摘要:

The acoustical characteristics of a rank of closed diapason pipes have been investigated experimentally to provide a basis for testing theories of scaling laws. Measured quantities determined for each pipe include pipe dimensions, sounding frequency, radiated sound pressure, jet speed at the lower lip, phase of jet crossing at upper lip, and pipeQas a function of amplitude. Comparison with current models of organ‐pipe mechanism will be attempted.

ISSN:0001-4966    

DOI:10.1121/1.2003153

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

A survey of noise emission reduction techniques is presented for propeller driven aircraft. Most of the audible noise is generated by the propeller tip traveling with a local velocity near that of the speed of sound. The feasibility of mechanical design steps (larger geared propeller and longer landing gear) required to reduce this speed was investigated. It was found that only new aircraft designs can be so configured. Existing aircraft will continue to operate. The attrition rate of these existing aircraft (1%–3% per year) is small, so that certain operational methods are desirable to achieve quieter airport environs. Procedures of administrative control, operational rules, a noise abatement power adjustments are described which decrease the noise exposure experienced on the ground. Enlightened land planning by county and state officials is described. [Work supported by FAA.]

ISSN:0001-4966    

DOI:10.1121/1.2003160

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Although S. N. Curle's very useful formula for aerodynamic sound radiated from a rigid surface can be applied to closed fluid circuits by the method of images, this procedure is not practical for cavities of complex shape. Sound fields in such cavities are best described with standing waves. However, substitution of an orthonormal mode expansion into the inhomogeneous wave equation results in volume integrals of dilatation source terms for the generalized model loads [N. A. Cumptsy and D. S. Whitehead, J. Sound Vib.18, 353–369 (1971)]. Since the dilatation field is usually not known, the formal solution is difficult to apply. This paper presents an expansion of the sound field in a cavity in terms of nonorthogonal functions which results in a coupled set of equations with the generalized loads in terms of surface pressures (as in Curle's derivation), plus quadrupole terms. When the equations can be conveniently uncoupled and the quadrupole terms neglected, this formalism is very useful. Some of the cavity and flow geometries for which these two simplifications can be made and discussed.

ISSN:0001-4966    

DOI:10.1121/1.2003162

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

We have reported previously (San Francisco ASA meeting in November 1975) on the intelligibility and discriminability of a low‐frequency formant speech does with both normal hearing and hearing impaired subjects. Since then we have endeavored to discover just how much degradation the speech suffers in the process of coding and at what stage of the coding it occurs. Using Form IV of the Diagnostic Rhyme Test as test material, we have presented a modified speech code (dealing with partials of the speech rather than formants as such) at various stages of coding to normal hearing subjects. (This was done to assess the adequacy of the code and to initially avoid training hearing impaired subjects.) The test is used in the usual “intelligibility” mode in which the subject hears a single stimulus and is asked to identify it as one member of a word pair for the following conditions: (1) speech directly as recorded, (2) speech low‐pass filtered (4.5 kHz) followed by analog‐to‐digital and digital‐to‐analog conversions, (3) speech synthesized from largest amplitude partials. In addition, the test is run in a “discrimination” mode in which the subject hears a pair of rhyming stimuli and is asked to judge whether they are the same or different for the above conditions and for conditions after low‐frequency transposing by a factor of four to one. Work is in progress with hearing impaired subjects.

ISSN:0001-4966    

DOI:10.1121/1.2003167

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

For those individuals unable to learn esophageal speech and for the period of time until adequate esophageal speech is developed, the successful use of an artificial larynx is of primary importance. The purpose of this paper is to present the results of an investigation which measured and analyzed the speech parameters of (1) rate, (2) duration, (3) pitch, (4) intensity, and (5) articulation of both good and poor artificial larynx users. In addition to the analysis of the above parameters, perceptual judgments of speech intelligibility and proficiency were obtained. The conclusions reached from this investigation have resulted in the establishment of criteria for training laryngectomized individuals in the use of an artificial larynx. The material presented can also be used as a diagnostic basis to determine why an individual is not functionally intelligible us using the artificial larynx.

ISSN:0001-4966    

DOI:10.1121/1.2003173

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP