摘要:

Previous action potential (AP) tuning curve methods have used a reduction in amplitude of the probe‐elicited AP as an indication of tone‐induced masking. The reduction criterion used in different studies has varied from 25% to 100%. For low level probe stimuli, which elicit a low‐amplitude AP, this is a sensitive indicator. In contrast, for high‐amplitude AP responses elicited by high‐level stimuli, the required reduction in absolute terms is large, making it an insensitive indicator. AP tuning curves have been recorded using a sensitive method for detecting masker/probe interaction with a fixed criterion, unrelated to the unmasked AP amplitude. For each masking condition, a derived response was obtained by digitally subtracting the tone‐masked AP waveform from the unmasked response. Derived responses are generated if there are ANY changes in the AP waveform induced by the masker, including amplitude changes, latency changes, or even changes in AP morphology not necessarily associated with the major peaks. A fixed criterion (10 μV) of tone‐derived (TD) response was used as an indication of interaction of the responses to the masker and probe. Tuning curves generated by this method were compared with those generated by conventional amplitude reduction (AR) methods. TD tuning curves show different characteristics, especially with respect to increasing probe levels. They appear to give a good representation of the array of afferent fibers responding to a probe stimulus. In addition, frequency regions making minor contributions to the AP are better represented in TD tuning curves.

ISSN:0001-4966    

DOI:10.1121/1.399717

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

The precision of spike response timing of 94 primary auditory cortex neurons was studied using conventional extracellular recording techniques in barbiturate‐anesthetized cats to which tone‐ and/or noise‐burst stimuli were presented using sealed sound delivery systems. Precision of spike timing was indexed using the standard deviation of the first‐spike latent period in responses evoked by repeated presentation of tonal stimuli systematically varied in frequency, amplitude, and/or repetition rate. Within a neuron, variability of first‐spike timing was usually proportional to the mean first‐spike latency, in agreement with previous reports. In cases where there was a systematic relation between the precision of response timing and the mean latency, a linear correlation accounted for up to 90% of the data variance. Across the 94 neurons, standard deviations seen in responses of minimum latency were related to minimal mean latencies, and were typically in the range from 0.15–1.5 ms. The data suggest that responses to transients in the cortex show a precision of spike timing which is only slightly worse than that seen in cochlear‐nerve fibers. This, however, is in dramatic contrast to previous evidence on the steady‐state temporal response of cortical cells, which is at least an order of magnitude poorer than that seen in auditory‐nerve fibers and many cochlear nucleus cells. These observations may be directly relevant to the known consequences of auditory cortex pathology in man.

ISSN:0001-4966    

DOI:10.1121/1.399718

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Psychophysical results using double vowels imply that subjects are able to use the temporal aspects of neural discharge patterns. To investigate the possible temporal cues available, the responses of fibers in the cochlear nerve of the anesthetized guinea pig to synthetic vowels were recorded at a range of sound levels up to 95 dB SPL. The stimuli were the single vowels /i/ [fundamental frequency (f0) 125 Hz], /a/ (f0, 100 Hz), and /c/ (f0, 100 Hz) and the double vowels were /a(100),i(125)/ and /c(100),i(125)/. Histograms synchronized to the period of the double vowels were constructed, and locking of the discharge to individual harmonics was estimated from them by Fourier transformation. One possible cue for identifying thef0’s of the constituents of a double vowel is modulation of the neural discharge with a period of 1/f0. Such modulation was found at frequencies between the formant peaks of the double vowel, with modulation at the periods of 100 and 125 Hz occurring at different places in the fiber array. Generation of a population response based on synchronized responses [average localized synchronized rate (ALSR): see Young and Sachs [J. Acoust. Soc. Am.66, 1381–1403 (1979)] allowed estimation of thef0’s by a variety of methods and subsampling the population response at the harmonics of thef0of the constituent vowel achieved a good reconstruction of its spectrum. Other analyses using interval histograms and autocorrelation, which overcome some problems associated with the ALSR approach, also allowedf0identification and vowel segregation. The present study has demonstrated unequivocally that the timing of the impulses in auditory‐nerve fibers provides copious possible cues for the identification of the fundamental frequencies and spectra associated with each of the constituents of double vowels.

ISSN:0001-4966    

DOI:10.1121/1.400329

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Time domain analysis of firing‐rate data from over 200 fibers from the auditory nerve of cat has been used to estimate the formats of the synthetic‐syllable stimuli. Distinct groups of fibers are identified based on intervals between peaks in the fiber firing rates. The large extent of some of these groups—over an octave in terms of characteristic frequency—and the lack of short intervals in the longer‐interval groups suggest that the behavior of the nonlinear cochlear filters for these signals is effectively wideband with steep high‐frequency cutoffs. The measured intervals within each group are very similar, and correspond to the period of the format that dominates the group’s response. These intervals are used to estimate the dynamic speech formants. The overall formant estimates are better than those of the previous spectral analyses of the neural data, and the details of lower‐formant dynamics are tracked more precisely. The direct temporal representation of the formant is contrasted with the diffuse spectral representation, the dependence of spectral peaks on nonformant parameters, and the distortion of the spectrum by rectification. It is concluded that a time‐domain analysis of the responses to complex stimuli can be an important addition to frequency‐domain analysis for neural data, cochlear models, and machine processing of speech.

ISSN:0001-4966    

DOI:10.1121/1.399719

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

It has previously been shown that a population of units classified as ‘‘primarylike’’ and located in the ventral cochlear nucleus of the anesthetized guinea pig was unable to signal the position of the higher formant‐related peaks (>1.5 kHz) of steady‐state vowels in terms of a temporal–place representation [Palmeretal., J. Acoust. Soc. Am.79, 100–113 (1986)]. In this paper, it is demonstrated that units characterized by a prepotential in their spike waveform and a primarylike post‐stimulus time histogram shapecanencode the relative position of the formant peaks present in the spectra of steady‐state vowels in terms of a temporal–place code. The possible reasons for the differences in the present results and the previous report are discussed.

ISSN:0001-4966    

DOI:10.1121/1.399720

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

A structural model is proposed for the processing of interaural intensity differences by the lateral superior olive. One fundamental assumption is that the incoming excitatory projections from the ipsilateral anteroventral cochlear nucleus innervate columns of LSO neurons serially according to threshold. A second fundamental assumption is that the inhibitory innervation from the ipsilateral medial nucleus of the trapezoid body is also serially arranged according to threshold but in the opposite direction along the LSO column. Using neurophysiological and neuroanatomical data for neuronal response curves, connectional patterns, and cell and synapse numbers, the model was formulated quantitatively and implemented for machine computation. Azimuthal location is encoded by the position along the LSO column where LSO cell firing first goes to zero. Accuracy of coding was tested for three different connectional schemes, for variations in neuronal parameters, and for cell and synapse death. Encoding is shown to be independent of absolute sound level and to vary linearly with interaural intensity difference.

ISSN:0001-4966    

DOI:10.1121/1.399721

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Previous experimental work has shown the influence of a rotating diffuser upon the diffusion of a reverberant field, upon the radiation impedance of a sound source in a reverberation room, and upon the boundary absorption. Some interesting results of the latter work require a quantitative interpretation, while others suggest a need for further investigation to obtain a detailed physical insight. In an effort to gain insight into and an interpretation of the latter work, a finite‐element approach is presented. This paper is an interim report on continuing research, and it reviews an investigation of the effect of a semicircular diffuser upon a two‐dimensional sound field in a rectangular room. A numerical relationship between the resonance frequencies of the acoustical modes in the room and the diffuser orientation is given. The sound‐pressure distributions of the acoustical modes are also given as the function of the diffuser orientation. A three‐dimensional cavity is used for experimental verification. In this cavity, only the sound waves in the horizontal plane will be affected by the diffuser. The experimental and numerical results agree closely.

ISSN:0001-4966    

DOI:10.1121/1.399722

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

In this study, the results of a field survey on annoyance caused by sounds from small firearms are presented. Dose–response relationships were determined for about 400 randomly selected residents around two military and three civil shooting sites. After completion of personal interviews, extensive sound measurements with different time‐weightings were carried out. Also, for the same respondents, the subjective effects of road‐traffic sounds were determined enabling a comprehensive comparison of dose–response relations for impulse sounds and road‐traffic sounds. The results show that A‐weighted equivalent sound‐pressure level,Leq, is a better acoustical measure for the prediction of annoyance caused by shooting sounds than the mean‘‘impulse’’ or ‘‘fast’’ time‐weighted levels of individual impulses. The results of a principal components analysis showed that the subjective effects of the shooting sounds could be reduced to one overall psychological dimension with high negative loadings on object‐centered and subject‐centered annoyances, moderate positive loadings on perceived quality of the environment and high positive loadings on habituation to the impulse sounds. From the comparison of the dose–response relations for shooting and road‐traffic sounds, it could be concluded that at least for relatively low and moderate levels, the A‐weightedLeqof shooting sound is about 13 dB lower than that of equally annoying road‐traffic sound.

ISSN:0001-4966    

DOI:10.1121/1.400341

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

The present paper deals with the solution of the title problem applying Lord Rayleigh’s optimization concept when solving integral equations by means of the Ritz method. Polynomial expressions containing a power‐law term with an undetermined exponent ‘‘γ’’ are used. Since the calculated eigenvalue constitutes an upper bound, by minimizing it with respect to γ, one is able to improve the value of the frequency coefficient. A lower bound is then determined using the method of traces. It is shown that both sets of results, upper and lower bounds, are quite close and are also in agreement with the numerical results obtained by means of a finite element algorithm.

ISSN:0001-4966    

DOI:10.1121/1.399723

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

The mobility power flow (MPF) approach is used in this paper to describe the flexural behavior of an L‐shaped plate structure consisting of thick plates with rotary inertia and shear deformation effects included in the analysis. The introduction of the thick plate effects significantly increases the complexity of the structural mobility functions used in the definitions of the power flow terms; however, because of the substructuring that is used in the MPF approach, the complexity of the problem is significantly reduced as compared to solving for the global structure. Additionally, with the MPF approach the modal behavior is described. The MPF analysis of the L‐shaped plate is performed for the case of point force excitation on one plate, with the two plates being identical in both size and thickness. The results of this analysis are compared to results from the finite‐element analysis (FEA) and the statistical energy analysis (SEA) and show very good agreement in the low‐ and high‐frequency regimes, respectively.

ISSN:0001-4966    

DOI:10.1121/1.400303

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP