摘要:

This paper contains an analysis for determining the time of arrival and Doppler‐frequency characteristics of a pulse transmitted to a target by reflection from a not‐too‐rough surface such as the sea bottom and gives numerical values for a typical sonar application. The analysis may be important in sonar signal processing associated with one‐way or round‐trip transmission and in the interpretation of data from marine geophysical surveys; it may, in addition, have application to propagation of electromechanical waves by ionospheric refraction.

ISSN:0001-4966    

DOI:10.1121/1.1910846

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP

摘要:

The paper deals with the detection of a passive sonar target in the presence of ambient noise and a plane‐wave interference. Target signal, interference, and ambient noise are assumed to be Gaussian random processes, the ambient noise being statistically independent from hydrophone to hydrophone. The receiving array is linear and consists of equally spaced hydrophones. The performance of conventional and likelihood‐ratio detectors is analyzed. In an interference‐dominated environment, the likelihood‐ratio detector can be superior by a substantial margin. Complete elimination of the interference can be accomplished at a cost of no more than one hydrophone.

ISSN:0001-4966    

DOI:10.1121/1.1910847

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP

摘要:

In observations and measurements on the acoustical properties of a number of rooms varying greatly in size, shape, ornament, and surface finish, several factors bearing on the quality of sound have been noted. The generally accepted requirements for the reverberation‐time characteristic as a function of frequency are rather stringent. It has been especially evident that when the high‐frequency reverberation times in a concert hall are significantly longer relative to those of the midfrequency and low‐frequency range than would normally occur, the acoustical conditions are judged unsatisfactory. A specific example of this condition has recently been studied in a new concert hall. Other factors relate to directional characteristics. It is concluded that highly isotropic reverberant sound is not pleasant, but confusing. Conditions are greatly improved if the preponderance of the reverberant sound approaches the listener from directions near the plane that includes the source and the listener's ears. For longer reverberation times, the quality is enhanced when it is possible to make some judgments of distance and direction by the binaural hearing sense, provided there is ample diffusion to suppress echoing. Binaural effects produce a sense of spaciousness, and this, rather than simply a prolonged reverberation time, is probably the principal effect giving rise to the exceptional acoustical properties of many large churches.

ISSN:0001-4966    

DOI:10.1121/1.1910848

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP

摘要:

The rate of increase of amplitude ofV(vertex) potentials with the SPL of tone bursts is very slow. In one experiment, the exponent of the power law was 0.15 at 250 Hz, 0.11 at 1000 Hz, and only 0.08 at 4000 Hz. Individual differences across subjects seemed more important than the interval between stimuli (1 sec vs 3.2 sec), and variability across trials often obscured the relation to intensity. In the presence of appropriate bands of masking noise, the input‐output curves rise abruptly from the masked threshold to approach the unmasked amplitude at a level about 30 dB above the corresponding masked threshold. The effect resembles recruitment of loudness. Tone pips and tone bursts of different frequency that were judged equally loud evoked slowVpotentials of approximately equal amplitude. In some subjects, however, bursts of white noise evoked significantly larger responses than equally loud tone bursts or pips. In spite of the partial similarities between them, the amplitude of theVpotential and the sensation of loudness are related differently to the parameters of the acoustic stimulus.

ISSN:0001-4966    

DOI:10.1121/1.1910849

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP

摘要:

A complex signal composed of a fundamental (525 cps) and a second harmonic (1050 cps) was created by systematically altering the phase of the second with respect to the first through six relative‐phase relationships (0°, 30°, 60°, 90°, 120°, and 150°). Four 100‐msec bursts of noise, one of which contained the complex waveform, were presented to four subjects; and they were forced to choose which of the four contained the signal. Ten different signal‐to‐noise ratios (S/N), covering a range of 10 dB around a subjective “threshold” value, were utilized. Forty judgments at each of these S/N ratios were made in each phase condition. The data revealed differences with regard to the detectability of the complex signal as a function of the relative phase of the components.

ISSN:0001-4966    

DOI:10.1121/1.1910850

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP

摘要:

Activity of single cells in cats immobilized with gallamine triethiodide was recorded with metal microelectrodes and displayed by an on‐line dot display. Tone burst, noise burst, click, and other stimuli at moderate intensities were presented through condenser microphones at both ears. Spontaneous activity ranged from less than 1 spike/sec to greater than 40 spikes/sec. Almost all units were affected by acoustic stimuli, either by enhancement of activity, reduction of activity, or a combination. Units were affected at the onset and/or termination of a stimulus, throughout a stimulus, or a combination. Best frequency of units ranged from less than 1 kHz to greater than 50 kHz. Over half the units responding to tone bursts exhibited a response range greater than12oct. Some units had double response ranges. The pattern of response to tone bursts of some units changed as the frequency of the stimulus was changed. A minority of the units showed responses only to special stimuli such as swept tones or continuous noise or tones. It appears that the coding of acoustic stimuli by single units of the primary auditory cortex of the cat is performed in a highly individualistic and variegated manner.

ISSN:0001-4966    

DOI:10.1121/1.1910851

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP

摘要:

The stimulus‐evoked activity of single units in the left primary auditory cortex (AI) of cats immobilized with gallamine triethiodide was observed as tone bursts, noise bursts, or clicks were presented at a moderate intensity to the right ear, to the left ear, and simultaneously to both ears. The right ear is represented more strongly in that more cells respond to monaural stimulation of the right ear than the left ear. An ear is said to be “represented” if a unit responds to stimulation of that ear, or if the response to stimulation of the other ear is modified by stimulation of that ear. There is extensive overlap of the populations of units representing the two ears; the population representing the left ear is almost completely contained within the larger population representing the right ear. The majority of units exhibited some form of binaural interaction. Binaural summation was the most common form of interaction; other units exhibited binaural inhibition or combinations of summation and inhibition.

ISSN:0001-4966    

DOI:10.1121/1.1910852

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP

摘要:

The scala tympani in guinea pigs was prefused with mammalian Ringer‐Locke's solution, in which NaCl was replaced with either choline chloride or sucrose. Cochlear potentials were recorded from the basal turn before, during, and subsequent to the perfusion. Complete replacement of the perilymph withNa+‐free solution did not alter the endocochlear potential and the cochlear microphonic immediately, although the action potential was abolished rapidly. In most cases, the depression of the action potential was reversible. The mechanism underlying the generation of the receptor potential is discussed, and it is concluded that production of cochlear microphonic is not dependent on the concentration ofNa+in the perilymph but on the presence of highK+concentration in the endolymph.

ISSN:0001-4966    

DOI:10.1121/1.1910853

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP

摘要:

Tetrodotoxin or procaine was introduced into the scala tympani or scala media. The cochlear potentials—including the negative potential in the organ of Corti—were recorded before, during, and after the introduction. Tetrodotoxin at a concentration of 5 × 10−8and 1 × 10−7g/ml blocked the action potential but had little effect on the resting potential and cochlear microphonic, when it was introduced into the scala tympani. On the other hand, the cochlear microphonic and action potential were depressed by 0.05%–0.1% procaine introduced into the scala tympani, whereas the endocochlear potential showed a temporary increase. The mechanism underlying the generation of the receptor potential is discussed, and it is concluded that the production of the cochlear microphonic depends on the presence of potassium ions in the endolymph.

ISSN:0001-4966    

DOI:10.1121/1.1910854

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP

摘要:

The optimum receiver for the case where signal is known except for phase has been suggested as a model for auditory detection of sinusoidal signals in noise. We have furthered application of this model in an effort to evaluate some of the parameters of monaural detection that are important for prediction. Of particular interest is bandwidth, or “critical band,” which was found to decrease as signal‐to‐noise ratio increases, the rate of decrease being a function of frequency. Bandwidths were derived from the parametric values of the ROC's that describe the detection performance of our observers. It was found that human ROC's are closely matched by ideal ROC's. The ROC's of our observers were obtained with a six‐category rating scale and our measure of detection wasds. Values ofdswere obtained at 500, 800, 1300, 2500, and 4000 Hz over a range of signal‐to‐noise (S/N) ratios. It was found that the relationship ofdsto S/N ratio at all signal frequencies could be summarized by a single equation, the psychometric function. Other equations are also given so that the psychometric function for any signal frequency may be determined simply from a knowledge of the power per unit bandwidth of the masking noise.

ISSN:0001-4966    

DOI:10.1121/1.1910855

出版商:Acoustical Society of America    

年代:1968

数据来源: AIP