摘要:

Experiments were conducted on the effects of various expected noise conditions upon autonomic system activity in men during rest and work (bicycle ergometer). Skin temperature and heart rate were not appreciably, if at all, affected by any of the noises. Wide‐band, predominantly low‐frequency noise, at a level of 92 dB,A‐weighted, generally caused a decrease in pulse amplitude (indicative of constriction of peripheral blood vessels) during either work or rest, whereas an equally intense one‐third octave band of random noise, center frequency of 3150 Hz, had no appreciable effect on pulse amplitude. Repeated exposures to the wide‐band noise showed some adaptation or habituation of the pulse amplitude response during conditions of either work or rest. The results were the same for fast rise time (impulsive) bursts of wide‐band noise as for bursts with slow, gradual onsets. Rapid interruptions of wide‐band noise caused less of a decrease in average pulse amplitude than did uninterrupted noise. It is suggested that constriction of peripheral blood vessels in response to expected intense low‐frequency or wide‐band noises is more related to auditory, reflexive protective mechanisms than to autonomic system responses generally considered to be stressful to the organism.

ISSN:0001-4966    

DOI:10.1121/1.384446

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

This paper describes a set of eight quantitative merit criteria for the design of concert halls, used in a developed automated computer optimization procedure based on a modified method of images. Idealized optimum hall configurations and surface absorption coefficients are determined based on each criterion. The acoustical merits of the optimum designs for a hall with given floor and stage areas are evaluated and compared to those of an existing hall with acclaimed acoustical quality. They are also compared to those calculated when the total sum of all the eight merit criteria is used as the optimizing objective function. The study represents a first attempt at optimizing acoustic space based on quantitative figures of merit. The developed technique can be invaluable in giving insight into the effect of improving a particular design objective on the configuration and absorption coefficients, as well as how the improvement of one merit criterion can affect the other criteria.

ISSN:0001-4966    

DOI:10.1121/1.384447

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A computer model for generating world ocean sound velocity profile (SVP) information is presented. It employs a ’’least‐squares’’ predictor to combine National Oceanographic Data Center (NODC) archival SVP data with any amount of available new sound velocity measurements that might be available. A technique is presented in the paper for the analysis of NODC World Ocean SVP data which is highly efficient. The technique is called empirical orthonormal function (EOF) analysis and it is capable of a very large compaction of the data set. This method provides a very compact presentation of the total statistical nature of the SVP data bank. The end result is a computer model which permits the optimum utilization of all archival data and any new data at a given place and time in world oceans to produce a new complete SVP. Of even greater significance is the fact that the form of the predicted SVP profile is such that it is easily employed in any propagation loss prediction model that is currently in use.

ISSN:0001-4966    

DOI:10.1121/1.384448

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A constant‐Qdigital spectral analysis scheme is described which exploits the ’’perfect fifth’’ symmetry of the 12‐tone musical scale.

ISSN:0001-4966    

DOI:10.1121/1.384449

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A method is described for calculating average signal array gain for cw acoustic signals in a multipath medium. The two‐path case is considered; the extension to many paths is straightforward but tedious. Only phase fluctuations are treated; the signals arriving along the two paths may have different amplitudes, but these amplitudes are assumed constant in time and uniform across the array aperture. It is suggested that for beam formation by delay and sum the array signal gain for single path represents the upper limit of performance for multipath. The calculation of gain requires a knowledge of the signal correlation across the array aperture for each path, as well as the signal correlation between the first arrival at one hydrophone and the second arrival at another as a function of hydrophone spacing.

ISSN:0001-4966    

DOI:10.1121/1.384450

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The present manuscript begins with a review of the literature on two‐tone nonlinearity and proceeds to the description of anadhocmodel of auditory nonlinearity which can account for several of the features of the psychophysical data on various two‐tone nonlinearities, in particular, (f2−f1), (2f1−f2), and two‐tone suppression. The two basic components of the model are (1) a nonlinearity which is a series combination of the classical power‐series and compressivep‐law nonlinearities and (2) an intensity‐dependent (nonlinear) filtering scheme. The conceptual model proposed here not only describes the psychophysical data accurately, but also offers possible explanations for some of the apparent discrepancies between psychophysical and physiological data on two‐tone nonlinearities.

ISSN:0001-4966    

DOI:10.1121/1.384451

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Previous determinations of the swimbladder contribution to the fish backscattering cross section have been hindered by ignorance of the acoustic boundary conditions at the swimbladder wall. The present study circumvents this problem by direct comparison of target strengths of three gadoid species and mackerel — anatomically comparable fusiform fish which respectively possess and lack a swimbladder. The relative swimbladder contribution to both maximum and averaged dorsal aspect backscattering cross sections is shown to be approximately 90% to 95%, which is higher than most other estimates. The new results were established for fish of 29‐ to 42‐cm length and acoustic frequencies of 38 and 120 kHz.

ISSN:0001-4966    

DOI:10.1121/1.384452

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A series of 30 randomly timed calls was played to free‐living spring peepers (Hylacrucifer) calling at their breeding pond. The effect of each random call (RC) in the timing of the immediately following call of the frog was ascertained. The results showed that precise entrainment by delayed response or alternation occurs when the RC’s are placed after the refractory periods of the preceding calls of the frogs. However the frogs are sensitive also to RC’s heard in the refractory period. In such cases they advance the next call to an extent dependent on the position of the RC in the refractory period. The results are interpreted in relation to signal interactions of other animals and to models of pacemaker oscillators.

ISSN:0001-4966    

DOI:10.1121/1.384462

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Subjects were exposed to alternate conditions of quiet and noise (computer line printer noise at 100 dB,A‐weighted) while performing a demanding, rapidly paced, psychomotor task. Heart rate, peripheral pulse amplitude, and peripheral blood volume were monitored throughout four 8‐min test sessions. There appeared to be no increase in physiological stress or in errors in task performance during the noise as compared to the quiet test segments. An attempt is made to explain possible causes of differences between the results obtained in this study and those reported for a earlier, somewhat similar, study by Cohenetal. [’’Noise Effects, Arousal, and Human Information Processing Task Difficulty and Performance,’’ Department of Psychology and Industrial Engineering, North Carolina State University, Raleigh, NC (1973)].

ISSN:0001-4966    

DOI:10.1121/1.384410

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A new type of ultrasonic pulse‐echo method that makes use of interaural localization is described in this Letter. The basic idea of this method is to receive pulse echoes reflected from an object with two receiving transducers and to hear the echo signals stereophonically after they are converted to audible frequencies. The principles of the system and some results of preliminary experiments that make use of an ultrasonic pulse of 500 kHz are presented.

ISSN:0001-4966    

DOI:10.1121/1.384411

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP