摘要:

An experimental frequency multiplex system has been completed for with a 10‐channel voice‐excited vocoder. This system reduces the band width required for speech transmission from 3 to 1.4 kcps, thereby achieving a bandwidth reduction of better than 2:1.

ISSN:0001-4966    

DOI:10.1121/1.1919308

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A scheme for detecting the fundamental periods of speech signals is described. It is based on the output signals of contiguous bandpass filters and their Hilbert transforms.

ISSN:0001-4966    

DOI:10.1121/1.1919309

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

In this Letter, it is shown that a recently, proposed “vector” pitch detector is equivalent to an autocorrelation pitch detector.

ISSN:0001-4966    

DOI:10.1121/1.1919310

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The weighted average normal mechanical impedance of a circular area on an elastic half‐space does not depend markedly on the assumed pressure distribution. Its absolute value is almost independent of frequency at least until the wavelength m equal to the circumference of the circular contact area, but the loss tangent varies almost linearly with frequency up to a value of about 1 at this cutoff. These conclusions are valid only for structures large as compared with a wavelength.

ISSN:0001-4966    

DOI:10.1121/1.1919313

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The implicit restrictions of Pachner's analyses, for the determination of the farfield directivity function from nearfield measurements [J. Acoust. Soc. Am.28, 86–92 (1956)] are discussed, with extension and clarification of recent comments [J. Acoust. Soc. Am.35, 1666–1667 (1963)]. Pachner's analyses appear inadequate to describe radiation from even cophasal vibration of a finite surface, except as an engineering approximation for flat surfaces with large rigid baffles.

ISSN:0001-4966    

DOI:10.1121/1.1919314

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

This paper postulates as a worthy, but often overlooked, objective of acoustical research the discovery, definition, and development of means to achieve an acoustical environment that shall be most conducive to man's welfare, his health, his enjoyment of the arts, his means of self‐expression. The ways in which much acoustical research and the applications thereof to architectural and psychological problems deviate from or ignore this ideal are cited. Means to achieve it are proposed.

ISSN:0001-4966    

DOI:10.1121/1.1919315

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A 12×4×4‐ft model tank is utilized to measure the underwater acoustic backscatter from a wind‐driven surface. A single transducer is used to transmit and receive a 0.1‐msec pulse at a repetition rate of 1000 pulses/sec. The carrier frequency is varied in the range from 200 kc/sec to 2 Mc/sec, which gives an acoustic wavelength/root‐mean‐square water‐waveheight ratio from 0.2 to 2.0. Observations of the relative energy return are made as a function of the incident angle for a fixed path length. A mathematical model is hypothesized that predicts the backscattered energy as a function of incident angle, transducer‐beam pattern, frequency, and surface statistics. Curves are presented that compare the observed data with the mathematical model. [This investigation supported by the Acoustics Program, U. S. Office of Naval Research, and the U. S. Naval Underwater Ordnance Station, Newport, R. I.]

ISSN:0001-4966    

DOI:10.1121/1.1939190

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Preliminary results are given on a comparative study of various objective talker‐recognition procedures, based on spectrographic analysis of 7 replicate utterances of each of 10 words by each of 10 different speakers. The spectrograms are quantized into 17 frequency channels and approximately 50 time channels. Different summarizations are applied to the spectrograms, including marginal energies, totalled across time, in each frequency channel; marginal energies for each time channel; and momentlike descriptions of energy distribution of the time margin. Various combinations of these summarizations were used as inputs to different multivariate distance measures, including (a) distance from unknown to a speaker centroid, using a metric based on a covariance matrix pooled over all speakers; (b) distances based on eigenvectors, using a classical discriminant‐analysis approach; (c) distances based on metrics, employing individual speaker covariance matrices. Percent correct identification varied from 22% (discriminant analysis, using one eigenvector of energy margin on time) to 97% [distance (a) applied to the frequency margins]. Frequency classification of energy is better than time classification; distance (a) is better than the others; certain words are much better than others.

ISSN:0001-4966    

DOI:10.1121/1.1939195

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

As part of a long‐term study on the growth of patterning in children's language, a considerable body of spontaneous speech was collected from children in grades 1 through 5 and from adults. The speech was recorded with a pair of condenser microphones on two tracks. Phonetic transcriptions were made using a 41‐symbol alphabet. Editing and normalization were shunned so that the statistical analysis could be used in studies of speech perception, learning, psycholinguistics, and linguistic structure. Phonetic transcriptions were analyzed by digital computer. The major data are (1) frequency distributions of singlets, pairs, and triplets, (2) mean phonetic “word” and “sentence” length, (3) the Markovian information in the sequential constraints of successive pairs and triplets, and (4) various distributions induced on the basic ones by linguistic rules, e.g., place and manner of articulation, stress, and intonation. Comparisons show the free speech of children and adults to be remarkably similar both in the distribution of units and in sequential structure. Implications of our findings for research in speech and psycholinguistics are discussed. [Work supported by the U. S. Department of Health, Education, and Welfare.]

ISSN:0001-4966    

DOI:10.1121/1.1939201

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A simple analysis shows that, when a transient plane wave in an elastic medium is reflected at a plane boundary with a lossy medium, the transient waveform of the reflection is affected by the loss parameters of the second medium. If the attenuation in the second medium is small and if the ρcproducts of the two media are matched, then the reflected waveform is the convolution of the incident waveform with the integral of the Fourier transform of attenuation as a function of frequency. Thus, attenuation for a lossy solid or liquid can be obtained by this external‐pulse technique. Where attenuation is some simple function of frequency, its Fourier transform is some recognized generalized function. Sample waveforms have been observed, using airborne sound in specially prepared tubes.

ISSN:0001-4966    

DOI:10.1121/1.1939206

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP