for localization after 30 days, but there was no difference between devices. Speech perception was better for both devices than for unaided listening when the target speech came from the poorer hearing side or in front, and the interfering babble came from the better-hearing side. There was no consistent difference between devices. APHAB scores were better for SoundBite than for BAHI. Conclusions: Speech perception and sound localization were similar for the two types of device, but the SoundBite led to lower aided thresholds and better APHAB scores than the BAHI.

    View details for DOI 10.3109/14992027.2013.809483

    View details for Web of Science ID 000324402100003

    View details for PubMedID 23859058

  • Diagnostic measurements and imaging technologies for the middle ear The Middle Ear, Science, Otosurgery and Technology, S Puria, RR Fay and AN Popper, Eds., Springer, NY, NY Popelka, G., Hunter, LL 2013; Chapter 8
  • A New Standardized Format for Reporting Hearing Outcome in Clinical Trials OTOLARYNGOLOGY-HEAD AND NECK SURGERY Gurgel, R. K., Jackler, R. K., Dobie, R. A., Popelka, G. R. 2012; 147 (5): 803-807

    Abstract

    The lack of an adequate standardized method for reporting level of hearing function in clinical trials has hampered the ability of investigators to draw comparisons across studies. Variability in data reported and presentation format inhibits meta-analysis and makes it impossible to accumulate the large patient cohorts needed for statistically significant inference. Recognizing its importance to the field and after a widely inclusive discussion, the Hearing Committee of the American Academy of Otolaryngology-Head and Neck Surgery endorsed a new minimal standard for reporting hearing results in clinical trials, consisting of a scattergram relating average pure-tone threshold to word recognition score. Investigators remain free to publish their hearing data in any format they believe is interesting and informative, as long as they include the minimal data set to facilitate interstudy comparability.

    View details for DOI 10.1177/0194599812458401

    View details for Web of Science ID 000314285800001

    View details for PubMedID 22931898

  • Is It Valid to Calculate the 3-Kilohertz Threshold by Averaging 2 and 4 Kilohertz? OTOLARYNGOLOGY-HEAD AND NECK SURGERY Gurgel, R. K., Popelka, G. R., Oghalai, J. S., Blevins, N. H., Chang, K. W., Jackler, R. K. 2012; 147 (1): 102-104

    Abstract

    Many guidelines for reporting hearing results use the threshold at 3 kilohertz (kHz), a frequency not measured routinely. This study assessed the validity of estimating the missing 3-kHz threshold by averaging the measured thresholds at 2 and 4 kHz. The estimated threshold was compared to the measured threshold at 3 kHz individually and when used in the pure-tone average (PTA) of 0.5, 1, 2, and 3 kHz in audiometric data from 2170 patients. The difference between the estimated and measured thresholds for 3 kHz was within 5 dB in 72% of audiograms, 10 dB in 91%, and within 20 dB in 99% (correlation coefficient r = 0.965). The difference between the PTA threshold using the estimated threshold compared with using the measured threshold at 3 kHz was within 5 dB in 99% of audiograms (r = 0.997). The estimated threshold accurately approximates the measured threshold at 3 kHz, especially when incorporated into the PTA.

    View details for DOI 10.1177/0194599812437156

    View details for Web of Science ID 000314267600018

    View details for PubMedID 22301102

  • The effect of continuous positive airway pressure on middle ear pressure LARYNGOSCOPE Lin, F. Y., Gurgel, R. K., Popelka, G. R., Capasso, R. 2012; 122 (3): 688-690

    Abstract

    While continuous positive airway pressure (CPAP) is commonly used for obstructive sleep apnea treatment, its effect on middle ear pressure is unknown. The purpose of this study was to measure the effect of CPAP on middle ear pressure and describe the correlation between CPAP levels and middle ear pressures.Retrospective review of normal tympanometry values and a prospective cohort evaluation of subjects' tympanometric values while using CPAP at distinct pressure levels.A total of 3,066 tympanograms were evaluated to determine the normal range of middle ear pressures. Ten subjects with no known history of eustachian tube dysfunction or obstructive sleep apnea had standard tympanometry measurements while wearing a CPAP device. Measurements were taken at baseline and with CPAP air pressures of 0, 5, 10, and 15 cm H(2)O.The percentage of normal control patients with middle ear pressures above 40 daPa was 0.03%. In the study population, prior to a swallowing maneuver to open the eustachian tube, average middle ear pressures were 21.67 daPa, 22.63 daPa, 20.42, daPa, and 21.58 daPa with CPAP pressures of 0, 5, 10, and 15 cm H(2) 0, respectively. After swallowing, average middle ear air pressures were 18.83 daPa, 46.75 daPa, 82.17 daPa, and 129.17 daPa with CPAP pressures of 0, 5, 10, and 15 cm H(2)0, respectively. The postswallow Pearson correlation coefficient correlating CPAP and middle ear pressures was 0.783 (P < 0.001).Middle ear air pressure is directly proportional to CPAP air pressure in subjects with normal eustachian tube function. Middle ear pressure reaches supraphysiologic levels at even minimal CPAP levels. Although further investigation is necessary, there may be otologic implications for patients who are chronically CPAP dependent. These findings may also influence the perioperative practice of otologic and skull base surgeons.

    View details for DOI 10.1002/lary.22442

    View details for Web of Science ID 000300680200035

    View details for PubMedID 22252535

  • Most, SP, Corey CL, Popelka, GR, Barrera JE: An Analysis of Malar Fat Volume in Two Age Groups: Implications for Craniofacial Surgery Craniomaxillofacial Trauma & Reconstruction Most, S., Most, SP, Corey CL, Popelka, GR, Barrera JE 2012; 5 (4): 231
  • Long-Term Safety and Benefit of a New Intraoral Device for Single-Sided Deafness OTOLOGY & NEUROTOLOGY Murray, M., Miller, R., Hujoel, P., Popelka, G. R. 2011; 32 (8): 1262-1269

    Abstract

    To determine the long-term safety and benefit of a new intraoral bone conduction device (SoundBite Hearing System by Sonitus Medical) for single-sided deafness (SSD).A multi-center, controlled, nonrandomized, prospective unblinded study of SSD patients wearing the device over a 6-month period.Ambulatory care centers typical of those where SSD patients are diagnosed and treated.Adults (N = 22) with acquired, permanent SSD and no current use of any other SSD device.Continual daily wear of the new device for 6 months.Comprehensive medical, audiologic, and dental measures; aided thresholds; Abbreviated Profile of Hearing Aid Benefit scores, and an SSD questionnaire.There were no related adverse events or changes in the medical or audiologic findings at the end of the trial compared with the beginning. There were no significant changes in the mean aided thresholds (p > 0.01) or the mean dental measures (p > 0.05) at 3 or 6 months compared with pretrial measures. The mean Abbreviated Profile of Hearing Aid Benefit benefit scores showed improvement (p < 0.01) for the Background Noise, Reverberation, and Ease of Communication subscales and the Global scale at 3 and 6 months. The results of the SSD questionnaire indicated that the vast majority (>90%) of the subjects reported satisfaction and improvement in a variety of areas after wearing the device long term.The SoundBite system is safe and continues to provide substantial benefit for SSD patients with continual daily use over a 6-month period.

    View details for DOI 10.1097/MAO.0b013e31822a1cac

    View details for Web of Science ID 000294948900017

    View details for PubMedID 21799455

  • Auditory Impairment in Infants at Risk for Bilirubin-Induced Neurologic Dysfunction SEMINARS IN PERINATOLOGY Shapiro, S. M., Popelka, G. R. 2011; 35 (3): 162-170

    Abstract

    Classical and subtypes of kernicterus associated with bilirubin toxicity can be differentiated in part with physiological auditory measures that include auditory-evoked potentials and measures of cochlear integrity. The combination of these auditory measures suggests that bilirubin exposure results in auditory system damage initially at the level of the brainstem, progressing to the level of the VIII cranial nerve and then to greater neural centers. There is no evidence of neural damage at the level of the cochlea. Auditory neural damage from bilirubin toxicity ranges from neural timing deficits, including neural firing delays and dyssynchrony, to neural response reduction and even elimination of auditory neural responses. This condition is comprehensively described as auditory neuropathy spectrum disorder. Independent measures of cochlear function and auditory neural function up to the level of the brainstem can effectively diagnose auditory neural damage resulting from bilirubin neurotoxicity. Intervention, including cochlear implants can be effective.

    View details for DOI 10.1053/j.semperi.2011.02.011

    View details for Web of Science ID 000292057900010

    View details for PubMedID 21641490

  • Efficacy and Safety of an In-the-Mouth Bone Conduction Device for Single-Sided Deafness OTOLOGY & NEUROTOLOGY Murray, M., Popelka, G. R., Miller, R. 2011; 32 (3): 437-443

    Abstract

    To determine the efficacy, benefit, and safety of a new in-the-mouth bone conduction device (SoundBite Hearing System) for single-sided deafness (SSD).A multicenter, controlled, nonrandomized prospective unblinded study of SSD patients wearing the device.Ambulatory care centers typical of those where SSD patients are diagnosed and treated.Adults (ages >18 and <80 yr) with acquired, permanent SSD (N=28) and no current use of any SSD device.Continual daily wear of the new device over a 30-day trial period.The Hearing in Noise Test (HINT), the Abbreviated Profile of Hearing Aid Benefit (APHAB), comprehensive pretrial and posttrial medical, audiologic, and dental examinations and an SSD questionnaire.The Hearing in Noise Test scores improved an average of -2.5 dB after 30 days, compared with wearing no device (p<0.001). The Abbreviated Profile of Hearing Aid Benefit scores improved (p<0.05) for all subjects for the Global and Background Noise subscales and for all but 1 subject for the Reverberation and Ease of Communication subscales. There were no medical, audiologic, or dental complications.The SoundBite system is safe and effective and provides substantial benefit for SSD patients with continual daily use over a 30-day period.

    View details for DOI 10.1097/MAO.0b013e3182096b1d

    View details for Web of Science ID 000288239800020

    View details for PubMedID 21221045

  • Stimulus Frequency Otoacoustic Emissions in Wild-Type and TECTA Mice WHAT FIRE IS IN MINE EARS: PROGRESS IN AUDITORY BIOMECHANICS Pikhart, K. N., Popelka, G. R., Moleti, A., Sisto, R., Oghalai, J. S., Xia, A., Puria, S. 2011; 1403

    View details for DOI 10.1063/1.3658102

    View details for Web of Science ID 000301945200051

  • Safety of an Intra-Oral Hearing Device Utilizing a Split-Mouth Research Design Journal of Clinical Dentistry Miller, R., Hujoel P, Murray, M, Popelka, GR 2011; 22 (5): 159-62
  • Preliminary Evaluation of a Novel Bone-Conduction Device for Single-Sided Deafness OTOLOGY & NEUROTOLOGY Popelka, G. R., Derebery, J., Blevins, N. H., Murray, M., Moore, B. C., Sweetow, R. W., Wu, B., Katsis, M. 2010; 31 (3): 492-497

    Abstract

    A new intraoral bone-conduction device has advantages over existing bone-conduction devices for reducing the auditory deficits associated with single-sided deafness (SSD).Existing bone-conduction devices effectively mitigate auditory deficits from single-sided deafness but have suboptimal microphone locations, limited frequency range, and/or require invasive surgery. A new device has been designed to improve microphone placement (in the ear canal of the deaf ear), provide a wider frequency range, and eliminate surgery by delivering bone-conduction signals to the teeth via a removable oral appliance.Forces applied by the oral appliance were compared with forces typically experienced by the teeth from normal functions such as mastication or from other appliances. Tooth surface changes were measured on extracted teeth, and transducer temperature was measured under typical use conditions. Dynamic operating range, including gain, bandwidth, and maximum output limits, were determined from uncomfortable loudness levels and vibrotactile thresholds, and speech recognition scores were measured using normal-hearing subjects. Auditory performance in noise (Hearing in Noise Test) was measured in a limited sample of SSD subjects. Overall comfort, ease of insertion, and removal and visibility of the oral appliance in comparison with traditional hearing aids were measured using a rating scale.The oral appliance produces forces that are far below those experienced by the teeth from normal functions or conventional dental appliances. The bone-conduction signal level can be adjusted to prevent tactile perception yet provide sufficient gain and output at frequencies from 250 to 12,000 Hz. The device does not damage tooth surfaces nor produce heat, can be inserted and removed easily, and is as comfortable to wear as traditional hearing aids. The new microphone location has advantages for reducing the auditory deficits caused by SSD, including the potential to provide spatial cues introduced by reflections from the pinna, compared with microphone locations for existing devices.A new approach for SSD has been proposed that optimizes microphone location and delivers sound by bone conduction through a removable oral appliance. Measures in the laboratory using normal-hearing subjects indicate that the device provides useful gain and output for SSD patients, is comfortable, does not seem to have detrimental effects on oral function or oral health, and has several advantages over existing devices. Specifically, microphone placement is optimized for reducing the auditory deficit caused by SSD, frequency bandwidth is much greater, and the system does not require surgical placement. Auditory performance in a small sample of SSD subjects indicated a substantial advantage compared with not wearing the device. Future studies will involve performance measures on SSD patients wearing the device for longer periods.

    View details for DOI 10.1097/MAO.0b013e3181be6741

    View details for Web of Science ID 000276555200019

    View details for PubMedID 19816229

  • Sleep MRI Novel technique to identify airway obstruction in obstructive sleep apnea OTOLARYNGOLOGY-HEAD AND NECK SURGERY Barrera, J. E., Holbrook, A. B., Santos, J., Popelka, G. R. 2009; 140 (3): 423-425

    View details for DOI 10.1016/j.otohns.2008.11.037

    View details for Web of Science ID 000263810600028

    View details for PubMedID 19248956

  • Single breath CO measurements normalized to 5% CO2 in Coombs' test positive neonates PHYSIOLOGICAL MEASUREMENT Engel, R. R., Popelka, G. 2007; 28 (9): 977-988

    Abstract

    A portable, prototype instrument that measures peak CO, CO2 and H2 concentrations of breath samples was evaluated on 58 antibody positive, blood group incompatible infants. The reproducibility of 108 duplicate breath CO determinations improved when the result was normalized (CO(n)) for the simultaneously measured CO2 concentration (r = 0.97 versus r = 0.87). The average CO(n) for 18 antibody positive, ABO incompatible infants who received phototherapy was 1.2 ppm higher than the average for 32 who did not receive phototherapy (p < 0.001). There was a positive correlation between CO(n) and the duration of phototherapy (r = 0.75). Sodium acetate infusion and breath H2 did not affect the CO(n) results. In antibody positive infants, single breath CO to CO2 ratios provided more reproducible results than CO determinations that were not adjusted for the CO2 concentration. Therefore, a portable instrument that measures both gases on the same aliquot of exhaled air and that is not affected by H2 should have clinical utility as an indicator of heme catabolism and bilirubin production that is not distorted by hyper- or hypoventilation.

    View details for DOI 10.1088/0967-3334/28/9/001

    View details for Web of Science ID 000249755300002

    View details for PubMedID 17827647

  • Hearing Impairment Encyclopedia of Science and Technology, McGraw Hill Popelka, G. 2007
  • Novel Quantification of Airway Obstruction in Adult Sleep Apnea CHEST Barrera, J., Holbrook, AB, Santos, JM, Popelka, GR 2007; 132: 464
  • In vivo Imaging of mammalian cochlear blood flow using fluorescence microendoscopy OTOLOGY & NEUROTOLOGY Monfared, A., Blevins, N. H., Cheung, E. L., Jung, J. C., Popelka, G., Schnitzer, M. J. 2006; 27 (2): 144-152

    Abstract

    We sought to develop techniques for visualizing cochlear blood flow in live mammalian subjects using fluorescence microendoscopy.Inner ear microcirculation appears to be intimately involved in cochlear function. Blood velocity measurements suggest that intense sounds can alter cochlear blood flow. Disruption of cochlear blood flow may be a significant cause of hearing impairment, including sudden sensorineural hearing loss. However, inability to image cochlear blood flow in a nondestructive manner has limited investigation of the role of inner ear microcirculation in hearing function. Present techniques for imaging cochlear microcirculation using intravital light microscopy involve extensive perturbations to cochlear structure, precluding application in human patients. The few previous endoscopy studies of the cochlea have suffered from optical resolution insufficient for visualizing cochlear microvasculature. Fluorescence microendoscopy is an emerging minimally invasive imaging modality that provides micron-scale resolution in tissues inaccessible to light microscopy. In this article, we describe the use of fluorescence microendoscopy in live guinea pigs to image capillary blood flow and movements of individual red blood cells within the basal turn of the cochlea.We anesthetized eight adult guinea pigs and accessed the inner ear through the mastoid bulla. After intravenous injection of fluorescein dye, we made a limited cochleostomy and introduced a compound doublet gradient refractive index endoscope probe 1 mm in diameter into the inner ear. We then imaged cochlear blood flow within individual vessels in an epifluorescence configuration using one-photon fluorescence microendoscopy.We observed single red blood cells passing through individual capillaries in several cochlear structures, including the round window membrane, spiral ligament, osseous spiral lamina, and basilar membrane. Blood flow velocities within inner ear capillaries varied widely, with observed speeds reaching up to approximately 500 microm/s.Fluorescence microendoscopy permits visualization of cochlear microcirculation with micron-scale optical resolution and determination of blood flow velocities through analysis of video sequences.

    View details for Web of Science ID 000235346400003

    View details for PubMedID 16436982

  • Dynamics of Speech and Swallowing Association for Research in Otolaryngology Abstracts Popelka, G., Kent, RD 2006; 2006: 305
  • Auditory Function and Hyperbilirubinemia in the Developing Neonate Association for Research in Otolaryngology Abstracts Popelka, G., Martinosky, JW, Walden, RE, Gourley, GR 2005; 2005: 334
  • Newborn hearing screening with combined otoacoustic emissions and auditory brainstem responses. Journal of the American Academy of Audiology Hall, J. W., Smith, S. D., Popelka, G. R. 2004; 15 (6): 414-425

    Abstract

    Accurate assessment of neonatal hearing screening performance is impossible without knowledge of the true status of hearing, a prohibitive requirement that necessitates a complete diagnostic evaluation on all babies screened. The purpose of this study was to circumvent this limitation by integrating two types of screening measures obtained near simultaneously on every baby. Peripheral auditory function was defined by otoacoustic emission results. A complete diagnostic evaluation was performed on every baby who received a "Refer" outcome for auditory brainstem response screening. The integrated results for auditory brainstem response screening in an unselected group of 300 newborns estimated sensitivity at 100%, specificity at 99.7%, overall referral rate at 2.0%, and a positive predictive value of 83.3%. Conductive loss associated with amniotic fluid in the middle ear can persist several weeks after birth; conductive loss can produce a "Refer" outcome for auditory brainstem response screening; and auditory neuropathy can be detected with screening measures. Prevalence results were consistent with the published literature. The implications of this study are that otoacoustic emissions and auditory brainstem measures provide much more information than either alone and that both are needed for a comprehensive hearing screening program.

    View details for PubMedID 15341223

  • Identification of noise sources that influence distortion product otoacoustic emission measurements in human neonates EAR AND HEARING Popelka, G. R., Karzon, R. K., Clary, R. A. 1998; 19 (4): 319-328

    Abstract

    The objective of this study was to identify individual sources of noise and their contribution to the overall noise that influences valid measurement of otoacoustic emissions in neonates. The hypothesis was that careful selection of eliciting signals and signal processing parameters, unique analysis of measured results, and control of certain subject characteristics would allow isolation of these individual noise sources and determine their relative influence.Eliciting signal parameters were optimized and held constant to minimize equipment noise. Analysis of noise floors in relation to signal level was used to identify equipment-related noise associated with changes in signal parameters. Analysis of noise floor distributions was used to determine whether environmental noise entered the measurements via inadequate coupling of the probe to the ear. The acoustic characteristics of the middle ear were varied via subject selection to determine the influence of middle-ear characteristics on noise floor levels.The two sources of noise associated with the measurement equipment need not contribute to the noise floor for biologically relevant otoacoustic emissions measurements (eliciting signal levels between 30 and 75 dB SPL). Of the two pathways identified for environmental noise, the pathway resulting from an inadequate seal between the probe and the ear canal can be eliminated. One of the two sources of noise related to the subject, noise resulting from biologic activity unrelated to the ear can be minimized. However, the remaining factor, the status of the middle ear, has been shown to contribute as much as 6 dB to the overall noise floor.Careful selection of signal parameters and additional data analyses and procedural variables can isolate or control several sources of noise that influence distortion product otoacoustic emission measurements in neonates. Tight coupling between the probe unit and the external ear canal should be maintained for all measurements. Middle ear abnormalities can increase noise floors up to 6 dB.

    View details for Web of Science ID 000075390400007

    View details for PubMedID 9728727

  • GROWTH OF THE 2F(1)-F(2) DISTORTION-PRODUCT OTOACOUSTIC EMISSION FOR LOW-LEVEL STIMULI IN HUMAN NEONATES EAR AND HEARING Popelka, G. R., Karzon, R. K., Arjmand, E. M. 1995; 16 (2): 159-165

    Abstract

    Distortion product otoacoustic emissions (DPOAEs) for low stimulus levels (< 60 dB SPL) have been reported in adult humans under ideal conditions. In neonates, DPOAEs have been reported only for high-level stimuli. The purpose of this paper was to determine characteristics of the 2f1-f2 DPOAE for low-level stimuli in neonates and to assess the feasibility of obtaining such measures in a noisy environment. Subjects were 19 premature neonates presumed to have normal hearing based on systematic pneumatic otoscopy measures and evoked auditory brainstem responses. For stimuli centered at 2000 and 6000 Hz and presented over a range of 30 to 75 dB SPL, DPOAEs were measured employing linear time averaging for up to 128 time frames at each level. In quiescent subjects, the level of the noise floor was as low as that reported in cooperative adults under ideal conditions (approximately -30 dB SPL), and the functions were identical. That is, valid measures were obtained for very low stimulus levels (30 dB SPL), the rate of growth approached 1 dB/dB, and identical nonmonotonicities (saturation, plateaus, and notches) were observed as those reported for adults. When the noise floor was elevated due to subject activity, no valid data could be obtained for low-level stimuli even though the DPOAEs were at expected levels for high-level stimuli. These results have important implications for the use of such measures in this population because the DPOAEs associated with the metabolically active nonlinear cochlear processes at low stimulus levels may be contaminated with DPOAEs associated with other processes at high stimulus levels.

    View details for Web of Science ID A1995QQ26100003

    View details for PubMedID 7789667

  • GROWTH OF DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS WITH PRIMARY-TONE LEVEL IN HUMANS HEARING RESEARCH Popelka, G. R., Osterhammel, P. A., Nielsen, L. H., Rasmussen, A. N. 1993; 71 (1-2): 12-22

    Abstract

    This study addressed the hypotheses that the growth of the level of distortion product otoacoustic emissions (LDP) with primary-tone level reflects the behavior of a third-order nonlinear polynomial system, and that two sources exist for these distortion products. The results indicated that the 2f1-f2 otoacoustic emission in humans can be measured over a much larger stimulus range than reported previously, even for stimuli (L1 = L2) as low as 10 dB SPL (re 20 microPa). The input/output functions are best described as a straight line with a rate of growth of about 1 dB/dB of stimulus level. For stimulus levels at which metabolically active, nonlinear cochlear processes are in operation, the system does not behave as a simple third-order nonlinear polynomial. Small plateaus and sharp discontinuities or 'notches' can occur in the functions at stimulus levels of approximately 55 dB SPL. These characteristics are consistent with the notion of two separate sources of the LDP, one at low stimulus levels, and one at high levels. An alternative explanation is that the measured otoacoustic emission does not represent only the activity at a single location along the basilar membrane but includes the effects of interactions among similar signals arising from multiple locations, or from the original source via multiple paths.

    View details for Web of Science ID A1993MN14800002

    View details for PubMedID 8113130

  • CLINICAL-SIGNIFICANCE OF PROBE-TONE FREQUENCY RATIO ON DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS SCANDINAVIAN AUDIOLOGY Nielsen, L. H., Popelka, G. R., Rasmussen, A. N., Osterhammel, P. A. 1993; 22 (3): 159-164

    Abstract

    Parametric variations in the ratio of primary-tone frequencies were explored to optimize the amplitude of the 2f1-f2 distortion product otoacoustic emission for clinical purposes. Ten ears from 5 normally hearing human subjects were examined with primary tones geometrically centred around the standard audiometric frequencies of 0.5, 1, 1.5, 2, 3, 4, 6 and 8 kHz. The distortion product at the frequency 2f1-f2 (f1 < f2) was measured at six probe tone frequency ratios (f2:f1) varying between 1.15 and 1.40 using equal level primaries of 75 dB SPL. The results showed that a single f2:f1 ratio between 1.20 and 1.25 provides a reasonable value for clinical use in that it optimizes the magnitude of the distortion product at 2f1-f2, provides for sufficient resolution in the test frequency range, and is applicable to the standard clinical test frequencies.

    View details for Web of Science ID A1993LT52800003

    View details for PubMedID 8210955

  • CLINICAL-SIGNIFICANCE OF RELATIVE PROBE-TONE LEVELS ON DISTORTION-PRODUCT OTOACOUSTIC EMISSIONS SCANDINAVIAN AUDIOLOGY Rasmussen, A. N., Popelka, G. R., Osterhammel, P. A., Nielsen, L. H. 1993; 22 (4): 223-229

    Abstract

    The effect of systematic variations in the relative levels (L1, L2) of two primary tones (f1, f2) on the amplitude of the distortion product otoacoustic emission (DPOAE) at 2f1-f2 and f1 < f2 was investigated in 14 ears from 7 normally hearing human subjects. The primary tones (f2:f1 = 1.23) were geometrically centred at the standard clinical frequencies of 0.5, 1, 1.5, 2, 3, 4, 6 and 8 kHz. The quantity L1-L2 was varied systematically from -10 dB through + 10 dB with L2 held constant at 75 dB SPL for negative values, L1 held constant at 75 dB SPL for positive values, and L1 = L2 = 75 dB SPL at 0 dB relative difference. The maximum amplitudes of the distortion products were generated when L1 = L2 at all geometric centre frequencies except 8 kHz. The reduction of the DPOAE with reduction of L1 was linear at a rate that gradually increased as a function of geometric mean frequency. To a lesser extent, the reduction of the DPOAE with reduction of L2 also was linear but at a rate that systematically decreased as a function of geometric mean frequency. The results suggest, that to maximize the level of the distortion product for clinical purposes, the relative levels of the primary tones should be equal to each other, at least when overall stimulus levels are around 75 dB SPL and f2:f1 = 1.23.

    View details for Web of Science ID A1993MM67400003

    View details for PubMedID 8146586

  • HEARING-AID EVALUATION AND FITTING OTOLARYNGOLOGIC CLINICS OF NORTH AMERICA Popelka, G. R., Gates, G. A. 1991; 24 (2): 415-428

    Abstract

    Although many patients with hearing loss benefit from medical or surgical intervention, the vast majority have noncorrectable hearing disorders for which rehabilitation through amplification is indicated. There are three goals for the application of hearing aids: (1) to amplify normal conversational speech to levels that are maximally understandable to the patient; (2) to help the patient hear other environmental sounds; and (3) to assist in the educational or habilitative process for those children who sustain hearing loss prior to language and speech development. In addition, there are certain issues that require medical consideration when a wearable device is placed in the ear. This article describes current hearing aid technology; reviews its benefits, limitations, and application for typical patients; discusses the medical aspects of hearing aid fitting; and describes new hearing aid technology on the horizon.

    View details for Web of Science ID A1991FG96900013

    View details for PubMedID 1857620

  • HEARING LEVELS OF RAILROAD TRAINMEN LARYNGOSCOPE Clark, W. W., Popelka, G. R. 1989; 99 (11): 1151-1157

    Abstract

    The hearing sensitivity of 9427 railroad train crew members, determined during the first year of a company-wide hearing conservation program, was compared with hearing sensitivity in a control population not exposed to occupational noise. The hearing sensitivity of the trainmen did not differ significantly from that of the control population. Multiple regression analysis, which considered separately the effects of age and years of service, showed significant differences in hearing levels due to age, but no differences in hearing levels due to years of service. Evaluation of the data by risk categories developed by the National Institute for Occupational Safety and Health indicate that this group of trainmen had no risk of occupational noise-induced hearing loss. These analyses, combined with studies of locomotive cab noise, show clearly that trainmen are not typically exposed to hazardous occupational noise.

    View details for Web of Science ID A1989AY59200008

    View details for PubMedID 2811554

  • Factors which affect measures of speech audibility with hearing aids. Ear and hearing Popelka, G. R., MASON, D. I. 1987; 8 (5): 109S-118S

    Abstract

    Speech audibility may be defined as that proportion of a speech spectrum which is above a person's threshold. To optimize speech audibility with a hearing aid, several measures are needed. These include quantification of a speech spectrum, measures of hearing sensitivity, and measures of the "real ear" gain of the hearing aid. Some procedural factors must be considered to obtain adequate measures in a typical clinical setting. Those considered here are: (1) a modified Articulation Index to quantify a speech spectrum, (2) specification of hearing sensitivity with a narrowband sound field reference where the out-of-band rejection rate of the sound field stimulus is greater than twice the slope of the hearing loss, and (3) use of functional gain (measured directly or estimated using earphone and sound field results provided that the sound field stimulus has the required characteristics for measuring hearing sensitivity in the sound field) as a measure of the real ear gain of the hearing aid. Guidelines are given for the practical measurement of speech audibility in a typical clinical setting. The guidelines are appropriate for all measures of real ear gain including those obtained with all probe tube systems.

    View details for PubMedID 3678649

  • Development of an ear-level digital hearing aid and computer-assisted fitting procedure: an interim report. Journal of rehabilitation research and development Engebretson, A. M., Morley, R. E., Popelka, G. R. 1987; 24 (4): 55-64

    Abstract

    Recent progress on the development of an ear-level digital hearing aid is described. The work includes development of a body-wearable digital hearing aid and a computer-based hearing evaluation system that exploits the flexibility afforded by digital signal processing. The prescriptive criteria and fitting procedure used with the digital hearing aid are described briefly. Design considerations in the development of VLSI chips for an ear-level unit are discussed.

    View details for PubMedID 3430390

  • Computer-assisted hearing-aid evaluation and fitting program. Advances in oto-rhino-laryngology Popelka, G. R. 1987; 37: 166-168

    View details for PubMedID 3673811

  • New developments in hearing aid technology. Advances in oto-rhino-laryngology Popelka, G. R. 1987; 37: 162-165

    View details for PubMedID 3673810

  • AUDIOLOGICAL FINDINGS IN YOUNG-PATIENTS WITH HYPOPHOSPHATEMIC BONE-DISEASE ANNALS OF OTOLOGY RHINOLOGY AND LARYNGOLOGY Meister, M., Johnson, A., Kim, G. S., Popelka, G. R., Whyte, M. P. 1986; 95 (4): 415-420

    Abstract

    Audiometric tests were conducted on 19 subjects with hypophosphatemic bone disease to investigate whether auditory impairment like that reported in affected adults occurs in young patients. No hearing loss or significant auditory findings were noted among the children or young adult patients. However, sensorineural hearing loss of cochlear origin was identified in the three oldest subjects (40 to 58 years), although a history of noise exposure in two of them could explain the observations. The results indicate that if an association exists between hypophosphatemic bone disease and hearing impairment, the auditory signs will not develop until adulthood in treated patients. Additional studies of large populations of affected adults are needed to identify the incidence and mechanism(s) of the auditory system abnormalities and to assess any effect of medical therapy for the metabolic bone disease.

    View details for Web of Science ID A1986D708800018

    View details for PubMedID 3740719

  • COMPARISON OF HEARING-AID GAIN USING FUNCTIONAL, COUPLER, AND PROBE-TUBE MEASUREMENTS JOURNAL OF SPEECH AND HEARING RESEARCH Mason, D., Popelka, G. R. 1986; 29 (2): 218-226

    Abstract

    Measurements of functional gain were compared first to coupler gain for 57 subjects using one of three hearing aid-earmold combinations and second to probe-tube gain for 12 subjects using in-the-ear hearing aids. The average difference between functional and coupler gain plotted as a function of frequency yielded results that were similar to previous reports, with the greatest effects occurring at 3000 and 4000 Hz. Significant differences were seen among hearing aid-earmold combinations at 3000, 4000, and 6000 Hz. Standard deviations for measurements between 750 and 2000 Hz were less than 5 dB and could be explained by variability of functional gain measures associated with test-retest variability of thresholds measured in a sound field. Below 750 Hz and above 2000 Hz, standard deviations exceeded 5 dB. The greater variability may be explained by differences in earmold venting, acoustic characteristics of the ear canal, and stimuli used to measure functional and coupler gain. Neither room nor hearing-aid noise appeared to affect the results significantly. When functional gain was compared to insertion gain measured with a probe-tube system, the average difference across frequencies was less than 1 dB. The variability of the differences at all frequencies, with the exception of 6000 Hz, was within the range reported for functional gain measurements. It was concluded that functional gain can be accurately estimated using probe-tube measurements.

    View details for Web of Science ID A1986C611700008

    View details for PubMedID 3724114

  • FREQUENCY-SELECTIVITY AND THRESHOLDS OF BRIEF STIMULI SUITABLE FOR ELECTRIC-RESPONSE AUDIOMETRY AUDIOLOGY Davis, H., HIRSH, S. K., Popelka, G. R., Formby, C. 1984; 23 (1): 59-74

    Abstract

    Auditory evoked potentials are nearly all on-effects and the 'effective stimuli' for them are necessarily brief. Their frequency specificity is therefore limited, especially for the brainstem responses, because of the well-known trade-off between duration and frequency specificity. Brainstem responses are of special interest because they are unchanged in the sleep-like sedation that is required for difficult-to-test children. The middle-latency responses do not meet this requirement. Two patterns of tone burst that are appropriate and promising for the slow cortical potentials and for brainstem potentials, respectively, have rise and fall times of 2 periods of the modulated tone and plateaus of 10 (or 7) periods and 1 period, respectively. Their behavioral thresholds are nearly insensitive to difference in repetition rate between 4 and 40 stimuli/s. Their peak equivalent SPL threshold values at 500, 1 000, 2 000 and 4 000 Hz have been determined for 16 otologically normal ears. Using these reference levels, audiograms have been obtained for subjects with impaired hearing. The audiograms for 'flat' hearing losses do not differ significantly from the corresponding conventional pure-tone audiograms. The slopes for steep high-frequency hearing losses are underestimated, however, particularly with the brief (2-1-2) pattern. Nevertheless, the 2-1-2 pattern appears to be close to the best possible compromise.

    View details for Web of Science ID A1984SB59000007

    View details for PubMedID 6704060

  • ACOUSTIC IMMITTANCE MEASURES - TERMINOLOGY AND INSTRUMENTATION EAR AND HEARING Popelka, G. R. 1984; 5 (5): 262-267

    Abstract

    After a varied history over the past 15 years, basic acoustic immittance measures now include certain physical measures and certain physiological measures. This article reviews current concepts in the terminology and the instrumentation used for these basic measures. It is designed to provide an understanding of standard acoustic immittance measures and a framework for interpreting the results of special acoustic immittance procedures discussed in this issue.

    View details for Web of Science ID A1984TN31700002

    View details for PubMedID 6500195

  • AUDIOLOGIC FINDINGS IN A CHILD WITH A SINGLE-CHANNEL COCHLEAR IMPLANT JOURNAL OF SPEECH AND HEARING DISORDERS Popelka, G. R., GITTELMAN, D. A. 1984; 49 (3): 254-261

    Abstract

    Audiologic findings in a child who received a single-channel cochlear implant are presented. The measures used were threshold sensitivity to frequency-specific stimuli and results on various subtests from the Test of Auditory Comprehension (Trammel, 1976), the Monosyllable, Trochee, Spondee Test (Erber & Alencewicz, 1976), and the Minimal Auditory Capabilities Battery (Owens, Kessler, Telleen, & Schubert, 1981). The results for the implanted ear indicated uneven change in performance across measures compared to results with conventional amplification prior to receiving the implant. Performance of the implanted ear did not approach performance of the better contralateral ear. Observations by teachers and guardians indicated that there was no apparent change in auditory performance even after the cochlear implant had been worn for 6 months. Overall there was no evidence that the cochlear implant worn for 6 months provided any practical benefit to this child.

    View details for Web of Science ID A1984TD61200004

    View details for PubMedID 6547756

  • The significance of acoustic admittance procedures in the audiologic evaluation of multiply-handicapped children. British journal of audiology HIMELFARB, M. Z., Popelka, G. R., WEISER, A., SHANON, E. 1981; 15 (1): 21-24

    Abstract

    The specific contribution of admittance procedures in the diagnosis of hearing impairment was studied in a group of 53 handicapped children. The value of admittance procedures was assessed in relation to that of otoscopy and pure tone audiometry. Admittance procedures and otoscopy were successfully performed in all but one of the children and indicated conductive pathology in about 40% of the subjects, whereas pure tone audiometry was not feasible or inconclusive in 30.2% of the subjects. In 5.7% of the subjects admittance procedures proved the only diagnostic tool.

    View details for PubMedID 6452185

  • TYMPANOMETRY IN NORMAL NEONATES JOURNAL OF SPEECH AND HEARING RESEARCH HIMELFARB, M. Z., Popelka, G. R., SHANON, E. 1979; 22 (1): 179-191

    Abstract

    Acoustic conductance and susceptance tympanograms were obtained at 220 and 660 Hz in 34 neonates. The neonates were categorized into three age groups (8-24 hours, 24-60 hours, and 60-96 hours). Single-peaked, double-peaked, and monotonically increasing tympanograms were found. Static values for conductance, susceptance, admittance, resistance, reactance and impedance at the lateral surface of the tympanic membrane were computed from the tympanograms. There were no significant differences in mean static values among the three groups. At 220 Hz, the individual static reactance values were usually smaller than the static resistance values and often assumed a positive sign. At 660 Hz, the individual static reactance values always assumed a negative sign and were approximately equal to the static resistance values. The single- and double-peaked tympanograms apparently were the result of previously identified interactions between static resistance and reactance values. The data were compared to those of infants and adults. Tympanograms at 220 Hz were obtained for 13 of the original subjects at the age of three to four months. The data collected in this group were consistent with those reported in the literature for the same age group.

    View details for Web of Science ID A1979GQ29800014

    View details for PubMedID 502496

  • EFFECT OF SENSORINEURAL HEARING-LOSS ON ACOUSTIC STAPEDIUS REFLEX GROWTH FUNCTIONS JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Silman, S., Popelka, G. R., GELFAND, S. A. 1978; 64 (5): 1406-1411

    Abstract

    The growth function of the acoustic stapedius reflex was measured in subjects with normal hearing and sensorineural hearing loss of cochlear origin. The effects of age and magnitude of hearing loss were controlled. Activating stimuli were 500, 1000, and 2000 Hz tones and broadband noise. Stapedius muscle activity was inferred from acoustic impedance measures in the contralateral ear. The mean growth functions for tones were essentially linear in log-log plots with the rate of growth equal for the two groups. The mean growth function for the noise signal was curvilinear for the normal hearing groud had linear for the hearing loss group. Comparison of slope functions derived from the fitted data indicated that the rate of reflex growth for the noise signal, over a limited range above reflex threshold, is greater in ears with cochlear lesions than normal ears. For higher level noise signals, however, the rate of reflex growth is similar for normal and pathological ears. The effect of a cochlear lesion on the input-output function of the cochlea for both tonal and noise stimuli is to maintain the rate of reflex growth but shift the function along the intensity axis of a tonal signal and the response axis for a noise signal.

    View details for Web of Science ID A1978FW33500018

    View details for PubMedID 744841

  • EFFECTS OF EXPERIMENTALLY-PRODUCED MIDDLE-EAR LESIONS ON TYMPANOMETRY IN CATS ACTA OTO-LARYNGOLOGICA Margolis, R. H., Osguthorpe, J. D., Popelka, G. R. 1978; 86 (5-6): 428-436

    Abstract

    Tympanometry was performed before and after producing specific lesions in the middle ears of cats. The lesions selected for study included stapes fixation, ossicular discontinuity, and scarred tympanic membranes. Stapes fixation resulted in marked increases in middle ear impedance, easily detected with tympanometry. Ossicular discontinuity resulted in complex tympanometric shapes which were easily accounted for by simple interactions between acoustic resistance and reactance. The complex shapes that occurred in normal and abnormal ears with pressure changing from negative to positive resulted from more complicated interactions. Large surgical incisions in the posterior-superior quadrant of the eardrum were quite visible at otoscopy but could not be detected tympanometrically one month after surgery.

    View details for Web of Science ID A1978FX89300014

    View details for PubMedID 716865

  • COMMENTS ON ACOUSTIC-REFLEX RESPONSE FOR BONE-CONDUCTED SIGNALS ACTA OTO-LARYNGOLOGICA Popelka, G. R., Dubno, J. R. 1978; 86 (1-2): 64-70

    Abstract

    Previous studies which have measured acoustic-reflex responses to bone-conducted signals have not effectively differentiated reflex responses from artifacts. A convenient method for identifying such artifacts was developed and employed on some acoustic-reflex measures for bone-conducted signals. The findings indicated that artifacts result when a frequently-used acoustic admittance meter (Grason-Stadler 1720B) and a conventional bone vibrator were used to measure reflex responses for tonal and noise-activating signals. It was suggested that the method be employed in future studies which investigate the acoustic reflex in response to bone-conducted signals.

    View details for Web of Science ID A1978FL10200008

    View details for PubMedID 696297

  • INTERACTIONS AMONG TYMPANOMETRIC VARIABLES JOURNAL OF SPEECH AND HEARING RESEARCH Margolis, R. H., Popelka, G. R. 1977; 20 (3): 447-462

    Abstract

    To gain a better understanding of tympanometric results that have been difficult to interpret, such as asymmetrical and W-shaped tympanograms, acoustic susceptance and conductance tympanograms were measured from subjects with normal hearing and from subjects with well-defined middle ear pathology. Acoustic reactance, resistance, and impedance were computed and predicted from the measured data. Asymmetrical tympanograms derive in large part from the marked asymmetry in acoustic resistance as a function of ear canal pressure. W-shaped tympanograms result from interactions between reactance and resistance that occur when the two quantities assume similar absolute values or when reactance is mass controlled. A criterion for distinguishing between W-shaped tympanograms that are normal from those that are abnormal is discussed.

    View details for Web of Science ID A1977DV85900004

    View details for PubMedID 904307

  • EFFECT OF ACTIVATING SIGNAL BANDWIDTH ON ACOUSTIC-REFLEX THRESHOLDS JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Popelka, G. R., Margolis, R. H., Wiley, T. L. 1976; 59 (1): 153-159

    View details for Web of Science ID A1976BD74400023

    View details for PubMedID 1249314

  • LOUDNESS AND ACOUSTIC REFLEX JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Margolis, R. H., Popelka, G. R. 1975; 58 (6): 1330-1332

    View details for Web of Science ID A1975BB98300032

    View details for PubMedID 1206166

  • STATIC AND DYNAMIC ACOUSTIC IMPEDANCE MEASUREMENTS IN INFANT EARS JOURNAL OF SPEECH AND HEARING RESEARCH Margolis, R. H., Popelka, G. R. 1975; 18 (3): 435-443

    Abstract

    Tympanometry and acoustic reflex threshold data are reported for a series of presumable normal infants ranging in age from 55 to 132 days. In general, tympanograms displayed single peaks between +/- 50 mm H2O. Susceptance tympanograms with a 660-Hz probe frequency were sometimes characterized by monotonically increasing susceptance as ear canal pressure was changed from -200 to +200 mm H2O. Static values of acoustic conductance, susceptance, admittance, resistance, reactance, impedance, and phase angle were computed from tympanograms using the values of ambient and +200 mm H2O (0/+200 procedure) and maximum and minimum tympanometric values (MAX/MIN procedure). Comparison of the data from the two computational procedures suggested that the MAX/MIN procedure produces means and standard deviations of static values which are more manageable for establishing confidence limits with which to evaluate potentially pathological subjects. The MAX/MIN procedure resulted in lower mean values of conductance and susceptance for infant subjects relative to previously reported adult data using a similar computational procedure. Acoustic reflex thresholds were clearly present in all testable infants at coupler sound pressure levels similar to adult data, suggesting that the relations between reflex thresholds and hearing sensitivity demonstrated in adult subjects are similarly applicable to infant subjects. Mild sedation to induce sleep without altering the reflex would make acoustic reflex threshold measurement a useful procedure for screening large numbers of infants.

    View details for Web of Science ID A1975AS29400006

    View details for PubMedID 1186153

  • Letter: Acoustic reflex and critical bandwidth. journal of the Acoustical Society of America Popelka, G. R., KARLOVICH, R. S., Wiley, T. L. 1974; 55 (4): 883-885

    View details for PubMedID 4833084

  • GESTURES AND VISUAL SPEECH RECEPTION AMERICAN ANNALS OF THE DEAF Popelka, G. R., BERGER, K. W. 1971; 116 (4): 434-436

    View details for Web of Science ID A1971K077900013

    View details for PubMedID 5565841

Conference Proceedings


  • NEURAL PRESBYCUSIS - A DIAGNOSTIC DILEMMA Gates, G. A., Popelka, G. R. LIPPINCOTT-RAVEN PUBL. 1992: 313-317

    Abstract

    The combined term, sensorineural, is useful because clinical distinction between sensory and neural lesions is often difficult, and because sensory lesions may lead to secondary neural degeneration or, though rarely, a neural lesion may lead to secondary sensory degeneration. The threat of lawsuits for failure to identify treatable neurologic conditions has led to overuse of tests, while fiscal constraints exert pressure to limit expensive diagnostic testing. The purpose of this review of the relation between sensory and neural hearing loss is to provide a practical method to screen for neural lesions using pure-tone thresholds and a single speech discrimination score. The difference between the articulation index and the word recognition score of a patient provides a statistically reliable index of suspicion that may reduce the diagnostic dilemma of neural presbycusis.

    View details for Web of Science ID A1992JC39000005

    View details for PubMedID 1415492

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