摘要:

This paper discusses the application of coherence function techniques in developing semiempirical models of acoustical systems, with particular application to diesel engine noise. Pressure transducers, mounted in each of the combustion chambers, measured the cylinder pressures and a microphone mounted 1 m to one side of the engine measured the sound pressure. The frequency responses between each cylinder and the noise were computed. The frequency responses were used to predict the effect on the engine noise of varying combustion parameters such as injection timing. Previously, the effect on noise of combustion parameters has been determined by empirical means only. It is also shown that even though the inputs are highly coherent, it is still possible to determine the frequency responses for the case where the inputs are identical but delayed in time by fixed amounts, as is the case for multicylinder pumps, engines, and compressors.

ISSN:0001-4966    

DOI:10.1121/1.2002491

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The application of mechanical mobility and radiation factor methods to augment standard structure‐borne and airborne noise surveys in diagnosing structural contributions to vibroacoustic deficiencies on high performance vehicles is considered. Emphasis is placed on the development of a field‐oriented analysis method based on a normal mode interpretation of mobility and radiation factor measurements to characterize the dynamic response of the structural elements of such vehicles. These characteristics (i.e., natural frequencies, modal loss factors, mode shapes, relative noise transmission path strengths, modal density, termination mobilities, and acoustic radiation efficiencies) provide information which influences the selection, design, and performance of all transmission path noise control methods that are applicable to corrective redesign. The effects of modal density on such an analysis approach are briefly examined along with techniques to resolve modal information from normal modes closely spaced in the frequency domain. Applications of the methods to shipboard noise problems are presented. Mobility/radiation factor evaluations were found to provide an economical means of obtaining vibroacoustic design information for high performance vehicles where transverse modes govern the vibratory response of the vehicular shell.

ISSN:0001-4966    

DOI:10.1121/1.2002622

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Previous research has shown that subjects can respond to the onsets of sinusoidal signals more rapidly than to the offsets of such signals. The difference in the speed of response to onsets and offsets of monaurally presented signals was investigated for three different signal frequencies: 500, 1000, and 4000 Hz. For the two higher signal frequencies it was found that this difference in reaction time to onsets and offsets was greater for signals presented to the right ear than for signals presented to the left eat. This eat difference resulted mainly from slower responses to the offsets of signals presented to the right ear than to the offsets of signals presented to the left ear. This ear difference is unusual in that it was obtained with monaural presentations of simple stimuli: the ear differences most frequently reported are typically found with dichotic presentations of complex (speech) stimuli. Previously reported ear differences have been attributed to differences in hemispheric organization of the brain. The basis of the present results is unclear.

ISSN:0001-4966    

DOI:10.1121/1.2002674

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Traditional theories of phonology maintain that nominal compounds have a [1/3] stress pattern whereas nominal phrases are characterized by [2/1]stress [N. Chomsky and M. Halle,The Sound Pattern of English(Harper and Row, New York, 1968)]. However, there does not appear to be a sharp boundary between compounds and noun phrases, either in speaker's strategies for indicating stress, or in their perception of it. Indeed, there appears to be a continuum, where certain word pairs like “apple core” are definitely perceived and produced as compounds, others such as “boiling water” are usually noun phrases, and numerous others like “parcel post” or “box lunch” can be either. Durational and fundamental frequency data will be presented for three naive subjects who recorded 40 word pairs in sentence context. Additional subjects were given a written list of these sentences with the word pairs underlined and asked to circle the one syllable of each pair that should be most stressed. Certain classes of word pairs received more consistent stress assignments than others, but definite rules predicting stress seem to be difficult to formulate.

ISSN:0001-4966    

DOI:10.1121/1.2002734

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

An investigation was conducted to determine whether grammatical, semantical, and phonological constraints affect aural masking. The rationale for the study centered around conflicting reports in the literature as to the importance of content and linguistic rules for masking efficiency. Thirty‐six college‐age, normal‐heating, native speakers of English participated in six conditions of linguistic masking. Conditions differed in type and degree of linguistic violation of the competing message. Articulation scores computed in percentages served as measures. Significant differences in performance were discussed in terms of information theory, figure‐ground and closure concepts, linguistic analysis, attention, memory, and linguistic feature detection.

ISSN:0001-4966    

DOI:10.1121/1.2002789

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

A reversal in ear advantage for double‐contrast pairs of synthetic stop‐vowel syllables was reported at the 90th meeting of the Society. The ear advantage was an REA=51% for voiceless‐left, voiced‐right pairs, but an LEA=27% for voiced‐left, voiceless‐right pairs. We evaluated the generality of this reversal by using two criteria for syllable alignment: onset of periodicity and onset of burst. Three listeners who had demonstrated the reversal in a previous experiment were tested. The reversal was preserved in both alignment conditions, suggesting that it was not influenced by temporal delays inherent in either alignment criterion. The results will be discussed in terms of the “lag effect” [Berlinet al., J. Acoust. Soc. Am.53, 699–709 (1973)] and will be contrasted with findings obtained with natural CV's [Supported by PHS Grant No. NS‐12125.]

ISSN:0001-4966    

DOI:10.1121/1.2002844

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Precision determination of the power radiated by an ultrasonic transducer must account for the structure of the near‐field. A new procedure which does not requite modeling of the sound field is presented. Optical data acquired from passing parallel light through the sound field is processed using a Fourier transform projection theorem to construct a description of energy flow in a spatial frequency domain. The radiated power is then calculated from the values in this domain.

ISSN:0001-4966    

DOI:10.1121/1.2002901

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

This paper will describe measurements of sound pressures on the surface of a prolate spheroid whose length to diameter ratio is 6.9. The sound source was positioned a distance from the illuminated pole equal to the length of the body; irradiation was axisymmetric. Data at surface locations along the axis of the body was collected for acoustic wavelengths λ ranging from 1/150 to 1/38 of the interfocal distanced. A condenser microphone equipped with a long probe tube was used to avoid extraneous scattering from the sensor. Sound pressure levels, expressed relative to those measured on the illuminated pole, showed the existence of expected creeping‐wave interference patterns near the antipode and an illuminated spot on the pole. The measured levels on that pole are shown to decrease roughly as the reciprocal of frequency; they are 13 dB less than those at the illuminated pole ford/λ = 38. In the shadow zone the measurements are shown to be well approximated by Keller's deo‐metric theory of diffraction. Deviations from the theory on the order of 3 dB are observed at high frequencies and at coordinates off the antipode.

ISSN:0001-4966    

DOI:10.1121/1.2002964

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The statistical energy analysis is based on the expression for the power flow between coupled dynamic systems, each consisting of a multiplicity of modes. Usually, the expression is derived by properly identifying the modes as mechanical oscillators and by simply generalizing the expression for the power flow between two coupled mechanical oscillators. The latter expression states that the power flow is proportional to the difference in the “temperatures” of the two mechanical oscillators. In the generalization, cross‐modal terms are neglected and dismissed. In the presentation, the expression for the power flow between two multimodal dynamic systems that are coupled by a single link attached at localized positions on the dynamic systems is derived in full. The cross‐modal terms are identified and isolated. A number of conditions under which the cross‐modal terms tend to vanish so that they can be neglected are illustrated and discussed.

ISSN:0001-4966    

DOI:10.1121/1.2003028

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The mechanical response characteristics of the hand due to vibration directed into the hand by a vibrating handle was modeled as a three‐degree‐of‐freedom, mass‐spring‐damper system for vibration in each of three mutually orthogonal directions. The coupling that existed between the three mass elements and the relative values of the different components of the mechanical model correlated very well with the actual coupling and the physical relations that exist between the different layers of tissues in the fingers and hand. The model indicated that the mechanical response of the hand due to hand‐induced vibration was a function of the direction of the vibration relative to the hand and a function of the manner in which the vibrating handle was clasped. The model implied that vibration directed into the hand at frequencies below 100 Hz was transmitted through the different layers of tissues in the hand into the skeletal system and then up the arm. Vibration energy at frequencies above 100 Hz tended to be isolated to the tissued directly in contact with the vibrating handle.

ISSN:0001-4966    

DOI:10.1121/1.2002440

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP