摘要:

Comparisons are made of the intelligibility of continuous speech in noise under three listening conditions: Speech arriving simultaneously and in phase at the two ears; speech arriving at one ear later than the other; and speech arriving simultaneously, but in opposite phase in one ear. Time intervals between ears ranged from 200 μsec to 7 msec. Delaying speech to one ear under these conditions does increase intelligibility but is little, if any, better than the simple expedient of wiring the phones so that the wave form at one ear is inverted with respect to the other. With the materials and method used, the maximum increase occurs with a delay between ears somewhere between 0.5 and 1 msec, though there is some indication that delays 1 msec and longer may be slightly better under the most difficult listening conditions tried.

ISSN:0001-4966    

DOI:10.1121/1.1908508

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Measurements were made of the intelligibility of speech heard in noise and produced by different amounts of vocal force. Vocal force ranged from the weakest voiced whisper to a very heavy shout. The results show less than 5% deterioration in intelligibility over the range from a moderately low voice to a very loud voice (55 to 78 db in a free field at one m from the lips). Beyond these points intelligibility decreases abruptly and in a linear relation to decibel change in vocal intensity. Listeners' errors are analyzed to determine the effects of the extremes of vocal force on the intelligibility of different parts of the syllable and of different vowels.

ISSN:0001-4966    

DOI:10.1121/1.1908510

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

The absolute identification and differential discrimination of the sound level of tones were studied over a wide range of sound levels under comparable experimental conditions, and the results of the two experiments were compared in comparable units. Absolute identification improves and differential discrimination deteriorates as the range of sound levels examined increases. The net effect of these complementary changes is that the information associated with differential discrimination is roughly of the same magnitude as that associated with absolute identification.

ISSN:0001-4966    

DOI:10.1121/1.1908512

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

The characteristic feature of the method is that at any point in the sound field the conservation criteria are expressed in terms of the instantaneous values of the speed of propagation, the particle velocity, the excess pressure, and excess density. These criteria, together with the adiabatic assumption, determine explicit relations between any two of these quantities. Excess pressure and excess densities are here defined as departures from the equilibrium values that exist at the instant when the particle velocity is zero.For waves of finite amplitude these equilibrium values, as well as the speed of propagation, are found to depend on the intensity. The increment in the speed of propagation does not agree with that obtained by classical methods of analysis. The discrepancy found to be due to the omission in the classical forms of the continuity criterion of a term that specifies the effect of the rate of change in the speed of propagation.

ISSN:0001-4966    

DOI:10.1121/1.1908514

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Visualization of the vortex flow pattern in typical jets emitting jet tones was made by means of shadowgraph techniques to show the nature of the ever present process of vortex coalescence in the jet and how this determines the values of the eigenton sound frequencies radiated by the jet. These frequencies are super‐imposed on the noise background radiated by the jet. The dependence of (a) vortex shedding frequency from the orifice, (b) jet‐tone frequencies, and (c) translational velocity of the vortices on Reynolds number (Re) is shown.These studies were carried out with carbon dioxide jets discharging into the atmosphere. The flow channel geometry consisted of an orifice plate containing a sharp‐edged, circular orifice, 0.250 in. in diameter and 0.093 in. thick attached to a large stilling tank partly filled with sound‐absorbing material to eliminate any effects of cavity resonance on the jet. The studies were carried out over the range from Re zero to Re 7000, whereRe = vρt/μandvis mean velocity of discharge of jet; ρ, gas density;t, orifice plate thickness, and μ, gas viscosity.

ISSN:0001-4966    

DOI:10.1121/1.1908516

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

An arrangement for the determination of sound velocities in liquids by means of measuring pulse repetition rates is described which, although very simple, allows an accuracy of better than 1%.

ISSN:0001-4966    

DOI:10.1121/1.1908518

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Measurements of pressure and particle velocity in fluid‐filled bore holes have yielded several unexpected results, some of which can be explained by very simple computations. One is an acoustic square wave, a flat‐topped pulse which is generated when a slug of water, broken off from the main column by cavitation, rejoins the column. In another instance, the geometry is such that a wave along a steel casing is the first signal to arrive at a pressure detector, and the initial pressure is negative, although the explosive pressure generating the transient is initially positive. The manner in which a steel casing causes reversal of pressure in the “casing break” is described. An expression is also presented which relates the negative pressure observed at the bottom of an uncased well to the elastic constants of the fluid and solid. As a fourth example, initial upward motion of a geophone hanging in a bore hole is shown to be consistent with the circumstances under which the observations were made.

ISSN:0001-4966    

DOI:10.1121/1.1908520

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

This paper discusses the forbidden and allowed modes of radial vibrations in hollow cylinders of barium titanate. Theoretically, for a given ratio of outside diameter to inside diameter, it is possible to predict which of these higher modes will be observed. The theory has been checked experimentally and, within the limits of the experiment, has been found to be true.

ISSN:0001-4966    

DOI:10.1121/1.1908522

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

At very low temperatures the mean free paths of electrons in metals become so large with respect to their values at room temperature that they can acquire momentum from collisions with lattice vibrations which result in ultrasonic attenuation when the electrons are in the normal state. This attenuation drops to zero in the superconducting state. Original measurements in impure lead, tin, and copper showed an attenuation proportional to the square of the frequency which could be directly related to the electron viscosity calculated from the numberN, the massm, the mean free pathland the mean velocity 0 of the electrons.Recently some very pure tin samples have been obtained and much larger effects have been measured due to the increased conductivity at low temperatures. Six oriented samples have been measured and from the measurements the six elastic constants and six viscosity coefficients have been obtained. These correspond to those for a tetragonal crystal. As the mean free path becomes longer than the acoustic wavelength, the loss is determined by a scattering process and the loss for a given frequency approaches a limiting value in agreement with a theoretical prediction of Pippard. The loss for longitudinal waves is from 2.5 to 7.5 times the predicted value while that for shear waves is about 1.5 times the theoretical value of Pippard's.Measurements of the elastic constants have been made through the super conducting range and the only discontinuity that occurs is that due to the thermodynamically predicted value. The change for a longitudinal wave is less than that predicted for a volume change in agreement with a theoretical derivation. No relaxation effect occurs for the measured velocity even for very pure tin.

ISSN:0001-4966    

DOI:10.1121/1.1908524

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

The possibilities and limitations of different ultrasonic stroboscopes described by Bär for the special purpose of studying ultrasonic phenomena were investigated in greater detail. One type is appropriate for the measurement of the velocity of propagation of progressive ultrasonic waves. A modified setup offers special advantages for the precise determination of the sound velocity in a liquid relative to a standard liquid. Another optical arrangement is best suited for the study of ultrasonic fields; it was used for direct measurements of the Rayleigh phase shift at a liquid‐liquid interface and for photography of the phase field before an ultrasonic tranducer.

ISSN:0001-4966    

DOI:10.1121/1.1908526

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP