摘要:

This paper presents a method for calculating the performance of acoustic circuits containing lined ducts. The diameters of the ducts must be less than one‐half the wave‐length of sound in free air. The cases of long and short ducts are treated. For the latter, equivalent electrical circuits are given, and some discussion is given concerning the equivalent electrical circuits for long ducts. A brief list of formulas applicable to filters employing lined tubes is given.

ISSN:0001-4966    

DOI:10.1121/1.1906529

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

A general theory of sound transmission for normal wave incidence is developed for a structure containing two impervious layers, an air space, and two acoustical blankets. Equations for more simple structures are derived from the general case by setting some of the parameters equal to zero. A number of design charts are presented giving attenuation in decibelsvs.frequency for different structures with specific acoustic resistivity of the blanket material as a parameter. Experimental results are found to be in good agreement with the theoretical predictions. It is found that panels deviate from mass law behavior as their thickness is increased. Mass law behavior is obtained for panels of any thickness when a laminated construction is used to damp out flexural waves.

ISSN:0001-4966    

DOI:10.1121/1.1906530

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

The acoustical design and construction of the new Mutual‐Don Lee Broadcasting Studios in Hollywood were done under novel and very favorable arrangements. First, a careful check was made of the optimum acoustical characteristics to which it was decided to design the studios. Some of the best auditoriums for broadcasting were measured, and from these data as well as comments regarding the excellence and shortcomings of these auditoriums, the optimum characteristics for the new studios were determined.During the course of construction, acoustical measurements were made several times for the purpose of “tailor‐making” the acoustical characteristics of the studios. On the basis of the measurements, it was found that only a few minor modifications in acoustic treatment were necessary, such as changing the mountings of the Acousti‐Celotex materials in order to change the low frequency absorption characteristics as desired, and the areas used of these materials.The results are, close agreement between optimum and finally measured acoustical characteristics, and very satisfactory broadcast programs.

ISSN:0001-4966    

DOI:10.1121/1.1906531

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1906533

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1906534

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1906535

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

A graphical functionW(r,c) has been determined experimentally, in whichWis word articulation,ris the relative level of unclipped speech and the noise, andcis the amount of uniform, symmetrical, speech‐peak clipping. Preemphasis of the speech signal gave an approximately uniform speech spectrum prior to clipping. Uniform, random noise was mixed with the clipped speech before post‐equalization, making the final noise spectrum similar in shape to the speech spectrum. The real‐ear response of the earphones was compensated electrically to yield a uniform orthotelephonic response for the communication system, in the frequency range contributing significantly to articulation index. For constant clippingcnthe functionW(r,cn) approachesW(r, 0) as a limit for sufficiently large values ofr. Forc < r + 5, W ≑ W(r, 0). For the case of no clippingW(r) when transformed toW(A),Abeing articulation index, resembles closely the curve by Pollack.

ISSN:0001-4966    

DOI:10.1121/1.1917075

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

The study of the perception of speech is aided by instruments capable of representing physical patterns which are complex in frequency, time, and intensity. The sound spectrograph developed by Potter and co‐workers provides visual patterns which are highly suggestive for the isolation of the distinctive aspects of auditory patterns. However, comparison and judgment by ear are desirable, and this requires additional instrumentation to play back modified spectrograms, or completely synthetic spectrographic patterns which differ only in the particular characteristic under examination. The spectrograph developed for these studies records on film, portraying a dynamic range ofca.40 db by a linear density variation of 2.0. The use of a Photoformer to control the recording light permits compensation for non‐linearities of other components, or the intentional introduction of high contrast (compression), black‐to‐white reversal, or intensity‐contour characteristics into the spectrograms. The pattern playback uses these spectrograms directly, or after retouching or printing, to control the modulation at syllabic rates of an optical scanning beam which is then converted into sound. Synthetic spectrograms, hand‐drawn on a transparent medium, are used in a similar manner. Spectrograph and playback were designed for specific application to speech‐like sounds and to studies of the perception of such sounds. Design considerations and performance data are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1917077

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

A study was made of solo and ensemble performance of the same musical material as related to systems of intonation postulated by certain acoustical, musical, and psychological theories. In particular, it was desired to check earlier findings that unaccompanied performance and listener preferences approximate Pythagorean intonation and to extend a similar line of investigation to ensemble performance. Solo and ensemble performances by 24 well‐trained string quartet players were recorded from which stratified random samples of tones were obtained for frequency analysis. This analysis was made through the use of 16‐mm sound‐on‐film loops with a chromatic stroboscope (Stroboconn). The results confirm earlier findings for unaccompanied melodies and indicate that Pythagorean intonation is also most typical of ensemble performance. This tendency appears to dominate any “cultural conditioning” which may exist for equal‐tempered intonation.

ISSN:0001-4966    

DOI:10.1121/1.1917083

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

Medical authorities all agree that the noise problem is serious. How serious it is for a given industry can only be ascertained by a properly conducted noise survey which will give data on the noise levels to which its industrial workers are subjected and an audiometric survey which will give data on the hearing acuity of workers subjected to such environments. Noise level meters, filter sets and analyzers, and audiometers are available with which to conduct these surveys. There is need for standardization in the methods by which the two surveys are conducted and interpreted. There is need, also, for data on how the adverse effects of noise upon personnel in turn affect the quality of the product, labor turnover, absenteeism, accidents, and compensation claims. Industry, confronted with a serious problem, cannot wait for elaborate refinement of data but must act with the data available. Fortunately, industries all over the country are acting and the steps being taken are reviewed. More before and after studies are needed to help others tackle their problems. The steps taken at Hawthorne are summarized with a brief review of the fundamental theoretical problems involved in compensation claims. The role that the Acoustical Society of America can play in coordinating the efforts of all organizations interested in assisting industry to solve the noise problem is outlined briefly.

ISSN:0001-4966    

DOI:10.1121/1.1917091

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP