摘要:

In a recent issue of the Journal, Hall analyzed some data on ultrasonic absorption in a solution ofMgSO4in water, which the authors published several years ago. Hall noted the appearance of a second peak in the curve of αλvsfrequency, occurring at about 20 Mc. The authors have re‐examined these and other data taken in these solutions and have made some additional measurements at several concentrations and temperatures. The appearance of this second peak is confirmed, although the measurements are not of sufficiently high accuracy to fix the dependence of relaxation frequency upon concentration.

ISSN:0001-4966    

DOI:10.1121/1.1917690

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

By means of high speed digital counting pulse techniques, the velocity of ultrasound may be measured to 1 part in 104. The temperature coefficient of velocity may be measured to 1 part per million per degree Centigrade. A description of the method and equipment is included.

ISSN:0001-4966    

DOI:10.1121/1.1917695

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

To obtain stereophonic effects in the reproduction of recorded music a listener must have not only the equivalent of three‐dimensional sight to give him sound in depth, but also the equivalent of two‐dimensional sight to give him sound from different directions. When music is recorded binaurally these effects are obtained in such manner that they accurately convey information regarding conditions which existed at the time that the music was recorded. When reproduction is from binaural disk records, however, other second‐ and third‐dimensional effects which do not convey any information regarding these conditions may possibly be present and enhance the binaural effect so that the listener is not so well informed regarding the actual conditions. These other effects, conveying untrue information, can be used to produce stereophonic effects when music is reproduced from monaural records. It is concluded that an arrangement making use of these effects with reproduction from monaural records is usable for the purpose of obtaining an illusion of the actual presence of the musicians under some conditions, although the illusion created is that of a possible relative location of the musicians and not the actual relative location of the musicians when the music was recorded.

ISSN:0001-4966    

DOI:10.1121/1.1917700

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

A small unidirectional microphone has been developed with the following features: maximum sensitivity along the axis of the microphone; a high ratio of electrical output to size; a sharper directivity pattern than a cardioid; a directivity pattern that is independent of the frequency; a blast proof vibrating system. The high discrimination which this microphone exhibits to sounds which originate from the sides and rear makes it particularly suitable for long distance sound pick‐up in radio, television, sound motion pictures, and sound reinforcing systems.

ISSN:0001-4966    

DOI:10.1121/1.1917703

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

A summarization is given of the sound transmission qualities of a number of light‐weight aggregate structures constructed of blocks of various types, sizes, shapes, and aggregates. Sound transmission through such block walls is independent on the type of blocks and their thickness, internal shape, and porosity. Tests with surface sealing treatments indicate the relative contributions of transmission through the pores and through flexural wall vibration. Effective porosity is found to vary with shape and size of the internal cavities.

ISSN:0001-4966    

DOI:10.1121/1.1917708

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

Studies have been of the flow resistance and density of a series of commercially produced fibrous acoustical materials. Random samples of Fiberglas PF Board, TWF Wool, and Spuntex felt were taken from approximately 35 carloads of these various materials. The range of flow resistivities and densities were measured and are reported here. These data are correlated and compared to that previously reported.

ISSN:0001-4966    

DOI:10.1121/1.1917714

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

The probability distribution of zero‐crossing intervals has been calculated for signals consisting of a sine wave and filtered random noise. The distribution function obtained holds for a wider range of conditions than that found by S. O. Rice and agrees with Rice's result in the range of validity of that function. Experimental results will be presented which cover a wider range of conditions than do the theoretical calculations.

ISSN:0001-4966    

DOI:10.1121/1.1917725

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

A method was developed for getting a continuous and running record of pitch matches between the two ears over a frequency extent of one octave. The automatic recording audiometer, usually referred to as a “Bekesy” audiometer, measures hearing loss (amount of attenuation) as a continuous function of frequency. By using the automatic frequency and paper drive features of the Iowa version of the “Bekesy” audiometer but using the subject's adjustment of a second oscillator, instead of an attenuator, to drive the recording pen, a continuous tracing of pitch matches is available. A one‐second tone from the motor driven (standard) oscillator (controlling the paper drive) is presented to one ear and a two‐second tone from the subject's (variable) oscillator (controlling the pen writing mechanism) is presented alternately to the other ear. Between successive presentations of the standard tone its frequency is shifted continuously upward in increments of 0.77 percent. The listener, who controls the frequency of the variable tone, is instructed to keep the two alternating tones matched in pitch. In this manner 90 distinct pitch matches are made in each octave and a permanent record of the frequencies of the two oscillators is available. Ten music students made these pitch matches over the six‐octave interval from 150–9600 cps. In the ear in which the standard tone was heard various types and amounts of hearing loss were simulated by masking noises. Results indicate a correlation between the slope of the hearing loss and the amount and direction of the pitch shift. The pitch tends to shift away from a region of hearing loss to a region of no, or less hearing loss. Downward shifts in pitch were observed but were never as marked as the upward shifts.

ISSN:0001-4966    

DOI:10.1121/1.1917727

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

The frequencies of tones when metal rings are struck in radial and axial directions have been investigated in a variety of steel and bell‐metal rings. The classical formulas relating frequency with ring dimensions and physical properties of the materials compare closely with actual measurements except for thick rings. The fundamental tone is predominant in the smaller rings, but the fundamental fades and the overtones predominate as the rings increase in diameter and decrease in width and thickness. Comments are given on musical properties of rings which may be promising but which have not been fully explored.

ISSN:0001-4966    

DOI:10.1121/1.1917734

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP

摘要:

This paper discusses some of the research and development already undertaken or being considered in the fields of heart and circulatory diseases, neuro‐surgery, shock or blast effect on animals, impairment of hearing from military and industrial high level noise, and communication aids to surgery.

ISSN:0001-4966    

DOI:10.1121/1.1917743

出版商:Acoustical Society of America    

年代:1953

数据来源: AIP