摘要:

Plane, progressive, periodic sound waves of finite amplitude are considered. The well‐known solutions of Fay and Fubini are reviewed. At first glance, the two solutions seem contradictory, but, actually, each holds in a different region of the flow, the Fubini solution close to the source and the Fay solution rather far from the source. In the intermediate, ortransition, region, neither solution is valid. A more general solution is obtained by using a method commonly employed for waves containing weak shocks. For distances up to the shock‐formation point, the general solution reduces exactly to the Fubini solution. For distances greater than about 3.5 shock‐formation lengths, the general solution is practically indistinguishable from the sawtooth solution, which, in turn, is the limiting form of Fay's solution for strong waves. The form of the general solution shows clearly how, in the transition region, the Fubini solution gives way to the sawtooth solution. The problem of an isolated cycle of an originally sinusoidal wave is also considered. Finally, some limitations on the weak‐shock method are discussed. In the periodic‐wave problem, the general solution is found to be inaccurate for distances greater than 1/α, approximately, where α is the small‐signal absorption coefficient. In Appendix A, a brief extension of the analysis to spherical and cylinrical waves is given.

ISSN:0001-4966    

DOI:10.1121/1.1909986

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

The effect of a slow steady flow of ideal fluid upon a superimposed pure‐tone sound field is examined, especially for effects upon the acoustic admittance vector. It is assumed that the total field is derivable from a scalar potential and that terms of second order in Mach number are negligible. Blokhintsev's transformation [NACA Tech. Mem. No. 1399(1956)] to a flowfree acoustic problem is shown to be awkward, except for rigid, nonporous boundaries, because of complications in the transformed boundary conditions. For one dimensional fields, it is shown that the steady flow has no direct effect on the acoustic admittance or the magnitudes of acoustic pressure and particle velocity. However the steady flow may affect the terminating admittance of a one dimensional field, and thereby become evident within that field. If the correct value of terminating admittance is used in the analysis, then a flowfree acoustic solution will yield correct values for the magnitudes of the true pressure and particle velocity and for both magnitude and phase of the true admittance at every point.

ISSN:0001-4966    

DOI:10.1121/1.1909987

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Threshold signal‐to masker ratios for three sinusoids (250, 1000, and 4000 Hz) presented in a masker of corresponding frequency set to various levels were gathered and are presented. The masker was either continuous or pulsed‐on‐only during both signal intervals. The block up‐and down, two‐interval, forced‐choice psychophysical procedure was used. The relation between the obtained thresholds, and (1) the level of the masker, (2) whether the masker was continuous or pulsed, (3) other previously reported data for noise signals and maskers are especially considered. A discussion of these data as reflecting auditory nerve activity, loudness adaptation, increase of uncertainty and/or, a “drifting filter” is offered.

ISSN:0001-4966    

DOI:10.1121/1.1909988

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Threshold determination within the framework of the block up‐and‐down, two‐interval, forced‐choice (BUDTIF) method has been investigated using a computerized Monte Carlo technique. Two aspects of the results are presented in preliminary fashion. (1) In a block up‐and‐down threshold‐estimating method, modifications that yield minimal variance within individual runs may not automatically be assumed to yield minimal variance between successive threshold estimates. (2) The optimal number of trials per block was the smallest that yields a valid solution depending on the target performance level; use of a memory of more than one block for level change decisions is not indicated.

ISSN:0001-4966    

DOI:10.1121/1.1909989

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

The interference with intelligibility of monosyllabic words produced by continuous white noise, by modulated white noise, and by continuous speech (single talker) was studied during homophasic (N0S0) and antiphasic (NπS0) listening. Five signal‐to‐masker ratios, four modulation rates, and four magnitudes of modulation were used. Reception in the continuous noise was characterized by steeply sloping intelligibility functions and a 4.5‐dB masking‐level difference favoring antiphasic listening. Reception in modulated noise changed with the rate and depth of modulation. A 7‐dB modulation yielded intelligibility functions highly comparable to those for continuous noise having the same average level. By contrast, more extreme modulation (14, 21 dB, and complete interruption) produced better intelligibility under both homophasic and antiphasic conditions than did continuous noise. This effect was particularly great when noise was completely interrupted either 4 or 20 times/sec, under which circumstances intelligibility remained above in 80% in a speech‐to‐noise ratio of −24 dB. The advantage of antiphasic over homophasic listening, or masking‐level difference, was fairly similar for all conditions of modulated noise, averaging 3.9 dB. When the masking signal was a single competing talker, the antiphasic advantage dropped to 3.3 dB, and the intelligibility function did not duplicate any of the functions obtained in white noise, either continuous or modulated. Nonetheless, individual sets of conditions occurred where masking by speech and by modulated noise yielded equivalent performance, but the depth of modulation required for this equivalence varied with the speech‐to‐masker ratio being employed.

ISSN:0001-4966    

DOI:10.1121/1.1909990

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

144 observers, divided into eight groups of 18 each, were run in a two‐alternative, temporal, forced‐choice auditory‐signal‐detection task. At each of two signal intensities, four levels of information feedback were used. No feedback (NF); correct feedback on every trial (F100), on three‐fourths (F75), or half (F50) of the trials, with incorrect feedback on remaining trials. The results were that (a) NF and F100 led to higher probability of correct respondingP(C) than either F75 or F50 for both signal intensities; (b)P(C) for NF was higher under the higher intensity but lower under the lower intensity than for F100; (c) on trials immediately following trials on which observer's response and feedback agreed, detection rates were higher and false‐alarm rates were lower than following disagreement trials, whereas these differences were close to zero for F50. It is argued that feedback leads the observer to change his criterion following disagreements. The effect of this variability is to depress the mean detectability indexd′ of signal‐detectability theory.

ISSN:0001-4966    

DOI:10.1121/1.1909991

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

A gross, slow potential that is differentially sensitive to the frequency of a tone burst was recorded from the region of the auditory nerve in the hamster. An experimental paradigm similar to that employed in psychological studies of tonal masking was used to measure neural‐response amplitude change in the presence of a second tone. The influence of one tone upon the other, as evidenced by the neural response, yielded functions similar to the masking curves generated by human listeners. Increases in the level of the signal required increases in the level of the masker in order to maintain the masking criterion. High‐tone maskers were seen to be less effective than low‐tone maskers. Masking was viewed as a preempting of neural activity by the secondary tone.

ISSN:0001-4966    

DOI:10.1121/1.1909992

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

This study presents responses to dichotic clicks obtained from neurons of the medial superior‐olivary nucleus of anesthetized cats. The neurons described in this study evidenced interactive patterns to both time and intensity differences by changes in their probabilities of response and by shifts in their latency. These findings suggest a complex synaptic organization of neurons, some of which are responsive to large and some to small interaural time differences. The former neurons that show interactions to large time differences (ca. 10.0 msec) respond consistently to both monaural left and right clicks. Binaural clicks, however, significantly decrease the probability of firing in response to stimulation of the lagging ear. Some of the latter neurons that show interactions to small time differences (ca. 0–2.0 msec) fire only once, while others discharge twice to a monaural click; these single and double responders exhibit changes in latency and probability of their firings upon binaural stimulation and, in the case of the double responders, alterations in both spikes occur upon appropriate stimulation.

ISSN:0001-4966    

DOI:10.1121/1.1909993

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Brief tone pips were used as stimuli in two‐signal interference experiments to provide a basis for interpretation of intensity functions. Whole nerve action‐potential responses were recorded from the cochlea (guinea pig). Stimulation by a 6‐kcps pip interferes with the response to a 2‐kcps pip only when the latter reaches a magnitude (baseline peak measure) of 30–40μV, about 18 dB above a just detectable response. Interference depends more upon the strength of the 2 kcps pip than upon the strength of the 6‐kcps pip. The form of intensity functions for low‐frequency signals is dominated by a basal extension of excitatory region. Intensity functions for high‐frequency signals show less spatial change. The data suggest that there are tworesponse modesfor neural activity elicited by acoustic signals. For high‐frequency signals, synchrony of excitation depends upon envelope and there is little change in location of excitatory region along the cochlear partition with signal strength. For low‐frequency signals, synchrony depends upon the locations along the cochlear partition that exceed a critical amplitude, i.e., upon the velocity of the traveling wave. Broad‐band transient signals, such as clicks, may elicit neural activity in both response modes.

ISSN:0001-4966    

DOI:10.1121/1.1909994

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP

摘要:

Variations in the amplitude and polarity of evoked potentials with differences in intensity and arrival time of clicks delivered to the two ears were recorded from the superior‐olivary nucleus in cats with chronically implanted electrodes. An analog of the “time‐intensity” trade was seen in the cancellation of evoked potentials when time and intensity differences were opposed.

ISSN:0001-4966    

DOI:10.1121/1.1909995

出版商:Acoustical Society of America    

年代:1966

数据来源: AIP