摘要:

It has been observed that the word spoken in isolation can be defined in terms of its internal cohesion, that is, in terms of temporal compensation among its parts [I. Lehiste, J. Acoust. Soc. Amer.48, 110(A) (1970)]. We conducted a similar experiment using a word with a different syllabic structure. The results agreed with those of the previous experiment. However, when the same word which we used in isolation was included in a sentence, a different temporal organization was manifested. We conclude that the word is temporally organized in terms of the size of the utterance in which it participates. It appears that the larger the utterance, the higher the linguistic level at which temporal compensation takes place.

ISSN:0001-4966    

DOI:10.1121/1.1977518

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Eighty‐four neurons were recorded from and correlated with cytoarchitectural fields: 21 were located in the globular cell area, 19 in the multipolar cell area, 17 in the small spherical cell area, 11 in the octopus cell area, 8 in the dorsal cochlear nucleus, and 6 in the large spherical cell area. Eight neurons were successfully marked by intracellular injection of procion yellow. Units in small spherical cell area (best frequencies, 0.475–11.500 kHz) rarely display tight phase locking and show a characteristic “onset” response followed by decreased activity. Neurons in the multipolar cell area (best frequencies, 0.10–1.45 kHz) are mostly low‐frequency phase lockers. There is great physiological and cellular diversity in globular cell area (best frequencies, 0.24–34.10 kHz). Units in the octopus cell area (best frequencies, 1.4–21.5 kHz) typically display high rates of spontaneous and driven activity. Neurons in large spherical cell area (best frequencies, 0.8–14.5 kHz) have interspike interval histograms of spontaneous activity with short modes and rapid decay. Long modes and a high degree of symmetry characterize neurons in dorsal cochlear nucleus (best frequencies, 0.5–10.9 kHz). [Supported by NIH grants.]

ISSN:0001-4966    

DOI:10.1121/1.1977528

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Averaged auditory‐evoked vertex responses were obtained from eight normal‐hearing female subjects in response to 32 monaural 1000‐Hz tone bursts at 30 randomly presented combinations of recovery period (interstimulus interval) and stimulus intensity (sensation level). From curves describingN1−P2peak‐to‐peak amplitudes, an equation was derived that describes the combined effects of recovery period and stimulus intensity on evoked response amplitude. The results showed evoked response peak‐to‐peak amplitude to be a dual function of both recovery period and stimulus intensity. At a given stimulus intensity, evoked response amplitude was a logarithmic function of recovery period. At a given recovery period, evoked response amplitude was a power function of stimulus intensity. The combined effects of recovery period and stimulus intensity produced equal ratio changes in the slope and the intercept of the recovery function with equal ratio changes in stimulus intensity.

ISSN:0001-4966    

DOI:10.1121/1.1977533

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Electroencephalic energy transmission as a function of frequency for solder electrodes was investigated, since this type of polarizable electrode has multiple advantages over commercial nonpolarizable types for clinical evoked response audiometry. The electrode impedance was measured and replicated at nine infrasonic frequencies (0.1, 0.5, 1.0, 2.0, 3.0, 4.0, 10.0, and 20.0 Hz) in saline solution. The results of the investigation revealed that the impedance decreased as the frequency of a 1‐mV sine wave increased. At frequencies of 1 Hz and less, the impedance was high (17–30 kΩ), but dropped approximately 3 kΩ per octave from 11 Ω at 2 Hz to 3Ω at 20 Hz. There does not appear to be any significant advantage of a nonpolarizable electrode (e.g., silver/silver chloride) over the solder‐polarizable one as long as the latter has a surface area of at least 4–5 mm2and the EEG amplifier input impedance is not less than 1 MΩ. Further advantages of cost, construction, maintenance, and application in a population with a high damage risk to electrodes is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1977535

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A direct correlation between the flow and noise of a jet—between the “cause” and the “effect”—has been measured. Two kinds of correlation have been tried, namely: (1) the broad‐band turbulence signal (hot wire) with the broad‐band acoustic signal (microphone); (2) the narrow‐band filtered turbulence signal with the narrow‐band filtered acoustic signal. The data have been analyzed via the Proudman form of Lighthill's integral for aerodynamic noise. Either type of correlation yields the relative intensity and spectrum of the noise originating from unit volume of the jet; this leads to the variation of noise power per unit length of the jet and the over‐all spectrum. The peak normalized board‐band correlation of 1%–2% roughly implies that a turbulence “eddy” centered at the hot wire contributes only 1%–2% of the rms sound pressure at the microphone. The total effective number of uncorrelated noise‐producing “eddies” is thus of order (1/0.02)2, or some 2500 on an equal strength basis. [Work supported by Air Force Office of Scientific Research.]

ISSN:0001-4966    

DOI:10.1121/1.1977541

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Extensive surveys of both the near and far noise fields were made for a supersonic (nozzle design Mach number 1.5) cold model jet. The operating conditions selected for this investigation were (1) shock‐free mode at operating pressure ratio (reservoir pressure/ambient pressure), ξ=3.57 and (2) underexpanded mode at ξ=4.74. The experiments were conducted in a fully anechoic chamber. The purpose of this investigation was to extend the existing understanding of the noise field of a supersonic shock‐free jet at a moderate exit Mach number and the variations in its acoustic behavior when the nozzle was operated at underexpanded mode where strong shock waves were present. The main experimental results obtained are presented. It was found that the broad‐band and sound‐pressure spectra of apparent sources in each of the individual characteristic flow regions were similar. The strongest source for the shock‐free jet was located near the laminar core tip, whereas for underexpanded jet, the strongest source was found near the middle of the flow region containing shock waves. It is shown that the significant increase in the noise output at the underexpanded mode of operation was primarily contributed by high‐frequency components.

ISSN:0001-4966    

DOI:10.1121/1.1977542

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A relaxation process, based on organic particulate matter (plankton) in open waters, is described and theoretically derived. It is similar to a theoretically derived and experimentally verified process in aerosols and relates relaxation time to shear (Stokes) force. The derived formulas are applied to demonstrate probable significant differences among low‐frequency sound attenuation values in various water masses.

ISSN:0001-4966    

DOI:10.1121/1.1977548

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Crighton (personal communication) has used a multiple‐time scales expansion to solve the problem of a plane periodic finite‐amplitude wave. We have adapted this method, applying a multiple‐length scales expansion to the three‐dimensional nonlinear wave equation derived by Westervelt [J. Acoust. Soc. Amer.25, 535 (1963)]. When the secular terms in the second‐order equation are set equal to zero, a simplified nonlinear equation is obtained. For the plane‐wave case, this equation leads to a solution essentially like that of Earnshaw [Trans. Roy. Soc. (London)150, 133–148 (1860)]. The method is used to obtain an “Earnshaw‐like” solution of the problems in which the linear farfield solution is a spherical wave whose amplitude contains a directivity factorD(θ). In particular, the method works for the farfield radiation from a piston, and the “Fubini‐like” solution for this problem is presented. Other applications are the radiating disk, the dipole, and arrays. The method is also applicable when the farfield wave is cylindrical. [This work was sponsored by the U. S. Air Force Office of Scientific Research.]

ISSN:0001-4966    

DOI:10.1121/1.1977554

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A one‐dimensional model of a finite‐amplitude standing wave confined to a duct (wherein boundary‐layer effects at the walls produce energy losses greater than those arising from viscous and thermal effects in the body of the fluid) has been established. The resultant set of coupled nonlinear equations can be solved either by a perturbation technique or by assuming a Fourier superposition of standing waves. The perturbation solution has been performed through sixth order and reveals the poor convergence properties of this approach. The Fourier superposition results in an infinite set of coupled nonlinear algebraic equations which can be solved by successive approximations with the help of a digital computer. Results have been obtained forMb/δ1below 0.75 and−1.0⩽2Δω/ωrδ1⩽2.0, whereMis a Mach number,b = (γ+1)/2, γ is the ratio of specific heats of the gas,α1 = δ1ω/2c0, α1is the absorption coefficient for the fundamental component of the standing wave in the infinitesimal amplitude limit, ω is the angular frequency of the fundamental, Δω is the difference ω − ωr(where ωris the classically predicted resonance frequency), andc0is the speed of sound in the limitb= δ1= 0. Results show clearly that, for given Mach number, the strongest nonlinear distortions in wave‐form are to be observed at frequenciesabovethe classical resonance.

ISSN:0001-4966    

DOI:10.1121/1.1977558

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Semiconductor and solid‐state devices have been used extensively to measure and generate stresses and stress waves in solids, liquids, and gases. Semiconductor devices have been used as strain gauges to measure strains and to respond to acoustic pressures. p‐type silicon has a guage factor of over 100 times that of a metallic strain gauge. By using the amplifying regimes of Esaki diodes and transistors, a great increase in sensitivity is obtained and microphones have been constructed that are more sensitive than the carbon microphone. With the advent of monolithic transistor on single chips and films, it appears likely that the most stable and economical devices are obtained by separating the pickup and amplifying functions. p‐n junctions have a region (the depletion region) where electrons are excluded and if the semiconductor is piezoelectric, very high‐frequency transducers for generating mechanical waves in solids can be produced. Evaporation techniques can also be used to produce frequencies from lower ranges to very high‐frequency ranges. With the advent of more highly coupled piezoelectric crystals and ceramics, this technique may be extended further. Solid‐state transducers have also been constructed using the Hall effect and the magnetoresistance effect. These have been applied in measuring static and dynamic fluxes, as variable resistors without sliding contacts and as displacement meters and microphones.

ISSN:0001-4966    

DOI:10.1121/1.1977567

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP