摘要:

Resonance of the mouth cavity while playing the flute has been found to occur near 1000 Hz. Experiments with an artificial mouth show theQof this cavity is less than two when air is passing through the lips. The presence of this coupled cavity can affect the flute frequency by as much at 10 cents, and may increase the losses in the system by as much as one‐third.

ISSN:0001-4966    

DOI:10.1121/1.1913593

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Cross‐language studies have shown that Voice Onset Time (VOT) is a sufficient cue to separate initial stop consonants into phonemic categories. The present study used VOT as a linguistic cue in examining the perception and production of stop consonants in three groups of subjects: unilingual Canadian French, unilingual Canadian English, and bilingual French‐English speakers. Perception was studied by having subjects label synthetically produced stop‐vowel syllables while production was assessed through spectrographic measurements of VOT in word‐initial stops. Six stop consonants, common to both languages, were used for these tasks. On the perception task, the two groups of unilingual subjects showed different perceptual crossovers with those of the bilinguals occupying an intermediate position. The production data indicate that VOT measures can separate voicing contrasts for speakers of Canadian English, but not for speakers of Canadian French. The data also show that language switching in bilinguals is well controlled for production but poorly controlled for perception at the phonological level.

ISSN:0001-4966    

DOI:10.1121/1.1913594

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Measurements were made of the radiation force on an absorbing target for the Langevin situation. Determinations of apparent change in weight of a target using an electrobalance were made in distilled water,n‐propanol, and ethanol at a frequency of 5 MHz and acoustic power outputs in the milliwatt range. They indicate that within experimental error the Langevin radiation pressure is independent of B/A.

ISSN:0001-4966    

DOI:10.1121/1.1913595

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A method of calculating wave amplitudes by ray tracing is presented. It consists of an integration of six first‐order differential equations, and three second‐order quasilinear differential equations. The six first‐order equations are the ray equations, and an equation for an additional Euler angle ψ. Two of the second‐order equations are equations for two scale factors,h2andh3, of an oblique system a2, a3defined on the wavefront. The third second‐order equation determines the angle χ between a2and a3.

ISSN:0001-4966    

DOI:10.1121/1.1913596

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Insight into the role of atmospheric dust in the attenuation and dispersion of acoustic energy in the lower troposphere is gained by a comparison of theoretical attenuation coefficients and dispersion functions in the 100‐ to 107‐Hz range for the mechanisms of classical‐rotational absorption, molecular absorption, turbulent scattering, and dust absorption for a variety of dust and meterorological conditions. Over most of this frequency range the attenuation due to dust absorption is masked by one or more of the other attenuating mechanisms, but at lower frequencies there appear to be physically realizable dust and meteorological conditions wherein dust absorption may become significant. However, the most significant effect of atmospheric dust upon acoustic energy propagation lies in its dispersion, which is opposite in sign and much larger at lower frequencies than dispersion due to classical and molecular effects. The magnitudes of absorption coefficients and dispersion functions for dust are directly proportional to the particle concentration, and their frequency dependence varies with the particle size distribution.

ISSN:0001-4966    

DOI:10.1121/1.1913597

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The dependence of the shadowing function on grazing angle was optically measured on three rough surfaces which are identical except for the rms reliefs (and slopes) which had been scaled in the ratios 1 : 2 : 4. Both one‐ and two‐dimensional shadowing measurements were made. The one‐dimensional measurements are in good agreement with the one‐dimensional theory of shadowing developed by R. J. Wagner. In addition, the one‐ and two‐dimensional shadowing measurements are in excellent agreement with one another as would be expected for nearly isotropic surfaces.

ISSN:0001-4966    

DOI:10.1121/1.1913598

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A set of differential force and moment equilibrium equations for the in‐plane dynamic strains in an oval ring of variable thickness is determined. This set is reduced to algebraic form by substituting Fourier series for the stresses and deformations. The resulting matrix is then truncated and evaluated in order to determine the first five normal modes and the first eight natural frequencies for an elliptical ring of uniform wall thickness. Excellent agreement is shown between theoretical and experimental data for several aluminum rings of pseudoelliptical shape.

ISSN:0001-4966    

DOI:10.1121/1.1913599

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

An acoustic pulse propagating the ocean encounters weak thermal patches that scatter energy. If these patches are moving with a mean current perpendicular to the direction of propagation, a temporal fluctuation in the pulse‐averaged amplitude occurs. This study calculates the temporal frequency spectrum of the pulse‐to‐pulse amplitude fluctuations and finds the result in terms of a frequency convolution of Tatarski's CW spectrum found for the electromagnetic case, and the spectral distribution of the initial pulse. The result easily generalizes to amplitude, phase, and phase‐difference spectra, for plane, spherical, and beam‐wave pulses.

ISSN:0001-4966    

DOI:10.1121/1.1913600

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A mathematical procedure for deriving the complex spectral amplitudes generated by nonlinear interaction of the frequency components of a pulsed finite‐amplitude source in a nonviscous nondispersive fluid medium, within a distance prior to shock formation, is established. In order to illustrate the procedure, the nonlinear propagation spectra of a dual frequency pulse and a dual sweep linear FM pulse are derived.

ISSN:0001-4966    

DOI:10.1121/1.1913601

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Acoustic volume reverberation was measured at frequencies from 2.5 to 16 kHz at a number of stations in the Tasman Sea, the Coral Sea, and the north‐eastern region of the Indian Ocean. The dependence of volume backscattering strength on time of day, acoustic frequency, and depth beneath the sea surface were investigated. In the Coral Sea and the Indian Ocean, the average diurnal variation increased with decreasing frequency; but in the Tasman Sea the diurnal variation was almost independent of frequency. The volume backscattering strengths generally increase with frequency, but nighttime spectra are usually flatter than daytime spectra. Deep‐scattering layers were detected in the three areas at 40% of the daytime stations. Each of these DSL's had a single resonance frequency, 70% of them at 5 or 6 kHz. Most of the DSL's were at depths between 400 and 600 m. The results suggest that the volume reveration was due to backscattering by the swimbladders of mesopelogic fish.

ISSN:0001-4966    

DOI:10.1121/1.1913602

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP