摘要:

This paper describes a procedure for calculating the impact‐noise level of a bare stiff structural floor when excited with a standard tapping machine. Calculations are also given for the improvement in impact noise isolation achieved by adding to the structural floor (a) an elastic surface layer, (b) a locally reacting floating floor, and (c) a resonantly reacting floating floor.

ISSN:0001-4966    

DOI:10.1121/1.1912726

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A method was developed to measure empirically the dynamic characteristics of air‐pressure transducers and associated attachments utilized in speech research. With this method, frequency‐response data were collected for transducers used in measuring magnitudes of air pressure associated with speech production. The effect of attaching hypodermic needles (used for trachial punctures to measure subglottal air pressure) and plastic tubes (used for measuring intraoral and intraesophageal air pressures) to these transducers was also studied. In addition, frequency‐response data were collected for two low‐range pressure transducers that are used in conjunction with pneumotachographs (for measuring rates of airflow through the vocal tract). The effect of pressure magnitude upon the frequency response of an air‐pressure transducer was determined. Conclusions are offered on the basis of the data obtained, and implications for speech research are suggested.

ISSN:0001-4966    

DOI:10.1121/1.1912727

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The reliability of two methods in detecting the acoustic null with the Zwislocki bridge using trained listeners was investigated. One method consisted of the subjects listening directly from the bridge with a stethoscopic headset. The other method consisted of the signal being amplified and then detected by an oscilloscope readout and listening combined. There were no significant differences between methods even though the subjects preferred the direct listening method.

ISSN:0001-4966    

DOI:10.1121/1.1912728

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A piezoelectric ceramic material having low dielectric constant, high thickness coupling factor, high mechanical quality factor, high stability, and high operating temperature, has been prepared fromPbTiO3incorporated with 2.5 mol% ofLaO12and 1.0 mol% ofMnO2. Typical electromechanical constants of this material are as follows: dielectric constantε11T/ε0 230, ε33T/ε0 170; coupling factork330.46,kt0.46,k150.28,kp0.07,k310.04; mechanical quality factorQ1100, Poisson's ratio σE0.20. Frequency constantsNtandN3tof the fundamental and third‐harmonic thickness vibrations have temperature coefficients of −1.1 × 10−4°C−1and −2 × 10−5°C−1, respectively. Aging rates ofNtandN3t, are +0.02% and −0.02%/time decade at 30°C, respectively. The Curie point of this material exists at 470°C, andk33andktincrease gradually with temperature up to 400°C. This material has grain size of 2–3 μ and bending strength of 2 × 107kg/m2, and can be polished into very thin plate. ThePbTiO3ceramics have a high potential for use in electromechanical devices at high frequency and high temperature.

ISSN:0001-4966    

DOI:10.1121/1.1912729

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

An experimental investigation has been made of the sound‐absorbing properties of liquid‐base foams and of their ability to reduce jet noise. Protein, detergent, and polymer foaming agents were used in water solutions. A method of foam generation was developed to permit systematic variation of the foam density. The investigation included measurements of sound‐absorption coefficients for both plane normal incidence waves and diffuse sound fields. The intrinsic acoustic properties of foam, e.g., the characteristic impedance and the propagation constant, were also determined. The sound emitted by a 1‐in.‐diam cold nitrogen jet was measured for subsonic (300 m/sec) and supersonic (422 m/sec) jets, with and without foam injection. Noise reductions up to 10 PNdB were measured.

ISSN:0001-4966    

DOI:10.1121/1.1912730

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Liquid‐base foams are highly effective sound absorbers. A better understanding of the mechanisms of sound absorption in foams was sought by exploration of a mathematical model of bubble pulsation and coupling and the development of a distributed‐parameter mechanical analog. A solution by electric‐circuit analogy was thus obtained and transmission‐line theory was used to relate the physical properties of the foams to the characteristic impedance and propagation constants of the analog transmission line. Comparison of measured physical properties of the foam with values obtained from measured acoustic impedance and propagation constants and the transmission‐line theory showed good agreement. We may therefore conclude that the sound propagation and absorption mechanisms in foam are accurately described by the resonant response of individual bubbles coupled to neighboring bubbles.

ISSN:0001-4966    

DOI:10.1121/1.1912731

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Prescoring based upon the material contained in abstracts was used to allocate presentation times for the papers in Speech Communication submitted for presentation at the 80th Meeting of the Acoustical Society. After the papers were actually presented, their technical content, presentation quality, and discussion quality were judged. No casual relationships could be established between the prescoring and postjudging of the paper, although the papers allocated 15 min were judged statistically better in technical content than the papers allocated 5 or 10 min. It is hoped that this letter might entice others to conduct further experimentation and subjective assessment of different methods for improving professional meetings.

ISSN:0001-4966    

DOI:10.1121/1.1912732

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The purpose of the present letter is twofold: first to list some additional references dealing with recent applications of the boundary collocation technique and second to add some comments regarding the convergence of the method.

ISSN:0001-4966    

DOI:10.1121/1.1912733

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912734

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912735

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP