摘要:

This study evaluated frequency discrimination ability in 11 monkeys over an extended period of time using a repeating‐standard procedure and the method of constant stimuli. The intersubject variability of the difference limens for frequency (ΔF) was large, as reported by other investigators, but similar in magnitude to the variability of the difference limens for intensity (ΔI) from three of the same subjects in an intensity discrimination experiment. Continued training generally resulted in a rapid decrease in ΔF’s, followed by a longer‐term, slower decrease. For one subject ΔF’s slowly decreased throughout a 190‐week time period. This long‐term training effect was specific to frequency discrimination; a similar effect was not observed for the same subject tested in an intensity discrimination experiment. Finally, ΔF’s from the well‐trained monkeys of this study were larger than monkey ΔF’s from this laboratory reported in an earlier study, and than human ΔF’s. An anatomical explanation for the human/monkey ΔFmagnitude difference is explored.

ISSN:0001-4966    

DOI:10.1121/1.400112

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Three experiments were carried out that employed low‐frequency tone complexes with interaural delays that varied across the frequency domain. In the first experiment, threshold interaural delays were measured for three‐tone complexes for which one, two, or all three components were delayed. The center frequency was 750 Hz and the frequency spacing (Δf ) between components was 20, 50, 100, 250, or 450 Hz. For all Δf’s, the presence of two diotic components elevated the threshold interaural delays obtained for the third component relative to that obtained for a pure tone of the same frequency. In the second experiment, observers made left–right judgments regarding the direction of movement of signals for which two components were delayed by 25 μs to the left ear during one interval and to the right ear during the other interval, while a third component of a variable time difference was delayed to the opposite side as the tone pair. Subjects reported single intracranial images during each interval, and the data showed that interaural delays of one component to one ear could be offset by interaural delays of the other two components to the other ear. In the final experiment, threshold interaural delays were measured for five‐tone complexes in which one, two, three, four, or five components were delayed. The center frequency was 750 Hz and Δfwas fixed at 100 Hz. Thresholds decreased in a linear fashion as the number of delayed components increased, falling by about a factor of 5 as the number of delayed components went from one to five. These results are consistent with spectrally synthetic binaural processing, with the lateral position of intracranial images determined by a combination of interaural information across the spectrum. These effects could be brought about by a linear combination of the outputs of frequency‐specific cross‐correlation networks or by a wideband cross correlation of the signals at the two ears.

ISSN:0001-4966    

DOI:10.1121/1.400113

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

A new method for estimating audiograms using behavioral responses is presented. The method is based upon a modification of the Bayesian probability formula in which an outcome is predicted from a static set of events. In the new method, classification of audiograms by sequential testing (CAST), the probabilities of occurrence of audiogram patterns are dynamically updated according to the outcome of each test trial. Computer simulation using an infant response model suggests that the procedure is efficient, sensitive, and specific.

ISSN:0001-4966    

DOI:10.1121/1.400114

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

The transformations of sound by the auditory periphery of the ferret have been investigated using an impulse response technique for a large number of sound locations surrounding the animal. Individual frequencies were extracted from the detailed spectral transformation functions (STFs) obtained for each stimulus location and, using sophisticated spatial interpolation routines, were used to calculate the directional response of the periphery at that frequency. The strength of the directional response was directly related to the analysis frequency. Furthermore, as the analysis frequency was increased to 20 kHz, the orientation of the directional response increased in elevation from the horizon (E0°) to about E30°, while the azimuthal location remained fairly constant at 30° to 40° from the midline. For analysis frequencies above 20 kHz, the response became increasingly directional toward the ipsilateral interaural axis. The interaural level differences (ILDs) were also calculated for all animals studied. ILDs increased from around 5 to 25 dB over the range of frequencies from 3–24 kHz. The two‐dimensional patterns of iso‐ILD contours were roughly concentric and centered on the interaural axis for frequencies below 16 kHz. For higher frequencies, there was a tendency for the ILD contours to be centered on more anterior and inferior locations. The increased directionality of the auditory periphery with increasing analysis frequency, together with the presence of sharp nulls in the response at high analysis frequencies, is consistent with a diffractive effect produced by the aperture of the pinna. However, this simple model does not predict the directional responses over the low to middle frequency range.

ISSN:0001-4966    

DOI:10.1121/1.400115

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

In the previous paper the directional response characteristics of the ferret auditory periphery were examined. In this study further measurements of the spectral transfer functions (STFs) of the auditory periphery were obtained at locations close to the tympanic membrane. There was considerable variation in the STFs recorded from different animals and between recordings made at each end of the auditory canal in the same animal. However, calculation of the so called ‘‘location dependency function’’ demonstrated that changes in the location of the stimulus produced the same pattern of changes in the STFs in all recordings. Changes in the spectral transformation for azimuth locations in the ipsilateral auditory field were examined by calculating the horizon STF. The gain transformations of frequencies below 20 kHz were found to be asymmetrical about the interaural axis so that maximum gain was obtained for anterior stimulus locations. In contrast, the maximum gain for frequencies above 20 kHz was obtained for stimulus locations about the interaural axis, and movement of the stimulus location into either the anterior or posterior fields produced symmetrical reductions in gain. These changes were related to the directional properties of the periphery examined in the previous paper (Carlile, 1990).The spatial resolution of the monaural information provided by the peripheral STFs is dependent on the rate of change of the transformations as a function of azimuthal displacement of the stimulus location. This was examined by calculating the unsigned first spatial derivative for each frequency in the horizon STF. The spatial derivative of frequency was found to be high for locations about the posterior and anterior median planes. This is discussed in terms of the results of behavioral experiments examining the resolution of sound localization in the ferret and other mammals.

ISSN:0001-4966    

DOI:10.1121/1.400116

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

In a companion paper [Brownetal., J. Acoust. Soc. Am.88, 1385–1391 (1990)], a method for recording the electrically evoked whole‐nerve action potential in human cochlear implant users was reported. The procedure for recording the response requires that two biphasic current pulses, a ‘‘masker’’ and a ‘‘probe,’’ be presented at a rate and level sufficient to drive the auditory nerve into a refractory state. The present study was designed to assess the sensitivity of that recording technique to variations in stimulation parameters. The experiments described in this paper demonstrate that: (1) the EAP as recorded in the cat is triphasic and is defined by two negative peaks occurring at latencies of approximately 0.26 and 0.82 ms; (2) EAP amplitude is independent of the level of the masker stimulus for current levels equal to or greater than the current level of the probe stimulus; and (3) the time course of recovery of the EAP from the refractory state is stable over a range of both probe and masker current levels.

ISSN:0001-4966    

DOI:10.1121/1.400117

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Recent psychophysical studies have shown that the detection of an intensity increment superimposed on the center component (1 kHz) of a multitone complex (1,3,7, or 11 components) improves as more components are added outside of the critical band. It has been suggested that this form of intensity discrimination is based on a change in the neural profile. To test this hypothesis, neural profiles were constructed by plotting the degree of phase locking to the 1‐kHz tone as a function of each unit’s characteristic frequency (CF). Neural phase‐locking profile to the 1‐component signal at 1 kHz had a broad peak; however, the neural profile became narrower as the number of components in the signal increased. The just detectable increment for the 1‐component condition was −5 dBre: 1000‐Hz component level (3.86‐dB increment plus component levelre: component level), whereas, for the 3‐, 7‐, and 11‐component conditions, it was −15 dBre: component level (1.42 dB). The neural and psychophysical IDL for the chinchilla were similar for the 1‐component condition. However, the overall trends in the psychophysical and neural data are different. In the psychophysical studies IDL is typically poorest in the 3‐component condition and improves when more components are added. By contrast, the neural IDL was poorest in the 1‐component condition and improved when more components were added. In the multicomponent conditions, units with CFs in 492–1380 Hz were found to be most sensitive in detecting the intensity increment to the 1000‐Hz component.

ISSN:0001-4966    

DOI:10.1121/1.400118

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Two experiments were performed that evaluated the effects of ipsilateral‐direct broadband noise maskers on the gerbil brain‐stem auditory‐evoked response (BAER) to click stimuli. In experiment 1, clicks were presented at 27 Hz at levels including 70, 80, 90, and 100 dB pSPL. Noise conditions included a no‐noise control, and included noise levels varying in 10‐dB increments from 20 dB SPL to a maximum noise level of 50, 60, 70, and 80 dB SPL for click levels of 70, 80, 90, and 100 dB pSPL, respectively. Gerbil BAER peaks were labeled with small roman numerals to distinguish them from human BAER peaks. The dependent variables included waves i and v latencies and amplitudes. Peak latencies increased and peak amplitudes decreased with decreasing click level and increasing noise level. To a first approximation, peak latencies and amplitudes showed changes with increasing noise level that were similar across click level. With increasing click level, there was little or no effect on the i–v interval. There was an increase in the i–v interval with increasing noise level. In experiment 2, click level was held constant at 90 dB pSPL, and click rates included 15, 40, 65, and 90 Hz. For each click rate, noise conditions included a no‐noise control, and noise levels included 20, 30, 40, 50, 60, and 70 dB SPL. With increasing click rate and noise level, there was an increase in peak latencies, an increase in the i–v interval, and a decrease in peak amplitudes. The magnitude of peak latency and amplitude shifts with increasing click rate was dependent on noise level. Specifically, the magnitude of rate‐dependent changes decreased with increasing level of broadband noise. These data are compared to human BAER experiments, and are found to be in fundamental agreement.

ISSN:0001-4966    

DOI:10.1121/1.400119

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

The evolution of new concepts in wave theory have led to proof‐in‐principle experiments aimed at validating the generation of a specified wave front. Not only have these concepts initiated research in transient wave theory, but they have also caused renewed effort in multichannel signal processing. In this paper, the development of a processor to deconvolve a transient acoustic wave from sensor array measurements is discussed. The design of the multichannel deconvolver coupled with model‐based signal processing techniques using acoustic pressure field measurements is discussed. Here, it is shown that an efficient solution to this problem can be obtained using a vector form of the Levinson–Wiggins–Robinson (LWR) algorithm.

ISSN:0001-4966    

DOI:10.1121/1.400120

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

New solutions to the wave equation have been shown to exhibit enhanced localization and energy fluence characteristics. The transmission and reception of these localized waves create unique problems, since they are essentially transient wave fronts inbothtime and space. Nonetheless, the ability to transmit wave energy through space with these interesting properties has many potential applications in a variety of applications areas. To realize their potential, new methods must be developed to analyze and process these waves. In this paper, approaches to design receiving arrays to reconstruct these special transient waves from noisy measurement data are discussed.

ISSN:0001-4966    

DOI:10.1121/1.400121

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP