Showing papers in "Applied Acoustics in 1970"

TL;DR: In this article, the authors investigated the acoustical properties of a range of fibrous absorbent materials and showed that the characteristic impedance and propagation coefficient of these materials normalize as a function of frequency divided by flow-resistance.

TL;DR: The general design concept of the Flextensional Underwater Acoustic Transducer is presented and the five different possible shell designs are discussed and classified in one of five different classes.

TL;DR: In this paper, the authors describe the requirements of a physical unit intended to be the basis of traffic noise control because of the lack of demonstrated correlation of noise levels with nuisance, and discuss the relative merits of the two units and the direction of further research into traffic noise.

TL;DR: In this paper, the authors present a geometrical method for calculating the sound level distribution caused by noise sources of various shapes, i.e. a point source, a line source, and a plane source.

TL;DR: The results of an investigation of acoustical effectiveness of different dissipative duct silencers packed with lightweight porous materials are discussed in this paper, where the comparison of experimental results with that given by existing theories and empirical equations are also available.

TL;DR: In this article, the air discharged by a 12-in "Aphonic" (quiet) radial flow fan, further quietened by long oversize felt-lined ducts and package attenuators, was passed into a large acoustically-deadened test chamber through straight round (4-10 in diam.) ducts, and rectangular ducts of equivalent cross-sectional areas.

TL;DR: In this article, the effect of tool attachment on the resonant frequency was examined and experimental corrections made to the waveguides to maintain resonance at the design frequency, and it was found that accurate prediction of the required tuning correction could be made in each case by shortening the output end of the concentrator by an amount equivalent to the mass of the attached tool.

TL;DR: In this paper, an analytical solution to the problem of radial resonance in an annular disc is described and represented graphically, and a close approximation to this solution is derived by considering the mean circumference of the annulus to be an integral number of wavelengths.

TL;DR: In this article, the authors measured the absorption of porous materials as a function of humidity by the tube method and found that the absorption coefficient is considerably changed by humidity, for example, the coefficients of ‘Rock-Wool’ board at 2500 Hz are 66·1% in 76% R.H. and 72·7% in 93% RH.

TL;DR: In this paper, a panel of subjects assessed the noisiness of six cars at four constant speeds, and the sound pressure levels existing in the vehicles were measured in one-third octave bands from 25 to 10,000 Hz, and also using the A and B weighting networks.

TL;DR: In this paper, the authors measured the normal impedances of two sample thicknesses, for one absorbent at a given frequency, with these parameters the impedance of any thickness, for any angle of incidence, may be obtained.

TL;DR: In this article, the authors take an inventory of the causes of acoustical excitation and enumeration of the components of the machine responsible for the emission of sound in the main noise families: magnetic, mechanical and aerodynamic.

TL;DR: In this paper, the analysis of acoustical systems using electromechanical analogies is presented, and the effects of wall and partitioning on sound waves are considered, where simple mechanical machines and transducers are considered.

TL;DR: In this paper, it is recommended that where resilient linings are used, consideration should be given to the possible acoustic consequences, but insufficient evidence is available from which to make specific proposals.

TL;DR: In this article, Piezoelectric, capacitive, and electret microphones are described, and the calibration of such transducers is not easy by conventional methods, either continuous (high level SPL in a small volume) or impulsive (shock-tube).

TL;DR: In this article, a simple experimental method of quantitatively assessing and specifying the reception of musical detail in an auditorium is described, and the possibility of expressing reception of detail in terms of a confusion index is discussed.

TL;DR: In this article, measurements of the noise produced by two refrigerant compressors showed that complaints should be regarded as justifiable, and methods of reducing the noise are discussed and the particular method adopted is described in detail.

TL;DR: In this article, the but est de realiser une source sonore, de conception simple, a caracteristique spherique dans une gamme de frequences s'etendant jusqu'a 6.000 Hz.

TL;DR: In this paper, an analysis is made of using inexpensive model tests to optimise the design of airport noise barriers and to establish optimum design parameters for airport designers to obtain the lowest possible noise levels.

TL;DR: It was shown that the statistical model could also describe pedestrian noise in a traffic-free shopping precinct and can also be applied to traffic noise on an urban motorway and a fast inter-city road of the dual carriageway type.