摘要:

The peak amplitudes of solar signals are estimated by considering a particular mathematical model for the acoustic‐speed versus depth profile of the ocean and for the explosion waveform. The sound speed is assumed to vary asc2 = c02(1−α2s2)−1wherec0is the speed at the channel axis,sis the vertical distance from the axis, and α specifies the width of the channel. The source waveform is assumed to be a short sinusoidal wavetrain. It is found that the range dependence of the direct arrival in the received pressure amplitude is the product of two terms. The first is the expected cylindrical‐spreading loss. The second term oscillates with range. The amplitude of the oscillation depends on the source waveform and the range; for a 233‐cps, 8‐msec pulse at 100 NM (nautical miles), the amplitude is about 14 dB. The distance between successive maxima of the oscillation depends on α andc0, but is independent of range and source waveform. For values of the parameters that fit a typical North Atlantic profile, the distance between maxima is about 6 NM. The amplitude at successive maxima is found to decrease asr−34.

ISSN:0001-4966    

DOI:10.1121/1.1909832

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

A real‐time electronic spectrograph that produces a time‐versus‐frequency display on a cathode‐ray storage tube is described. ADELTIC(DElay Line TIme Compressor) is used to obtain high‐frequency multiplication ratios and, thereby, essentially real‐time analysis with a swept‐filter heterodyne analyzer. The device examines the time‐frequency structure of a stored sample. The resulting output displays the complete content of the store in one recirculation per bandwidth. The entire sample is thus analyzed in a fraction of a second. Pulses, tones, and noise transients were used to test the capabilities of the analyzer with respect to time resolution, frequency resolution, response to noise, and processing gain. Results of these tests and other illustrative examples of the analyzer output are presented, which show that (1) frequencies separated by one bandwidth or more can be resolved, (2) pulses shorter than the filter‐buildup time are lengthened whereas pulses longer than the buildup time retain their original length, and (3) the device does not respond to level changes of white noise at the input.

ISSN:0001-4966    

DOI:10.1121/1.1909833

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

The current procedure for assessing impact transmission through floors involves comparing the spectra of transmitted noise produced by a standard tapping machine. An obvious weakness in the method is that it does not really simulate footsteps. One is more interested, however, in how well the method rank‐orders floor structures as compared with the impressions of an apartment dweller listening to his upstairs neighbor. This project was intended to provide a partial answer to this complex question. Subjective comparisons were made of the “loudnesses” of footsteps on a concrete slab floor with various added structures. Comparison with FHA ratings indicates that the ratings exaggerate the differences between floors in the most unacceptable range, but that there is a reasonable degree of correlation among the important range of floors. A variation of the FHA procedure that improves the correlation is also reported.

ISSN:0001-4966    

DOI:10.1121/1.1909834

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

A test program was recently instituted by the United States Gypsum Company—Research Center, with the cooperation of the Riverbank Acoustical Laboratories, to determine the effect of ambient humidity on the sound‐transmission loss of a double‐leaf gypsum‐board partition system. The results of this test series were quite explicit. As the humidity was increased, a degree of freedom was introduced that allowed for lateral movement of the gypsum core and paper. These two skins were then able to perform independently of one another, causing the eventual shift of control frequency from 2800 to 350 cps—i.e., from coincidence to resonance control. In addition, these test data reveal that, at some frequencies, a difference of as much as 6 dB occurs between the high and low humidity levels, while at others the differential is 0 dB. These differences clearly indicate the need for standardization of the humidity conditions at the present commercial testing laboratories.

ISSN:0001-4966    

DOI:10.1121/1.1909835

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

A marked release from masking, or masking‐level difference (MLD), results when a monaural signal is presented with perfectly correlated (in‐phase) binaural noise, N0—Sm, rather than with monaural noise, Nm—Sm. When the noise in the nonsignal ear is introduced at a lower level than that in the signal ear, a smaller MLD results. In one experiment, MLD's were determined as a function of the intensity of the noise in the nonsignal ear with the interaural conditions of N0, Nπ, and NU as parameters; for N0, there is some release from masking even when the noise in the nonsignal ear is as much as 40 dB down from that in the signal ear. The following considerations led to a second experiment. A release from masking results when a sinusoid is presented monaurally Sm rather than binaurally and in phase S0 with perfectly correlated noise N0. With N0‐S0, when the sinusoid in one ear is reduced in intensity, rather than being removed entirely, a smaller MLD than for N0‐Sm should result. Therefore, MLD's were determined as a function of the ratio of the energies of the left‐ and right‐ear sinusoids with correlated noise N0. In all experiments, the signal (500 cps, 0.25 sec) was presented to the listener in one or the other of two temporal intervals, against a background of white noise. Psychometric functions were determined for each condition, and MLD's were estimated from these functions.

ISSN:0001-4966    

DOI:10.1121/1.1909836

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

Three groups of subjects were taught to identify, by label, complex sounds. With temporal overlap controlled, confirmation and prompting training procedures were compared. Despite recent emphasis on the superiority of prompting procedures, no significant difference in the efficacy of the two methods was observed.

ISSN:0001-4966    

DOI:10.1121/1.1909837

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

Intelligibility scores were obtained from 12 listeners for monosyllabic words presented monaurally with noises at one or both ears. Release from masking previously reported by Licklider [J. Acoust. Soc. Am.20, 150–159(1948)] was confirmed, but sizable differences between right and left ears in the amount of release were not found. However, one listener consistently had about 5% more release for speech at the right than the left ear.

ISSN:0001-4966    

DOI:10.1121/1.1909838

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

Two different assumptions about the shape of the filter in energy‐detection models for auditory signal detection are investigated. It is shown that, when the mean square output of the filters is equated, the variance calculated for the model whose filter consists of a single resonant circuit is half that of a model whose filter has a rectangular passband. Some implications of this result are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1909839

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

Liquid quantity measurement in aerospace vehicles during free fall is complicated by the fact that liquid in a partially emptied tank will cluster in globules distributed through the tank. The liquid quantity can be determined indirectly by measuring the volume of a gas occupying the “empty” volume of the tank. The volume flow from a low‐frequency acoustic source is divided by two fixed acoustic resistances. A portion flows into the unknown volume and a portion flows into a reference volume. The differential pressure between these volumes can be used as a measure of the unknown volume.

ISSN:0001-4966    

DOI:10.1121/1.1909840

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

Apparatus used to determine hypersonic velocity and absorption in liquids by spectroscopic analysis of light scattered from a single‐frequency laser beam is described. A measurement on dichloromethane is presented, the acoustic parameters are derived, and the significance of their relation to ultrasonic measurements and to the theory of relaxation mechanisms is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1909841

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP