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PubMed2000

Acoustic responses of the human middle ear.

Measurements on human cadaver ears are reported that describe sound transmission through the middle ear. Four response variables were measured with acoustic stimulation at the tympanic membrane: stapes velocity, middle-ear cavity sound pressure, acoustic impedance at the tympanic membrane and acoustic impedance of the middle-ear cavity. Measurements of stapes velocity at different locations on the stapes suggest that stapes motion is predominantly 'piston-like', for frequencies up to at least 2000 Hz. The measurements are generally consistent with constraints of existing models. The measurements are used (1) to show how the cavity pressure and the impedance at the tympanic membrane are related, (2) to develop a measurement-based middle-ear cavity model, which shows that the middle-ear cavity has only small effects on the motion of the tympanic membrane and stapes in the normal ear, although it may play a more prominent role in pathological ears, and (3) to show that inter-ear variations in the impedance at the tympanic membrane and the stapes velocity are not well correlated.

Acoustic Impedance Tests↗
PubMed2003

Acoustic analysis of pathological voices compressed with MPEG system.

The MPEG-1 Layer 3 compression schema of audio signal, commonly known as mp3, has caused a great impact in recent years as it has reached high compression rates while conserving a high sound quality. Music and speech samples compressed at high bitrates are perceptually indistinguishable from the original samples, but very little was known about how compression acoustically affects the voice signal. A previous work with normal voices showed a high fidelity at high-bitrate compressions both in voice parameters and the amplitude-frequency spectrum. In the present work, dysphonic voices were tested through two studies. In the first study, spectrograms, long-term average spectra (LTAS), and fast Fourier transform (FFT) spectra of compressed and original samples of running speech were compared. In the second study, intensities, formant frequencies, formant bandwidths, and a multidimensional set of voice parameters were tested in a set of sustained phonations. Results showed that compression at high bitrates (96 and 128 kbps) preserved the relevant acoustic properties of the pathological voices. With compressions at lower bitrates, fidelity decreases, introducing some important alterations. Results from both works, Gonzalez and Cervera and this paper, open up the possibility of using MPEG-compression at high bitrates to store or transmit high-quality speech recordings, without altering their acoustic properties.

Acoustic Stimulation↗
PubMed1987

Acoustic-immittance measures in normal ears.

A data base of acoustic-immittance measures in normal adults is presented. The subject pool consisted of 127 adults with normal hearing and a negative otologic history. Norms are presented for hearing thresholds, ipsilateral and contralateral acoustic-reflex thresholds, tympanometry, static acoustic-admittance measures, and middle-ear (tympanogram peak) pressure.

Acoustic Impedance Tests↗
PubMed1989

Static acoustic-admittance measures in normal ears: a combined analysis for ears with and without notched tympanograms.

A preliminary database of acoustic-immittance measures in normal adults was provided in an earlier publication (Wiley, Oviatt, & Block, 1987). Here, an additional analysis of static acoustic-admittance measures, based on the original database, is provided. Specifically, compensated static acoustic-admittance data for a 220-Hz probe signal are provided for 239 ears including those that did (N = 55) and did not (N = 184) demonstrate tympanometric notching for a 660-Hz probe signal.

Acoustic Impedance Tests↗
PubMed2005

Influence of sampling rate on accuracy and reliability of acoustic voice analysis.

It is universally recognized that sampling rate (F(S)) influences the reliability and validity of acoustic voice measurements; however, an exact relationship has not been determined. The purpose of this experiment was to investigate the influence of F(S) on acoustic voice quality measurements, while considering the influences of gender, intra-subject variability, microphone, environmental noise, data acquisition hardware, and analysis software as balancing factors. The impact of F(S), from 44.1 kHz to 10 kHz, was explored by analyzing 864,000 measures of fundamental frequency, jitter, and shimmer, using three software analysis systems: MDVP, TF32, and PRAAT. Results suggest that the recommended, acceptable, and critical F(S) for acoustic voice analysis are above 26 kHz, above 19 kHz, and 12 kHz, respectively. Thus, voice samples captured above 26 kHz can be used for data analysis and compared without introducing error due to F(S).

Acoustic Stimulation↗
PubMedDate not supplied

Acoustic immittance measures: terminology and instrumentation.

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.

Acoustic Impedance Tests↗
PubMedDate not supplied

Acoustic reflex averaging.

Signal averaging techniques have been applied to acoustic reflex measurement in order to meet the need for better temporal resolution and more accurate threshold delineation. We describe an approach to reflex measurement based on a signal averaging technique designed to examine both threshold and suprathreshold characteristics of the acoustic reflex. Results indicate that: (1) many supposed reflex threshold and latency aberrations are actually amplitude aberrations that are inappropriately classified because of instrumentation constraints; (2) reflex amplitude and waveform morphology can be recorded with appropriate fidelity using a signal averaging technique; (3) problems due to absolute amplitude variability can be minimized by using an index technique to assess amplitude relationships; (4) amplitude indices are sensitive indicators of neural pathology; (5) signal averaging and suprathreshold measurement of reflex amplitude and waveform morphology promise to enhance the sensitivity of acoustic reflex measurement.

Adult↗
PubMed1987

Basic acoustic considerations of ear canal probe measurements.

This publication contains a review of several acoustic investigations in which the effects of probe location on real-ear gain were examined through theoretical models based on acoustic properties of the average human ear and ear simulator studies. The results of these investigations are used to demonstrate the effect of standing waves and eardrum impedance on probe measurements made in the ear canal. Investigations were also conducted in the sound field with a KEMAR manikin. A commercial probe microphone system was used to measure the SPL and real-ear gain at various locations with the KEMAR ear canal. The results emphasize the critical effect of probe location on absolute or relative ear canal measurements and indicate the necessity to establish clinical procedures for probe measurements based on relevant acoustic principles.

Acoustic Impedance Tests↗
PubMed1995

Comparison of crossed and uncrossed acoustic reflex latencies.

OBJECTIVE: To compare morphologies of crossed and uncrossed acoustic reflex waveforms. DESIGN: Subjects were 12 young adults with normal hearing. A signal-averaging technique was used to compare onset and offset latencies of crossed and uncrossed acoustic reflex waveforms when maximum amplitudes were matched. RESULTS: Onset latency was similar for the two modes, but offset latency was significantly longer for the crossed reflex. Further, in individual subjects the difference between crossed and uncrossed offset latencies was inversely proportional to maximum reflex amplitude. CONCLUSION: Results emphasize the complex interaction between amplitude and latency characteristics of acoustic reflex waveform.

Acoustic Impedance Tests↗
PubMed1996

Maturation of the middle and external ears: acoustic power-based responses and reflectance tympanometry.

OBJECTIVE: The maturation of the external and middle ear in the human infant has significant effects on the interpretation of measured ear-canal responses to acoustic stimuli. A tutorial section is presented of power-based response functions, accompanied by a hierarchy of stimulus specifications contrasting pressure-based and power-based responses. An experimental section follows on reflectance tympanometry, the aims of which are to introduce and assess the feasibility of the technique and to discuss implications for tests of hearing development. DESIGN: A tympanometric measurement of admittance is used with an estimate of ear-canal area to calculate a so-called reflectance tympanogram as a function of frequency and static pressure in the ear canal. Selected results on 226 Hz reflectance tympanograms are reported for normal-hearing adults and for infants of age 3 to 6 mo with both normal and flat 226 Hz admittance tympanograms. A multifrequency reflectance tympanogram is reported for an adult. RESULTS: Measured at ambient ear-canal pressure, the acoustic external- and middle-ear responses of infants of age 1 to 6 mo are compared with those of adults. The admittance level is influenced by the ear-canal area, the interplay of compliant- and inertance-controlled effects in the middle ear, and the presence of losses. Ear-canal area is a major factor in distinguishing infant from adult responses. Energy reflectance provides a measure of middle-ear power transmission that is approximately independent of probe placement in the ear canal and that varies with maturation. These power-based responses, measured at ambient pressure, are contrasted with tympanometric measurements. Reflectance tympanometry is defined and easily measured in infants and adults. Some infants with flat 226 Hz tympanograms have energy reflectance in the normal range at higher frequencies (2 to 4 kHz). CONCLUSION: Acoustic measurements of power-based responses in the ear canal-reflectance, admittance, and impedance-provide insight into the maturation of the external and middle ear. Reflectance tympanometry tests the relative accuracy underlying the tympanometric measurement of compensated eardrum admittance and may have clinical utility.

Acoustic Impedance Tests↗
PubMed1989

Single vs. double acoustic reflectometry tracings.

Impedance tympanometry and acoustic reflectivity tests were obtained on 503 infants and children ranging from 3 months to 12 years of age during a 6-week period in a solo primary care practice. One hundred eighty-five of 1005 tracings from the acoustic otoscope with recorder demonstrated 2 reflectivities. This phenomenon occurred more commonly in infants than in older children and was not seen with reflectivities higher than 7 units. One hundred thirty-eight of the 185 double reflectivity tracings were associated with abnormal impedance tympanometry. The double reflectivity phenomenon may be important in helping to explain the false negative results occasionally seen with this technology in low and intermediate reflectometry scores. Future clinical research involving acoustic reflectometry should utilize the recording device and single and double reflectivity tracings should be handled separately in any analysis of data. Use of the recorder will also prevent false positive errors in the interpretation of some intermediate reflectivities.

Acoustic Impedance Tests↗
PubMed2004

Wideband reflectance measures of the ipsilateral acoustic stapedius reflex threshold.

OBJECTIVE: The purpose of this study was to develop a method for acoustically measuring the ipsilateral acoustic stapedius reflex threshold by using wideband shifts in energy reflectance and admittance. DESIGN: A group of 27 young adult subjects with normal hearing participated in the study. Contralateral reflex thresholds were first measured for a 4000 Hz activator tone (maximum level, 92 dB SPL), using a clinical method with a 226 Hz probe tone. Ipsilateral and contralateral reflex thresholds were then measured by using an experimental wideband reflectance and admittance system that used a band-filtered click (200 to 2000 Hz) as the probe stimulus, presented simultaneously with the 4000 Hz activator tone. Reflex thresholds for the wideband system were determined by using statistical tests of the magnitude of the reflex responses as well as their correlation with other reflex responses. RESULTS: Clinical and experimental reflex thresholds were obtained for 9 of the 27 subjects for all conditions. Clinical reflex thresholds were absent for 8 subjects for whom experimental reflex thresholds were present and were present for 5 subjects who had absent experimental reflex thresholds for one or more conditions. An additional 5 subjects had absent reflex thresholds in all conditions, consistent with the low maximum level of the activator. Wideband measures of contralateral reflex thresholds were approximately 3 dB lower than those obtained with the clinical system. The magnitudes of the group means of the reflex responses were similar for ipsilateral and contralateral stimulations. CONCLUSIONS: Wideband measures of reflectance and admittance may be used to estimate the ipsilateral acoustic stapedius reflex threshold by separating in frequency the spectral energies of the wideband probe stimulus from the activator stimulus. This technique holds promise for measuring reflex thresholds for individuals with absent reflex thresholds through the use of standard clinical methods.

Acoustic Impedance Tests↗
PubMed2003

The relation of lung volume initiation to selected acoustic properties of speech.

This study examined the relationship of speech breathing to other elements of speech production. It was hypothesized that initiating speech from different lung volumes would have an effect on different elements of the acoustic output. It was postulated that effects may be brought about by mechanical interaction as well as a dispersion of effort to mechanically unlinked elements of speech production, such as articulatory behavior. To this end, selected acoustic variables were studied in eight young healthy women who initiated speech from low, typical, and high lung volume levels. The acoustic variables studied were selected because they have been shown to be sensitive indicators of speech production performance. It was found that with increasing lung volume initiation levels, average sound pressure level, average fundamental frequency, and declination rate of fundamental frequency increased. It was also observed that vowel space was significantly smaller during low lung volume initiation levels relative to typical lung volume initiation levels. Vowel space reduction is discussed relative to "gaining down."

Acoustics↗
PubMed1978

Stimulated acoustic emissions from within the human auditory system.

A new auditory phenomenon has been identified in the acoustic impulse response of the human ear. Using a signal averaging technique, a study has been made of the response of the closed external acoustic meatus to acoustic impulses near to the threshold of audibility. Particular attention has been paid to the waveform of the response at post excitation times in excess of 5 ms. No previous worker appears to have extended observations into this region. The response observed after about 5 ms is not a simple extension of the initial response attributable to the middle ear. The oscillatory response decay time constant was found to change from approximately 1 ms to over 12 ms at about this time. The slowly decaying response component was present in all normal ears tested, but was not present in ears with cochlear deafness. This component of the response appears to have its origin in some nonlinear mechanism probably located in the cochlea, responding mechanically to auditory stimulation, and dependent upon the normal functioning of the cochlea transduction process. A cochlear reflection hypothesis received some support from these results.

Acoustic Impedance Tests↗
PubMed1980

Magnitude of the acoustic reflex for either homophasic (0 degrees) or antiphasic (180 degrees) binaural activating signals presented in a background of noise.

The threshold of the acoustic reflex (TAR) and the magnitude of middle-ear muscle response were measured for a homophasic (0 degrees) and an antiphasic (183 degrees) 550-Hz tone in a background of in-phase noise. Signal-to-noise ratio ranged from - 20 dB to 5 dB. Whereas previously reported data shows an effect of phase on the percept of loudness, no evidence of a phase effect was measured for acoustic-reflex responses. These results are interpreted as evidence against a relation between loudness and acoustic reflex for binaurally presented signals.

Acoustic Stimulation↗
PubMed1989

Some effects of signal bandwidth and spectral density on the acoustic-reflex threshold in the elderly.

The acoustic-reflex thresholds (ART) for multicomponent tonal complexes of varying bandwidth and spectral density were obtained from 20 normal-hearing (air-conduction thresholds less than or equal to 20 dB HL at 250-8000 Hz) young adults ranging in age from 20-30 years and 20 normal-hearing, old subjects ranging in age from 60-71 years. The results revealed that the ART decreased with spectral density, plateauing after seven components in the young group and after five components in the old group; the decrease in the acoustic-reflex threshold as a result of the increase in spectral density was less in the old than in the young group. The bandwidth effect (when bandwidth was plotted in hertz or octaves) on the acoustic-reflex threshold was present in the young adults, but substantially reduced in the elderly, as evidenced by the statistically significant interaction between subject group and signal bandwidth. The spectral density results are discussed in terms of their theoretic implications for the energy summation capacity and frequency resolution of the auditory system. The bandwidth results are discussed in terms of their theoretic implications for the frequency-resolving power of the auditory system.

Acoustic Stimulation↗
PubMed1992

Method to measure acoustic impedance and reflection coefficient.

A frequency-domain based system for measuring acoustic impedance and reflection coefficient is described. The calibration procedure uses a least-mean-squares approximation to the Thevenin parameters describing the source and receiver characteristics in which the data measured on closed, cylindrical tubes are matched to a viscothermal tube model. The system is intended for use in acoustical measurement in human ear canals, in which the cross-sectional area of the ear canal at the point of insertion is imprecisely known. This area is acoustically estimated from the impedance data, and the reflection coefficient is calculated in terms of this area and the impedance data. Measurements on a variety of closed tubes show the method is accurate over the frequency range investigated (less than 10.7 kHz). The time-domain reflection function is evaluated by transforming the reflection coefficient from the frequency domain, but the finite bandwidth of the measured data limits the accuracy of time-domain response measurements. The method is well suited for frequency-domain measurements in human ear canals.

Acoustic Impedance Tests↗
PubMed1996

Multicomponent acoustic distortion product otoacoustic emission phase in humans. II. Implications for distortion product otoacoustic emissions generation.

Phase characteristics and latency of 2f1-f2, 3f1-2f2, and 2f2-f1 acoustic distortion product otoacoustic emissions (DPOAEs) recorded in normally hearing adults have been described in a companion paper [Moulin and Kemp, "Multicomponent acoustic distortion product otoacoustic emission phase in humans. I. General characteristics," J. Acoust. Soc. Am. 100, 1617-1639 (1996)]. Phase-versus-frequency functions (PFF) have been recorded using two methods, depending whether f1 or f2 was swept in frequency, defining, respectively, an "f1 sweep" and an "f2 sweep" method. The present study compares 2f1-f2, 3f1-2f2, 4f1-3f2, and 2f2-f1 DPOAEs phase characteristics, and latencies obtained by these two methods. For lower sideband DPOAEs, the f2 sweep gave consistently longer latencies than the f1 sweep method, whereas no difference was obtained for the 2f2-f1 DPOAE. This suggests that the lower sideband DPOAEs and the 2f2-f1 DPOAE do not come from the same aspect of the traveling wave. The longer delay obtained with an f2 sweep is suggested to be due to an additional delay added by the proximity of the peak of the f2 traveling wave. The place-fixed and the wave-fixed models of DPOAE generation are discussed, and an "intermediate" model of DPOAE generation is introduced to explain such additional delay and the existence of phase irregularities which were observed in the PFF. The ratio of the latencies obtained by the two sweep methods is frequency dependent and a relation to cochlear frequency selectivity is suggested. Finally, analysis of the differences in latency of the different lower sideband DPOAE components allowed an estimation of the return latency of DPOAEs.

Acoustic Stimulation↗