摘要:

A device for stablizing a subject’s head is described which does not depend on earposts, allows for voluntary evacuation by the subject, and can be constructed at low cost. This particular cephalostat is used currently for stabilizing the head in studies of speech production where lip and jaw transduction devices, mounted external to the subject, are employed.

ISSN:0001-4966    

DOI:10.1121/1.381825

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

In recent studies involving the correlation of speech segment durations, the measurement error in locating segment boundaries has usually been ignored or assumed to be constant and small. Since the relative magnitude of the error in locating such a boundary may vary greatly depending upon its phonetic context and the procedures employed, thereby affecting the derived intersegment covariances profoundly, an experiment was designed to estimate these errors directly. Several tokens of four sentences containing syllables differing in the quality, length, degree of stress, and consonantal context of their nuclear vowels were copied onto two‐track tapes and sent to several professional phoneticians with instructions to measure the durations of the indicated vowels, on first one track and then, at least two weeks later, the other. The resulting measurement errors varied systematically in several ways: (1) long, stressed vowels had greater errors than short, unstressed ones; (2) initial voiced stops (/b/) were easiest to segment and approximants (/w/) hardest, with voiceless stops (/k/) and fricatives (/f/) intermediate; (3) great differences among phoneticians did not appear to depend in any obvious way upon the instrumentation used. The minimum standard deviation for measurements of vowel duration by the most accurate phoneticians ranged from about 2 to 5 ms; 95% confidence intervals for carefully measured vowel durations may therefore be expected to range from about 10 to 25 ms, depending upon the consonantal context of the vowel. Because of this range of intrinsic measurability of vowel durations, and therefore presumably other phonetic segments as well, the results of studies using covariance statistics of segment durations should be interpreted cautiously.

ISSN:0001-4966    

DOI:10.1121/1.381826

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The ’’tracking procedure’’ is a method to train and evaluate the reception of ongoing speech. A talker and a receiver engage in a dialogue for a designated period of time in which the receiver reports his perception of successive segments of read text and is corrected by the talker until the text is repeated verbatim. Performance is measured in number of words of text repeated correctly per unit of time. The procedure is illustrated by its application to a project for training and evaluating use of a vibrotactile–electrotactile aid to lipreading. Differences between experimental conditions are described over time in terms of absolute words per minute, percent increment of aided over unaided words‐per‐minute scores, and percent of normal listening rate. Data from identification tests with syllables, words, and sentences are also presented. Tracking is suggested as an additional procedure for communication training in aural rehabilitation or classroom settings and for evaluation of other communication systems.

ISSN:0001-4966    

DOI:10.1121/1.381827

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Preschool children (mean age of 4 years, 6 months) imitated 15 synthesized formant patterns representing both English and alien vowels. The first three formant frequencies of the imitations were measured from spectrograms. Generally, the children were successful in reproducing the relative formant patterns of the stimuli, although they tended to produce alien vowels as proximal English vowels. The reliability of imitation was better for stimuli modeled on English vowels. Combined with earlier results for men, women, and six‐year‐old children, the data are consistent with nearly straight isovowel lines in theF–FandF–Fplanes. The most linear relationship, with a good separation of the mean data for four age–sex groups, was noted for vowel [i]. The results for preschoolers, like those for adult subjects, indicate that the precision of vowel imitation is limited as much, if not more, by auditory resolution as by motor‐articulatory performance, because the formant variability in imitation is commensurate with data on difference limens for vowel formant frequency.

ISSN:0001-4966    

DOI:10.1121/1.381828

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Auditory‐nerve responses and cochlear microphonics are produced in cats by pulsed 5‐MHz ultrasonic energy from a transducer placed against the dura mater. The pulses must be relatively intense (∠30 W/cm2) to produce a response, but can be sufficiently brief (less than 70 μs) that the brain tissue is not observably heated. The cats apparently respond to radiation pressure transients accompanying the absorption of the ultrasound in the brain tissue. Both the amplitude and latency of theN1neural responses to the ultrasound can be matched to those produced by relatively weak tone pips or clicks from an external source. The cochlear microphonic (CM) produced by a pulse shows a prominent ringing at 5–10 kHz in different cats; the amplitude of theN1response exhibits broad maximum, for constant amplitude pulses, at pulse widths of 20–60 μs. This variation ofN1response amplitude with pulse width is similar to that of a high‐pass filter with a cutoff frequency at the dominent frequency of the CM, which is tentatively identified with a ringing frequency of the skull.

ISSN:0001-4966    

DOI:10.1121/1.381829

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Two classes of waveguides are studied: acoustic waveguides conducting pressure waves generated by a constant‐velocity source; and structural waveguides excited by a constant force shaker. The high‐pass cutoff frequencies of propagating modes of both waveguide classes equal the natural frequencies of the corresponding standing‐wave modes of the waveguide cross section. In acoustic waveguides, cutoff frequencies correspond to an infinite impedance at the source. In structural waveguides, cutoff frequencies coincide with vanishing drive‐point impedance, the resonant mode short circuiting the other modes. This distinctive behavior is associated with the prescribed excitations and definition of drive‐point impedance rather than with the nature of the waveguide.

ISSN:0001-4966    

DOI:10.1121/1.381830

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A new ultrasonic imaging system is proposed which uses a moving asymmetric random phase mask with a δ correlated property. It is shown that the system can achieve higher resolution and less attenuation compared with a conventional system using second‐order correlation‐function analysis. The system presented in this letter also has the advantage that it is not affected by additive Gaussian noises which are independent of the signal. The usefulness of the system is demonstrated by experimental results for one‐dimensional objects.

ISSN:0001-4966    

DOI:10.1121/1.381813

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The backward detection masking of 10‐ms tonal targets by a 150‐ms tonal mask was contrasted with the backward recognition masking of the same tones by the same mask. The target‐mask interval required for 75% correct performance was about eight times as great in the recognition condition as in the detection condition. Furthermore, a generalized improvement in performance occurred over the initial course of training in both the detection and recognition conditions. In a second experiment it was found that a remote mask produced greater backward recognition masking but less backward detection masking. That these differences were observed with the same subjects, at the same level of training, and with identical stimuli, indicates that procedural differences alone cannot account for the differences between backward detection and recognition masking.

ISSN:0001-4966    

DOI:10.1121/1.381840

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The purpose of this investigation was to determine the relationship among speakers’ heights, weights, body surface areas, and speaking fundamental frequencies. The recordings of 30 speakers’ readings of a standard prose passage were analyzed by means of the Fundamental Frequency Indicator (FFI) to obtain their speaking fundamental frequency characteristics. The speakers’ heights and weights were obtained by means of standard measurement procedures, and their body surface areas were calculated. Pearson product‐moment correlation coefficients, computed separately for men and women, indicated that speakers’ heights, weights, and body surface areas were not significantly correlated with their speaking fundamental frequencies; female speakers showed a slight negative correlation while male speakers showed a low, positive trend. Implications of these findings and suggestions for future research are discussed.

ISSN:0001-4966    

DOI:10.1121/1.381808

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A simple random‐guessing model of the dichotic two‐response paradigm is used to predict the proportions of single‐ and double‐correct responses at different performance levels. Comparisons with real data show that the proportions of double‐correct responses are generally overpredicted. By introducing an additional free parameter to account for nonindependence of channels (ears), the model is made to fit closer to empirical data, but the value of the parameter is not the same for different sets of data. This may be due to differences in stimulus characteristics between experiments. While the model is oversimplified in many ways, it nevertheless provides a rudimentary formal framework for the interpretation of dichotic data, particularly with regard to changes in the proportions of single‐ and double‐correct responses with performance level.

ISSN:0001-4966    

DOI:10.1121/1.381809

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP