摘要:

An equivalent‐tone method for calculating the loudness of sounds is described. With this method the spectrum of the sound is divided into frequency bands which are treated as pure tones in determining their loudness. The individual values of loudness are added to obtain the total loudness of the sound. Calculations for bands of white noise and for complex tones are compared with subjectively obtained data of Pollack and Fletcher and Munson. The agreement between calculated and experimental values is good. It is felt that improvement of the method must await further psychoacoustic data.

ISSN:0001-4966    

DOI:10.1121/1.1906756

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

In the course of previous investigations, Dix, Hallpike, and Hood have concluded that the phenomenon of loudness recruitment is attributable to disordered function resulting from injury or disease of the hair cells of Corti's organ.In the present paper, an account is given of an experimental study of certain loudness changes caused by adaptation of the hair cell responses to pure tone stimulation.Two outstanding characteristics of the adapted state are defined: “on‐effect normality” and “relapse.” Both resemble very closely those described by Matthews in the case of adaptation occurring the muscle stretch receptors of the frog.Further studies in a number of human subjects show that both of these characteristics are exhibited regularly by the unadapted hair cell responses of individuals suffering from degenerative changes of the hair cells.These studies appear to establish a very close similarity between “on‐effect normality” occurring in the case of the adapted normal sense organ and the phenomenon of loudness recruitment, as demonstrated by the alternate binaural loudness balance procedure of Fowler in the case of the unadapted but diseased sense organ.The experimental findings are considered to favor the view that loudness recruitment is one element of a complex disturbance of cochlear function due to disease or injury of specific elements of the cochlear sensory apparatus, namely the hair cells of Corti's organ.

ISSN:0001-4966    

DOI:10.1121/1.1906757

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

The method of best beats has been employed to estimate the intensities of aural harmonics and of combination tones. It has been generally assumed that the listener hears best beats when the exploring tone produces in the cochlea a disturbance that is equal in magnitude to that of the aural harmonic or of the combination tone being measured. However, as the experiments to be reported will show, when the tone to be measured is near the absolute threshold or is partially masked, the most prominent beats will be heard when the intensity of the exploring tone exceeds that of the unknown tone. Consequently, since aural harmonics and combination tones are partially masked, their intensities will be overestimated when the method of best beats is used. The present paper concerns the magnitude of this error of overestimation.A procedure is presented by which a better estimate of the intensity of an aural harmonic or of a combination tone may be made. When the tone being measured by the method of best beats is well above threshold, the listener hears beats over a wide range of intensities of the exploring tone, and the error of over‐estimation is small. However, when the tone being measured is near threshold, there is a small range of audible beats, and the error of overestimation is of considerable magnitude. It is therefore possible to correct for this error by determining the range of intensities of the exploring tone over which beats are audible as well as the intensity of the exploring tone required for best beats. Application of this procedure to the measurement of a second aural harmonic is illustrated.An explanation is given of the fact that the intensity of a tone near its absolute threshold will be overestimated by use of the method of best beats. This explanation is formulated in terms of the relation of the minimum and the maximum of the envelope of the beating complex to the listener's threshold for the tones that beat.

ISSN:0001-4966    

DOI:10.1121/1.1906758

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

A discussion is made of two lines of evidence that bear upon the problem of the relative importance of place and frequency principles in auditory theory. The first line of evidence has to do with the relation between pitch discrimination and the degree of specificity of action in the cochlea and brings us to an evaluation of the principle of maximum stimulation. A consideration of loudness discrimination data discloses a serious limitation on our ability to appreciate the point of maximum in the cochlear activity and, in general, to make use of a spatial pattern. We must conclude that for the low tones whose patterns are broad the place principle contributes little or nothing to pitch discrimination, and the frequency principle has to serve this function alone.A study of the evolution of the ear brings out still more clearly the relative roles of place and frequency principles. Hearing in some degree is present throughout the vertebrate series, and even the lowest forms have frequency ranges of several octaves and exhibit a fair degree of tonal discrimination. Yet, these lower forms possess an ear of exceeding simplicity, an otic sac in which there is little evidence of mechanical differentiation. It follows that these primitive ears must operate as frequency receptors, with ranges and discriminative abilities that depend simply upon the patterns of impulses conveyed by the auditory nerve. It appears, therefore, that in the history of the ear the frequency principle came first as the basis of tonal reception, and only sometime later in the course of evolutionary development was it joined by the place principle.

ISSN:0001-4966    

DOI:10.1121/1.1906759

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

One of the central problems in auditory theory is to reconcile (a) the acute perception of slight changes in pitch displayed by the human listener with (b) the broad tuning of his cochlear analyzing mechanism. This paper attempts to describe and to relate a number of theoretical solutions to that problem. The hypotheses involve mechanisms, both mechanical and neural, for sharpening the analysis inherent in the cochlear transformation from frequency of stimulation to locus of vibration. These mechanisms operate in the domain of place—they are place theories that supplement the classical place theory. In a future paper, we plan to describe and discuss other sharpening mechanisms that operate in the domain of time.

ISSN:0001-4966    

DOI:10.1121/1.1906760

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

An artificial mastoid for testing bone conduction receivers is described. It consists essentially of a stiff metal bar which has a fundamental resonant frequency above the measurement range, with a strain‐sensitive translating element fastened to the under side and a compliant pad on top.The translating element is a slab of activated ceramic, which is essentially invariant to humidity and temperature changes. The compliant pad generally used is Koroseal No. 74, which simulates the flesh over the mastoid prominence reasonably well. Koroseal No. 15 simulates flesh better but is less rugged. Calibration methods are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1906761

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

Speech articulation and quality tests were made on an all‐pass system capable of advancing or delaying one frequency band relative to the rest of the spectrum. Parameters in the investigation were (a) width of the advanced or delayed band, (b) amount of advance or delay, and (c) position in the frequency spectrum of the advanced or delayed band. Data were taken at signal‐to‐noise ratios of 30 db and 0 db. The results indicate that maximum impairment of speech intelligibility and quality occurs when the delays and advances are of the order of14 second, and when the band that is advanced or delayed is near the center of the speech spectrum and has an articulation index equal to 0.5. These findings are related to data from statistical studies of the timing of speech energy bursts.

ISSN:0001-4966    

DOI:10.1121/1.1906762

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

The fundamental wavelength of a spherical resonator with a circular aperture is calculated. The result,λ/2π = R(2πR/3a)12(1−0.14324a/R+0.08455(a/R)2), whereadenotes the aperture andRthe sphere radius, is the correct form of an expansion as far as terms of relative order (a/R)2, inclusive. A procedure for approximating to the wavelength of a resonator with arbitrary shape is also described.

ISSN:0001-4966    

DOI:10.1121/1.1906763

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

A general expression is derived for the force owing to radiation pressure acting on an object of any shape and having an arbitrary normal boundary impedance. It is shown that boundary layer losses may lead to forces that are several orders of magnitude greater than the forces owing to classical radiation pressure. Steady forces arising from an asymmetric wave form are compared with the other forces. A sound wave, consisting of equal parts of fundamental and second harmonic components, can cause forces ten or more orders of magnitude greater than the forces owing to radiation pressure to be exerted on small particles.

ISSN:0001-4966    

DOI:10.1121/1.1906764

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP

摘要:

A method for treating the scattering and absorption of sound in the presence of non‐uniform boundary conditions is applied to the case of an infinite strip of material (of given width) placed on an infinite, otherwise hard, wall. The strip is assumed to be characterized by a normal acoustic impedance that may possess a resistive component.The wave equation is reformulated as an integral equation over the strip. A variational expression is found for the amplitude of sound scattered by the strip in any direction. The total cross section for scattering plus absorption is determined from the amplitude of specular reflection according to a well‐known cross‐section theorem. Comparison with Pellam's results for absorption by such a strip shows that the methods used have an accuracy better than 2 percent over the entire frequency range.

ISSN:0001-4966    

DOI:10.1121/1.1906765

出版商:Acoustical Society of America    

年代:1951

数据来源: AIP