摘要:

Two cases of impulsive discharge, balloon burst and engine exhaust, are experimentally investigated to find scaling laws for the discharge time τ and the pressure amplitudeAof the acoustic pulse. Observations show that the flow may be modeled as a pressure reservoir of dimensionDand overpressure Δpsuddenly discharging through an aperture growing with time. IfWis a characteristic aperture velocity, the aperture area varies as (Wτ)2for the balloon burst and asWτ for the engine exhaust. The flow is driven by a complex, unsymmetric wave field within the volume. It is shown thatD/τ∝ (CiW2)1/3andA/Δp∝ (Ci/W)4/3for the balloon burst, whereCiis the sound speed in the reservoir. The corresponding quantities for the engine exhaust pulses are (CiW)1/2andCi/W.

ISSN:0001-4966    

DOI:10.1121/1.381975

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A transition matrix relating the coefficients of scattered waves to those of incident waves in elastic solids is derived by applying Betti’s third identity and orthogonality conditions for a set of basis functions. The transition matrix for a fluid inclusion, a cavity, a rigid inset, or a solid inclusion in a fluid can all be derived from the general result for an elastic inclusion of arbitrary shape by taking proper limiting values of the general result. This limiting process is illustrated for the case of a spherical inclusion.

ISSN:0001-4966    

DOI:10.1121/1.381986

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The acoustic radiation from an elastic cylindrical shell defined by nonconcentric cylindrical surfaces and submerged in an acoustic fluid is studied. The driving mechanism is a time‐harmonic internal pressure. In particular, the influence of the nonconcentricity parameter δ on the resulting radiation field is examined. The solution is obtained by means of an expansion in powers of this parameter about the concentric solution, δ=0. Each order of solution is solved in closed form by means of boundary integral equation methods. Results are given for the zeroth and first‐order solutions and it is seen that ajth driving mode will introduce nearest neighbor (j−1 andj+1) modes in the first‐order solution.

ISSN:0001-4966    

DOI:10.1121/1.381961

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

It is shown that this problem can be reduced to the same mathematical form as the equivalent smooth‐walled problem. Consequently, the form of the general expressions obtained for the distribution of scattered acoustic intensity among the waveguide modes and for the azimuthal beam pattern in a specified waveguide mode obtained in an earlier paper [G. R. Sutton and J. J. McCoy, J. Acoust. Soc. Am. 60, 833–839 (1976)] are appropriate to this more general problem.

ISSN:0001-4966    

DOI:10.1121/1.381987

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Small bubbles in 4.2 K liquid helium were observed to be stable for several seconds in ultrasonic standing waves and to be acted on by acoustic radiation pressure. Applications are made to recent predictions of the evaporation–condensation resonance of small vapor bubbles.

ISSN:0001-4966    

DOI:10.1121/1.381988

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Attenuations versus frequency and depth in the ocean have been calculated from Fisher and Simmons [J. Acoust. Soc. Am 62, 1037 (1977)] relations for point source and distributed surface sources with isotropic, cosϑ, and cos2ϑ radiation distribution.

ISSN:0001-4966    

DOI:10.1121/1.381989

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Frequency spectra of axially symmetric extensional vibration of an isotropic disk plate have been calculated for the critical value, 1/3, of Poisson’s ratio σ of the disk material, and the spectra have been compared with the earlier works on spectra for σ<1/3 (0.18) and those for σ≳1/3 (0.37). In spite of absence of the imaginary loop in the present dispersion curve, there appears to be no drastic change in spectral pattern. The frequency of the present spectra increases rather rapidly with decreasingr(diameter/thickness ratio), showing no thickness dependence even near the normalized cutoff frequencyk. It is suggested from the present spectra that disk material with σ of 1/3 is not suitable for application of disk in the thickness extensional mode.

ISSN:0001-4966    

DOI:10.1121/1.381949

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Descriptions of the effects of sonic booms or air blasts by observers in buildings have included such statements as ’’noticeable vibrations’’ in addition to phrases such as ’’the house rattles,’’ ’’the windows rattle,’’ or ’’bric‐à‐brac rattles.’’ Analysis of studies of human response to vibrations, vibration complaints in the Toronto area, special tests by Kryter at Edwards Air Force Base, and laboratory studies of human response to sonic booms show that perceived vibration is not normally a factor that contributes significantly to human response to airborne, large‐amplitude impulse noise. Rather, human response is solely the result of the impulse noise itself and of audible noise due to induced radiation from vibrating surfaces.

ISSN:0001-4966    

DOI:10.1121/1.381950

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A method is outlined for estimating, from a statistical sample of exposure times and noise levels, the percentage of noise‐impacted workers who are overexposed according to the OSHA regulation.

ISSN:0001-4966    

DOI:10.1121/1.381951

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Collicular auditory neurons in cats were exposed to human speech sounds, and responses to the vowel /a/ in isolation and in connected speech were compared. The fundamental frequency coded was found to be independent of CF, response type (’’on’’ type or slowly adapting), and directional sensitivity to frequency change. This suggests that the coding of speech sounds depends on the periodicity of the neural‐response pattern. Responsiveness was generally greater to segmented vowels; it seems probable that a neuron’s response adapts to and is suppressed by preceeding speech stimuli. The context in which a message is embedded may be very important for the processing of speech sounds.

ISSN:0001-4966    

DOI:10.1121/1.381952

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP