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Expressions are derived for the acoustical impedance of a rectangular enclosure and of a finite annular cylindrical enclosure. The derivation is valid throughout the frequency range in which all dimensions of the enclosure are much less than the wavelength. The results are valid throughout the range from adiabatic to isothermal conditions in the enclosure. The effect is equivalent to placing an additional, frequency-dependent complex impedance in parallel with the adiabatic compliance. As the thermal boundary layer grows to fill the cavity, the reactive part of the impedance varies smoothly from the adiabatic value to the isothermal value. In some microphones, this change in cavity stiffness is sufficient to modify the sensitivity. The resistive part of the additional cavity impedance varies as the inverse square root of frequency at high frequencies where the boundary layer has not grown to fill the enclosure. The thermal modification gives rise to a thermal noise whose spectral density varies asymptotically as l/f(3/2) above the isothermal transition frequency. 相似文献
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Byrd D Lee S Riggs D Adams J 《The Journal of the Acoustical Society of America》2005,118(6):3860-3873
The complexities of how prosodic structure, both at the phrasal and syllable levels, shapes speech production have begun to be illuminated through studies of articulatory behavior. The present study contributes to an understanding of prosodic signatures on articulation by examining the joint effects of phrasal and syllable position on the production of consonants. Articulatory kinematic data were collected for five subjects using electromagnetic articulography (EMA) to record target consonants (labial, labiodental, and tongue tip), located in (1) either syllable final or initial position and (2) either at a phrase edge or phrase medially. Spatial and temporal characteristics of the consonantal constriction formation and release were determined based on kinematic landmarks in the articulator velocity profiles. The results indicate that syllable and phrasal position consistently affect the movement duration; however, effects on displacement were more variable. For most subjects, the boundary-adjacent portions of the movement (constriction release for a preboundary coda and constriction formation for a postboundary onset) are not differentially affected in terms of phrasal lengthening-both lengthen comparably. 相似文献
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Results of an experimental and theoretical study of nonlinear acoustic effects (amplitude-dependent loss, resonance frequency shift, second and third harmonic generation, and sound by sound damping) in a limestone bar resonator are reported. The observed effects are analytically described in the framework of phenomenological equations of state with allowance for the low-frequency hysteretic nonlinearity and the high-frequency dissipative nonlinearity. Experimental and analytical dependences of nonlinear effects are compared to find the parameters of the hysteretic and dissipative nonlinearities of the limestone sample studied. 相似文献
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Studies that have examined age effects in the human middle ear using either admittance measures at 220 or 660 Hz or multifrequency tympanometry from 200 to 2000 Hz have had conflicting results. Several studies have suggested an increase in admittance with age, while several others have suggested a decrease in admittance with age. A third group of studies found no significant age effect. This study examined 226 Hz tympanometry and wideband energy reflectance and impedance at ambient pressure in a group of 40 young adults and a group of 30 adults with age > or = 60 years. The groups did not differ in admittance measures of the middle ear at 226 Hz. However, significant age effects were found in wideband energy reflectance and impedance. In particular, in older adults there was a comparative decrease in reflectance from 800 to 2000 Hz but an increase near 4000 Hz. The results suggest a decrease in middle-ear stiffness with age. The findings of this study hold relevance for understanding the aging process in the auditory system, for the establishment of normative data for wideband energy reflectance, for the possibility of a conductive component to presbycusis, and for the interpretation of otoacoustic emission measurements. 相似文献
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《Journal of sound and vibration》1985,100(2):181-190
The relative importance of the acoustical contrasts of a warning sound with other irrelevant sounds and with the ambient noise has been investigated in the context of the perception of warning sounds and the effects of hearing protection being worn by normally hearing subjects. The results indicate that both contrast factors had an influence on the attention demand of the auditory warnings, but that the contrast with the irrelevant sounds was more potent for the specific stimuli investigated. Thus, they emphasize the importance of including a typical recognition requirement when assessing the attention demand of warning sounds. A small additional reduction in the attention demand of both sounds was evident when the subjects were wearing hearing protectors. This effect could occur in the industrial setting, but further research is required to establish its extent and implications. 相似文献
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The design and realization of an acoustical directional coupler are presented. Its application as a reflectometer, i.e. for direct measurement of the acoustical reflection coefficient of materials, is described. 相似文献
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本文从立体声影院声学原理有关系的心理声学、电声学和建筑声学出发阐述了立体声影院声学设计方法和原则,并以重庆山城六声道宽银幕立体声影院声学设计、装修和实测结果作为例子进行了介绍。 相似文献
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Two experiments have been carried out to investigate the effects of using different stimuli, various intensities, and repeated stimulus presentation on the ability to localize sounds in the vertical plane. It was found that noise can be localized more accurately than a speech stimulus. Increasing the sensation level of the stimulus reduces localizational errors up to a sensation level of 70 dB, where the error appears to reach a plateau at about 3·5°. There is little or no apparent learning process involved in the task of auditory localization. 相似文献
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The effect of grazing mean flow on acoustical characteristics of the micro-perforated panel absorber
There are three effects of grazing mean flow on acoustical characteristics of the micro-perforated panel absorber(1) on radiation impedance of the orifice,(2) on acoustical impedance of the construction at sound wave angle incidence,(3) on sound propagation property in a duct lined by absorber.Based on the acoustical fundamental principle,these effects were analyzed respectively,and relative formulas were derived. Some qualitative tendencies were shown that radiation impedance of an orifice,value ofξin function coth(ξ) which estimates cavity impedance,and transmission loss in a lined duct all will decrease with flow speed increases as well as the resonant frequency will move to lower frequency caused by Doppler Effect,when sound wave propagation direction is the same with flow direction. The discussion was also supported by a relative experimental study. 相似文献