ISSN:0001-4966    

DOI:10.1121/1.1915147

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP

摘要:

A sound decay curve in a reverberation room was photographed by means of an oscillograph. Computing the rate of decay from this film the total absorption in the room can be computed. The average results obtained by this method may be in close agreement with those obtained by the ear using the usual reverberation method, but the method as at present developed requires a prohibitive amount of time and labor.

ISSN:0001-4966    

DOI:10.1121/1.1901886

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP

摘要:

A survey of experimentation dealing with effects of various acoustic stimuli on motor functions, simple cerebral functions, complex cerebral functions, respiratory functions, cardiovascular functions, feeling‐tone and emotional functions, and on the organism at work. Some thirty experiments cited show that acoustic stimuli have a wide variety of effects on mental and physiological functions and help explain general reactions of people to noise. Way for future development of more relevant studies shown.

ISSN:0001-4966    

DOI:10.1121/1.1901888

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP

摘要:

Modern methods for employing under‐water sound as an aid to navigation are based upon the binaural sense.The earliest devices, exemplified by the “C” tube, etc., mechanically placed the ears of the observer on the extremities of a beam to be rotated in a horizontal plane beneath the sea. Such cumbersome equipment was improved by employing fixed under‐water receivers in conjunction with an adjustable compensator for obtaining a binaural balance.Electrical lag lines have replaced acoustical tubes for obtaining the necessary time lag to affect compensation. The effectiveness of such a two‐spot system is hampered whenever more than one sound source is present. This difficulty was subsequently overcome by obtaining a directional sensitivity by means of a multi‐spot system which compensates simultaneously for a binaural and maximum focus.Observations upon the compensators may likewise be made upon sounds traveling in a vertical plane. This enables continuous depth soundings to be taken with the vessel under way at full speed, a valuable feature.Apparatus has also been perfected for acoustic depth soundings by timing the echo of sound reflected from the sea bottom. The use of super‐audible sound waves, which can be projected in a slightly diverging beam, offer great possibilities for the location of icebergs, etc.

ISSN:0001-4966    

DOI:10.1121/1.1901891

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP

摘要:

An Electro‐Mechanical Frequency Analyzer, previously reported (Physical Review, August 1, 1929) has been adapted to the determination of the sound spectra of aircraft in flight. The complex source of sound is converted into potential fluctuations by a microphone and high quality amplifier. The output of the amplifier is applied to a modified quadrant electrometer, the needle of which forms part of a sharply resonant mechanical circuit. The natural period of the mechanical circuit is made continuously variable by a tri‐filar suspension and can be determined from a single micrometer reading. An analysis of a complex source is made by observing the amplitude of vibration and natural period of the mechanical circuit for each component. By a previous calibration of the instrument these observations are sufficient to determine the amplitude and frequency components of the complex sound. The instrument has been used to measure the sound spectra of typical passenger and military planes in flight.

ISSN:0001-4966    

DOI:10.1121/1.1901892

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP

摘要:

Systems for the reproduction of music are limited in the frequency range and in the amplitude of the sounds which they can reproduce without distortion. In order to determine what requirements such a system should meet for faithful reproduction of common forms of music, those instruments which were believed to contribute largely to low or high frequencies, or to have large amplitudes at any frequency, have been investigated. Those examined were: bass drums of three sizes, snare drum, cymbals, triangle, bass viol, bass saxophone, bass tuba, trombone, trumpet, French horn, clarinet, flute, piccolo, piano, and organ. Several measurements have also been made upon complete orchestras.The measurements included average and peak sound pressures corresponding to the whole spectrum, and also the same quantities in thirteen bands of frequencies which together covered the complete spectrum. Several hundred peak measurements were taken in each band, each measurement representing the highest peak in one‐eighth second of music. They were taken in such a way that the frequency of occurrence of the peaks in ten amplitude zones, each zone covering six decibels, was obtained. The musician in each case played a representative selection for his instrument, lasting two or more minutes.With the complete orchestra, the highest peaks were found to lie in the region between 2,000 and 4,000 c.p.s. The greatest peaks below 64 c.p.s. were obtained when the bass drum was prominent, while the greatest peaks above 8,000 c.p.s. were very plainly due to the cymbals.

ISSN:0001-4966    

DOI:10.1121/1.1901894

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP

摘要:

Up to the present, the acoustics of auditoriums has rested on a purely empirical basis. A more satisfactory situation would be reached if we knew a physical quantity which had some definite value for all rooms, regardless of size, which are considered acoustically good. Such a condition is that∫t0t1 Lt dt = −32.6wheret0is the time a sustained source of sound,Ē, is cut off;t, the time the sound becomes inaudible: andLt, the loudness of the sound at any instantt. For a test tone of 1000 cycles we takeĒto be 35.3×1010cubic feet of sound of threshold density per second, which is a fair average of sources met with in practice. All rooms which have been considered acoustically good satisfy this condition. This implies that the ear is a ballistic instrument during the period of hang over of a sound, and suggests that rooms should be adjusted so that the loudness of all pure tones shall decay at the same rate, independent of frequency. The absorption material used must have a definite frequency characteristic to obtain this result. This characteristic turns out to be very near to that which an audience of people exhibits. An audience is recognized as being nearly ideal absorption material.

ISSN:0001-4966    

DOI:10.1121/1.1901899

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1915171

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1915172

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1915173

出版商:Acoustical Society of America    

年代:1930

数据来源: AIP