摘要:

When an auditory stimulus is presented at a repetition ratefrof about 40/s, a robust steady‐state auditory evoked potential (AEP) is recordable [R. Galamboset al., Proc. Natl. Acad. Sci. (USA)78,2643–2647 (1981)], and has an approximate sinusoidal waveform with frequencyfr. A similar phenomenon is encountered when auditory evoked magnetic fields (AEMFs) are measured at the scalp with a SQUID magnetometer. We have determined thefrdependence of the steady‐state AEPs and AEMFs for the same human subjects. Using the assumption of a sandwich system (linear transformation‐zero memory nonlinear transformation‐linear transformation) response, we have also produced computer simulations of thefrdependence of steady‐state responses from measured transient‐response data. The simulations account fairly well for the steady‐state data. The stimulus was a 500‐Hz tone pip presented withfrvarying from 3‐50/s. The AEMF was recorded from a point around theT4location, and the AEP was recorded between electrodes atCZand the mastoid process of the test ear. Preliminary results for optimalfr's are 40‐45/s for the AEPs and 30‐35/s for the AEMFs. [Work supported by NINCDS, NSF, and the Purdue University Biomedical Support Fund.]

ISSN:0001-4966    

DOI:10.1121/1.2021996

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

During the first 7 months of life, C57BL/6 mice demonstrate progressive sensorineural hearing loss for high frequencies (>12 kHz), with little loss of sensitivity for lower frequencies. Auditory brainstem responses (ABRs) were obtained from C57 mice of both sexes aged 1 to 7 months. Stimuli (1 ms duration, 0.1 ms rise‐fall, 10/s rate) of two types were used: For “low‐pass” (LP), stimuli frequencies above 12 kHz were filtered from white noise; for “high‐pass” (HP) stimuli frequencies below 12 kHz were filtered. A wound clip over the vertex served as the active electrode and a bite bar was the reference. Thresholds of ABR wave I progressively increased by about 20 dB (re:20 μPa) by 7 months for the HP stimulus but increased by only 5 dB for the LP stimulus. Ratios of amplitudes of later ABR waves to early waves increased with age for high intensity stimuli. Amplitude‐intensity function slopes of waves IV and V (but not I‐III) increased with age. Both effects were more pronounced for HP stimuli. Sex differences were not observed in any of these findings. In summary, early and late ABR waves of hearing‐impaired C57 mice change in different ways with age, and the changes depend on the frequency spectrum of the stimulus. [Supported by a Research Career Development Award and a grant from NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2022001

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Previous findings [B. E. Mulligan, L. S. Goodman, D. P. Gleisner, and M. L. Faupel, J. Acoust. Soc. Am. (in press)] have indicated a stepwise dependence of binaural loudness on interaural phase for 250‐, 500‐, 650‐, 1000‐, 1200‐, and 1400‐Hz tones presented in “quiet.” The steps in loudness were found to occur at interaural phase angles which correspond to the natural limits of confusion‐free zones for tones of these frequencies. In the present research, observers reported the intracranial position of tonal stimuli which were laterally displaced by means of various combinations of interaural phase and intensity imbalances. It was found (for the same frequencies listed above) that the rate at which interaural phase was “traded” against interaural intensity changed abruptly near the limits of the confusion‐free zones. In addition, observers encountered greater difficulty in making reliable judgments of image position when phase was shifted near these limits.

ISSN:0001-4966    

DOI:10.1121/1.2022006

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

The pulsation threshold is the signal level at which a series of brief signals appears to be (illusorily) continuous when the intervening intervals are filled with a “masker” (different signal source). It is generally measured by an adjustment or tracking procedure. As a function of the frequency relation of the signal and “masker,” pulsation threshold results are similar in many respects to simultaneous masking patterns. It has been suggested that the two techniques are generally measuring the same aspects of hearing. This was tested by using a 2AFC PEST procedure: pulsation threshold was defined as the signal level for 75% correct discrimination between illusory continuity (signal on only when masker off) and true continuity (signal on at all times). Results were essentially identical to those obtained with a 2AFC PEST simultaneous masking procedure, as well as with a standard tracked pulsation threshold procedure. Given the difficulty which naive subjects often have with finding a stable criterion for pulsation threshold judgments, the 2AFC procedure may be preferable to adjustment tasks. [Work supported by the Deafness Research Foundation.]

ISSN:0001-4966    

DOI:10.1121/1.2022011

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

In a previous study, we demonstrated that the pitch of a complex tone could be changed and maintained in the direction of another complex tone with which it had been associated. Questions in the present study were whether the pitch change would generalize to the nonconditioned ear and to other similar tones. Information was also desired on possible long‐term characteristics of the pitch change. Experimental stimuli were pitch‐shift tones of 1150‐1350‐1550‐1750 and 1250,‐1450‐1650‐1850 Hz. Each was used with different subjects to test both up and down pitch changes. These tones are normally judged to have pitches of about 190 and 210 Hz, respectively. The conditioning tone was the first five harmonics of fundamental 200 Hz. To establish the pitch change, this tone and one of the pitch‐shift tones were heard together for 30 min each day for 5 nonconsecutive days. The results indicated that the average pitch change of about 8 Hz: (1) generalized to the nontest ear after being initially ear specific, (2) generalized more readily to higher rather than lower tones relative to the conditioned tone, and (3) was still maintained at approximately 3 mo after the conditioning sessions.

ISSN:0001-4966    

DOI:10.1121/1.2022016

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Goldman, Weiler, and Davis (1981), Davis and Weiler (1975), etc. found an increase in reaction time (RT) to 400‐Hz test tones accompanying a 500‐Hz adapting tone. Tests were only done after 7 min of the adapting tone. Goldmanet al.(1983) reported on sequential reaction times taken from 15 s to 3 min after the adapting tone began, and found that only the 15‐s test showed an increase in RT, with later times not significantly different from baseline. The current data extends this finding into the “recovery” period following cessation of the 500‐Hz adapting tone. The initial recovery RT showed an unexpected increase in latency followed by shorter values not significantly different from baseline. As the changes in RT during adapting did not show learning across repeated sessions, an alternate explanation based on attention will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2022021

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

The application of nonlinear acoustics to seismic profiling, exploration, and sedimentary geophysics has long been recognized as having great potential, due to the unique opportunities for high resolution measurements. These measurements, in turn, open new avenues for theoretical developments in areas of sediment characterization and acoustic modeling for scattering and propagation. The present paper reviews the utilization of a parametric research tool in sub‐bottom profiling experiments conducted offshore southern California and Oahu, Hawaii. An instrument capable of parametric operation in the 1–5 kHz band with a nominal 3° beamwidth was used in a transient mode to generate a Ricker wavelet with a 0.8‐ms duration. The results of normal incidence sub‐bottom profiling are presented to demonstrate the precision mapping of bedrock stratigraphy, including tilted bedding, faulting, the presence of discrete inhomogeneities, etc. Results on the profiling of the unconsolidated sediment layers are also presented, demonstrating the existence and quantification of microlayering. The stochastic properties of the sedimentary microlaying are computed from the data for use in an acoustic scattering model. [Work supported by the U.S. Navy Office of Naval Research.]

ISSN:0001-4966    

DOI:10.1121/1.2022023

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Results are reported indicating the importance of spectral change in the identification of isolated vowels in Canadian English, including vowels usually considered monopthongal. Brief (30‐ms Hamming windowed) segments were extracted from the “steady‐state” (INITIAL) and “offglide” (FINAL) portions of 40 isolated vowels (ten categories × four speakers). Pairs of sections, separated by 10 ms, were presented to listeners in three conditions: (1) INITIAL‐FINAL (I‐F), (2) INITIAL‐INITIAL (I‐I), and (3) FINAL‐INITIAL (F‐I). Listeners' error rates were comparable for the I‐F condition (14%) and the original tokens (13%), but considerably higher for I‐I (32%) and F‐I (38%) conditions. The fundamental and the first two formant frequencies were measured in each of the “steady‐state” and “offglide” sections. These measures were used to predict listeners' identification using a model of the type described in Assmann, Nearey, and Hogan [J. Acoust. Soc. Am.71,975–989 (1982)]. Observed patterns of confusion were generally similar to model predictions.

ISSN:0001-4966    

DOI:10.1121/1.2022027

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

In front‐back vowel continua cued by variations ofF2, a critical‐band (Z) representation of formant frequency was found to relate linearly to the judged “phonetic goodness” of the vowels: changes inF2 (ΔF2) which are equal along theZscale, produce nearly equal changes of judged “phonetic‐goodness” (ΔG) [Espinoza‐Varas, J. Acoust. Soc. Am. Suppl. 174,S66 (1983)]. We replicated the previous experiments in sensorineural impaired listeners (low‐frequency hearing loss, gradually sloping audiograms), who typically exhibit broadened critical bands. The vowel continua ranged from /u/ to /i/, /ɔ/ to /ɛ/, or /a/ to /æ/. On each continua the frequencies ofF1 andF3 were fixed, and the frequency ofF2 varied from the value appropriate for the back vowel to that appropriate for the front vowel in 6–12 steps of 0.5Zeach.F0 was 120 Hz. The 400‐ms, steady‐state vowels were generated by parallel synthesis; listeners categorized the stimuli and rated their “phonetic goodness.” A highly consistent deficit (across subjects and vowel pairs) in the impaired listeners' performance is the poorer ability to assess how good an examplar of a vowel class a given stimulus is. The relation between ΔF2 and ΔGis no longer linear. This deficit is observed even though the ability to identify the vowels may be “normal.” The results appear to corroborate the possibility of a close relation between the judgment of “phonetic goodness” of vowels and the critical‐band level of frequency analysis [Supported by AHFMR and NSERC.]

ISSN:0001-4966    

DOI:10.1121/1.2022037

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

There are systematic deviations in acoustic measurements of the syllable onsets of perceptually isochronous rhyming monosyllables differing in initial consonant structure [C. Fowler and L. Tassinary, Atten. Perform.IX,521–535 (1981)]. In the present study we examine the corresponding intervals of monosyllables that differ in (1) vocalic nucleus or (2) coda. Metronome‐timed tokens of both alliterative and homophonous sequences were measured from the productions of two talkers. The observed intervals between syllable onsets and those between vocalic onsets show a pattern consistent with the hypothesis that talkers and listeners are sensitive to a syllable‐internal event, perhaps the articulatory onsets of the vowels. [Work supported by NICHHD.]

ISSN:0001-4966    

DOI:10.1121/1.2022041

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP