摘要:

Minimum Audible Angles (MMA) for divers were determined for 3.5 kHz, 6.5 kHz, and broad‐band white‐noise pulses having a duration of 100 msec, a rise‐decay time of 10 sec, and a repetition rate of 1/sec. In Expt. 1 six divers performed the right‐left discrimination with no training or feedback and the mean MAAs obtained were 21.5° for the 3.5‐kHz signal, 14.5° for the 6.5‐kHz signal, and 9.8° for the white‐noise signal. In Expt. 2 four of the original six divers were given feedback from their performance with the white‐noise signal at a single small angle. The mean MAAs obtained after training were 11.3° at 3.5 kHz, 11.5° at 6.5 kHz, and 7.3° with white noise. It was concluded that if one assumes that the MAA reflects the general level at which the binaural system operates then it seems likely that man will be an effective sound navigator in the water.

ISSN:0001-4966    

DOI:10.1121/1.1913335

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Localization of sound sourcesoutsidethe median plane is influenced primarily by differences in head shadow and arrival time of the signal at the two ears of the observer. For sources locatedwithinthis plane, localization is influenced primarily by the irregularities of the pinna. By progressively occluding these cavities, it is shown that localization ability decreases with increasing occlusion, that it is better for signals in the anterior than in the posterior sector of the median plane, and that high‐frequency signal content is more important than the low. A number of hypotheses regarding localization in the median plane are noted.

ISSN:0001-4966    

DOI:10.1121/1.1913336

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Several experiments to determine the effects of two‐tone interaction in the cochlea are described. Nonlinear effects result when the cochlear partition is stimulated by a sinusoid whose frequency falls in a very narrow frequency band surrounding, but not including, the resonant frequency at the point under the recording electrode. These nonlinear effects are manifested as a negative shift in the dc potential accompanied by a partial or complete suppression of the cochlear microphonic potential to a second tone presented at the same time. This suppression is best seen in the first and second turns of the cochlea. Similar suppression effects accompanying a dc shift are obtained by artificially displacing the basilar membrane from its resting position by an asymmetrical change in hydrostatic pressure in the perilymph. The functional relations governing suppression were determined and the results compared with those obtained in two‐tone inhibition experiments in auditory nerve fibers. The results support the conclusion that inhibitory effects seen in nerve fibers, stimulated by two tones simultaneously, reflect mechanical events in the cochlear partition and subsequent changes in the effective stimulating waveform triggering the auditory nerve.

ISSN:0001-4966    

DOI:10.1121/1.1913337

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The feasibility of encoding multivariate information within the temporal microstructure of an auditory display is examined. Four pulse variables—ear of arrival, polarity, amplitude, and interpulse interval—were independently encoded pulse‐by‐pulse within auditory pulse trains. A fifth variable—conditional memory, representing the previous state of one of the variables—also served as an independent variable in combination with other variables. An informational constraint of up to 1 bit/pulse was imposed upon the combination of variables. Each variable was binary coded and constraints were imposed upon the combination of variables by means of a parity sum across variables. The accuracy of discrimination of a constant informational constraint falls with the number of variables contributing to the parity sum, and with the number of randomly manipulated variables outside of the parity sum. Excellent discrimination of the informational constraint was achieved for one condition with four independently controlled variables. Specific contributions of pulse variables were strikingly more discriminable than others.

ISSN:0001-4966    

DOI:10.1121/1.1913338

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Assuming a logarithmic relationship between place and characteristic frequency, proportionality between the latter and phase velocity, and a loss factor independent of place, the wave equation for the basilar membrane displacement can be integrated analytically. The main theoretical results are as follows: (1) The low‐frequency phase slope equals approximately −Kωr(x), whereKis a dimensionless constant and ωr(x) is the characteristic frequency at placex; (2) the asymptotic high‐frequency amplitude slope equals −6(K+1) dB/oct; (3) just above resonance the phase reaches a minimum value of about −Krad. The Rhode (1971) low‐frequency phase‐slope data yieldsK=27±3. The asymptotic high‐frequency amplitude slope should therefore be (168±18) dB/oct. Surprisingly, the great frequency selectivity of the cochlea as reflected in the large numerical value of the high‐frequency amplitude‐slope isnotdetermined by hydromechanicallosses, which primarily influence behavior, near resonance, but the constantKwhose physical meaning is approximately “2π times the number of wavelengths” on the membrane for low frequencies. With the above value forK, the number of wavelengths becomes about five—considerably more than found by von Békésy. Nevertheless, it is interesting to note that the phase slopes and high‐frequency amplitude slopes of von Békésy (1960, pp. 446–463) are not inconsistent the light of the present theoretical calculations. If the membrane becomes stiffer at the high amplitudes at which von Békésy made his measurement,bothphase and amplitude slopes would be decreased.

ISSN:0001-4966    

DOI:10.1121/1.1913339

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Threshold adaptation for 500, 1000, 2000, and 4000 Hz was studied with the Carhart, Rosenberg, and Owens tone decay tests using 40 normal‐hearing subjects. Differences in tone decay were evaluated for effects of experimental technique, frequency, hearing level and SPL of the stimuli. There were no significant differences between the results obtained with the three experimental conditions. Appreciable differences in the amount of decay (10 dB or greater) were shown only for 4000 Hz in terms of mean decay. Appreciable amounts of decay (to 25 dB) were found for 1000, 2000, and 4000 Hz in terms of individual test results. All frequency comparisons displayed significantly different ranking at the 0.05 level of confidence. As frequency increased in hertz, tone decay increased in decibels. Effects of hearing level and SPL of the stimuli were without statistical significance.

ISSN:0001-4966    

DOI:10.1121/1.1913340

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The adoption of dBA‐type hearing damage risk criteria and the consequent use ofA‐weighted sound levels to identify areas of auditory hazard have created a need for a measure of the dBAattenuation of ear protectors. In Study 1, the dBAattenuation values of 30 ear protectors are calculated in 619 industrial noise spectra. It is found that the same ear protector may offer 20 dB more dBAattenuation to one noise than to another but that noises of likeC‐Avalue are subjected to approximately the same dBAattenuation. Noises are therefore sorted into five classes according toC‐Avalue, and average dBAattenuation values for each class are calculated for each ear protector. This type of information makes it possible to select adequate ear protectors even though only theC‐ andA‐weighted sound levels of the noise environment are known. In Study 2, a simple procedure is developed for calculating the dBA attenuation values of any ear protector for the fiveC‐Aclasses defined in Study 1. The procedure incorporates correction factors which ensure that, for the average protector, the calculated dBAattenuation values are obtained in 90% of spectra.

ISSN:0001-4966    

DOI:10.1121/1.1913341

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The aim of this study was to determine the relative importance of source parameters (fundamental frequency and waveform) versus formant parameters (resonant frequency and number) in identifying meaningless complex sounds. Sixteen sounds were generated differing on four dimensions, each having two values. These were the source waveform, containing either all harmonics or odd harmonics only; the fundamental frequency, either 90 or 142 Hz, ratio=1.6; the number of formants, one or two; and the frequency of the formant(s) either low (600 Hz, or 600 and 1550 Hz) or high (940 Hz, or 940 and 2440 Hz) high/low ratio = 1.6. Twenty‐four listeners were trained to identify these sounds. The results show that fewer confusions were made between pairs of sounds (1) as the number of dimensions on which they differed increased, and (2) as the dimension (single or in combination) changed, from formant number to formant frequency region, to fundamental frequency, to source waveform. Listeners appear to make a generalized classification along a single dimension which seems to vary systematically with waveform complexity and periodicity.

ISSN:0001-4966    

DOI:10.1121/1.1913342

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The occurrence of the wolfnote in the cello is shown by direct tonal analysis to be caused by the beating of two equally forced oscillations. The fundamental sinusoidal component of vibration of the string is shown to split at the wolfnote into a pair of oscillations separated by a frequency interval equal to that of the stuttering frequency of the wolfnote. In one of the two cellos investigated, higher partials up to the third are also split into pairs, their separation being the multiple of the harmonic number and the separation of the fundamental pair. Further evidence is obtained to support the interpretation of the wolf as beating between two equal forced vibrations from a frequency analysis of the bowed‐string vibration for different stopped string lengths. The frequencies of vibration of the string bear a close resemblance to those obtained in coupled electrical resonant circuits.

ISSN:0001-4966    

DOI:10.1121/1.1913343

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Some measurements of the propagation of ultrasonic pulses through packs of spherical and nonspherical particles of different diameters are reported. The packings include evacuated and compressed media. The values of sonic velocity measured together with the measured bulk elastic properties of one such packing yield a reasonable value for Poisson's ratio, tending to 0.5 for the assembly. Increasing contact pressure between particles, or the presence of interstitial air affect the properties considerably.

ISSN:0001-4966    

DOI:10.1121/1.1913344

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP