摘要:

A masking procedure has been developed to rank apartment floor‐ceiling systems in order of their resistance to the transmitted sound of footfalls. Results obtained subjectively show that the current international standard for rating impact noise transmission using a tapping machine incorrectly ranks some wood‐framed floor‐ceiling systems. When the described procedure is used to mask tapping machine noise, the floors are also incorrectly ranked. This inadequacy continued even though low frequencies, below the 89‐Hz cutoff of the 100‐Hz 1/3 octave, were included in the masking procedure. Because the masking procedure described is subjective, the problems associated with the development of an objective test are also discussed. A simple objective test method is suggested for future development.

ISSN:0001-4966    

DOI:10.1121/1.1914442

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The Monte Carlo technique is proposed for the determination of the acoustical pressure‐time history at chosen points in a partial enclosure, the central idea of this technique being the tracing of acoustical rays. A statistical model is formulated and an algorithm for pressure is developed, the conformity of which is examined by two approaches and is shown to give the known results. The concepts that are developed are applied to the determination of the transient field due to a sound source in a homogeneous medium in a rectangular enclosure with perfect reflecting walls, and the results are compared with those presented by Mintzer based on the Laplace transform approach, as well as with a normal mode solution. In contrast with these, the Monte Carlo method is not restricted to the case of perfectly reflecting walls, since absorptive walls can be handled. Possible future developments are indicated which would, it is believed, make the Monte Carlo method a valuable tool when boundary conditions are complex or when the medium is inhomogeneous.

ISSN:0001-4966    

DOI:10.1121/1.1914443

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Dilational vibration modes have been shown to produce an undesirable “coincidence type” response in the sound‐transmission spectrum of lightweight‐core sandwich panels in the medium to high‐frequency range. In particular, it was found that the dilatational coincidence region often occurs at considerably lower frequencies than those coincidence effects produced by flexural vibration. The governing characteristic frequency equations were developed by employing the Rayleigh‐Ritz Energy Principle for a sandwich panel with variable dimensions and properties. The present solution also employs a general strain energy relation without restricting the skin materials to be identical. Eight characteristic natural frequencies representing dilatational, flexural, and longitudinal vibration were determined for the fundamental as well as higher order modes as a function of panel dimensions and material properties. Throughout this study particular attention was given to the influence of core properties on the dilatational natural frequencies. Experimental panels with various face and core materials were tested under random incidence sound‐transmission conditions and found to compare favorably with the theoretical predictions.

ISSN:0001-4966    

DOI:10.1121/1.1914444

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

We discuss initial research on a model of binaural hearing in which the peripheral transduction from acoustical waveforms to firing patterns on the auditory nerves is explicitly described. In most of this initial research, attention is focused on interaural time discrimination, and the processing that follows the peripheral transduction (the central processing) is assumed to be ideal. By imposing limitations on the central processing and computing the consequences for performance, we find that performance at least as good as experimentally observed performance can be achieved with central processing that is substantially restricted.

ISSN:0001-4966    

DOI:10.1121/1.1914445

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The frequency selectivity of the peripheral ear (e.g., at the VIIIth nerve level) is so acute that onset and offset transients in responses to short signals produce a nonnegligible extension of the signal duration. Thus, peripheral excitation patterns produced by signals which were separated in time can overlap and thereby mask each other. We refer to this type of masking astransient masking. Published data on nonsimultaneous masking and the results of two new experiments are compared with the masking that may be expected from filter transients. It is concluded that backward masking is mainly due to interactions at the level of the filter outputs, and that in forward masking, in addition to a short‐term component, a long‐term component is distinguishable. The latter has an exponential decay with a time constant of approximately 75 msec, and is probably related to physiological adaptation effects.

ISSN:0001-4966    

DOI:10.1121/1.1914446

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Recent studies, together with others dating back as far as 1851, leave little doubt that the cavities and convolutions of the pinnae play an important role in the localization of signals that originate in the median plane. Less clearly understood, however, is the nature of the clues that are utilized in arriving at a localization decision. Results of the present study indicate that, insofar as localization in the anterior sector of the median plane is concerned, clues associated with the cavities of the pinna have an important monaural component. Binaural reception also plays a significant role including confining the apparent location of the resultant image within, or near, the median plane. Such a centralizing influence is an essential requirement for optimizing this type of localization. Clues of a secondary nature were found to be associated with the range of frequencies between about 0.7 and 3.5 kHz.

ISSN:0001-4966    

DOI:10.1121/1.1914447

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A comprehensive theory is formulated for the central formation of the pitch of complex tones, i.e., periodicity pitch [Schouten, Ritsma, and Cardozo, J. Acoust. Soc. Amer.34, 1418–1424 (1962)]. This theory is a logical deduction from statistical estimation theory of the optimal estimate for fundamental frequency, when this estimate is constrained in ways inferred from empirical phenomena. The basic constraints are (i) the estimator receives noisy information on the frequencies, but not amplitudes and phases, of aurally resolvable simple tones from the stimulus and its aural combination tones, and (ii) the estimator presumes all stimuli are periodic with spectra comprising successive harmonics. The stochastic signals representing the frequencies of resolved tones are characterized by independent Gaussian distributions with mean equal to the frequency represented and a variance that serves as free parameter. The theory is applicable whether frequency is coded by place or time. Optimum estimates of fundamental frequency and harmonic numbers are calculated upon each stimulus presentation. Multimodal probability distributions for the estimated fundamental are predicted in consequence of variability in the estimated harmonic numbers. Quantification of the variance parameter from musical intelligibility data in Houtsma and Goldstein [J. Acoust. Soc. Amer.51, 520–529 (1972)] shows it to be dependent upon the frequency represented and not upon other stimulus frequencies. The quantified optimum processor theory consolidates known data on pitch of complex tones.

ISSN:0001-4966    

DOI:10.1121/1.1914448

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A phenomenological model for displacement of a point on the basilar membrane is developed by formulating a system of nonlinear differential equations:ẍi(t) + 2Di[1 + ηẋi2(t)]ẋi(t) + ω0i2xi(t) = Cxi−1(t), fori= 1, 2, …, 10, wherex0(t) is the input (stapes displacement) andx10(t) is the output. This model, which behaves effectively linearly at low levels and nonlinearly at high levels, shows that asinglenonlinear system is adequate to account for the followingfrequency‐dependentnonlinear phenomena of the peripheral auditory system: (1) limiting of the output level; (2) decrease ofQwith increasing input level; (3) decrease of the most effective frequency with increasing input level; (4) changes in phase angle of the output with input level; (5) changes in shape of the click response waveform with input level; (6) two‐tone suppression withf1=CFandf2>CF; (7) generation of the combination tone 2f1−f2in response to two tonesf1

ISSN:0001-4966    

DOI:10.1121/1.1914449

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The critical masking interval, the time period during which noise is effective in masking a brief click, was measured in two independent experiments. The first paradigm was the temporal analog of Fletcher's critical band experiment. That is, the click was presented in the temporal center of the noise, and its threshold was measured as the masker duration was varied. The second paradigm investigated the temporal analog of Greenwood's [J. Acoust. Soc. Am.33, 484–502 (1961a)] masking experiment; that is, a click was moved temporally through the noise burst. The two paradigms yielded similar numerical estimates of the critical masking interval. Further, the critical masking interval was not greatly affected by the stimulus' bandwidth.

ISSN:0001-4966    

DOI:10.1121/1.1914450

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The discharge rate of single auditory‐nerve fibers to tone bursts was measured after exposure to continuous tones. Both the exposure tone and the test tone bursts were at the fiber's characteristic frequency. Following exposure, the discharge rate to the test bursts is transiently depressed. For moderate exposures (180 sec or less in duration and less than 80 dB SPL), the recovery of discharge rate to the preexposure level is well described by a single rising exponential. The time constant of the recovery increases as the level or duration of the exposure increases; time constant decreases as the level of the test bursts is increased. For all exposure and test conditions employed, time constants were in the range 1–30 sec. The relevance of these data to hypotheses about the mechanisms of adaptation in the auditory periphery is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1914451

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP