摘要:

Profoundly deaf persons hear only time and intensity variations in amplified speech and must rely on lipreading to perceive speech segments [N. Erber, J. Acoust. Soc. Am.51, 1224–1227 (1972)]. These persons may perceive prosodic features of sentences by hearing. It is not known whether linguistically significant variations in duration and intensity of speech segments are perceived by reference to the inherent duration of those segments and thus, are dependent upon intelligibility. Subjects responded to three sentence tests wherein the sentences differed in either phrase‐structure, major constituent boundary (MCB), or contrastive stress. Responses were by forced choice to the prosodic features; subjects were not required to identify words. Stimuli were presented under audition‐alone, vision‐alone, and audiovisual conditions. The acoustic signal was noise, amplitude modulated by the sentence materials. The audiovisual condition resulted in highest mean scores. Identifying phrase‐structure, audition‐alone scores were near chance levels. Vision‐alone and audiovisual scores were close in value, suggesting that time and intensity cues supplemented visual cues to a small extent. Identifying MCB location, vision‐alone scores were near chance levels. Audition‐alone scores were equivalent to audiovisual scores, suggesting that time and intensity variations provided primary cues. Identifying contrastive stress location, score data suggested that the acoustic signal allowed detection of contrastive stress and the exact word was located with visual cues. These results indicate that an unintelligible speech signal may supplement lipreading by providing certain prosodic information, increasing perceptual strategies available to profoundly deaf persons.

ISSN:0001-4966    

DOI:10.1121/1.2004250

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

In order to improve the recognition of consonants by our tactual vocoder [T. Ifukube, 9th ICA, I‐72 (1977)], a tactually cued vocoder was designed for the deaf. In this apparatus, the acoustic cues of Japanese monosyllables were extracted automatically in real time using a microprocessor. These cues were displayed on a small vibrator matrix with 16 × 6 piezoelectric devices so as to be perceivable by the vibrotactile sense of a fingertip. Experimental results showed that unvoiced consonants, except plosives, could be detected at about 90% correct rate. Sixty‐eight Japanese monosyllables were separated into three groups (fricatives, plosives, and others) and were detected at a rate of about 80% correct. The possibilities for the practical use of our cued vocoder were discussed based on the results of tactile speech recognition by the deaf.

ISSN:0001-4966    

DOI:10.1121/1.2004260

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Piezoelectric polymer has several unique properties compared with conventional piezoelectric materials, namely (1) low acoustic impedance, (2) high flexibility, (3) a relatively low dielectric constant, (4) high breakdown voltage, (5) resistance mechanical and thermal shock. A thin sheet of wide area can be easily produced, and it can be properly given local piezoactivity. At the present stage, polarized stretched films of polyvinylidene fluoride (PVDF) are considered to be most promising in practical use. Various transducers with PVDF films have been developed in the field of acoustics from audio engineering to ultrasonics, such as microphones, headphones, loudspeakers, electromechanical transformers, ultrasonic transducers, and so on. Principles and constructions of these transducers especially for ultrasonics are described including several new constructions which have been recently proposed. Applications of these transducers to electronic devices as well as ultrasonic imaging systems are also described.

ISSN:0001-4966    

DOI:10.1121/1.2004263

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Analog‐to‐digital conversion is required for digital processing of signals in a number of areas of acoustics. Examples include voice communications, underwater sound, acoustic imaging, and room acoustics. For each such signal, analog bandlimitation (prior to sampling and quantizing) is necessary to prevent aliasing distortion. Typically, the bandlimitation is accomplished by electrical filtering. As the cost of integrated digital logic diminishes, the expense of electrical filtering becomes a significant part of the total conversion cost. Similar factors apply in the desampling operation, or digital‐to‐analog conversion. We report here a design technique for acoustic filters which can perform the requisite band limitation. The filters can be made an integral part of the transducer assembly, both for transmitter and receiver. We present theoretical designs for fourth‐ and sixth‐order low‐pass filters that are appropriate for voice digitization, and we evaluate these designs by computer analysis. Next, we show physical implementations of the filters, and assemble them with two types of electret microphones. Finally, in an anechoic environment, we make acoustic measurements on these devices and demonstrate the validity of the theoretical design.

ISSN:0001-4966    

DOI:10.1121/1.2004267

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Various types of ultrasonic detectors for use in liquids over the frequency range 0.5–10 MHz are being constructed employing thinfilm piezoelectric polymers. These include small‐diameter probes, linear elements, annular rings, and other configurations. Their response characteristics are being evaluated using acoustic impulse techniques. Experimental data will be presented that indicate the possibility of their use as broadband nonintrusive (i.e., acoustically transparent) detectors of ultrasound in water and other liquids. [Work suggested in part by DNR.]

ISSN:0001-4966    

DOI:10.1121/1.2004269

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

“Outdoor living” suggests voluntary exposure to weather and other stimuli, among them noise. The effects of noise on outdoor living are functions of societal factors, the purposes of being outdoors and, of course, the intensity, quality, and source of the noise. This paper discusses some of the concepts involved in relating noise to outdoor living, a brief history of the subject, and current research as reflected by the papers presented at the May 1978 ASTM Community Noise Symposium, as well as by other sources. Included are comments on community noise impact on hearing, human response to transportation noise, and speech interference and community annoyance.

ISSN:0001-4966    

DOI:10.1121/1.2004278

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

This paper presents an overview of noise impact considerations in modern Hawaii, emphasizing those which are different from most mainland situations. The favorable year‐round climate encourages outdoor recreation in public parks and the natural ventilation of residential and school buildings. However, this lack of closure often causes the noise from modern transportation systems to be excessive. Also, because of limited useable land, the high density of open housing often causes problems with acoustical privacy. Examples of the variation in freeway traffic noise with height in an “open” high‐rise building will be shown. The high background noise levels created by the tradewinds in certain tropical foliage will be cited and examples shown of use as an acceptable masking noise. Likewise, the use of surf noise in planning deluxe condominium complexes will be cited. Two unique transportation noise sources will be discussed: 24‐h sugar cane hauling operations and gas‐turbine‐powered interisland hydrofoils. Noise‐abatement efforts at Honolulu International Airport will be cited, including the effectiveness of a new runway built on an ocean reef and a fixed, 15‐sensor noise‐monitoring system with a unique feature to log aircraft type automatically. Some noise problems related to the tourist industry will be discussed, e.g., the containment of entertainment sounds, tour bus noise, and hotel mechanical equipment noise affecting naturally ventilated homes.

ISSN:0001-4966    

DOI:10.1121/1.2004280

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

In recent years computer models have been developed that make it possible to calculate the day‐night levels around airports at a reasonable cost. Determining the number of people exposed to various noise levels has always been a time‐consuming and expensive operation because it required extensive manual data gathering. This paper discusses how the output from an airport noise prediction model (NOISEMAP) has been modified so that the output is suitable as input into a commercially available computer program that automatically collects demographic data within an arbitrary polygon. A discussion of how the information produced can then be used in environmental impact reporting is given. This includes using the fractional impact method for defining impact.

ISSN:0001-4966    

DOI:10.1121/1.2004289

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Measurements of the absorption coefficient of ultrasonic waves is in all cases larger than can be explained by viscosity and heat conduction. The benchmark paper by Herzfeld and Rice [Phys. Rev.31, 691 (1928)] introduced a third factor, namely vibrational relaxation, which for many substances accounted for most of the excess absorption. The remaining excess absorption has led to the concept of a volume viscosity, which has been historically associated with structural and other relaxation mechanisms. We have observed that when accurate absorption data is available for such diverse substances as gases, liquids, and polymers in which there is an absence of vibrational and structural (e.g., water) relaxation mechanisms, the ratio of volume to shear viscosity is exactly 2/3. We present numerous data to support this. The consistency of this ratio, and its temperature independence, suggests that the viscous counterpart to the Lamé constant λ″ is negligibly small. That is,ηv = λ″ + 2ηs/3, ηv/ηs≈ 2/3, therefore λ″ ≈ 0. Furthermore, if λ″ ≈ 0, α/αclass= 1.5 is to be expected, and therefore, in the many substances where this is observed there is no need to postulate a structural relaxation mechanism beyond that which leads to shear viscosity. Finally, when ηv/ηs>2/3, as in the case of water, λ″ is greater than zero. The meaining of λ″ as a measure of structural relaxation is explored.

ISSN:0001-4966    

DOI:10.1121/1.2004292

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The ultrasonic absorption of 1‐proline, 1‐serine, and 1‐arginine were measured in the frequency range of 3–90 MHz using an automatic recording ultrasonic spectrometer. Ultrasonic velocity was measured at 5 MHz using a single‐crystal interferometer of a variable path, and hypersonic velocity was measured by Brillouin scattering. To study the reaction, appropriate pH values were achieved by the addition of NaOH. Ultrasonic absorption as a function of pH value in all amino acids show a maximum, and so it is considered that the obtained excess absorptions are due to proton transfer reaction. The observed spectra of 1‐proline and 1‐serine have been analyzed in terms of single relaxation behavior, and the rate constants and the volume change have been obtained. Ultrasonic absorption of 1‐arginine show two relaxations due to α‐amino group and β‐guanidine group. In the latter one, the ultrasonic absorption α/f2was constant below 90 MHz, and then the relaxation frequency would be in the far region above the present experimental frequency. Therefore, the ultrasonic velocity at 5 MHz was compared with the hypersonic velocity.

ISSN:0001-4966    

DOI:10.1121/1.2004294

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP