摘要:

Subjective duration of broadband noise impulses is investigated. At equal subjective duration, the physical durations of impulses may differe by up to 10%, the accruacy of duration measurements. For impulses shorter than 500 msec, subjective doubling of duration requires a ratio of physical durations larger than two, typically 2.6. This result is achieved by the method of constant stimuli. The subjective duration of impulses can be traced back to the corresponding temporal masking patterns. A model of subjective duration is proposed as follows: Whenever the sound pressure level of the temporal masking pattern reaches a critical value, marks are set. The temporal distance between these marks corresponds to the subjective duration of the sound. Applying the model, subjective doubling of impulse durations can be predicted from temporal masking patterns with an accuracy of typically 10%.

ISSN:0001-4966    

DOI:10.1121/1.381277

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Intensity discrimination was measured for pulsed sinusoids of various frequencies (200–8000 Hz) and sensation levels (5–80 dB). The data for all frequencies were fitted by a single function, ΔI/I=0.463 (I/I0)−0.072, whereI0is intensity at threshold,Iis the intensity of the tone, and ΔIis the increment needed to obtain 71% correct in a two‐interval forced‐choice adaptive procedure. The form of this function is in good agreement with data reported in comparable studies but differs markedly from the data reported by Riesz [Phys. Rev. 31, 867–875 (1928)]. An analysis of the actual values of ΔI/Ireported in the other studies indicates a range larger than would be predicted on the basis of individual differences among observers in this study. The data are also discussed differences among observers in this study. The data are also discussed in terms of the predictions of current theoretical models.

ISSN:0001-4966    

DOI:10.1121/1.381278

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Frequency discrimination was measured for frequencies from 200 to 8000 Hz and for sensation levels from 5 to 80 dB using pulsed sinusoids as stimuli in an adaptive two‐interval force‐choice psychophysical procedure. An analysis of variance indicated significant effects of frequency and sensation level, and of the interaction between frequency and sensation level. The effect of sensation level is greatest at low frequencies and decreases at high frequenices, being quite small at 8000 Hz. The data are used to evaluate the predictions of current theoretical models.

ISSN:0001-4966    

DOI:10.1121/1.381251

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The interaction between backward and forward masking was investigated for conditions in which a signal is presented in the same ear as the masker, monotically, or in the contralateral ear, dichotically. The SPL of a signal required for equal detectability was determined in both monotic and dichotic backward and forward masking paradigms and in paradigms that combined backward and forward masking. In most cases, the combination of the various masking conditions produced a greater effect than either masker alone. Further investigation of the interaction of monotic forward and dichotic backward masking was conducted. Within intermasker intervals of 15, 25, and 45 msec signal SPL’s for equal detectability were determined for different temporal placements of the signal. The results indicated that when a contralateral backward masker is added to a forward masking paradigm, the signal must be increased by a constant amount to remain equally detectable. However, this constant increase was larger for the 15‐msec masker separation than either the 25‐ or 45‐msec separations.

ISSN:0001-4966    

DOI:10.1121/1.381253

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

When pulsed sinusoids are presented to the ears with an interaural temporal difference but with no rise–decay time or filtering, three values of interaural time are present: onset, ongoing, and offset interaural differences. Lateral discrimination based on interaural temporal differences was studied for such stimuli. The sinusoids were either equal‐energy or constant‐intensity 65 dB SPL tones. The frequencies of the tones ranged from 150 to 4050 Hz and the durations covered a range of 2 msec–1 sec. The threshold value of interaural time obtained in the lateral discrimination task increased as a function of increasing frequency when intensity was maintained constant. When equal‐energy signals were used, the change in lateralization as a function of changes in frequency depended on signal duration. All lateral discrimination thresholds were approximately the same when the onset and offset temporal differences were reduced or eliminated by applying a bandpass filter, high‐pass filter, or a rise–decay time, or by presenting the signals with only an ongoing temporal difference. Low‐pass filtering the 4050‐Hz signals produced lateral discriminations approximately equal to those obtained with no filtering. These results suggest that low‐frequency information is the crucial variable for lateralization sinusoidal stimuli presented with onset, ongoing, and offset interaural temporal differences.

ISSN:0001-4966    

DOI:10.1121/1.381254

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Experiments were performed to examine changes in the intelligibility of temporally interrupted sentences when white noise was introduced during the speech–free interval. In experiment 1, listeners received the test material under two conditions at five interruption rates ranging from 0.77 to 3.85 interruptions per second (ips). In one instance the speech‐free interval was silent, while in the other it was switched to noise of the same average level as the speech. Experiment 2 examined the intelligibility of the speech message as a function of signal‐to‐noise (S/N) ratio. The switching rate was held constant at 1.5 ips and the S/N ratio was varied from −30 to +18 dB. Results indicated that for the particular interruption conditions selected, speech switched to noise is significantly more intelligible than speech interrupted by silence. In addition, intelligibility of the interrupted sentences in the presence of intervening noise varies with the S/N ratio.

ISSN:0001-4966    

DOI:10.1121/1.381255

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Mathematical modeling of acoustical systems is a popular design tool. To verify math models for acoustical systems of small physical size, probe‐tube microphones are often used. Unfortunately, the presence of the probe tube, itself, sometimes affects the sound field being measured. One way to solve the problem is to account for this effect by incorporating a model of the probe tube into an overall math model of the entire system. Equations for analyzing sound transmission through probe tubes are not available in most contemporary acoustics textbooks. This paper describes a method for mathematically modeling the acoustical characteristics of probe‐tube microphones using equations developed in 1950 for application to transient fluid flow in pipes. The accuracy of the method is demonstrated by mathematically simulating a probe‐tube calibration experiment in the laboratory. The experimental data and data derived from the math model agree quite well over the frequency range from 10 to 10 000 Hz. This shows that the math model of the probe‐tube microphone used in this experiment was correct. The result also suggests that this model may be included in an overall system model, given that several restrictions listed in this paper are closely followed.

ISSN:0001-4966    

DOI:10.1121/1.381256

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The pressure sensitivities of two 1/2‐in. electret, two 1‐in. ceramic, and two back‐vented 1‐in. condenser microphones were measured for numerous combinations of temperature, percentage relative humidity, and frequency. The two condenser microphones were calibrated by the reciprocity technique at each combination of temperature, relative humidity, and frequency. The condenser microphones were then used as calibrated sources to determine the pressure sensitivities of the other microphones. Insert voltage techniques were used to eliminate the environmental effects on the electronics. It was found that the back‐vented condenser microphones are insensitive to changes in relative humidity. At frequencies considerably below their resonance frequencies they exhibited only a very small change in sensitivity with temperature. At frequencies closer to the resonance frequency the temperature coefficient increases approximately fourfold. The temperature and humidity coefficient for the electret and ceramic microphones could not be determined due to the instability in their sensitivities which produced changes that were larger than those induced by the temperature and humidities.

ISSN:0001-4966    

DOI:10.1121/1.381257

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A general relation between the farfield amplitudes of the diffraction and the radiation problems by a rigid body is deduced.

ISSN:0001-4966    

DOI:10.1121/1.381258

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

In May 1965, a comprehensive set of 3.5‐kHz propagation‐loss measurements was obtained under downward‐refraction conditions in an area 40 NM south of Montauk, Long Island, New York. A technique for measuring bottom loss in shallow water, derived by taking advantage of the downward‐refraction conditions, was applied to the test area. A bottom‐loss value of 1.3 dB per bounce was inferred from the measurements and was shown to compare favorably with theoretical loss values generated using sediment information for the test area. As a result of that agreement, a computer model based on ray theory and bottom‐impedance considerations was developed to describe shallow‐water propagation in the test area (at least under downward‐refraction conditions). To validate this model and further test the validity of the bottom‐loss measurement, some additional measurements were conducted in the same test area during May 1967. This paper presents the propagation‐loss results collected during the May 1967 measurements and compares them with those predicted by the model developed from the earlier set of measurements.

ISSN:0001-4966    

DOI:10.1121/1.381259

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP