bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sound Diffraction by Rigid Spheres and Circular Cylinders
Authors: Wiener Francis M. 
Published: September 2005

The results of calculations of the pressure distribution on the surface of a stationary rigid sphere and a stationary rigid circular cylinder of infinite length, when exposed to a plane progressive sound wave, are compared with experiment. A small probe microphone was used to measure the sound pressures on the surface of the obstacles in a room essentially free from acoustic wall reflections under a variety of experimental conditions. The sound pressures p on the surface are conveniently expressed relative to the free-field pressure p0 in the undisturbed incident wave.
In the case of the sphere, reasonably good agreement was obtained between theory and experiment in the range of 13 &lt;ka &lt; 10, where k is the wave number of the incident wave and a the radius of the obstacle. In particular, the existence of the “bright” spot diametrically opposite the point nearest the sound source was verified experimentally. This comparison of experiment with theory affords a valuable means of estimating the validity of the experimental procedure.
In the case of the cylinder whose axis was oriented parallel to the wave front of the incident wave and whose length was chosen to equal its diameter, the pressures were measured for the most part in the median plane. There is a marked similarity between the results obtained for this finite cylinder and the results obtained for a sphere. The pressure at the point in the median plane farthest away from the source of sound (θ = 180°) is substantially equal to the free-field pressure only for ka &lt; 5. As the frequency is increased further, the sound pressure near θ = 180° drops rapidly up to and most likely beyond ka = 10 at an approximately constant rate, in decibels per frequency octave. A small microphone located on the surface of such a cylinder at θ = 180° will exhibit a low pass filter action with a cut-off at k ≈ 5.
Tables are furnished of the ratio p/p0 computed for a rigid circular cylinder of infinite length. This ratio is tabulated in magnitude and phase in the range of 12 ⩽ ka 10, for azimuths θ varying from 0 to 180° in 10-degree steps. The results are very similar to the spherical case for θ not exceeding about 150 degrees. There is only an insignificant trace of the bright spot at θ = 180°.
The Variation of Phase Along the Basilar Membrane with Sinusoidal Vibrations
Authors: Békésy Georg V. 
Published: September 2005

An optical means of measuring phase relations in the cochlea is described. With the stapes set into sinusoidal vibration, the phase relations, measured along the length of the cochlear partition, show that a traveling wave has been set up. The form of resonance which appears does not correspond at all with that to be found in a simple vibrating system. Measurements are presented for a frequency of 200 c.p.s. of the amplitude and phase of vibration at various places along the cochlear partition. From these is derived a curve showing the longitudinal bending of the partition with the traveling wave at two different points in time.
Very small changes in the form of vibration can easily be demonstrated by the measurements of phase. By this means it is shown that the basilar membrane cannot be released from tension since it is not normally under tension. The elastic properties of the various distinguishable tissues within the cochlear partition were measured. These measurements show that only the elasticity of the basilar membrane changes through the length of the cochlear canal. The other portions of the partition are quite constant throughout the entire distance.
Further, the non-linearity in the vibration of the partition was investigated with results which indicate that the observed lowering of pitch of a tone when the loudness is increased cannot be produced by mechanical means.
Properties of Liquids at High Sound Pressure
Authors: Briggs H. B. , Johnson J. B. , Mason W. P. 
Published: September 2005

When sound of high amplitude is transmitted into a liquid by means of a mechanical driving device, the ultimate limitation to the power that can be transferred is cavitation or breakdown of the liquid under high internal stresses. A study of cavitation has resulted in establishing the following results. Under steady-state conditions, light liquids filled with air cavitate when the negative acoustic pressure reaches the atmospheric pressure. When liquids are degassed, their natural cohesive pressure becomes effective and they will withstand a negative acoustic pressure. It is found that the total negative pressure required to cause cavitation is equal to the sum of the cohesive pressure—tensile strength—and the ambient pressure. Viscous liquids have a higher cohesive pressure and a proportionality has been established between the logarithm of the viscosity and the cohesive pressure. The amount of power that a liquid can withstand increases markedly as the pulse length is shortened.
An explanation of these phenomena is attempted on the basis of Eyring's theory of viscosity, plasticity and diffusion. On this theory natural holes exist in the liquid into which molecules can jump, leaving holes behind them. A jump occurs when the molecule has accumulated enough heat energy to surmount an activation potential barrier of energy value E0. Cavitation appears to be the result of coalescing of the natural holes in the negative pressure phase of the cycle. Since a molecule has to jump from a hole in order that this can coalesce with another hole, the cavitation pressure is proportional to the activation energy which in turn is proportional to the logarithm of the viscosity. The increased power-transmitting capacity for short pulse lengths is a result of the finite time taken for the small holes to grow in size to a large enough hole to cause rupture of the liquid.
Frequency Response Fluctuations in Rooms. I. Experimental Investigation
Authors: Roop R. W. 
Published: September 2005

The steady-state frequency response of a room is being studied in detail as part of a broad investigation of diffusion. Following Wente we define transmission irregularity as: Φ ≡  ∑ ν1ν2 (PL)max − (PL)minν2 − ν1 db/c.p.s. where (PL)max and (PL)min represent the values of the pressure level at individual maxima and minima in the frequency response curve in the frequency band ν2 − ν1.
For measurements of Φ, the requirements on the rate of frequency sweeping, (dνdt), and the writing speed of the recording instrument, R, are: (dνdt) &lt; 2k2π∛ and R &gt; 10π∛2.3⋅1k(dνdt) where k is the decay constant. Measurements of the transmission irregularity have been made as a function of frequency between 100 and 5000 c.p.s., with a source in one corner of a small rectangular room and a microphone in various standard positions. The resulting curves exhibit a rapid increase in Φ at low frequencies and a gradual decrease in Φ at frequencies above 1000 c.p.s.
Methods of Measuring Speech Spectra
Authors: Stevens S. S. , Egan J. P. , Miller G. A. 
Published: September 2005

A comparison was made of several alternative methods and devices for analyzing speech in terms of its acoustic spectrum (a time average of the sound-pressure level per cycle vs. frequency). A general procedure, applicable to a wide variety of analyzing instruments, consists of a comparison made between a known acoustic spectrum and an unknown spectrum (speech). For maximum convenience, the known spectrum should be a “white noise” whose spectrum level is a constant number of decibels per cycle. This spectrum is used as a standard to provide an over-all calibration of the entire recording and analyzing system. In practice, the shape of the speech spectrum is obtained directly as the difference in decibels, in each pass band of the analyzer, between the level obtained for the white noise and the level obtained for the speech.
In order to measure conveniently the spectrum of the noise used as the standard of reference, a graphic analyzer was devised as follows: A Hewlett-Packard wave analyzer, Type 300A, was modified to give access to the 20,000-cycle voltage al the input to the meter system. This voltage was used to drive either of two types of graphic recorders. Continuous analyses from 0 to 16,000 c.p.s. can be made with various constant band widths.
The procedure of comparing a known with an unknown spectrum eliminates the necessity of calibrating separately the recording, reproducing, and analyzing equipment. In the analysis of speech, only the calibration of the microphone need be considered as a final correction to the data. This procedure also makes it possible to obtain accurate analyses despite the use of voice recording and reproducing equipment having unknown frequency characteristics.
Although the choice of filter cut-off frequencies is arbitrary, it has been found most convenient to analyze speech by dividing it up into bands that stimulate equally wide regions on the basilar membrane. This is accomplished by choosing filter cut-offs at equal intervals along the mel scale of subjective pitch.
Within the limits of observational error the same answer is obtained when speech is analyzed by any of three different measuring systems: (a) square-law integrator (audio spectrometer), (b) linear integrator, (c) R.C.A. noise meter and Esterline Angus graphic recorder. When, with any of these systems, a speech spectrum is determined as the difference in decibels between the two analyses — that for white noise and that for speech — the speech spectrum can be stated in terms of sound-pressure level per cycle averaged over each of the nominal pass bands of the filters. Very narrow pass bands (5 c.p.s.) reveal details in the speech spectrum not disclosed by the wider filter bands.
Flow-Resistance Characteristics of Fibrous Acoustical Materials
Authors: Nichols R. H. 
Published: September 2005

The flow resistance of a material is highly important as a factor in determining its acoustical performance in various applications, particularly in the blankets used for soundproofing of aircraft cabins. It is desirable, therefore, to know the manner in which the flow resistance of a lightweight acoustical material varies with such physical parameters as thickness, density, size and shape of fibers, and type of construction (“felting”) of the material.
From an experimental study of a large number of fibrous acoustical materials, the following empirical relation has been established for materials of high porosity (0.9 to 1.0): Flow resistance, R = KS(1+z)Tz 1r2 where K is a constant, characteristic of a particular material, S is the surface density of the blanket of material, T is the thickness, and r is the cross-sectional radius of the fibers. The type of construction of the material determines the value of x in the exponents. This value generally lies in the range from 0.3 to 1.0.
The Performance of Cup-Mouthpiece Instruments
Authors: Long T. H. 
Published: September 2005

It is shown by a qualitative analysis that the playing of cup-mouthpiece instruments must be associated with the existence of a pressure antinode at or near the mouthpiece, and that harmonic production in such instruments can be adequately explained by the acoustic overload in the air column.
A quantitative analysis discloses the “mechanism” by which the odd series of modes of vibration occur at frequencies related to each other by the 1, 2, 3, 4 integers of the complete harmonic series.
A Method for Measuring Acoustic Source Impedance
Authors: White J. E. 
Published: September 2005

The acoustic output impedance of a sound source can be determined from relative pressure measurements following a procedure which requires rather simple equipment and practically no time for processing data. The sound source must have a radiating area which is essentially a piston and which can be coupled to a closed tube of variable length. The tube is terminated by a rigid plug in which a pressure-measuring microphone is mounted flush with the surface. Thus the microphone measures the pressure at the terminating plug as the length of the air column is varied. These pressure measurements are related to the acoustic impedance of the source by the expression (P0/Pl)2 = sin2kl[R2 + (X − cotkl)2], where p0 is the zero length or blocked pressure, pl is the pressure at length, k is 2π divided by the wave-length, l is the length of the air column, R is the specific acoustic resistance ratio for the source, and X is the specific acoustic reactance ratio for the source.
The principal value of the method lies in the fact that for any chosen length, the possible values of the pressure ratio represent a family of circles on acoustic impedance coordinates. Thus a chart can be very easily prepared from which the source impedance can be read and recorded as the data are taken. The circles can be labeled in decibels so that the only data reduction required is the subtraction of the pressure at length l in decibels from the blocked pressure in decibels. The author used the method in the “cut and try” development of a sound source for an acoustic filter experiment, where the dozens of impedance determinations would have represented a prohibitive amount of work if even moderately complicated data processing had been required.
Attenuation of Sound by Light-Weight Multiple Structures
Authors: Beranek Leo L. , Work George A. 
Published: September 2005

Nichols and Wallace et al. have described aircraft acoustical treatments and apparatus for measuring the attenuation provided by them. This paper presents a theory and charts for calculating the attenuation of sound by six different multiple structures as a function of dimensions, specific flow resistance, density, and frequency. Five of the structures are typical of those used in aircraft, and two are types used in lightweight office partitions.
The calculations are checked against experimental data taken on a modified form of the apparatus of reference 2. The agreement between experiment and theory is satisfactory. Differences between attenuations measured here and those described in reference 1 are explained.
A Monitor Speaker
Authors: Carruthers Walter W. , Brettell George A. 
Published: September 2005

The first portion of this paper is a discussion of the design philosophy of a monitor speaker. Attention is paid to the apparent inconsistency between pressure measurements and A-B tests with original material. Comment is made on the effects of change in directional pattern of the radiated sound. The performance of an experimental monitor loudspeaker is evaluated.
The second portion of the paper is a description of the experimental speaker. The configuration, significant dimensions, and motional impedance measurements are reviewed.
The U. S. Navy Underwater Sound Reference Laboratory, Orlando, Florida
Authors: English Bruce V. 
Published: September 2005

A discussion will be given of the purpose and aims of the Laboratory with relationship to the other underwater sound laboratories in the country, and a description of the various acoustic measuring systems and measuring techniques employed in the Laboratory. Included in the discussion of systems and techniques will be the high frequency system from 50–3500 kc, the low frequency system from 0–100 cycles (0–100 lb. p.s.i. and 34–100°F), the two intermediate frequency systems, 0.02 to 150 kc, and the pressure system, 10–150 kc at 0–300 lb. p.s.i.
Emphasis will be placed on the high frequency system and the high pressure system, and the methods of measurement under each system.
The Attenuation of Ultrasonic Sound Waves in Water
Authors: Leonard R. W. 
Published: September 2005

The attenuation of sound waves in distilled water has been measured in the frequency range from 50 to 450 kilocycles. The results are in good agreement with those of Fox and Rock in the range above 10 megacycles.
Measurements on filtered sea water from 50 to 180 kilocycles give values for the attenuation about 10 times as great as those obtained for distilled water. The measurements in sea water are in reasonable agreement with the measurements of other experimentors in the frequency range from 20 to 50 kilocycles.
The data to be presented were obtained by the reverberation method, using an improved spherical resonator.
Principles of group audio teleconferencing
Authors: Stockbridge C. D. , Curtis T. H. , Mitchell O. M. M. 
Published: October 2005

Group teleconferencing is a viable alternative to face-to-face meetings especially when staff time or travel funding is limited. To be effective, an audio teleconference system must provide natural speaking and listening conditions for any participant in any location; constraints must be minimized. This paper discusses the principles underlying the choice of
(1) meeting tasks for teleconferencing,
(2) meeting room size and location,
(3) noise level and reverberation treatment,
(4) equipment, including microphone type and placement,
(5) two- and four-wire transmission facilities, and
(6) conference bridges.
Once installed, utilization of the system depends on how potential users perceive the system in terms of their own requirements. Factors which have been found to affect user perception and use of group audio teleconference systems will be reviewed.
On the nonmonotonic behavior of cubic distortion products in the human ear
Authors: Weber R. , Mellert V. 
Published: October 2005

The cubic difference tone (CDT) 2f1−f2 is measured by compensation as a function of the stimulus level L and of the frequency ratio f2/f1 of the primaries f1, f2 (f1&lt;f2) in the 2−kHz region. Relative minima of the cancellation level LCT are observed for a certain range of the stimulus level L and the frequency ratio f2/f1 which can be regarded as a ’’region of existence’’ for these nonmonotonicities. No satisfactory explanation can be given for the observed nonmonotonic behavior of the CDT. In a second part some research is done on the quasicubic difference tone (QCDT) f1+f2−f3 that can be perceived under certain stimulus conditions if three tones f1, f2, f3 are presented to a normal human ear. Its dependence on the amplitude and on the frequencies of the primaries is comparable to the analogous behavior of the CDT. In particular, the QCDT f1 + f2 − f3 shows the same nonmonotonicity as a function of the stimulus frequencies as the CDT 2f1 − f2. From this similarity, it can be concluded that the nonmonotonic mechanism is not primarily dependent on the special excitation of the basilar membrane that is evoked by the primaries.
Subject Classification: 65.56.
Radiation−driven magnetoacoustic waves in a confined gas
Authors: Sarma L. V. K. V. , Sarma M. S. 
Published: October 2005

Radiation−driven magnetoacoustic waves are studied in an electrically conducting and thermally radiating gas confined between two plane stationary walls which are placed perpendicular to the direction of one−dimensional motion of the gas. One of the walls provides a sinusoidal input of blackbody radiation and the other wall is a perfect reflector. Two types of damped harmonic waves are excited which form a system of standing waves traveling in the positive and negative directions. One of the waves is a magnetoacoustic wave and the second has attributes basically due to radiation. The effects of magnetic field on the pressure and velocity are examined. It is seen that the pressure and velocity decrease in a warm gas, i.e., for the moderate values of Boltzmann number. However, their response increases in a hot gas, i.e., for very small values of the Boltzmann number. The contributions to pressure and velocity due to the second type of waves are insignificant in a warm gas and further decreases with the increasing strength of the magnetic field. In the case of hot gas the contributions to the pressure response are significant.
Subject Classification: 28.50; 35.60.
Reply to ’’Comments on ’Level and zero crossings in volume reverberation signals’ ’’ [J. E. Ehrenberg and C. A. Erickson, J. Acoust. Soc. Am. 57 961–963 (1975)]
Authors: Spindel R. C. , McElroy P. T. 
Published: October 2005

We discuss our approximation in treating the case of slightly non-Gaussian reverberation with narrow-band transmissions. We indicate that our empirical model for the zero crossing rate yields a good fit to field data.
Subject Classification: 30.40; 60.20.
Acoustic waves in ducts with sinusoidally perturbed walls and mean flow
Authors: Nayfeh Ali H. 
Published: October 2005

An analysis is presented of the propagation of acoustic waves in a hard-walled duct with sinusoidally perturbed walls and carrying mean flow. The results show that resonance occurs whenever the wavenumber of the wall undulations is approximately equal to the difference between the wavenumbers of any two propagating modes. It is shown that neither of the resonating modes could exist in the duct without strongly exciting the other resonating mode.
Subject Classification: 20.45, 20.60; 28.60.
Monaural detection with contralateral cue. V. Interstimulus interval in MDCC and amplitude discrimination
Authors: Taylor M. M. , Smith S. M. 
Published: October 2005

The effect of the interstimulus gap (ISG) between the two intervals of a 2IFC task was determined for MDCC tasks and for monaural and binaural amplitude discrimination, for ISG values ranging from 30 to 1000 msec. Increasing ISG improved performance, but differently depending on the task. For all tasks, there was a short latency period followed by a linear rise in (d′)2 followed by a period of asymptotic performance, as ISG was increased. For practical purposes, ISG values of 500 msec probably give near optimum performance except for untrained observers or for difficult listening conditions, in which cases 700 msec should usually suffice. The duration of the latency period depended strongly on task and observer. For MDCC tasks, there was a trading relationship between E/N0 and ISG. In amplitude discrimination, however, short ISG, or small E/N0 formed limiting conditions for which performance could not be improved by changing values of the other variable. The concepts of asymptotic efficiency, rate efficiency, and time efficiency were defined and used to demonstrate intraobserver consistency and interobserver differences across the various tasks.
Subject Classification: 65.75, 65.62, 65.58.
Temporal acuity as a function of frequency difference
Authors: Wier Craig C. , Green David M. 
Published: October 2005

Several experiments are reported relating to the temporal resolving power of the auditory system. The experimental task was to discriminate between the two signals generated when a waveform was played either forward or backward in time (a condition in which the two signals have identical energy spectra). A two-segment waveform of total duration T was generated. The first T/2 segment was a sinusoid of one frequency and the second T/2 segment was a sinusoid of a different frequency. Each trial contained two observation intervals. In one interval the frequency change was from high to low, in the other interval low to high. As the total duration decreases discrimination becomes more difficult. It is nearly perfect for durations as short as 2 msec when the frequency of one segment is 1000 Hz and the other frequency 2000 Hz (ΔF=1000 Hz). For smaller values of ΔF, even at very short durations (4 msec), discrimination is about like that obtained in a simple frequency discrimination experiment.
Subject Classification: 65.70, 65.54.
Ambient noise level above plane with continuous distribution of random sources
Authors: Sutherland Louis C. 
Published: October 2005

Extending an analysis previously developed by E. A. G. Shaw and N. Olson [J. Acoust. Soc. Amer. 51, 1781–1793 (1972)], it is shown that the residual noise level above a plane containing a continuous distribution of random uncorrelated sources decreases very slowly with elevation for typical values of an air-absorption coefficient. The analysis is applicable to measurement or evaluation of community noise over a wide area with the use of an elevated measurement position.
Subject Classification: 50.80, 28.45.