摘要:

The horizontal contact resonance, which is formed by the resonant system due to the mass of a vibration pickup and the contact compliance of a setting point, causes errors in measurement and places restrictions on the measurement frequency range. The characteristics of the horizontal resonance depend on the type and condition of the ground surface and the method of planting the vibration pickup. This paper indicates the characteristics of the horizontal contact resonances of the rectangular vibration pickup with various base shapes, and derives expressions for a coupled motion of the pickup. It is suggested that the horizontal resonance and the response of the coupling system of the rectangular vibration pickup are significantly affected by the height of the center of gravity, the base area, and the base shape. The relationships are represented by a simple curve for the horizontal resonance. The agreements between the analog equations derived here and the values of the measurement on actual fields are well within the accuracy required for engineering analysis. The derived solutions provide adequate accuracy for practical applications to machine foundations with various rectangular bases.

ISSN:0001-4966    

DOI:10.1121/1.384750

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

An acoustic field which varies sinusoidally in time is completely determined by the complex values of its pressure on two concentric spheres. We have developed an experimental procedure which carries out such a measurement. If the source of sound is located inside the inner sphere, we experimentally obtain an expansion in spherical waves whose outgoing and incoming (that is, reflected) components are independently determined. This paper describes both the apparatus and the underlying theory, and presents illustrative results on the wave reflected from the wall of an anechoic chamber.

ISSN:0001-4966    

DOI:10.1121/1.384751

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

We suggest that a class of speech coders can be designed from criteria that are perception‐specific. Such a class represents a middle ground between ’’waveform’’ coders and speech‐specific ’’source’’ coders. We argue that, within perceptually acceptable limits, a bandpass portion of a speech signal can be represented by its short‐time spectral amplitude ‖ Sn ‖ and its phase derivative ?n. Both parameters are evaluated at the center frequency ωnof the passband whose spectral width isWnrad/s. We show that the short‐time spectral amplitude is identical to the Hilbert envelopeAnof the passband waveform. As a by‐product, we show that the bandwidth occupied by bothAn2andAn2?nis the same as that for their parent bandpass signal, but their spectra are translated to the range 0 toWn. No comparable statements can be adduced forAnand ?n, but on practical grounds, we conjecture that useful low‐pass limits of less thanWn/2 can be applied to both. Finally, we outline techniques to utilize the passband parametersAn, ?n,An2andAn2?nin digital voice coding.

ISSN:0001-4966    

DOI:10.1121/1.384752

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

We report a series of computer experiments aimed to increase our understanding about the sufficiency of the short‐time amplitude spectrum for speech coding, and to examine how bandpass segments of the speech spectrum might be represented parametrically. For this purpose we utilize the absolute value of the short‐time Fourier transform and the time‐derivative of the short‐time phase, evaluated at frequency intervals chosen according to auditory criteria. We analyze and digitally encode these parameters. We find that a frequency resolution corresponding to contiguous 1/6‐octave bands, spanning the range 200 to 3200 Hz, is a perceptually satisfactory design, and permits digital coding of respectable quality at transmission rates in the range 20 to 16 K bits/s. We also find that a combination of subband coding and short‐time spectrum coding leads to comparable results and provides added economy in processing.

ISSN:0001-4966    

DOI:10.1121/1.384753

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

In order to determine whether the concept ’’phoneme boundary’’ has validity independent of the particular experimental paradigm used to measure it, four procedures were used to locate phoneme boundaries on two acoustic continua: a VOT continuum, and a formant transition continuum. The procedures were a standard identification test, a version of the method of adjustment, an adaptive psychophysical procedure (PEST), and a version of the method of limits. The procedures differed in reliability, and there were substantial individual differences in the locations of the phoneme boundaries, but the correlations between boundary locations for each subject found by the different methods were quite high. Thus the ’’locus of the phoneme boundary’’ represents an internal variable which can be measured in a number of different ways. We also examined a subsidiary question. A hardware synthesizer does not produce identical waveforms given the same stimulus parameters twice. Do these different tokens produce the same perceptual responses? In the identification tests, different tokens of the various stimuli elicited different average rating responses. Thus, there are reliable (but quite small) token effects for synthetic speech stimuli which can affect phonetic perception.

ISSN:0001-4966    

DOI:10.1121/1.384754

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

This paper addresses the question of whether the nonlinear amplitude response of the ear depends only on stimulus level or on both level and frequency. The level of the quadratic distortion productfh+flwas estimated using the tone‐on‐tone masking paradigm under a 2AFC transformed UP–DOWN procedure. The higher frequency tone (fh) was maintained at 1.2 times the lower (fl=250, 500, 1000, or 2000 Hz). Changes in the maximum and minimum threshold as maskee phase changes, [the monaural phase effect (MPE) amplitude], changes in the phase of the aural distortion product, and changes in the growth of the combination tone amplitude were examined as functions of primary frequency and level. The results indicate that MPE amplitude is simply a function of S/N ratio between the combination tone and the masking at that frequency. Distortion product phase varies over 360 ° with respect to the primary tones and is unrelated to primary frequency or intensity. Within listeners the range of distortion product phase is more narrow (70–90 deg) at a single frequency. The absolute level of the summation tone does not correlate well with primary frequency and the growth rate of the combination tone varies with frequency and observers over a range of 1.1–2.3 dB/dB. The results suggest frequency independent nonlinearity when the ratio of primary frequencies is constant.

ISSN:0001-4966    

DOI:10.1121/1.384755

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Consistent lateralization judgement can be obtained with interaural delays in the envelope but not in the carrier of high‐frequency sinusoidal signals that are amplitude modulated. At low frequencies the situation is reversed and delays in the carrier, but not the envelope, can be detected. Delays in quasi‐frequency‐modulated or frequency‐modulated waveforms allow lateralization by some observers but require much larger delays for performance as good as that obtained with amplitude‐modulated signals. The implications of some of these observations for models of the envelope extraction process are discussed.

ISSN:0001-4966    

DOI:10.1121/1.384756

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Evidence is provided from forward masking conditions of an auditory detection study demonstrating that an early temporal integration system summates auditory information for 3 msec or less. The output of this early system is the input to another system that applies a compressive nonlinear transformation and summates auditory information for a considerably longer period of time.

ISSN:0001-4966    

DOI:10.1121/1.384757

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Perceptual dimensions underlying similarity ratings and preference judgments of the quality of hearing‐aid‐processed speech were derived via multidimensional‐scaling procedures, and were correlated with 15 indices of electroacoustic performance to determine those electroacoustic characteristics contributing maximally to quality judgments. Connected discourse was tape recorded through 20 conventional hearing aids and presented in a paired‐comparison paradigm to ten normal listeners for similarity ratings and quality preference judgments. Analysis of the group similarity matrices revealed only one definitive perceptual dimension, low‐cutoff frequency, that was common to the listeners. In a three‐dimensional INDSCAL solution, this electroacoustic factor correlated −0.87 with dimension 1. Listeners strongly preferred hearing aids with relatively low low‐cutoff frequencies; dimension 1 correlated −0.76 with their preferences. The quality judgments of some listeners were found via KYST analysis to exhibit a multidimensional structure, with low‐cutoff frequency remaining the most salient dimension. Secondary dimensions varied across these several listeners, and included response irregularity, equivalent input noise level, high‐cutoff frequency, and intermodulation distortion. Thus, the data provided evidence that, while low‐cutoff frequency dominates listener judgments, a multidimensional model may underlie the perceptual strategies used by some listeners to form quality judgments of hearing‐aid‐processed speech.

ISSN:0001-4966    

DOI:10.1121/1.384758

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Changes in the pitch of a short tone pulse (25 msec, 1000 Hz), following a leading tone, were measured at various leading‐tone frequencies and for various time intervals between the leading tone and the tone pulse. The results show that poststimulatory pitch shifts away from the pitch of the leading tone are significant and reproducible. It is suggested that poststimulatory pitch shifts may influence the results of various psychoacoustic experiments on pitch perception.

ISSN:0001-4966    

DOI:10.1121/1.384759

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP