David J. Lilly

Sources and mechanisms of DPOAE generation: Implications for the prediction of auditory sensitivity

Otoacoustic emissions (OAEs) have become a commonly used clinical tool for assessing cochlear health status, in particular, the integrity of the cochlear amplifier or motor component of cochlear function. Predicting hearing thresholds from OAEs, however, remains a research challenge. Models and experimental data suggest that there are two mechanisms involved in the generation of OAEs. For distortion product, transient, and high-level stimulus frequency emissions, the interaction of multiple sources of emissions in the cochlea leads to amplitude variation in the composite ear canal signal. Multiple sources of emissions complicate simple correlations between audiometric test frequencies and otoacoustic emission frequencies. Current research offers new methods for estimating the individual components of OAE generation. Input-output functions and DP-grams of the nonlinear component of the 2f2-f2 DPOAE may ultimately show better correlations with hearing thresholds. This paper reviews models of OAE generation and methods for estimating the contribution of source components to the composite emission that is recorded in the ear canal. The clinical implications of multiple source components are discussed.

Multiple frequency, multiple component tympanometry: new approaches to an old diagnostic problem.

Tympanometry with low-frequency probe tones provides useful clinical informaton for patients with disorders of the tympanum, the tympanic membrane, and the Eustachian tube. Low-frequency, single component tympanometry, however, is relatively insensitive to many lesions that affect the ossicular chain. This review focuses upon a collection of four, interrelated acoustic measurement techniques that have been developed for identification and differential diagnosis of those middle ear disorders that do not always yield pathognomonic patterns with conventional tympanometry. Specifically, the initial hypotheses, the methods, normative data and representative clinical findings are summarized for: (1) a multiple frequency magnitude array; (2) a multiple frequency phase-angle array; (3) a three-dimensional array; and (4) a differential sound pressure level and phase plot

Tympanometric Findings in Patients With Enlarged Vestibular Aqueducts

Objectives The purpose of this study was to study systematically some relationships between the resonance frequency of the middle‐ear transmission system and the volume of the endolymphatic duct and sac in patients with an enlarged vestibular aqueduct (EVA).

An overview of wideband immittance measurements techniques and terminology: you say absorbance, I say reflectance.

This article reviews the relationships among different acoustic measurements of the mobility of the tympanic membrane, including impedance, admittance, reflectance, and absorbance, which the authors group under the rubric of immittance measures. Each of these quantities is defined and related to the others. The relationship is most easily grasped in terms of a straight rigid ear canal of uniform area terminated by a uniform middle ear immittance placed perpendicular to the long axis of the ear canal. Complications due to variations from this geometry are discussed. Different methods for measuring these quantities are described, and the assumptions inherent within each method are made explicit. The benefits of wideband measurements of these quantities are described, as are the benefits and limitations of different components of immittance and reflectance/absorbance. While power reflectance (the square of the magnitude of pressure reflectance) is relatively invariant along the length of the ear canal, it has the disadvantage that it ignores phase information that may be useful in assessing the presence of acoustic leaks in ear-canal measurements and identifying other potential error sources. A combination of reflectance and impedance magnitude and angle give a more complete description of the middle ear from measurements in the ear canal.

Consensus statement: Eriksholm workshop on wideband absorbance measures of the middle ear

The participants in the Eriksholm Workshop on Wideband Absorbance Measures of the Middle Ear developed statements for this consensus article on the final morning of the Workshop. The presentations of the first 2 days of the Workshop motivated the discussion on that day. The article is divided into three general areas: terminology; research needs; and clinical application. The varied terminology in the area was seen as potentially confusing, and there was consensus on adopting an organizational structure that grouped the family of measures into the term wideband acoustic immittance (WAI), and dropped the term transmittance in favor of absorbance. There is clearly still a need to conduct research on WAI measurements. Several areas of research were emphasized, including the establishment of a greater WAI normative database, especially developmental norms, and more data on a variety of disorders; increased research on the temporal aspects of WAI; and methods to ensure the validity of test data. The area of clinical application will require training of clinicians in WAI technology. The clinical implementation of WAI would be facilitated by developing feature detectors for various pathologies that, for example, might combine data across ear-canal pressures or probe frequencies.

What drives mechanical amplification in the mammalian cochlea

The recent report by Peter Dallos and colleagues of the gene and protein responsible for outer hair cell somatic motility (Zheng, Shen, He, Long, Madison, & Dallos, 2000), and the work of James Hudspeth and colleagues demonstrating that vestibular stereocilia are capable of providing power that may boost the vibration of structures within the inner ear (Martin & Hudspeth, 1999), presents the tantalizing possibility that we may not be far away from answering the question what drives mechanical amplification in the mammalian cochlea? This article reviews the evidence for and against each of somatic motility as the motor, and a motor in the hair cell bundle, producing cochlear mechanical amplification. We consider three models based on somatic motility as the motor and two based on a motor in the hair cell bundle. Available evidence supports a hair cell bundle motor in nonmammals but the upper frequency limit of mammalian hearing in general exceeds that of nonmammals, in many cases by an order of magnitude or more. Only time will tell whether an evolutionary dichotomy exists (Manley, Kirk, Köppl, & Yates, 2001).

Some Effects of Multiple Sclerosis on Speech Perception in Noise: Preliminary Findings

The present investigation examined speech perception in noise of adults with and without multiple sclerosis (MS). Institute of Electrical and Electronic Engineers (IEEE) sentences were presented at a constant level of 65 dBA L(eq) (equivalent continuous noise level [4 dB exchange rate]) from a loudspeaker located at 0-degree horizontal azimuth and 1.2 m from the study participant. Uncorrelated multitalker babble was presented from four loudspeakers positioned at 45-, 135-, 225-, and 315-degree azimuths and 1.7 m from the study participant. The starting presentation level for the babble was 55 dBA L(eq). The level of the babble was increased systematically in 1 dB steps until the subject obtained 0% key words correct on the IEEE sentences. Results revealed a significant difference in speech perception between the two groups at nine signal-to-noise ratios. Some clinical implications of these results are discussed.

Wideband acoustic immittance measurements of the middle ear: introduction and some historical antecedents.

This supplement focuses on some of the most recent acoustic measurements within the occluded, human external auditory meatus (EAM). The goal of this introduction is to provide an overview of basic and clinical EAM measurements that evolved in the 20th century and some relations between these measurements and wideband acoustic absorbance. The authors review some of the major efforts that have been used to evaluate the condition of the human, adult middle ear transmission system, the middle ear cavity, and the function of the Eustachian tube. They have grouped most of this work under the rubric of “acoustic immittance.” A historical perspective helps one appreciate that the measurement of wideband acoustic absorbance is not a totally new procedure. Rather, it is the latest enhancement to aural acoustic-immittance measurements. An enhancement that can expand ones ability to characterize middle ear function and effects of ear disease on that function. It also allows clinicians evaluate middle ear function for frequencies whose wavelength is shorter than the length of the EAM.

Development of a "virtual cocktail party" for the measurement of speech intelligibility in a sound field.

This technical report describes an approach to the measurement of speech intelligibility for sentences presented in a sound field in the presence of 16-talker babble. More specifically, we detail our (1) selection and preparation of target speech materials, (2) selection and preparation of experimental babble, (3) analog instrumentation, (4) software routines for attenuator control, (5) calibration, (6) experimental subjects, and (7) experimental protocol. In the final section of this report we present speech-intelligibility data from 16 young adults (21-30 yr of age) with normal hearing sensitivity for pure-tone signals.

Cross‐language speech intelligibility in noise: The comparison on the aspect of language dominance

The purpose of this study is to obtain information about the influence of language characteristics on the results of speech intelligibility in two different languages: English and Japanese. This study investigates the speech intelligibility of both English and Japanese under quiet and noisy situation on 14 bilingual subjects aged 23 to 42 years with normal hearing. As test materials, the CID W‐22 word lists which are meaningful monosyllables are used for English and the 57‐S word lists which are nonsense monosyllables are used for Japanese. The subjects whose dominant language is English are 6. Results show that percentage‐correct of speech intelligibility is higher in Japanese than in English at lower intensity and noisy situation. This advantage in Japanese is seen regardless of the language dominance. It is considered that the phonetic characteristics and the simple structure of Japanese can make it relatively resistant to the hard listening condition. [Work supported in part by Japan Foundation for Aging and Health.]