摘要:

The variations in intelligibility of a temporally interrupted connected discourse passage that result from changes in both switching conditions and message rate were studied. Six normal‐hearing listeners estimated the intelligibility of ten, 15‐sec speech samples presented monaurally at 36 interruption conditions (12 interruption rates × 3 speech‐time fractions) for each of two speaking rates. Results indicated that for a given speech‐time fraction, changes in intelligibility as a function of interruption rate depend on the precise temporal correspondence of switching and message parameters. Specifically: (1) for slow interruption rates, where on‐time and off‐time are greater than average word duration, temporal features of the message are relatively unimportant and intelligibility varies directly with speech‐time fraction; (2) intelligibility functions will begin to recover from minimum at an interruption rate where off‐time is equal to, or just shorter than, average word duration; (3) differences in performance along the recovery portions of the functions for the two message rates are negligible when intelligibility is expressed in terms of percent off‐time relative to average word duration. It is apparent that a trading relation exists between speech‐time fraction and interruption rate. Within certain limits, decrements resulting from lowering the speech‐time fraction can be overcome by increasing the switching rate.

ISSN:0001-4966    

DOI:10.1121/1.1913646

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Brillouin scattering studies have been carried out in a number of aqueous electrolyte solutions at various concentrations up to 4M. Two types of results have been obtained: (1) hypersonic velocity data from the frequency shift of the Brillouin components; and (2) hypersonic absorption coefficients from the line widths of the Brillouin components. The results compare favorably with those from ultrasonic velocity and absorption data at lower frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1913647

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Propagation of plane pulses in an elastic half‐space reinforced by parallel, uniformly distributed elastic fibers is analyzed using an approximate continuum theory. Comparison of the results with experimental data for the case of fibers normal to the half‐space boundary shows excellent agreement. Typical results are also presented for other fiber orientations.

ISSN:0001-4966    

DOI:10.1121/1.1913648

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Sound sources from vibrating circular and ribbed rectangular plates are detected by holographic means using a microphone scanner and associated photographic equipment. Reconstruction of the wavefront from the acquired acoustical holograms reveals the areas on the plates which generate the far‐field acoustic radiation. In all cases, the plates were driven below their coincidence frequency. The location of the sound sources on the plates supports the theory of acoustic radiation from complex vibrators except for irregularities which are due to inhomogeneities of the plate material, nonlinearities of the holographic technique, and the speckle effect.

ISSN:0001-4966    

DOI:10.1121/1.1913649

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A new mode of driven nonlinear vibrations of a stretched string is investigated with reference to conditions of existence, properties, and regions of stability. It is shown that this mode exhibits negative resistance properties at all frequencies and driving force amplitudes. Discovery of this mode helps to fill certain gaps in the theory of forced nonlinear vibrations of strings.

ISSN:0001-4966    

DOI:10.1121/1.1913650

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A method is described for determining the elastic constants of a crystalline material from measurements of the first two longitudinal frequencies of long bars of rectangular cross section. The method is based upon the relationships between the elastic constants and both Young's modulus and the dispersion of longitudinal waves. The expression for the dispersion, derived with the aid of perturbation theory, is applicable to specimens of the most general (triclinic) anisotropy. The method yields the following values for the elastic compliances of silicon (in cm2/dyn × 1013):S11 = 7.704±0.4%,S12 = −2.234±2.8%,S44 = 12.692±2.5%. A self‐consistency check yieldsS12 = −2.254±11.5%. These values are compared to those of other workers using high‐frequency methods.

ISSN:0001-4966    

DOI:10.1121/1.1913651

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The surface‐backscattering strength is calculated according to Rayleigh theory for surface excursions much smaller then the sound wavelength. By taking account of self‐shadowing and modulation of grazing angles, the validity of the result is extended to arbitrary roughness. The predictions of this new composite‐roughness scattering model are compared with a small set of experimental data.

ISSN:0001-4966    

DOI:10.1121/1.1913652

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The measurement capability of a 2.5‐m‐diam anechoic steel tank for calibrating underwater electroacoustic transducers has been considerably increased by the installation of a nearfield transducer array. Because the boundary conditions required for valid measurements with the array are less restrictive than those that apply without the array, both the size of transducers and the frequency range of measurement are greater than was permissible formerly. Design criteria for the array are given. Data gathered from two years experience are presented to show the array's performance at 7 MPa (1000 psi) hydrostatic pressure and at the temperatures 3° and 25°C.

ISSN:0001-4966    

DOI:10.1121/1.1913653

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Acoustic backscattering strengths of the sea floors in the Java Trench, and the Tasman Sea near Sydney, have been measured for the first time. The results obtained for the Java Trench area are, on average, several decibels lower than the Tasman Sea results, which are similar to results that have been published for the bottom of the Atlantic Ocean. In each area, the standard deviations of the station‐to‐station variability are generally around 5 dB. All of the backscattering strengths increase with frequency; the rate of increase is greater at the lower grazing angles. The backscattering strengths also increase with grazing angle, and the rate of increase is greater at the higher grazing angles. Sea floors at depths from 4 to 7 km have similar backscattering strengths to each other, whereas sea floors at 1 to 2 km depth tend to have lower backscattering strengths.

ISSN:0001-4966    

DOI:10.1121/1.1913654

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The two‐dimensional stochastic equation for ray acoustics is used to study sound propagation in turbulent wakes generated by ocean‐going vehicles. It is assumed that both surface and underwater wakes can be represented by two‐dimensional axisymmetric refractive‐index fields. Random inhomogeneities are included in the fields by stochastically varying the refractive index. Ray plots and intensity contours are presented for a number of typical wake configurations. The sound‐channeling effect of wakes is clearly demonstrated.

ISSN:0001-4966    

DOI:10.1121/1.1913655

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP