bluuebunny/crossref_metadata_2025 huggingface dataset:
Response of a Narrow-Band Filter to a Linear FM Pulse with Large Time-Bandwidth Product
Authors: Sinnott John
Published: September 2005

Asymptotic solutions are presented for the response of a narrow-band filter excited by a linear FM pulse with large time-bandwidth product. A complete solution is derived for a Gaussian filter and three homographs are presented.
Computed Frequency and Angular Distribution of the Normal Modes of Vibration in Rectangular Rooms
Authors: Sepmeyer L. W.
Published: September 2005

This paper describes the mathematical model used for computing both the frequency and angular distribution of the normal modes in rectangular rooms. The criteria adopted were computed for each half-octave band over the first 4 octaves of normalized frequency for rooms with dimension ratios ranging from 313:1 to 1:1. Considerable variation in the frequency-spacing criterion exists not only for changes in room dimensions but also from one half-octave band to the next. No clearly defined optimum room dimension, as predicted by Bolt, emerges from this study. The angular-distribution index is more regularly behaved with rather definite stratification apparent as a function of the room height/length ratio, when the height direction is taken as the angular reference. When both the frequency and angular criteria are combined, only a few small regions of dimension ratios appear to be good. From these regions, p = 0.69, q = 0.43; p = 0.83, q = 0.65; p = 0.82, q = 0.72, together with p = 1/21/3, q = 1/41/3, appear to be among the best. For rooms having satisfactory mode distribution, an approximate formula has been developed for determining the lowest midband frequency for which a room may be used for measurements of continuous spectrum sounds. The formula turns out to be a constant divided by the cube root of the volume, where the constant is a function of the measuring bandwidth and the number of normal modes required therein. For 20, 12, and 9 modes in 1-, 12-, or 13-oct bands, the constants are 1150, 1280, and 1355 cps, respectively.
Interference Patterns in Reverberant Sound Fields. II
Authors: Waterhouse Richard V. , Cook Richard K.
Published: September 2005

Contour charts are given of the sound fields near one, two, or three reflecting surfaces at fight angles, for random sound incidence. The charts show contours of the mean-squared pressure in decibels as a function of position in the region within two wavelengths of the boundary surfaces. The boundary conditions at the reflecting planes are pressure-reflecting (normal velocity component equal to zero) or pressure-release (pres- sure equal to zero). By reciprocity, the charts also give the relative radiation resistance of a point source as a function of position near such reflectors. The formulas used are tabulated; they extend and in some places correct formulas given in an earlier paper [J. Acoust. Soc. Am. 27, 247–258 (1955)]. The features of the sound fields near the reflectors are discussed, and some applications to acoustical measurements in reverberant sound fields are considered.
Feedback and Noise-Signal Detection at Three Performance Levels
Authors: Campbell Richard A.
Published: September 2005

The effect of the presence or absence of feedback, or immediate positive reinforcement, was studied at 3 performance levels: 88%, 75%, and 62% correct. The BUDTIF (Block Lip and Down, Two-Interval—Forced-choice) experimental procedure was utilized. Signal-to-noise ratios were varied in a 104-trial run (about 7 min) so as to maintain the desired performance level. The noise was set to 35 dB SL. One group of naive subjects was used; each subject was presented one of the 6 conditions of performance level and feedback for 5 consecutive runs. Another group of experienced subjects was presented with all 6 conditions in each of six 1-h sessions. Threshold signal-to-noise ratios, intrarun variability of levels utilized, the time per run, and interrun variability were determined. No statistically significant and systematic effect of feedback was found.
Thermal Relaxation in Oxygen with H2O, HDO, and D2O Vapors as Impurities
Authors: Henderson Malcolm C. , Clark Anna Vincent , Lintz Paul R.
Published: September 2005

Using the 100% relative-humidity technique for controlling the mole function of water vapor, the Napier (relaxation) frequency of oxygen has been measured as a function of the mole fraction of various water vapors, consisting of pure H2O, pure D2O, and three mixtures thereof. Pure H2O gives, as is well known, a quadratic in H, the mole fraction; pure D2O gives a linear relation down to 0.7×10−3. The mixtures show a linear relation above 1.5×10−3 and a curvilinear approach to zero below that. Calculation indicates that the heterogeneous molecule HDO is far more effective as a thermal equilibrator for oxygen than either of its homogeneous parents. Quantitatively, with (f/p)m in cps per atm and h in mole fraction ×103, the results are:

100% H2O: (f/p)m = 7+183h+132h2;

50% D2O: (f/p)m = −664+1100h;

80% D2O: (f/p)m = −490+908h;

92% D2O: (f/p)m = −250+585h(above h = 1.3);

92% D2O: (f/p)m = 7+275h+100h2(below h = 1.3);

99.8% D2O: (f/p)m = −85+385h.
Control of the Acoustic Scattering Characteristics of a Rigid Sphere by Surface Loading
Authors: Senior T. B. A.
Published: September 2005

The problem of an acoustic wave incident on a rigid sphere “loaded” in a narrow azimuthal region is considered. The solution appears as the superposition of the field scattered by the unloaded sphere and that radiated by an active slot coincident with the load, with the radiation strength of the slot related to the loading characteristics in the combined problem. By varying the loading impedance, wide degree of control over the scattering behavior of the sphere can be achieved even when only “passive” loads are permitted. Numerical results are presented.
Acoustic-Ray Equations for a Moving, Inhomogeneous Medium
Authors: Uginčius Peter
Published: September 2005

An ordinary vector differential equation is derived for the acoustic-ray paths in a moving, inhomogeneous medium in which the velocity and index of refraction can be general functions of position. This equation is used to obtain the curvature of the rays for an atmosphere with a constant wind and with a speed of sound that is an arbitrary function of the height. The equations of the rays are obtained as solutions in terms of quadratures, which are then evaluated in closed form for two special cases: an atmosphere with a constant speed-of-sound gradient and one with a constant temperature gradient.
Phase Distortion of a Pulse Caused by Bottom Reflection
Authors: Cron Benjamin F. , Nuttall Albert H.
Published: September 2005

The phase distortion of a plane-wave pulse owing to bottom reflection at incident angles more grazing than the critical angle is considered. Two general methods of investigation, using the time and frequency domains, are given; they employ, respectively, the Hilbert transform of the incident pulse and the complex envelope signal. Applications to two typical SONAR pulses—a carrier frequency amplitude-modulated by a rectangular pulse and a Gaussian pulse—are given, along with graphs of the results. It is concluded that negligible distortion occurs, there being only a phase shift of the carrier, when the Q of the waveform is moderately larger than unity, the exact value depending on the smoothness of the transmitted pulse.
Rectified Diffusion during Nonlinear Pulsations of Cavitation Bubbles
Authors: Eller Anthony , Flynn H. G.
Published: September 2005

A gas-filled bubble in a liquid will generally dissolve because of diffusion of gas out of the bubble into the surrounding liquid. However, when set into motion by an acoustic field, a bubble may grow by a process called rectified diffusion. This process can counteract the effect of diffusion for values of the acoustic-pressure amplitude greater than some threshold value. This threshold has been determined by a theory that uses computed radius-time curves for bubbles pulsating nonlinearly rather than assumed infinitestimal, sinusoidal motions. For radius-time curves calculated by a digital computer, this threshold has been computed for a sequence of values of gas concentration, bubble radius, and acoustic frequency.
Measurements of the Resonant Frequency of a Bubble near a Rigid Boundary
Authors: Howkins S. D.
Published: September 2005

The resonant frequency of an air bubble in water near a plane rigid boundary was measured by varying the frequency of a sound source immersed in the water. The bubble was observed through a microscope and judged to be resonant when standing waves just appeared on its surface. The values of resonant frequency measured in this way, for bubbles having a radius in the range 1/10–3 cm (frequency range 100–3000 cps), were found to be in close agreement with a theory due to Strasberg. Another set of measurements over the same frequency range, for a bubble trapped in a hole that was drilled in the rigid surface, was also in close agreement with theoretical predictions. Some additional observations were made at higher amplitudes, where it was found that the presence of the hole affected the motion of the bubble in some ways. In the absence of a hole, a long time-scale oscillation of the bubble shape was observed.
Gap between Good Acoustics for Speech and for Music
Authors: Rienstra Albert R.
Published: September 2005

Scientific evidence seems to indicate that the gap between good acoustical conditions for speech and for music is irreconcilable, especially for churches. This gap is especially important to church acoustics because church music demands more reverberation than any other type of music and clarity of speech is as demanding as for any other type of auditorium. It is shown herewith that the gap is not as great as was heretofore considered.
Fixing of Dust Figures in a Kundt's Tube
Authors: Pilrsa H.
Published: September 2005

Experiments on the fraction of Kundt's figures noticed by R. B. Hastings and Yung-Yao-Shih were made and influence of several fixing agents investigated.
Proposed Laboratory Standard of Normal Hearing
Authors: Corso John F.
Published: September 2005

In recent years there has been a growing concern about the adequacy of the present American reference for normal hearing of pure tones. Results of earlier studies indicate that survey data tend to confirm the present zero reference, but data from laboratory studies have provided some basis for the contention that the present reference is too high. The purpose of the present study was to provide more definitive data on the threshold of hearing for pure tones through an extended laboratory investigation. Audiometric measurements were made on three groups of subjects ranging in age from 18 to 24 years inclusive. All subjects were otologically normal and showed a life history of minimal exposure to high intensity noise. Two groups were tested with ANB-HIA earphones and a 5-db step testing procedure in the method of limits; the other group was tested with Permoflux PDR-8 earphones and a 2-db step testing procedure. The results of the study indicate significant differences between the groups tested with the two types of earphones, as well as between male and female subjects. In general, excellent agreement was found with other laboratory studies. The threshold curves of the present study expressed in terms of coupler pressures are offered for consideration as a proposed laboratory standard for normal hearing.
Applications of the Monte Carlo Method to Architectural Acoustics
Authors: Allred John C. , Newhouse Albert
Published: September 2005

The Monte Carlo method of numerical analysis is applied to the determination of mean free paths and acoustic weighting factors relating probability of collision with walls in rectangular parallelopipeds. The method of calculation is discussed and its extension to determination of reverberation times in coupled rooms and auditoria is evaluated. Tables of relative wall collision probabilities are given for rectangular parallelopipeds of various proportions.
Frequency Equations for the Normal Modes of Vibration for a Plate Bounded by Parabolic Cylinders When Rotary Inertia and Transverse Shear are Considered
Authors: Nakonechny Basil V. , Callahan W. R.
Published: September 2005

In this paper, the partial differential equations governing the motion of plates when transverse shear and rotary inertia are considered are solved for plates bounded by parabolic cylinders. Three cases have to be considered, depending on the shape of the plate. They are: Case I: a plate bounded by two parabolic arcs (v = v1, u = u1, u = −u1); Case II: a plate bounded by three parabolic arcs (v = v1, v = v2, u = u1, u = −u1); Case III: a plate bounded by four parabolic arcs (v = v1, v = v2, u = u1, u = −u2). After converting the partial differential equations and boundary conditions into parabolic coordinates, product solutions are assumed and solutions of the resulting ordinary differential equations appear as definite integrals. The eight different types of boundary conditions entering into the theory, for each case, are satisfied by taking linear combinations of products of these definite integrals. The elimination of the arbitrary constants in each boundary problem leads to the frequency equation for the normal modes of vibration. The frequency equations for Case II and Case III are given by determinants of the 12th order equaled to zero, whereas for Case I the determinant is of the 6th order. In the classical theory, the frequency equations far Case II and Case III are given by determinants of the 8th order equated to zero, whereas for Case I a determinant of the 4th order is required.
Diffraction Constants of Transducers
Authors: Bobber Robert J.
Published: September 2005

The concept of a transducer diffraction constant as the ratio of the blocked diaphragm pressure to the incident free-field pressure is examined for meaning, definition, and application in the general case. The concept is extended to a transmitting transducer, and a transmitting diffraction constant that is equal in value but reciprocal in concept to the conventional or receiving constant is developed from the acoustical reciprocity theorem. The relationship among the diffraction constant D, the radiation resistance R, and the directivity factor δ is given as D2 = Rδ/R0, where R0 is the radiation resistance of a simple source. The electrical analog of the diffraction constant D is found to be an ideal transformer with the turns ratio D:1. The electrical analog of a complete and reciprocal projector medium hydrophone system is presented.
Scattering of Acoustic Waves by Pressure Fluctuations
Authors: Pollock Franklin
Published: September 2005

The scattering of acoustic radiation by limited regions of pressure fluctuations is considered. The hydro-dynamic equations are expanded into a hierarchy of acoustic equations of increasing nonlinearity and the first three of these is solved for the particular scattering problem. The scattered energy is given in terms of correlation functions for the pressure of two different points and for the pressure and its time derivative at two different points.
Direct Method of Accelerometer Calibration
Authors: Brennan J. N. , Nisbet J. S.
Published: September 2005

Present methods for accelerometer calibration include small-amplitude sinusoidal drive, large-amplitude sinusoidal drive, and pulse-integration (ballistic pendulum) methods. The first of these is of limited use because it fails to reveal nonlinear effects and pulse saturation. The second is difficult to accomplish except at a limited number of frequencies, while the third gives very little high-frequency information. A method of direct calibration, using bonded wire strain gauges as a standard, is described. The method is valid over a very wide frequency range, up to 40 kc with present instrumentation. Several examples of the use of the method are discussed. Results show that the method is an easy one to use and that it quickly reveals any deficiencies of accelerometers and their amplifiers, if present, e.g., “droop” resulting from insufficient low-frequency response, overloading of cathode follower, loss of high-frequency detail caused by too low cutoff of accelerometer filter, hash caused by accelerometer resonance, etc. Limitations of the method and evaluation of accuracy also are discussed. This method has been found to give a complete picture of the actual operation of the accelerometer and associated circuits quickly and accurately, and the results are easily interpreted.
Propagation of Finite-Amplitude Ultrasound in a Relaxing Liquid
Authors: Ryan R. P. , Attanasio C. R. , Beyer Robert T.
Published: September 2005

Perturbation analysis is used to obtain expressions for the harmonic content of finite-amplitude waves propagated in a relaxing liquid. Comparison is made with similar expressions for the nonrelaxing case. Experimental measurements were made with 2.57-MHz rf pulses in a 0.2-M aqueous solution of MnSO4 to test the theoretical results. Agreement is excellent for the fundamental frequency. The second-harmonic curves have the correct shape but are 10% 15% smaller in absolute magnitude.
Piezo-Optic Frequency Analyzer
Authors: Ogawa Tomoya
Published: September 2005

A new frequency analyzer using a set of ADP crystal resonators is described. The signal to be analyzed is applied to the electrodes of the crystals, which have different resonance frequencies. The crystal is placed between the crossed polarizers, and the existence of the signal component is observed as the brightness of the beam coming through the crystal with the corresponding resonance frequency.
Acoustic Modes of a Hemispherical Room
Authors: Flanagan J. L.
Published: September 2005

The acoustic modes of a hard-walled hemisphere are derived. Inside the enclosure the standing waves for the velocity potential are described by Ψ(r,θ,φ)=cossin(mφ)[Plm(cosθ)]j1(ωlqrc), where m and l are positive integers, m ⩽l, c is the sound velocity, Ptm are the associated Legendre functions, jt are the spherical Bessel functions, and ωlq are the ordered radian frequencies of the allowed modes. The eigenvalues are roots of [∂∂rjl(ωrc)]r=a = 0, where a is the radius of the hemisphere. Only the standing waves for which (m+l) is even are shown to satisfy the hemispherical boundary. Implications of the results to acoustic treatment for a hemispherical room are discussed.
Sound Synthesizer with Optical Control
Authors: Fujimura Osamu
Published: September 2005

A new sound synthesizing system controlled by an optical program pattern (similar to the Sonagram) has been devised. The system employs ADP crystals with different resonance frequencies as the mechanical filter bank with electrical input and optical output. As the source signal, any electrical wave form can be used, and the pitch of voiced sounds can be controlled by a separate pitch channel. Possibilities of development of some variations for the visible speech playback and a Vocoder system without any electrical filter bank are described.
Theoretical Analysis of the Solion Polarized Cathode Acoustic Linear Transducer
Authors: Larkam C. W.
Published: September 2005

Solions are electrical components involving charge transport by solution ions as contrasted to electrons, holes, or gas ions. Four general types of solion acoustic transducers may be distinguished on the basis of mechanism underlying the transducer action. One of these, the polarized cathode type, offers a combination of advantages, which includes low threshold pressure, high power gain, stable zero, and direct-current transmission. Individually constructed models with a nominally linear pressure response have been used successfully in the study of infrasonic disturbances transmitted through the earth and atmosphere as well as under water. Yet, design and construction methods have not previously been perfected to a degree that would ensure wide usage. The relatively sluggish motion of the charge carriers in the electrolyte of the transducer is at the same time a necessary condition for transducer action and a factor limiting the dynamic response. A theoretical analysis is presented to explain the observed behavior of the existing devices of this type and to indicate what may be expected from transducers having the benefit of more-refined fabrication techniques.
Some Characteristics of the Flexural Vibrations of Orthogonally Stiffened Cylindrical Shells
Authors: Hoppmann W. H.
Published: September 2005

The paper presents a résumé of a theoretical study of the problem of flexural vibrations of the wails of orthogonally stiffened cylindrical shells. Frequency equations are given for the stiffened shells. In addition an experimental method of verifying the theory is described. Experimentally determined frequencies for an isotropic as well as two different designs of orthogonally stiffened shells are given in tables. The experimental and corresponding theoretical results are discussed.

A peculiar dip in the frequency spectrum which was discovered by Arnold and Warburton for uniform isotropic shells is shown to exist theoretically and is verified experimentally for stiffened shells. In addition, there is shown to be a bias in the excitability of the modes of vibration as determined experimentally. The reason for this phenomenon is discussed.

The principal axes of stiffness are in the longitudinal and transverse directions for the shells under study. In one case the axis of maximum stiffness is in the longitudinal direction and in the other case it is in the transverse direction. As the stiffness tensor is the same for the two cases, except for orientation, an opportunity is provided for examining the effect of rotating the stiffness axes through 90°.
Analysis of the Flute Head Joint
Authors: Benade A. H. , French J. W.
Published: September 2005

The acoustical nature of the head joint of a transverse flute is examined in mathematical detail. The effective length of the flute is altered in the amount by an embouchure correction Δlc = (c/2πf) arctan {(e/2π) (f/r)/(2fr2 − f2)}, where f is the playing frequency, e is the speed of sound in the contained air, r the (17-mm) cork-to-embouchure distance, and f1 a parameter (near 1450 cps which is essentially the frequency of a Helmholtz resonator made by plugging the bore with a second cork a distance r below the embouchure. This correction is roughly constant at 42 mm over the normal playing range. Effects of cork position, lip position, and embouchure-hole size are discussed in detail, as is the effect of cavity resonances in the player's own mouth. Tuning errors caused by the edgetone-regeneration mechanism are shown to be correctible by a head joint taper perturbation. Three designs are analyzed, which produces a flattening at low frequencies, zero effect near 600 cps, and a maximum sharpening near 1000 cps. Above, this the correction returns smoothly to zero at the upper playing limit near 2000 cps. In the high register, the correction is produced jointly by the taper and the vent holes. The whole analysis is summarized by means of a detailed comparison of the Boehm design of flute with the older cylindrical-head, taper-bore model and with the purely cylindrical flute.
Speech Communications as Limited by Ambient Noise
Authors: Webster J. C.
Published: September 2005

Speech-intelligibility scores as a function of noise level are studied for face-to-face, sound-powered-phone, and amplified speech (earphone and loudspeaker) communication conditions. The speech-interference level (SIL) for octaves of noise centered at 500, 1000, and 2000 cps (0.5/1/2) is used as the measure of noise level. By using this noise measure, much of the work in this field can be brought together and interpreted. It is noted that “noisy” and “very noisy” spaces are associated with SIL's such that “shouting” or “very loud” voice levels (or 95-dB speech levels) are required for conversations at 1.5 or 3 ft, and this is the region where telephone conversations are judged to be “difficult” or “unsatisfactory.” All of these adverse noise conditions occur at the region where ear protection will aid intelligibility and at the boundary where ear protection should be used to protect against hearing losses. Where people must converse or communicate via some interior communication device, 0.5/1/2 SIL's above 70 dB should be avoided. At 0.5/1/2 SIL's greater than 90 dB, the wearing of hearing protection should be made mandatory and every noiseproofing technique (except a noise shield for the microphone) should be employed. At 0.5/1/2 SIL's above 100 dB, every noise-proofing technique should be employed
Sound Propagation in Near-Stoichiometric Ti-Ni Alloys
Authors: Bradley David
Published: September 2005

Experimental data on sound velocity illustrate the unusual velocity-temperature relationship of near-stoichiometric nickel-titanium alloys. The effect of temperature cycling, annealing, pressure, minimum exposure temperature, and time is also shown.
Applications of the Monte Carlo Method to Architectural Acoustics. II
Authors: Allred John C. , Newhouse Albert
Published: September 2005

Previous Monte Carlo studies of the statistical value of the mean free path and the frequency of collision of a geometric ray with the walls of a rectangular parallelepiped are revised and amplified. A systematic increase in the ratio of the mean free path calculated from statistical studies to the mean free path taken as 4V/S is observed to occur as the parallelepiped deviates from a cubical to a long, narrow, or a wide, low shape. The ratio of statistical mean free path to 4V/S and the relative collision frequencies with various walls as compared with normalized wall areas are given in tabular form.
Detection of Multiple Component Signals in Noise
Authors: Green David M.
Published: September 2005

The detectability of a complex signal, one generated by adding two sinusoids, and partially masked by white noise, is determined. Several frequencies and three durations are used for the signal. The experimental determinations are compared with three mathematical models. These models are all interpretable as an extension of the critical band concept. The data are best explained by a model in which it is assumed that two or more critical bands may be linearly combined. This implies that the auditory mechanism may change the appropriate parameters of the analysis process in order to match the signal to be detected.
Ultrasonic Attenuation Caused by Scattering in Polycrystalline Metals
Authors: Papadakis Emmanuel P.
Published: September 2005

Ultrasonic-attenuation measurements have been made on fine-grained specimens of several metals. The grain-size distributions and ultrasonic velocities in these metals were also determined. The experimental attenuation is in good quantitative as well as qualitative agreement with current theory. Nickel and three iron alloys, one 30% nickel reported previously, the second 12% chromium (type 416 stainless steel), and the third 17% chromium and 1% carbon (type 440-C stainless steel), all gave good results. Brass also gave good results, but copper showed much twinning, which as yet is unaccounted for.
Difference Limen for Tone Diminution
Authors: Kirk Roger E.
Published: September 2005

The difference limen for tone diminution was investigated with diminution rate, fundamental frequency, and tonal complexity as parameters. Electronic means provided two tones whose diminution rates were independently adjustable. The tones were alternately presented to subjects over PDR-8 earphones. The method of constant stimuli was used in determining the difference limen.

The relative difference limen for tone diminution is of the order of 412 to 512% over the range of diminution rates investigated. The difference limen is relatively independent of fundamental frequency and tonal complexity. The relationship between the difference limen and diminution rate is described by an equation of the form Y = 0.048X where Y and X are measured in db/sec.
Numerical Solution for Sound Velocity and Absorption in Cylindrical Tubes
Authors: Shields F. Douglas , Lee K. P. , Wiley W. J.
Published: September 2005

A numerical solution of the Kirchhoff equation for the propagation constant of longitudinal sound waves in infinitely long cylindrical tubes has been obtained. The solution, which avoids the wide-tube approximations, shows that the percentage errors in the von Helmholtz-Kirchhoff tube velocity correction and tube absorption are both roughly equal to the percentage the velocity correction is of the free-space velocity. The error in the von Helmholtz-Kirchhoff equations can be plotted as a function of fD/a, pD/ηa, and γ. (f is the sound frequency, D the tube diameter, a the free-space velocity, p the gas pressure, η the viscosity, and γ the ratio of specific heats.) Recent absorption measurements in Ar are in agreement with values calculated numerically, but measured velocities indicate the need for considering molecular slip at the tube wall. Thermal relaxation is introduced into Kirchhoff's basic equation by using the Eucken relation k/coη − (9γ −5)/4 and considering γ to be the ratio of complex relaxing specific heats. Viscothermal and relaxation effects are found to be additive only if the frequency is near the cutoff frequency for the first unsymmetric mode and the f/p values do not extend to the megacycle/second atmospheres range.
Harmonic Distortion in Cochlear Models
Authors: Tonndorf Juergen
Published: September 2005

According to Békésy, the envelope over the train of waves traveling along the cochlear partition is asymmetrical; the distal slope being steeper than the proximal one. In experiments on cochlear models, this asymmetry was seen to increase with intensity. Introduction of artificial “eddies” of varying velocity into the model (while the intensity was kept constant) indicated that the “eddies” were responsible for the observed increase in asymmetry of the envelope. Theoretical considerations showed that the “eddies” convert the (trochoidal) particle motion within the cochlear fluids into a cycloid form of motion. The bilateral effects of this particular cycloid motion lead to the following alteration of the displacement pattern of the cochlear partition: (1) to an amplitude decrement with distance (accounting for the above asymmetry of the envelope); (2) to peak clipping; and (3) to an aysmmetry, the displacement being larger toward the tympanic than toward the vestibular scala. These theoretical results were confirmed by an observed change of the particle orbits. Their elliptical shape became “flattened,” containing both odd and even harmonics. Resolution of this distorted pattern of fluid motion along the cochlear partition was in accordance with the place principle of frequency localization.
Rating Scales in Detection Experiments
Authors: Larkin W. D.
Published: September 2005

The use of rating scale isosensitivity data to test a discrete, two-state model for binary choice detection experiments is shown to be inappropriate unless new assumptions are made. It is argued that, whatever assumptions are added, rating-scale isosensitivity curves will be different from binary-choice isosensitivity curves. The suggestion is made that a multistate model may be more appropriate than a two-state model for rating experiments, but the resulting isosensitivity curves appear to be too similar to those of signal-detectability theory to make rating-scale data useful for deciding between the theories.
Dependence of Temporary Threshold Shift at 4 kc on Intensity and Time
Authors: Ward W. D. , Glorig A. , Sklar D. L.
Published: September 2005

The results of a series of studies, using normal ears, on the effects of broad-band noise (a noise having equal energy in all octave bands from 75 to 10 000 cps), can be summarized in two equations. The growth of temporary threshold shift (TTS) at 4 kc is given by TTS2 = 1.06R(S − 85)[log10(T/1.7)], where TTS2 is the TTS in db 2 min after cessation of a T-minute exposure to a noise having a sound pressure level (SPL) of S db; R is the fraction of the time that the noise is on. This equation holds for T>5 min, 85<S<110 db (perhaps higher), and all values of R provided that the noise bursts are 250 msec to 1 min long. The recovery from 2-hour exposures is described by TTSt = TTS2[1−0.37 log10(t/2)], where TTSt is the TTS remaining after t minutes of recovery. This equation holds when t is 2 min or more, and when TTS2 does not exceed 50 db.

Thus the relation between intensity and duration for constant TTS at 4 kc is much more complicated than predicted by the equation IT = K of classical psychophysics, or the I12T = k recently suggested, although both are approximately true in particular regions. Furthermore, it is evident that a noise on only part of the time is much less dangerous than one on continuously.
Digitized Voice-Excited Vocoder for Telephone-Quality Inputs, Using Bandpass Sampling of the Baseband Signal
Authors: Gold Bernard , Tierney Joseph
Published: September 2005

A voice-excited vocoder transmits a portion of the baseband signal to serve as the synthesizer excitation signal. When the input speech comes from a carbon-button transmitter via a telephone line, the transmitted baseband must begin above 300 cps. Thus, a low pass sampling scheme for baseband digitization is inefficient. A particular bandpass sampling procedure that is applicable to a digitized VEV is described in this note. The baseband signal is sampled by two pulse trains each of frequency equal to the center frequency of the signal spectrum but displaced from each other by one-quarter of the sampling period. To recover the signal, both sample trains are applied to a desampling filter identical to the original baseband filter, This technique makes possible the specification of a 9600 bit ser VEV for ordinary telephone speech. Testing was done on a laboratory vocoder together with a general purpose computer simulating a real-time sampler-quantizer, Six bit quantization of the bandpassed samples was shown necessary to produce synthetic speech that was samples was shown necessary to produce synthetic speech that was compatable in quality to that produced by the VEV in the analog mode.
Ultrasonic Absorption and Dispersion in Monatomic Gases. II
Authors: Enns R. H.
Published: September 2005

The propagation of ultrasound through a classical, dilute, monatomic gas has been previously studied in terms of the Boltzmann collision equation with the collision term replaced by the relaxation model ∂f∂t]coll = −(f−f̄)τ where f̄ was the displaced Maxwellian distribution in the presence of the sound wave and the relaxation time τ was assumed to be independent of the instantaneous particle velocity v. This model, although yielding the correct qualitative behavior at low frequencies, did not yield the classical result for the slope of the absorption curve. Rather than taking τ to be independent of v, it is now assumed that τ −l v where the mean free path l is now v independent. That this new model might yield some improvement in the slope of the absorption curve at low frequencies is suggested by the fact that model yields the correct ratio of the thermal conductivity to the shear viscosity: namely, (15/4)(K/m), as opposed to the result 5 (K/m) obtained on assuming τ to be independent of v. Some slight improvement is obtained, but the classical absorption does not result. The reason for this is briefly discussed.
Spontaneous Electrification of Dust Figures in a Kundt's Tube
Authors: Staszewski W. , Adamczyk B.
Published: September 2005

It is the purpose of this paper to present evidence that in a Kundt's tube under suitable conditions spontaneous electrification of dust particles takes place. Appreciable time is needed for the particles to acquire a measurable charge, the sign of which depends on the material of the tube as well as that of the dust.
Advantages of the Discriminability Criterion for a Loudness Scale
Authors: Garner W. R.
Published: September 2005

It is argued that a loudness scale based on the discriminability criterion would be better than one based on those methods which assume that direct numerical responses adequately reflect the nature of the loudness experience. The evidence and argument presented show: First, there is just as good a logical basis for accepting the discriminability criterion as for accepting the direct response criterion. In both cases we have to assert face validity which is arbitrary and may be incorrect. Second, the scales based on the discriminability criterion show less interobserver variability, are influenced less by specific experimental conditions, and are less affected by stimulus context than scales based on the fractionation procedure—the major direct response method used. Third, and most important, most of the direct response procedures themselves give results which agree with scales based on a discriminability criterion. It is, in fact, only the ratio scaling or fractionation procedures which give results at variance with all the rest.
Maintenance of Alertness by a Loud Auditory Signal
Authors: Pollack Irwin , Knaff P. Robert
Published: September 2005

An extremely serious operational problem is the maintenance of a high level of visual target detection performance during long periods of watch. Will a loud auditory signal aid in the maintenance of a high performance level under these conditions? Apparently, it will. When the failure to detect a target was coupled with the occurrence of the blast of a truck horn, average visual target detection percentages increased substantially, especially for the less proficient observers.
Adjusting the Method of Adjustment: SD vs DL
Authors: Cardozo B. L.
Published: September 2005

The spread σ in the final settings of repeated adjustment processes is often taken equal to (or at any rate proportional to) the difference limen d as found by a method of forced choice. A detailed investigation into the adjustment process shows that this is not necessarily correct. In principle, σ = (ξd)12, where ξ is the (average) move length in the adjustment process. This implies that σ is proportional to the square root of the difference limen if σ is constant. Normally, however, the subject intuitively chooses ξ roughly equal to 13d, so that σ∼d holds in most practical cases. These ideas are applied to binaural frequency discrimination of sinusoids, the duration of which is variable.
Residual Effects of Low Noise Levels on the Temporary Threshold Shift
Authors: Trittipoe William J.
Published: September 2005

The present study measures the temporary threshold shift (TTS) following two conditions of high-level noise exposure: (1) a control condition where the high-level noise is preceded by a period of silence; (2) an experimental condition where the high-level noise is preceded by noise levels which alone produce no apparent TTS. When the non-TTS-producing noise was coupled with the high-level noise, a greater threshold shift resulted than when equivalent periods of silence preceded the same high-level noise.
Effects of Several Mental Tasks on Auditory Fatigue
Authors: Collins William E. , Capps Mary Jayne
Published: September 2005

Eight male subjects were exposed for 3 min to a 4000-cps fatigue tone at 40 dB SL. Each subject was tested under four task conditions: mental arithmetic (MA), written long division (LD), threshold determination (TD) on a 500-cps tone, and reverie (REV). Temporary threshold shifts (TTS) were computed by comparing pre- and post-fatigue thresholds. MA produced significantly more TTS than any other condition and LD resulted in greater shifts than REV. Amount of auditory fatigue can vary with the type of mental activity performed by the subject.
Signal Detection as a Function of Frequency Ensemble. I
Authors: Veniar Florence A.
Published: September 2005

This paper presents the results of an experimental investigation of the detection of a signal in noise as a function of signal ensemble size and ensemble frequency range. By signal ensemble size we mean the number of signals of different frequency that are equally likely to occur and which the observer must try to detect. By ensemble frequency range we mean the frequency separation between the lowest and the highest frequency signals included in that ensemble. Data are presented for the four observers who took part in the experiment. The results obtained are compared with predictions based upon three mathematical models. Using efficiency measures, the results obtained are also compared with performance expected of a mathematically optimum detector. Finally, the possibility is suggested that the models discussed are not necessarily mutually exclusive, but rather complementary in the over-all view of detection.
Correlation with Similar Uniform Collinear Arrays
Authors: Jacobson Melvin J.
Published: September 2005

This report is concerned with the nature of the mean output of a single correlator receiving system when the input is a narrow frequency band signal arising from a localized source in space. The signal is received by two uniform, collinear arrays having an equal number of omnidirectional receivers. The mean output as a function of steering is bounded by the product of the space factors of the two arrays, so that the gross nature of the mean can be determined by investigating the main lobe width and side lobe level of the space factor product. These two quantities are studied as functions of the number of receivers, the receiver spacing in wavelengths, and source direction.
Study of Some Cues in the Perception of the Voiced Stop Consonants
Authors: Hoffman Howard S.
Published: September 2005

Previous research involving synthetic speech reveals that both the second- and the third-formant transitions play a role in the perception of the voiced stops, |b|, |d|, and |g|. The present experiment examined an additional cue (burst frequency), repeated a portion of the previous research, and collected more information about how the cues act in various combinations.

Synthetic speech sounds containing one cue, all possible combinations of two cues, and all possible combinations of three cues were tested on a large group of listeners.

Burst frequency was found to act as a cue for the perception of the voiced stops in much the same manner as this variable affects the perception of the unvoiced stops. To the extent that the present experiment overlapped previous research, the two sets of findings were in very close agreement. When cues were combined, they shared in the control of perception in such a way that the contribution of any one cue was largely independent of the nature and the number of the other cues present in the sound. The individual cues seemed to have directional properties somewhat like vectors. The addition of cues produced effects somewhat like the addition of vectors.
Temporary Shifts in Auditory Thresholds of Chinchilla after Exposure to Noise
Authors: Peters Edward N.
Published: September 2005

Initial information is presented on temporary threshold shifts in chinchilla as measured by behavioral audiometry. Data are presented for two animals after selected exposures to either a 12- or 1 oct band of high-frequency noise.
On the Effect of Missile Motion on Rocket Noise
Authors: Powell Alan
Published: September 2005

On the assumption that turbulent mixing accounts for the major part of rocket noise, it is tentatively suggested that the rocket noise intensity at a given point on a missile varies as [Mj − MmMj]2(1 − Mm)2, where Mj is the highly supersonic Mach number of the jet efflux relative to the exit, and Mm is the subsonic Mach number of the missile, both referred to the speed of sound in the external air. The frequency characteristics are little affected.
Broad-Band, Thermally Generated Noise Voltage of a Resonant Electroacoustic Transducer
Authors: Kendig Paul M.
Published: September 2005

Utilizing a simplified equivalent circuit for an electroacoustic transducer with a single resonance, it is shown that the mean-square thermally generated noise voltage for the entire frequency range is just kT kc2/C0, where k is the Boltzman constant, T is the Kelvin temperature, kc is the effective electromechanical coupling coefficient, and C0 is the clamped capacitance. This voltage is generated by the mean total thermal energy kT in the circuit, which results from the circuit's two degrees of freedom. From impedance measurements on a transducer with two pronounced resonances, it has been shown that this relationship, with some modifications, approximates the conditions existing in a transducer with multiple resonances. Expressions for the equivalent noise pressure of a transducer and applications to the measurement of low-level signals with a resonant transducer are discussed.
Genesis of Endolymphatic Hypoxia Following Acoustic Trauma
Authors: Misrahy G. A. , Arnold J. E. , Mundie J. R. , Shinabarger E. W. , Garwood V. P.
Published: September 2005

(1) Loud bursts of pure tone tend to decrease slightly the hydrogen diffusion rate into the first turn of the scala media of the eupneic guinea pig and markedly in the hyperventilated animal (2) White noise increases the rate of diffusion of hydrogen gas into the auditory cortex of the nonanesthetized cat. (3) Acoustic trauma produces vascular stasis in exposed blood vessels of the hamster cheek pouch.

These results are interpreted as indicating that the endolymphatic hypoxia following loud sound is due to a decrease in the oxygen supply/demand ratio resulting from (a) an increase in metabolism, and (b) no change, or decrease in cochlear blood flow and/or permeability of the stria vascularis.
Radiation Impedance of a Piston on Cohesive Soil
Authors: Niemoeller Arthur F.
Published: September 2005

An experimental investigation was made to determine the mechanical radiation impedance of a rigid piston on the surface of clay soil. The force on and the velocity of the piston were measured to determine both the real and imaginary parts of the radiation impedance as a function of excitation frequency of the piston. Measurements were made for six different combinations of moisture and density of the soil, and results of these measurements are presented in graphical form. In the frequency range 50–200 cps, the load presented to the piston by the soil is essentially the same as would be presented by a mechanical compliance, the value of which varies with both moisture and density of the soil. The value of this compliance was computed for six different combinations of moisture and density. Second-order dependence of compliance on moisture and density was assumed, and coefficients in a second-order equation relating compliance to moisture and density were computed. The three-dimensional surface that represents this equation is presented in graphical form. Errors in the results are discussed.
Intelligibility at High Voice Levels and the Use of a Megaphone
Authors: Pickett J. M. , Pollack Irwin
Published: September 2005

A small megaphone was tested for use in direct voice communication high levels of vocal output against backgrounds of noise. Intelligibility scores were determined for 12 talkers, speaking with and without the megaphone, over a range of field voice levels of 70 to 100 db SPL (at 1 m). Nearly the entire over-all acoustical gain produced by the megaphone was realized in improved intelligibility above backgrounds of white noise and low-frequency noise. The acoustical gain of the megaphone permitted a lower voice level, and, hence, delayed the deterioration in intelligibility associated with distortions due to shouting. Frequency shifts in the voice spectrum were measured, with and without the megaphone, over a range of vocal efforts from conversational to maximum shout. Control tests demonstrated that the voice-frequency shifts associated with shouting are not the primary factor in the deterioration of intelligibility; the frequency shifts appear to be only symptomatic of serious vocal distortions in shouting.