摘要:

The U. S. Army Corps of Engineers Construction Engineering Research Laboratory has sponsored research to determine the cost benefit relationships for Army housing construction noise abatement. Before these cost benefit relationships could be obtained, realistic analytical models of construction site noise emissions were developed. The models were compared with noise measurements of construction activity at Fort Hood, Texas. Data comparing the construction noise model with noise measurements for different phases of construction are presented and discussed. The construction noise models are used together with proposed acceptability criteria to quantify the degree of noise abatement required at Fort Hood, Texas. Data were obtained and are presented for the costs of various construction equipment and site noise abatement methods required to achieve property‐line or noise‐sensitive land‐use criteria sound levels. Preliminary noise‐abatement cost benefit relationships are presented.

ISSN:0001-4966    

DOI:10.1121/1.2015668

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Direct radiator and horn loudspeakers present many different array problems. Some of these, such as the change in the directional radiation patterns as a function of size and frequency and the development of columar loudspeaker designs have received considerable attention in the literature. Others, however, such as the arraylike interaction of individual drivers in a single loudspeaker and the performance of large arrays of wide‐bandwidth loudspeaker systems have been given considerably less treatment. This paper will review these topics using array analysis considerations.

ISSN:0001-4966    

DOI:10.1121/1.2015673

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A group audio teleconferencing system (GATS) is an audio communications link between groups of people in different locations. Its operation depends in a complex manner on the operation of the system components: room acoustic environments, terminal equipment, transmission facilities, and conference bridges. The main problems encountered are room reverberation, room and circuit noise, chopping of speech by voice switching, and loss contrast (differences in speech levels from various rooms). Solutions to problems of reverberation will be discussed in accompaning papers (Stockbridgeet al.and Curtiset al.). This paper discusses solutions to the problem of loss contrast, in particular, use of standard level sound source in alignment and testing of GATS. References will be made to a working example of GATS—the General Service Administration Teleconference System.

ISSN:0001-4966    

DOI:10.1121/1.2015681

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

During the launch and ascent flight phases for large space vehicles such as the Space Shuttle, the vehicle itself and the payload it carries can be subjected to high‐level acoustic energy produced by the first‐stage rocket motors. It is highly desirable that certain vehicle and payload components be environmentally qualified before flight and considerable effort has been expended in the search for suitable noise sources that could be used conveniently for the proof testing of space‐vehicle structures and payloads. It had been suggested that the exhaust noise of a Nike solid propellent rocket motor might be suitable to reproduce the interior noise environment that had been predicted for the Shuttle Orbiter cargo bay during lift off. The Nike motor is easy to handle, readily available in reasonable quantity, and relatively low in cost. In order to document the noise field of a typical Nike motor during static firing, noise measurements were recently accomplished at the NASA Wallops Flight Center during the firing of two Nike boosters. The boosters were mounted vertically with the exhaust nozzle up and an array of 16 microphones was located around the test stand. Two boosters of different ages were fired in order to determine the degree of correlation between noise measurements made on motors having different loading dates. This paper presents the results of these measurements in octave and 1/3‐octave form along with appropriate overall noise‐level listings. There was very good agreement between the data as measured for the two Nike motors tested although the first motor was loaded in 1955, and the second motor was loaded in the early 1970's. As applied to the specific case of the Space Shuttle; the noise field of the Nike motor provided a reasonable reproduction of the estimated interior noise levels for the cargo bay in the frequency range of 63–1000 Hz.

ISSN:0001-4966    

DOI:10.1121/1.2015685

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Three acoustics research projects which have successfully used continuous tone color CRT display techniques will be discussed. (1) A 16‐mm movie will be show which displays the vibrational mode shape of a free‐flooded, piezoelectric cylinder transducer, as well as the nearfield pressure patterns which change as a function of time. This movie was produced for NUC by Dr. Henry Christiansen of Brigham Young University, using equipment at the University of Utah. Data was provided by NUC using mathematical models based on finite‐element methods. (2) Slides will be shown of additional three‐dimensional displays generated at NUC using a computer program, MOVIE‐NUC, which was adapted by Christiansen to run on NUC equipment. One such example is for an ambiguity surface displayed in three dimensions using color contours to enhance the intensity component. (3) An additional application to be shown will be slides of two‐dimensional displays of large ocean areas. Pacific and Atlantic Ocean bathemetry data will be displayed using color contours. Other parameters to be displayed include the amount if intrusion of the ocean bottom into the sound channel and shipping density.

ISSN:0001-4966    

DOI:10.1121/1.2015697

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The present study investigated perceptual cues for the word‐final fricative‐affricate contrast, e.g., as indish‐ditch. When the closure interval between vowel and fricative indishis increased, listeners perceiveditch. The duration of closure interval necessary for the perception of the affricative varies as a function of both friction rise time and friction duration. Thus, duration of closure interval, duration of friction, and friction rise time can be traded off in the perception of an affricate. The phonetic equivalence of these acoustically dissimilar cues can be readily accounted for on the view that they are the distributed acoustic consequences of the gestures that distinguishdishfromditch. To suggest this, of course, is to suggest a link in speech between perception and production. [Work supported by NICHD.]

ISSN:0001-4966    

DOI:10.1121/1.2015715

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A series of four adaptation experiments using Thai subjects is being carried out in order to investigate a possible phonetic contribution to adaptation effects on a voicing continuum. Thai subjects divide a VOT continuum into three phonological categories at the labial and dental places of articulation but only two phonological categories (voiceless inaspirates and voiceless aspirates) at the velar place. The effects of −70‐msec labial and velar adaptors on both a labial and a velar VOT continuum were determined. If there is a phonetic contribution to adaptation, a −70‐msec velar adaptor should produce a significant boundary shift between voiceless inaspirates and voiceless aspirates on both the velar and the labial VOT continua, while a −70‐msec labial adaptor will affect neither boundary. If, however, adaptation takes place solely at an acoustic level, both adaptors will shift the boundary between velar voiceless inaspirates and voiceless aspirates, but will not affect the boundary between labial voiceless inaspirates and voiceless aspirates. Preliminary results indicate the presence of a phonetic contribution to the adaptation effect. [Work supported by NICHD.]

ISSN:0001-4966    

DOI:10.1121/1.2015728

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Synthetic stimuli (generated at Haskins Laboratories) were used to elicit monaural identification and discrimination data for two seven‐step place continua /ba‐da; pa‐ta/, and two seven‐step voicing continua /ba‐pa; da‐ta/. Five subjects who demonstrated categorical perception participated in three dichotic experiments. Using the same stimuli, dichotic experimental tapes with stimulus onset asynchonies ranging from 0 to 200 msec were made. Subjects were instructed to identify the stimulus presented to the right ear, which was always the leading syllable and a canonical form (step one or seven of the four continua). The first experiment employed canonical forms as the masker. Experiment two used stimuli from steps two‐six from the voicing continua whereas experiment three used corresponding stimuli from the place continua. The target intelligibility data from experiments two and three were compared with data collected with data collected from experiment one and the monaural experiment. The influence of acoustic versus phonetic competition in the dichotic backward masking paradigm is discussed. [Work supported in part by NIH and Sigma XI.]

ISSN:0001-4966    

DOI:10.1121/1.2015734

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Previous research [K. M. Dewar, L. L. Cuddy, and D. J. K. Mewhort, “Human Learning and Memory,” J. Exp. Psych.3, 60–67 (1977)] has shown that the pitch of a single tone from a tone sequence was recognized more accurately when recognition was tested within the context of the original sequence that when it was tested in isolation. Relational factors, e.g., pitch contour and interval coding, may operate to help overcome the basic limitations on processing the pitch of isolated tones. The role of pitch versus temporal context and the effect of contour changes were examined. Musically trained and untrained listeners were presented with partial‐context and full‐context conditions (where they were given some information about the pitches surrounding the test pitch) along with a temporal‐context condition (where they were given information only about the temporal position of the test tone). Random seven‐tone sequences generated by a PDP‐11 computer were used, each tone being presented for one‐half second. For all listeners, performance was better in the partial and full‐context conditions than in the temporal‐context condition. Listeners made significantly more errors when the contour (the pattern of ups and downs) of the test sequence remained the same as the standard that when it changed, regardless of the distance between the correct and incorrect pitches. Listeners did make fewer errors the father apart the pitches. [Work supported by the Canadian National Research Council.]

ISSN:0001-4966    

DOI:10.1121/1.2015738

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Periodicity pitch resulting from dichotic presentation of harmonically related tonal complexes generated by amplitude modulation of pure tones was investigated. In the first experiment, AM signals were presented dichotically in such a way that if the individual components from each ear were combined and rank ordered, a single pitch was heard. Otherwise, separate pitches were heard at each ear. Pitch fusion was investigated as a function of frequency spacing between components and frequency region. In the second experiment, loudness balances were attempted at each ear for the periodicity pitch percept as a function of the intensity of tonal complexes. (identical to those used in the first experiment) at the other ear. The purpose of this experiment was to determine if pitch strength of tonal complexes could be increased at one ear by the simultaneous presentation os a complementary complex at the other ear. The results of the experiments are discussed in terms of the time fine‐structure theories, the pattern‐transformation theory, and the optimum processor theory.

ISSN:0001-4966    

DOI:10.1121/1.2015751

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP