摘要:

The low‐frequency voltage/pressure sensitivity of piezoelectric right circular cylinders is derived for three common polarization schemes. The acoustic pressure on the three major surfaces is considered variable, thereby allowing for any configuration of shielding. Derived sensitivities are illustrated for a common piezoelectric ceramic material (Clevite PZT4).

ISSN:0001-4966    

DOI:10.1121/1.2016350

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

It is well known that earthquakes can be devastating in terms of life and property. Along with the preservation of life, one of the more important concerns during these natural disasters is the survival of vital power and communications equipment. Over the past several years significant progress has been made in seismic design and analysis, and in techniques for simulation of seismic loads for purposes of equipment qualification. A review of the present state of the technology is presented with particular emphasis on seismic design approaches and test capabilities.

ISSN:0001-4966    

DOI:10.1121/1.2016356

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Previous papers reported on the use of a nonlinear differential equation (containing a Ramberg‐Osgood term) to represent the inelastic, seismic behavior of a single‐story steel frame. The structure was tested on the shaking table at the Earthquake Engineering Research Center at the University of California, Berkeley. The correlation between the predicted and measured acceleration time histories was exceptionally good. However, the computed displacement time histories did not predict the permanent offset experienced by the structure. The reason for this shortcoming is that the hysteretic behavior of virgin steel is different in the first inelastic excursion than it is in subsequent excursions. The Ramberg‐Osgood model can represent only the subsequent hysteretic behavior. To alleviate this deficiency, the present paper presents a two‐phase model. One set of parameters is established for the initial phase of the response, in which hysteretic behavior is approximately elastic, perfectly plastic; and another set is established for the second phase, in which the hysteretic behavior has a more rounded transformation from elastic to plastic deformation. The importance of this work lies not so much in its application to steel, as in its potential for application to degrading materials like reinforced concrete and masonry.

ISSN:0001-4966    

DOI:10.1121/1.2016360

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

This research investigates the effect of ear protectors on the intelligibility of speech in noise. The listeners are adults, 35–65 years old, with normal hearing, bilateral high frequency or flat loss between 500 and 4000 Hz. They may be fluent or poorly conversant with spoken English. Taped lists of 25 words are presented free field under a variety of conditions in which the signal‐to‐noise ratio (+5 and −5 dB), the spectrum of the background noise (white versus crowd), and the presence of ear protection are varied. Preliminary data indicate that in normal listeners the number of words correctly repeated decreases as signal‐to‐noise ratio decreases and that speech perception is poorer in noise than in quiet. When ear protectors are worn for speech presented in crowd noise some improvement in hearing is evident. In contrast, for this condition subjects with a high‐frequency loss show a marked deterioration in performance. [Work supported by Ontario Min. Health.]

ISSN:0001-4966    

DOI:10.1121/1.2016366

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

There have been many attempts at speech transposing for the deaf by bringing speech information into lower‐frequency bands to make use of residual low‐frequency hearing. Because of the unusual hearing loss configuration referred to in the previous paper, it was decided to try translation in the opposite direction (i.e., to the high‐frequency residual hearing band). This presentation will describe the hearing aid, construction, present some speech recorded through the aid, and discuss some considerations taken to insure the aid did not jeopardize the patients' residual hearing. Patients' experiences with the aid (lowering of speech detection threshold, distinguishing tone glides, and increased awareness of the environment) will also be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2016371

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Various types of acoustic cues have been shown to influence the voiced‐voiceless decision for initial prestressed consonants. In the present study, a selective adaptation method was used to investigate possible feature extraction devices underlying the perception of voicing. Two [da‐tha] continua were constructed, each ranging in voice onset time (VOT) from 0 to 55 msec in 5‐msec steps. The total transition duration of each stimulus was 15 msec in one series and 70 msec in the other. Differential effects were obtained for within‐ and cross‐series adaptation along a VOT dimension by presenting an adapting stimulus from each series with the same absolute VOT(25 msec). The present results support the view that models of voicing perception based strictly on absolute VOT detectors are inadequate. Further, they suggest that a sequence of decisions grounded in cue extraction is the basis for the voicing percept.

ISSN:0001-4966    

DOI:10.1121/1.2016376

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The perceptibility of various phonetic features during word recognition was assessed by having listeners detect systematic mispronunciations of words in a short story. Mispronunciations were produced by changing a single‐consonant segment to produce a nonsense word (e.g., “boy” to “poy”). The rationale behind the experiments was that, in order to perceive a word as mispronounced, the listener must make a phonetic discrimination. Therefore, the listening for mispronunciation task examines the use of phonetic information during the process of recognizing words from fluent speech. The results of six experiments revealed that changes involving prestressed word‐initial‐stop consonants were detected more often than changes involving any other consonant. Thus, voicing changes were better detected in stops than in fricatives (70% versus 38%). Changes in manner of articulation were also better detected in stops than in fricatives (84% versus 53%). Changes in place of articulation in stops were better detected than place changes in nasals (77% versus 64%) and voicing changes in stops were better detected than place changes in nasals (75% versus 69%). Voicing and place changes in stops were consistently well detected (at least 70%) over three speakers differing in speech style and rate. The results showed that phonetic features are more perceptible in stops than in other consonants in fluent speech. The results suggest that stop consonants in word‐initial position provide the most important and reliable phonetic information about a word's identity in fluent speech. They therefore play a special role in the word recognition process.

ISSN:0001-4966    

DOI:10.1121/1.2016379

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Differences in acoustic memory effects between consonants and vowels have led to the assumption that transience of the acoustic signal may affect persistence in immediate memory [Crowder, J. Verb. Learn. Verb. Beh.10, 587–596 (1971); Crowder, J. Exp. Psychol.98, 14–24 (1973)]. The present study was undertaken to determine whether less transient consonants are more persistent than natural stop consonants. Stop stimuli with lengthened F2 and F3 transitions employed in a perceptual study reported on at the last meeting of this society were utilized. Data resulting from stimulus suffix and recency effect tests indicate that these stimuli give results characteristic of short‐transitioned stops. Thus, transience is not a factor in acoustic storage.

ISSN:0001-4966    

DOI:10.1121/1.2016387

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A model of the utterance production process is proposed in which segmental substitution errors arise from confusion between two simultaneously available and similarly represented planning segments. This model predicts that each segment will serve equally often as the intended target and as the intrusion in errors. Further, the relative frequency that intended segment typexis replaced by intrusion segment typeyshould be the same as the relative frequency thatyis replaced byx, for allx≠yof the confusion matrix. These predictions are confirmed by the pattern of substitutions for 23 consonantal segments in two independently collected corpora of 1351 and 1471 errors. A small number of consistent exceptions are discussed in light of a patatalization process that occurs in spoken English. One interesting implication of these observations is that “stronger” segments do not tend to replace “weaker” segments in speech errors, no matter what the definition of strength. (Work supported in part by an NIH grant.]

ISSN:0001-4966    

DOI:10.1121/1.2016393

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Fundamental theories for noise generated by flow over surfaces exist for only a few simple surface shapes. The role of turbulence in noise generation by complex surfaces should be essentially the same as for simple surfaces. Examination of simple‐surface theories indicates that the spatial distributions of the mean velocity and turbulence (intensity, spectra, and integral scale length) are sufficient to define the noise emission. Measurements of these flow properties were made for a number of simple and complex (STOL aircraft blown flaps) surfaces. The configurations were selected because their acoustic characteristics (i.e., shape of radiation pattern and velocity power law) are quite different. The spatial distribution of the flow properties around the complex surfaces and approximate theory are used to qualitatively explain the varied acoustic characteristics. The data properties possess some simplifications, which can be used in the theories. The major simplification is that the turbulence spectra are essentially described by the isotropic turbulence relationship, independent of the surface configuration and of the location in the flow field. This result is used to partially explain why the shape of acoustic spectra vary little and why acoustic model data accurately scale to larger size.

ISSN:0001-4966    

DOI:10.1121/1.2016400

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP