bluuebunny/crossref_metadata_2025 huggingface dataset:
Receiver Operating Characteristics and Psychometric Functions Determined under Simple- and Pedestal-Detection Conditions
Authors: Leshowitz Barry
Published: September 2005

Receiver operating characteristic (ROC) curves and psychometric functions for detection of 1000-Hz sinusoids presented against a background of narrow-band noise were obtained using a one-interval rating-scale procedure. Signals were added to noise alone (simple detection) or to noise plus sinusoidal pedestal (pedestal detection). While almost all stimulus-oriented theories of signal detectability predict a monotonically decreasing relation for the slope of the ROC curve as a function of signal strength, slopes of the empirically determined ROC's never showed a systematic decrease with increases in signal amplitude. Significant differences between the range of the psychometric functions for simple- and pedestal-detection conditions were noted. Two modifications of the basic signal-detection approach, a fluctuating criterion model and a neural counting scheme, are proposed to account for the data. An investigation of the neural counting model was carried out in computer simulation, and the influence of various exponents in the power-law transducer function relating stimulus energy and neural counts was examined. Implications of the theoretical and empirical results for our notions about the nature of the underlying probability distributions and decision mechanisms are discussed.
Auditory Detection and Recognition under Conditions of Lateral, Temporal, and Composite Uncertainty
Authors: Lowe G. , Earle D. C.
Published: September 2005

The effects of temporal and lateral uncertainty were separately shown to produce decrements in the detectability of a tonal signal in noise. Rating procedures were used, together with left/right recognition responses where appropriate. When both dimensions of uncertainty were present simultaneously, the interaction was found to be complex. Observed false-alarm rates provided a reliable index of the possible detection strategies involved in these tasks.
Noise Masking of a Change in Residue Pitch
Authors: Patterson Roy D.
Published: September 2005

A comparison was made of the effectiveness of noise in masking (1) a change in the frequency of a sinusoid, and (2) a change in the repetition rate of a pulse train that had no low-frequency energy. The sinusoid and the pulse train had the same pitch. It was found that, whereas the change in the pitch of the sinusoid was better masked by low-frequency noise, the change in the residue pitch produced by the filtered pulse train was more easily masked by high-frequency noise. These results replicate the findings of Small and Campbell (1961). We conclude as they did that the basis for the residue pitch of the pulse train is its high-frequency components. In a second experiment, a pair of sinusoids was used to produce the residue pitch. The same masking technique was employed, and again the results indicate that the residue pitch is not based on a nonlinear distortion component, but rather is based on information being transmitted through high-frequency components (2100 Hz).
Influence of Contralateral Noise on Auditory Intensity Discrimination
Authors: Swisher Linda P. , Dudley John G. , Doehring Donald G.
Published: September 2005

Auditory intensity discrimination at 2000 Hz was determined for the left and right ears of normal listeners at intensity levels of 23 to 78 dB sound-pressure level (SPL) in the presence of contralateral white noise and sawtooth noise from quiet to 63 dB SPL. It was hypothesized that contralateral noise might affect the left temporal lobe in a manner analogous to left-temporal excision, resulting in improved intensity discrimination only in the left ear. Results showed that intensity discrimination was significantly improved in both ears by contralateral noise for subjects receiving test tones of 38 dB and above. Contralateral noise did not improve intensity discrimination in subjects who received test tones of 38 dB and below, but the difference limens for the left ear were significantly smaller in both quiet and noise. The original hypothesis was not upheld, and further study of the limiting conditions for the enhancement of differential sensitivity by contralateral noise is suggested. The finding of left-ear superiority for lower-level test tones is discussed in relation to right-hemisphere dominance for nonverbal stimuli.
Determination of the Rate of Change of Fundamental Frequency with Respect to Subglottal Air Pressure During Sustained Phonation
Authors: Lieberman Philip , Knudson Ronald , Mead Jere
Published: September 2005

The rate of change of fundamental frequency with respect to transglottal air pressure was determined for a single male speaker by sinusoidally varying buccal air pressure while the speaker sustained short episodes of pronation at various fundamental frequencies. The speaker phonated at two levels of “effort,” i.e., “soft” and “loud” phonation with and without auditory feedback. The sensitivity of the larynx to variations in transglottal air pressure varied from 3 to 18 Hz/cm H2O. Fundamental frequency was most sensitive to variations in transglottal air pressure at high frequencies and in the “soft” mode of phonation. The minimum transglottal air pressure for sustained phonation was 2–3 cm H2O. These results are consistent with some earlier studies and a recent theoretical model of laryngeal activity. These results further indicate that variations in subglottal air pressure and adjustments in laryngeal muscular tension both play a role in regulating fundamental frequency during normal speech.
Piezoelectric Shakers for Wide-Frequency Calibration of Vibration Pickups
Authors: Jones E. , Yelon W. B. , Edelman S.
Published: September 2005

This paper describes a piezoelectric shaker consisting of a combination of damped resonant cylindrical elements. Material characteristics and design parameters are chosen so that the resonances of the combined elements overlap to provide “good” motion over a wide frequency range. Data from three shakers are presented to show how a suitable set of shakers can be used for the calibration of vibration pickups at frequencies up to 100 kHz.
On the Effects of Stochastic Boundary Perturbations on Acoustic Wave Propagation—The Theory
Authors: Bugnolo Dimitri S.
Published: September 2005

A theoretical procedure is developed in an effort to solve the acoustic propagation problem in the ocean in the presence of stochastic boundaries. The result for the mean and mean-squared value of the acoustic field should prove useful in calculating many of the effects of a stochastic surface, without the necessity of treating the surface as a separate problem.
Stability of the Cochlear Microphonic over Time in an Anesthetized Preparation
Authors: Price G. Richard
Published: September 2005

The cochlear microphone (CM) has been viewed as stable over long period of time. Recent experiments in which CM was used as an index of hearing loss noted changes occurring as a function of time alone. Experiments were therefore conducted to study these changes. Shifts in CM sensitivity were measured at 13 frequencies in 13 anesthetized cats for periods of up to 300 min. The animals became less sensitive as a more or less linear function or time, the average shifts amounting to about 4 dB. The shifts are regular enough that data can be corrected to allow for them: however, the cause of the shifts their eventual size, and their reversibility all remain to be established.
Suggested Simplified Presentation of One Aspect of Finite-Amplitude Field Theory
Authors: Welsby V. G.
Published: September 2005

Rewriting the equation of state, with volumetric strain as the variable instead of density strain, brings out clearly the fact that the second-order source density representing the behavior of finite-amplitude acoustic waves is determined by a parameter defined as the second-order compressibility of the medium.
ON THE MEASUREMENT OF THE TEMPERATURE RISE IN COMPOSITE PIEZOELECTRIC STACKS
Authors: Royster L. H.
Published: September 2005

A brief description of an experimental technique utilized to measure the temperature rise in a composite piezoelectric stack is presented.
Nature of the Sonic-Boom Problem
Authors: Hubbard Harvey H.
Published: September 2005

Significant factors of the sonic-boom problem are shown to be numerous and to involve a variety of scientific and engineering disciplines. Special mention is made of the rôles of aircraft design, aircraft operations, and the atmosphere in affecting the sonic-boom ground exposures and the effects of sonic booms on people, buildings, etc. The material of this paper is introductory to the more detailed discussions that follow.
Effects of Sonic Boom on People: St. Louis, Missouri, 1961–1962
Authors: Nixon Charles W. , Borsky Paul N.
Published: September 2005

The vicinity of St. Louis, Missouri, was exposed to approximately 150 sonic booms during a 10-month period from July 1961 to April 1962. Ground overpressures, ranging up to about 3 lb/sq ft. were carefully measured for a series of 17 of the supersonic flights. Data obtained from over 2300 direct interviews, analyses of complaints, and engineering evaluations of alleged damage were related to information on aircraft operations and sonic-boom overpressure measurements. Most residents interviewed indicated some interference with routine living activities, yet less than 1% filed formal complaints. Alleged building damage was superficial in nature and consisted mostly of cracks in brittle surfaces. There were no reports of direct adverse physiological effects.
Experience in the United Kingdom on the Effects of Sonic Bangs
Authors: Warren C. H. E.
Published: September 2005

Over the past five years, a number of exercises involving the making of bangs have been staged in the United Kingdom. The bangs have been made both by flying aircraft at supersonic speeds and by firing explosive charges. From this work, information has been obtained on the intensities and waveforms of aircraft sonic bangs as measured outdoors, on the nature of the disturbances that are recorded inside buildings, and on the subjective reactions of people to these bangs. The paper summarizes the results of this work.
Assessment of Sonic-Boom Problem for Future Air-Transport Vehicles
Authors: Baals Donald D. , Foss Willard E.
Published: September 2005

The economic feasibility of the supersonic transport is critically dependent upon specification of the sonic-boom requirements. Aircraft-design techniques and modifications to the mission profile are evaluated relative to the sonic-boom intensity. An intermediate-range, domestic, supersonic transport optimized from considerations of the sonic boom is analyzed relative to potential boom levels. Future air vehicles, such as the hypersonic transport and ballistic transport, are discussed relative to their sonic-boom characteristics.
Mechanism of Binaural Fusion in the Hearing of Speech
Authors: Sayers Bruce McA. , Cherry E. Colin
Published: September 2005

The mechanism of binaural fusion is here discussed as a form of statistical operation based upon the brain's execution of running cross-correlation of the two ear signals. The technique of measurement of the degree of binaural fusion, outlined in our earlier paper, is here extensively applied to sine waves, to chords of sine waves, to intoned vowels and to running speech; such technique results in curves which assess listener's judgments as to whether a source of sound lies in the right or left hemisphere of subjective space. An extended theory is also developed here explaining these judgment curves in detail. Finally, a discussion is made of the importance of having an understanding of the mechanism of binaural fusion, in any consideration of our binaural directivity sense and our speech discrimination sense (the “cocktail, party problem”).
Nonlinear Properties of Circular Orifices
Authors: Thurston George B. , Hargrove Logan E. , Cook Bill D.
Published: September 2005

The results of an experimental study of the nonlinear fluid flow properties of thin, square-edged, circular orifices are described. Liquids were used at low frequencies. The flow conditions considered are a sinusoidal oscillation of the fluid in the orifice and a sinusoidal oscillation with a steady flow component added. For the sinusoidal flow condition the pressure differential developed across the orifice contains higher odd harmonics. The addition of a steady flow component adds second harmonic to the pressure as well as influences the magnitude of the odd harmonics. Further, in this case, the steady pressure component is a function of the magnitude of both the sinusoidal and steady flow components. An equation descriptive of the pressure-flow relation is presented. In this equation the orifice properties are specified by three constants, two of which are the acoustic resistance and acoustic inertance as normally measured at low amplitudes of excitation. The relations derived from this equation are compared with experimental measurements.
A Continuously Variable Filter for Acoustic Applications
Authors: Fant Gunnar
Published: September 2005

The heterodyne filter, developed at the RIT, Stockholm, Sweden, is a laboratory transmission system for the speech frequency range. It can be used as a band pass filter with continuously variable low frequency cut-off and high frequency cut-off of very steep attenuation characteristics, 1–2 c.p.s. per db and 60-db attenuation outside the band pass range. The two cut-off frequency settings can be chosen independently in the frequency range 0–4000 c.p.s. One frequency dial on the panel controls the band width, another controls the low pass cut-off. A band suppression action can also be obtained. In this case the band width is restricted to 2 alternative values. The mid-frequency will be continuously variable, 0–4000 c.p.s. The heterodyne filter is meant for articulation and hearing tests in acoustic research work but can also be used as a wave analyzer with continuously variable band-width of 50 c.p.s.-4000 c.p.s. in the frequency range of 20–12,000 c.p.s.
Supplementary Paper No. 2. Individual Differences in Noise Masked Thresholds
Authors: Webster J. C. , Gales R. S. , Lichenstein M.
Published: September 2005

Absolute and thermal noise masked pure tone thresholds were obtained for 3666 people at the 1948 San Diego County Fair. For groups having equal absolute hearing losses, slightly greater masked losses were found for the older age groups (over 40), females, and individuals who had not worked in noise, had not had musical training, and who were aware of hearing difficulty. It was further found that those with predominantly low frequency losses had greater masked losses than those with predominantly high frequency losses. Ratios of the intensity of the tones to intensity per cycle of the masking noise were obtained for masked thresholds of people whose corresponding absolute thresholds varied over a seventy-db range. These ratios are plotted as a function of absolute hearing loss.
The Fenestration Operation and Some Acoustic Problems
Authors: Walsh T. E.
Published: September 2005

The fenestration operation is designed to allow sound to by-pass the fixed conductive mechanism in the middle ear in conductive deafness. This is done by: (1) exposing the lateral horizontal canal and the ampullated end, (2) making an opening into this canal, and (3) sealing the opening with a flap of skin from the posterior aspect of the external auditory canal. The objective of the fenestration operation is to restore serviceable hearing to those with conductive deafness. Clinical evaluation of cases suitable for this operation is described. Important requisites are: (1) freedom from aural infection, and (2) good cochlea function. It is found that speech tests are most reliable in diagnosis and prognosis and the concept of the “Social Adequacy Index” has proved valuable as a prognostic method. The results of our series are given. The clinician is faced with certain problems in this work which he would present to physicists for answers.
A Reactance Tube Circuit Applicable to Microphone Calibration
Authors: von Wittern W. W. , von Gierke H. E.
Published: September 2005

A reactance tube circuit was developed which acts as a capacitance without any resistive component for frequencies within the range one to four megacycles. This capacitance may be modulated by an alternating voltage in the frequency range 30 cycles per second to 200 kilocycles per second in such a manner that the capacity change is independent of the modulating frequency and is proportional to the modulating voltage. This circuit is useful when it is desired to produce or measure absolutely a periodic change of capacity. It was applied in this instance to the amplitude and phase calibration of a condenser microphone. For this purpose the microphone was excited by the electrostatic actuator method. The microphone was inserted in a tuned high frequency circuit and modulated this circuit by its capacity changes. The reactance tube was connected parallel to the microphone and the modulation of its capacitive current was so adjusted that it compensated in amplitude and phase the capacity change of the microphone. The modulating voltage of the reactance tube is then a direct measure of the capacity change of the microphone. The absolute value of the pressure producing this change of capacity of the microphone was found, at low frequencies, by pressure chamber calibration. The phase shift of the microphone is measured by the phase shift between the microphone actuator voltage and the modulating voltage of the reactance tube. The reading of the compensation was made very accurately by using high amplification. One of the advantages of this zero method is that the frequency response of the amplifiers, the attenuation and phase shift of the narrow band filters used between the stages, need not be known. The amplitude and phase calibration of condenser microphones, up to 200 kilocycles per second, have been accomplished using this method.
Ultrasonic Measurement Technique for Small Specimens
Authors: McSkimin H. J.
Published: September 2005

Phase comparison at high ultrasonic frequencies is found to be particularly suited to velocity measurements for small solid specimens such as single crystals. For moderate accuracy and a minimum of equipment a pulse overlap method is used for determining the frequency at which the path length contains an integral number of wave-lengths. For greater precision, and for measuring small changes in velocity (as a function of temperature, for example) balanced circuits with calibrated phase shifters may be employed. The use of 14 λ-plastic seals between driver and specimen minimizes phase errors at the reflecting interfaces.
Calculation and Measurement of the Loudness of Sounds
Authors: Marshall J. L. , Beranek L. L. , Cudworth A. L. , Peterson A. P. G.
Published: September 2005

In a previous paper a method was described for calculating the loudness of pure tones, combinations of tones, and continuous-spectrum noise from measurements made with contiguous-band analyzers. This method is supported by recently published results on loudness. The basis of the method is the hypothesis that the loudness of a noise spectrum can be obtained by dividing the spectrum into bands, replacing each band by a pure tone of equivalent r.m.s. amplitude and then determining the loudness of each tone from equal-loudness contours and a loudness vs. loudness-level function. The total loudness is then the sum of the loudnesses of the individual bands. Comparisons of calculated levels with experimental results of subjective loudness judgments are made assuming an analyzer with ten contiguous frequency bands, each 300 mels wide, and an analyzer with five contiguous frequency bands, each about 600 mels wide. The calculations are made using the equal loudness contours of Fletcher and those of Churcher and King. An important feature of this method is that its operations can be performed electronically, thus providing a design basis for a loudness meter. The operating principles of such a meter necessitate a set of band-pass filters, and a non-linear network to simulate the ear's response within each band. A meter designed and constructed for this purpose is described.
Stylus-Groove Relations in the Phonograph Playback Processes
Authors: Miller Frank G.
Published: September 2005

The motion of a reproducer stylus in a phonograph groove has been subjected to a mathematical analysis which includes the joint effects of tracing distortion and elastic deformation of the groove wall. The lateral motion of the stylus at fundamental frequency is obtained as a product of three factors: (1) A stylus-groove response function which increases slowly to a major peak occurring at resonance between the compliance of the groove walls and the effective mass of the stylus, and then falls off rapidly; (2) a translation loss which is small at low frequencies but becomes complete at a cut-off wave-length determined by the stylus radius, the tracking force and the elastic properties of the record material; and (3) a scanning loss which arises when the dimensions of the contact surface between stylus and groove wall become significant in comparison with the recorded wave-length. It is found to be still possible to calculate the harmonic and intermodulation distortion products on the basis of rigid-wall tracing distortion theory provided the amplitudes of the predicted distortion terms are multiplied by both the stylus-groove response function and the scanning loss function. Non-linear effects of deformation turn out to be negligible in comparison with tracing distortion. Measurements made with a series of recordings programmed to exhibit these effects confirm the analysis in all important respects.
Some Applications of Square-Wave Testing Techniques to the Evaluation of Disk Recording Systems
Authors: Bradshaw Samuel R. , Wathen-Dunn Weiant
Published: September 2005

Pertinent aspects of the theory of square-wave testing will be discussed, and data will be presented showing how certain facts concerning the over-all response-frequency characteristic and equalization may be determined, as well as resonances in various parts of the system. Given an adequate recording system, a short cut of “square waves” on the outside of each record provides the user with a rapid means of determining whether or not his playback system is properly equalized and otherwise adequate for reproducing the recorded material.
Free-Field Thresholds vs. Pressure Thresholds at Low Frequencies
Authors: Rudmose Wayne
Published: September 2005

In an earlier paper data were reported indicating there was no difference between minimum audible field and minimum audible pressure at low frequencies. No satisfactory explanation was available at that time as to why these results differed from previously published data except the statement that body noises, breathing, etc., had been minimized. Further work has now produced a satisfactory explanation. Furthermore, if a well-sealed volume of 6 to 7 cm3 is maintained invariant over the eardrum and the mechanical isolation of the signal source progresses from good to bad, the difference between MAF and MAP varies from 0 to about 16 db. Data have been obtained for deviation of MAP from MAF as the volume and mechanical isolation are kept constant, the seal being broken by measurable amounts. Finally, to study the effect for the smallest possible volume, the plugged ear was fed acoustically from a high impedance source that was well-isolated mechanically. With this arrangement the results indicate that for the 2-cm3 volume the difference between MAP and MAF can be made less than 4 db by carefully controlling the subject. This control involves the position of the teeth, tongue, arms, etc.
A Warble Tone Audiometer Test Suitable for Group Administration over Loudspeakers
Authors: Webster John C.
Published: September 2005

Using warble tones to reduce the effect of standing waves and utilizing a design of multiple crossings of the auditory threshold, a reliable audiometer test was developed. It was recorded on a phonograph disk and is suitable for either headset or speaker administration to large groups of people. The rate of warble is 5 c.p.s. and the extent is ± 12.5 percent at 500 c.p.s. and ± 125 c.p.s. for the frequencies 1000, 2000, 4000, and 8000 c.p.s. A modification of the usual pulsed-tone method is utilized. Each test item consists of from zero to four pulses, but each succeeding pulse within an item is softer than the preceding pulse. The pulses are chosen to give hearing loss levels of 40, 30, 20, 10, and 0 db. Five crossings are made of any person's threshold as long as his hearing loss is between 5 and 35 db. This test was given binaurally to 200 college students over both headsets and speakers. The group pure tone test described by Harris was given binaurally over headsets as a control test. The test-retest reliability of the warble tone test did not differ statistically from the group pure tone test. Validity measures among all of these group tests and between each of the group tests and individual tests will also be reported.
A New Pure Tone Group Audiometer Test
Authors: Allison Ralph E. , Larr Alfred L.
Published: September 2005

Free-field audiometer testing is practical. Loud speakers used in a reasonably quiet room with a five percent frequency warble on a pure tone give a relatively uniform sound pattern throughout the test room. Each person records the number of pulses he hears. A light indicates the listening period. The use of a muff over one ear makes monaural testing practical. An unweighted noise level of 40 db will allow testing at normal threshold. Eliminating the matched earphones and wires to each testing position makes the equipment trouble free and comparatively inexpensive. Many persons can be tested rapidly in an ordinary school room. A study of comparative results of the tests of public school and college students indicate that an accuracy of 5 db with reference to individual tests can be expected. The construction of the equipment will be shown by slides.
Cylindrical Barium Titanate Transducers
Authors: Johnston T. F. , Wertz F. D.
Published: September 2005

Transducers have been constructed from barium titanate ceramic cylinders. To provide mechanical strength and waterproofing the cylinders were cast in Catavar 101 thermosetting resin. Performance data, including directivity patterns, frequency response, and impedance measurements are presented. In general, the performance is comparable to that of crystal or magnetostrictive transducers but the units are much easier to construct.
Maximum Directivity Index and Efficiency of Linear Arrays
Authors: Pritchard Robert L.
Published: September 2005

The maximum directivity index of a symmetrical, linear array has been calculated as a function of the number and spacing of the elements in the array. Data so obtained make it possible to design an array to yield a specified value of the maximized directivity index. In general, the directional response patterns of such arrays do not have minor lobes of equal, nor of small, amplitude, although the minor lobes are sometimes smaller than for a uniformly excited array. Except for arrays comprising elements spaced an integral number of half-wave-lengths, the maximum directivity index exceeds that for a uniform array. For element spacings exceeding a half-wave-length, the difference is slight, but as the spacing is progressively decreased, the improvement becomes more significant but is finally obtained at the expense of requiring large, out-of-phase excitation. In an effort to evaluate the practicability of using such “super-directive” arrays, expressions have been derived for the sound transmission efficiency of the array, and the electrical power available in sound reception, as a function of the manner of excitation and type of transducers comprising the array.
Scattering of Sound by Cylinders and Spheres
Authors: Faran James J.
Published: September 2005

Measurements of the distribution-in-angle of sound scattered by solid cylinders, one-half to two wave-lengths in diameter, revealed anomalies not predicted by the analysis in which it is assumed that the scattering objects support only compressional waves. The theory of sound scattering by isotropic circular cylinders and spheres has been extended to take into account the effect of both shear waves and compressional waves inside the scattering bodies. The results can be expressed in terms of scattering functions already tabulated. Theoretical scattering patterns calculated on this basis are in good agreement with the experimental results that had previously been regarded as anomalous.
Autocorrelation Analysis of Speech Sounds
Authors: Stevens K. N.
Published: September 2005

A method of speech analysis using the short-time autocorrelation function has been investigated. The conventional autocorrelation function, commonly used in studies of stationary time series, is here modified by including only a finite, weighted interval of integration. This modified result is termed the “short-time” autocorrelation function. It is defined mathematically by the equation, φ11(τ, t) =  ∫ −∞∞ h(t − σ)f1(σ)f1(σ − τ)dσ, where f1(t) is the original time function, h(t) is a weighting function, and τ represents the delay time. When f1(t) represents a speech signal, φ11(τ, t) may be visualized as a three-dimensional representation of the signal, similar to the well-known intensity-frequency-time display. The two representations are related, since the Fourier transform of φ11(τ), the autocorrelation function, is the power spectrum. Correlation functions for a variety of speech sounds, spoken separately and in words, have been measured. Apparatus for accomplishing this includes an acoustic delay tube to obtain the delay τ, an electronic function multiplier, a simple exponential weighting and integrating network, and a recorder to display φ11 as a function of t for selected values of τ. Correlation function plots derived from these measurements have been interpreted by comparison with wave forms and sound spectrograph patterns. For voiced sounds, prominent formant frequencies can be clearly distinguished in the correlation function. Fricatives and other sounds having non-periodic character can in many cases be differentiated more easily by correlation analysis than by frequency analysis.
Intelligibility of Amplitude- and Time-Quantized Speech Waves
Authors: Licklider J. C. R.
Published: September 2005

Previous work has shown that speech remains intelligible even after its wave form has been reduced by infinite peak clipping, or by differentiation plus infinite peak clipping, to an irregular succession of rectangular waves. Evidently the intelligibility may be carried by the temporal pattern of zero-crossings in the normal or in the differentiated wave form. To simplify the speech wave still further, it is necessary to operate upon the temporal pattern. This has been done by subjecting the rectangular speech waves, which may be thought of as already quantized (in fact, dichotomized), to time quantization. Time quantization is achieved by permitting the wave to switch from one of its two amplitude values to the other only at predetermined instants. These instants are separated by equal intervals Δt. Method A follows the rule: if the input wave (the rectangular speech wave) switches one or more times during an interval, the output switches at the end of the interval. Method B follows the rule: if the input wave switches an odd number of times during an interval, the output wave switches at the end of the interval. With Δt = 100 μsec., time quantization has only a small effect upon the intelligibility of the rectangular speech. With Δt = 200 μsec., method B yields marginal communication, but method A does not. Curves relating intelligibility to Δt are shown for both methods. Amplitude- and time-quantization makes it possible to transmit speech with simple pulse modulation circuits, to recognize patterns with the aid of simple coincidence circuits, to store speech in the form of binary digits, to make synthetic speech sounds with a pencil and ruler, and to reduce the computation of the autocorrelation function essentially to counting. These possibilities are explored.
Correlation Coefficients as Criteria for Randomness of Reverberant Sound Fields
Authors: Cook Richard K. , Edelman S.
Published: September 2005

A reverberation room which is used to measure sound absorption coefficients should have a completely random sound field. This we define to be a field such that at every point within the room, plane waves of a particular frequency having the same average intensity for all directions and phases will have passed by after a sufficiently long time (short, however, in comparison with the reverberation time) has elapsed. For such a sound field, we find the correlation coefficient to be R = sin kr/kr, where k = wave number and r = distance between two microphones whose pressures are being correlated. The correlation coefficient is R = 〈p1p2〉Av/(〈p12〉Av〈p22〉Av)12, where p1 is the sound pressure at one microphone, p2 that at the other, and the averages are for long times. Results of measurements of R as a function of k and r for steady sound sources in our 15,000 cu. ft. reverberation room will be presented. Results for bands of frequencies will also be presented.
A Long-Tube Method for Field Determinations of Sound Absorption Coefficients
Authors: Jones E. , Edelman S. , London A.
Published: September 2005

To determine whether acoustical materials installed in Government buildings meet specifications of acoustical properties and to determine the effect of various methods of maintenance on the acoustical properties of acoustical materials, a modification of the familiar laboratory impedance tube has been adapted for field measurements of the absorption coefficient at 512 c.p.s. only. The absorption coefficient for reverberant sound is calculated on the basis of a semi-empirical development described at the last meeting by A. London. The apparatus will be described and results of simulated field tests on several acoustic materials will be presented giving a comparison between the reverberation room measurement and the simulated field test as well as the standard deviation of several tests made on the same material. A means of allowing for the errors inherent in the method in calculating the absorption coefficient for reverberant sound will be indicated.
The Correlation of Non-Linear Resistance, Flow Resistance, and Differential Resistance for Sharp-Edged Circular Orifices
Authors: Westervelt Peter J. , Sieck Peter W.
Published: September 2005

According to Sivian's analysis of the acoustic resistance of small orifices a close correlation should exist between three kinds of measurable resistance in small orifices. If the losses are mainly due to the kinetic energy acquired by the air in the orifice the non-linear acoustic resistance RN, the analogous flow resistance RF, and the analogous differential resistance RD, are related thus: RN = 12RF, RD = 2RF. The non-linear acoustic resistance RN of orifices of 0.375 cm and 0.50 cm diameter has been obtained from plane wave transmission loss measurements made in a three-inch tube equipped with a ρc termination. Orifice thicknesses were varied from 0.05 to 1.25 cm. In this manner RN was measurable at incident pressures greater than that required to cause a deviation from constancy in the transmission loss. It was found that, in the non-linear region, the sound pressure of the wave transmitted by the orifice depends on the square of the incident sound pressure. This relation has been verified for incident sound pressure levels ranging from 115 to 160 decibels, and for frequencies from 238 to 800 c.p.s. (All levels considered were well into Region 4 of Ingaard's “phase diagrams.”) Analogous flow resistance measurements have been made on the same orifices for average particle velocities from 100 to 1,600 cm/sec. The analogous flow resistance was found to be given, within ± 30 percent, by a formula derived by Sivian from kinetic energy considerations. In most cases RN was found to be 25 percent greater than RF/2, and essentially independent of frequency over the range considered. For this comparison RN is taken at a peak orifice particle velocity equal to the orifice average velocity at which RF is measured. The differential resistance RD is the small signal acoustic resistance measured with a superimposed unidirectional flow. RD has been found to be approximately equal 2RF.
On the Turbulence Limit for Sound through Apertures
Authors: Ingård Uno
Published: September 2005

It has been shown that when sound passes through an aperture, steady circulations are generated, and are succeeded at larger amplitudes by turbulence. The turbulence is in general the most important of the non-linear phenomena associated with the acoustic conductivity of the aperture. It is now shown that turbulence always exists if the particle displacement amplitude in the aperture exceeds the thickness of the aperture. Under some conditions (to be discussed) turbulence commences at lower amplitudes, in which case the threshold is determined by the particle velocity rather than the amplitude. The orifice reactance is always constant throughout the non-turbulent region, and decreases sharply as turbulence sets in. The non-linear part of the orifice resistance is velocity determined below turbulence. In the turbulent region the resistance is either velocity or amplitude determined, depending on whether the turbulence threshold is velocity or amplitude determined, respectively.
Finite Amplitude Distortion in a Spherically Diverging Sound Wave in Air
Authors: Allen Clayton H.
Published: September 2005

Quantitative measurements have been made of the pressure amplitudes, pn, of each of the first six harmonics in a free progressive sound wave of finite amplitude in air. Measurements were made in the spherically diverging region of the field generated by a piston source approximately five wave-lengths in diameter vibrating sinusoidally at 14.6 kc. At distances, x, from the source and for source amplitudes, a0, such that the product xa02 is sufficiently small, it has been found that pn is proportional to a0n and, after removing the common factor 1/x which accounts for spherical divergence, pn is proportional to x(n−1 /2. At much larger values of xa02 the wave attains a “stable form.” For sufficiently high acoustic levels in the wave of “stable form” pn ≐ p1/n and the pressure wave is saw-toothed as predicted theoretically for a plane wave by R. D. Fay. The experimental data also indicate that by increasing the source amplitude the acoustic pressure of the fundamental in the steady state at a distance x from the source may be made to approach, but not exceed a limiting value proportional to x−3/2.
Stage I Edge Tones
Authors: Burkhard M. D. , Nyborg W. L. , Schilling H. K.
Published: September 2005

A careful study has been made of magnitudes and distributions—in-space of stage I edge tone sound fields emanating from a particular jet-edge (JE) system (jet cross section: 0.015 × 1.000 in.). Directivity patterns about an axis parallel to the airflow direction assume either of several distinct forms, depending on operating conditions. At frequencies below 10 kc the patterns are approximately those that would result if the airstream oscillatory motion was that of a simple vibrating reed. Pressure amplitude measurements suggest that under some circumstances the air stream swings completely from one side of the edge to the other during a cycle. In reaching the latter conclusion, calculations were made of the modulation coefficient M. We define this dimensionless quantity by the equality M = Q1/Q; here Q is the steady volume flow of air through a JE system and Q1 is the corresponding effective peak-to-peak alternating volume flow; values of Q1 are determined from pressure amplitude measurements on the basis of general source theory. Our measurements yield M-values ranging from 0.2 at 0.5 kc to around unity at 7.5 kc.
The Impact of Acoustics on Music
Authors: Tanner Robert H.
Published: September 2005

This paper discusses the parallel histories of acoustics and music from the days of ancient Greece until now, pointing out the manner in which the acoustical conditions have influenced to a very considerable extent the type and style of music composed at any period, and by any particular composer. (The effect of the acoustics of the Thomas Kirche in Leipzig on the organ and choral music of Bach is one of the more obvious examples.) Thus it is seldom possible nowadays to recreate completely the composer's original intentions, except in such unusual circumstances as in the Bayreuth Theatre which Wagner himself designed especially to suit his own music. At the same time, the changing demands of composers have considerably influenced the architecture and acoustics of concert halls and theatres, and this interplay between acoustics and music has produced a steady development in both fields. But today's acoustical designer is faced with the problem of producing halls and studios, capable of accommodating the largest symphonic combinations and also providing reasonably satisfactory acoustics for the accurate recreation of the works of early composers. A possible solution of this difficulty, deriving historically from the theatres of ancient Greece, is examined in some detail.
An Experimental Study of Temperatures Produced by Ultrasonic Radiations in Bone Marrow, Bone, and Adjacent Tissues
Authors: Baldes E. J. , Nelson Paul A. , Herrick J. F.
Published: September 2005

As early as 1932 Freundlich, Sollner, and Rogowski proposed the use of ultrasonics in medicine for diathermy. They were able to demonstrate that bone marrow could be heated. The results of their study indicated clearly that further experiments needed to be done to extend these preliminary observations. We have completed a study of the temperatures produced by ultrasonics in bone marrow, bone, and adjacent tissues in the extremities of the dog. The frequency used in these studies was 800 kilocycles per second. The maximum output of the ultrasonic generator was approximately 15 watts. High temperatures can be produced in bone marrow and bone with relatively low outputs of ultrasonic energy. The adjacent tissues are heated only moderately. Ultrasonics must be used with caution in the proximity of bones because the temperatures produced in bone and bone marrow may rise to dangerous levels within a very few minutes.
The Production of Variations in Plants and Animals by Acoustic Vibrations
Authors: Wallace Raymond H.
Published: September 2005

Tests with seedlings of sunflower and other plants exposed from 1 to 25 seconds to an ultrasonic field of six watts per sq. cm have resulted in both somatic and genetic variations. Usually, as is to be expected, the parents show no effects. The children and grandchildren, however, have shown a wide range of modifications including leaf shapes, flower forms, vigor or lack of vigor, sterility, pigment deficiencies, seed shape, color and size, etc. Several strains of these descendents have now reached the fourth and fifth generation and some variations originally present have now disappeared while others not present in the first or second generation have appeared. Some pigment variations have inherited well to the fourth generation. One particular albino strain has maintained itself with no difficulty in the open field. The albino individuals of this strain have been grown as grafts onto green stock and have produced seeds from selfed flowers. To the present all the seedlings from these selfed albinos have been albinos. This technique of grafting albinos onto green stock has not only resulted in the carrying to maturity of what is ordinarily a lethal, but in addition has shortened the maturity date from seed to seed from 90 days to 30 days.
Reflection of Acoustic Waves from a Medium of Variable Velocity
Authors: Heller Gerald S.
Published: September 2005

When an acoustic wave starting out in a homogeneous medium encounters a medium in which the velocity begins to increase or decrease but is otherwise continuous, a reflected wave results. The reflection coefficient can be calculated exactly for either a linear or exponential velocity variation. The intensity reflection coefficient for either case is of the order of g2/ω2, if ω2/g2 >> 14, where g is the velocity gradient and ω the angular frequency (for the exponential case g is the gradient at the start of the exponential variation). A slice of inhomogeneous medium with constant velocity gradient also lends itself to simple theoretical treatment. The case of oblique incidence, with constant velocity gradient, has been treated using the W.K.B. approximation. This yields an intensity reflection coefficient R given by R = 1/[16(ω/g)2 cos6 θ + 1] under the same approximation as above, where θ is the angle of incidence at the boundary between the homogeneous and inhomogeneous media. Numerical results for all these cases will be discussed. Progress is continuing for the case of oblique incidence on a slice of inhomogeneous medium and for a case in which total reflection occurs.
An Investigation of Wave Propagation in Thin Rubber Rods
Authors: Cramer William S.
Published: September 2005

A comparative study was made of the velocity and attenuation of longitudinal, torsional, and flexural waves in thin rubber rods. Measurements were carried out for wave-lengths large compared with the diameter of the rod, and for attenuations sufficient to eliminate appreciable reflection from the end. The range of frequencies was from 1 to 10 kc. The longitudinal and flexural waves were excited by a phonograph cutter head suitably orientated, and the torsional wave by a rotating coil mechanism. The vibrations were picked up with a phonograph pick-up bearing lightly on the rubber. By rotating the pick-up head through 90° it could be set for detecting either longitudinal or transverse vibrations. The pick-up arm was mounted on a motor-driven carriage allowing an automatic, continuous written record to be made of amplitude vs. distance. The wave-length was measured by the distance between points of equal phase on the rod. The whole unit was mounted in an insulated box with circulating, thermostatically controlled air. Emphasis was placed on comparing the results for the several types of waves for the same sample under identical conditions. Representative measurements on commercial synthetic rubbers are included.
Experimental Determination of Acoustic Wave Fronts
Authors: Tamarkin Paul , Boyer George L. , Beyer Robert T.
Published: September 2005

When acoustic signals are detected by a microphone, an electric signal is also picked up. The latter produces a spatial modulation of the acoustic signal. This effect was used by Labaw to make a point by point determination of a progressive acoustic wave front in water. The effect is analyzed in this paper and an electronic device is described which reduces the time required for measuring the wave fronts to about one third that previously needed. The device employs a phase discriminator which compares the phase of the electric and acoustic signals at a given point. Since the phase of the electric signal is sensibly constant throughout the tank, this signal is used as a reference level. An output current is obtained which is proportional to the phase difference of the two signals. Measurements are then made by locating points with zero current output. Typical experimental measurements are given.