bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Elastic Constants and Decrements from the Resonances of a Free Bar
Authors: Crawford G. , Semmelink A.
Published: November 2005

An electrodynamic method of initiating and detecting, independently, the flexural, longitudinal, and torsional vibrations of a free bar is described. A thin copper strip is attached to each end of the bar. The three types of vibrations are determined by the permanent-magnet configuration, which is placed close to the copper strip. This carries an alternating current for the driver; while for the receiver the voltage induced in the strip is measured. It is shown how the logarithmic decrement of the bar material, as well as the elastic constants, can be calculated from the test results. An outline of an approximate theory is given. It is easy to obtain and predict corrections that are within 2% of the more-rigorous correction factors for flexural vibrations of rectangular bars. Tables of correction factors are provided for bars having thickness-to-length ratios from 0 to 0.30 and Poisson's ratios from 0 to 0.45 for the first three modes of vibration.
Hydroelastic Solutions of the Sloshing of a Liquid in a Cylindrical Tank
Authors: Bhuta Pravin G. , Koval Leslie R.
Published: November 2005

The problem of sloshing (free surface oscillations) of a liquid in a cylindrical tank having rigid walls and a flexible bottom (a thin elastic plate) is studied for both the axisymmetric and asymmetric cases. The coupled boundary-value problem of the liquid and the elastic bottom is solved for small motions. The frequency equations are obtained and the effect of the coupling investigated. It is shown that the frequency equations reduce properly to the various limiting cases. The orthogonality of the coupled mode shapes is investigated and a theorem concerning the coupled mode shapes is proved.
Statistical Analysis of Admittance Functions
Authors: Lyon Richard H.
Published: November 2005

The point-input admittance to a structure governs the input power and the local response to a point force. The average value and variation of this power and response have been computed on the basis of a simple statistical model of the structure. This is done by calculating the average values and standard deviation of the real part and the square of the modulus of the admittance at a single frequency and over bands of noise. The results are applied to the estimation of power flow into and response of a flat plate. Confidence levels for the estimates are obtained by assuming a form for the distribution of the admittance function. The paper is concluded by a discussion of the adequacy of the statistical model and possible applications of the results. [This research has been sponsored by the U. S. Bureau of Ships contract NObs 86680.]
Diagnostic Articulation Testing in the Design of Speech-Processing Devices
Authors: Hecker Michael H. L. , Phyfe Douglas L.
Published: November 2005

The utility of simplified nonsense-syllable tests containing stimuli of the form /h∂′CVC/ for measuring the performance of existing speech-communication links on specific consonant and vowel features has been demonstrated [K. N. Stevens et al., J. Acoust. Soc. Am. 35, 1116(A) (1963), Paper G10]. It has been suggested that selected nonsense-syllable material may also be used repeatedly on experimental speech-processing devices for the purpose of optimizing certain critical adjustments or design parameters. The present paper illustrates this application of diagnostic articulation testing by considering the design of a new voicing indicator for a digital channel vocoder. An initial test revealed a number of “voicing” errors among fricative consonents. These errors could be reduced by modifying the characteristics of a low-pass filter, as indicated by a second test, but the changes that were made increased “place” errors among stop consonants. The third test showed that the introduction of a slight delay could check these errors.
Thermal Perturbations in Woodwind Bores
Authors: Benade A. H.
Published: November 2005

When the player blows warm, damp air into the mouthpiece of a wind instrument, he alters not only the average sound velocity (ignored here), but also the effective cross-sectional area by way of a change in ρc. The fractional change in cross section is (ΔS/S)=0.003+0.002T. Here, T is the centigrade temperature excess at the point of interest in the bore. Eleven thermocouple sampled air temperatures along oboe, clarinet, and flute bores. The upper ends were all near 35°C, falling to nearly the 22° ambient at the lower end. The fractional cross-section alteration A0 at the mouthpiece is always about 2.5%. The oboe bore becomes one described by S=S0⋅(x/x0)2−m, with m=A0/loge [1+(l/x0)] = 0.015. The fractional length correction for the nth mode is (Δl/l)=(0.23m)/n. The first mode is flattened 6 cents and the basic octave is stretched 3 cents. The clarinet acquires a reverse conicity, with (Δl/l)=(2A0/π2) (2n−1)−2. The lowest mode is flattened 9 cents, and the twelfth is stretched 8 cents. A similar conicity arises in the flute, but gives no frequency shifts. An unwarmed flute, or one played in a drafty room, has its fundamental sharpened and the basic octave shrunken up to 15 cents. In oboes and clarinets, cold playing conditions considerably exaggerate the effects already described for them.
Harmonic Structure of the Tone of the Bassoon
Authors: Lehman Paul R.
Published: November 2005

The purpose of this investigation was to examine quantitatively and in greater detail than had previously been possible the harmonic structure of the steady-state tone of the basson. First, an attempt was made to determine the general characteristics of the tone of the instrument, particularly with respect to the presence and location of formants and the extent to which the harmonic structure varies with intensity. In addition, an attempt was made to determine the extent to which the harmonic structure of the tone varies among players of recognized ability. Eleven bassoonists from the Philadelphia, Boston, Berlin, Cleveland, and Detroit symphony orchestras participated in this study. Finally, seven tests were made of the tone of the author in an attempt to determine the extent to which the harmonic structure varies from sampling to sampling in the tone of a single individual. In each test, every chromatic pitch from low B-flat through high C was examined at three dynamic levels. It was found that there is a strong formant extending approximately from 440 to 494 cps and a weaker formant from 1220 to 1280 cps. Although the spectra of different players resemble one another in general, they differ sufficiently in detail so that no one sampling can be said to characterize adequately the tone of the instrument. To a lesser extent, the same is true of different samplings of the tone of a single individual.
System for Measuring the Acoustical Response of Wind Instruments
Authors: Hall Jody C.
Published: November 2005

The system developed for measuring the frequencies for resonances in wind instruments has proven to be useful also in giving indications that correlate well with musicians' evaluations regarding the response, or “feel,” of the instrument. Acoustical-response measurements give detailed information regarding the elements that combine to give the total response felt by the musician, since he “feels” more than one resonance peak simultaneously over much of the playing range. Examples showing the correlation between measured data and typical musician reaction on different instruments are shown and demonstrated.
Behavior of Piezoceramic Projector Materials under Hydrostatic Pressure
Authors: Nishi R. Y. , Brown R. F.
Published: November 2005

Experimental work on the effect of hydrostatic pressure on the piezoelectric and high-field dielectric properties of two piezoceramic projector materials is presented. The two materials, a modified barium titanate and a modified lead zirconate titanate, are characterized by a low dielectric loss at high fields. In the pressure range of 0 to 10 000 psi and at nonresonant driving fields up to 3 kV/cm, the changes observed in the dielectric constant and piezoelectric strain constants with hydrostatic pressure were less than 10%, and no significant changes were found in the dielectric loss. Aging studies at 10 000 psi showed that the dielectric constant and dielectric loss for both materials reached constant values after a few minutes. Possible mechanisms for the observed effects are discussed.
Use of a Hydroacoustic Transducer in Continuous Seismic Profiling
Authors: Wisotsky Serge , Clay Clarence S. , Liang William L.
Published: November 2005

The hydroacoustic transducer is an acoustic radiator actuated by an electrohydraulic positioning servo. It was used during April 1963 as a low-frequency, broad-band source in continuous geophysical profiling experiments aboard Hudson Laboratories research vessel J. W. GIBBS (T-AGOR-1). The transducer has a 2-ft diam acoustic piston driven by a 14-in.-sq. hydraulic ram, fed through 200 ft of hydraulic lines from a 35 GPM, 2000- to 3500-psi, shipborne hydraulic power supply. The transducer controller consisted essentially of a 10-W electronic servoamplifier fed by various audio signals. The experiment is similar to that described by Clay and Liang [Geophysics 27, 786–795 (1962)]. In this experiment, most of the data were obtained with either 1-sec 100-cps bandwidth chirps or noise pulses within the total range of 80–400 cps. Short 250-cps pings were also used. The signal returns were processed with a polarity correlator. In this system, one compresses the coded pulse of relatively long time duration and low amplitude into a short pulse of high amplitude. In the 200- to 300-cps range, the radiated pulse is estimated to be about 900 J energy and 500 J in the 100- to 200-cps frequency range. Seismic profiles were made in the Hatteras Abyssal Plain area in water depths of 3000 f and subbottom penetrations of 34- to 114-sec travel time were recorded. Two and three subbottom reflections were often observed. [Hudson Laboratories, Columbia University Informal Documentation No. 33. This work was supported by the Raytheon Company and the U. S. Office of Naval Research.]
Small-Size, Low-Frequency Utility Source for Underwater Acoustic Measurements
Authors: Lubell Alan H.
Published: November 2005

This paper describes a partially developed small-size underwater acoustic radiator capable of providing a 90-dB source level for frequencies between 300 and 400 cps. It uses the “Tonpilz” configuration to obtain resonance at a low frequency with an electrostrictive ceramic stack only 12 in. long. The 12-in.-diam radiating face provides a radiation Q of 6.5 at 400 cps. The entire unit measures 12 in. diam ×15 in. long and has a weight in water less than 100 lb. To meet the needs of higher power, an experimental unit consisting of four of the above sources mounted to form a close-fitting square array has been investigated. Computed values of mutual impedance indicate that large improvements in efficiency, bandwidth, and power-handling capability may be obtained in this manner. Acknowledgment is made of the prior work on similar sources by Peter Weber of Hudson Laboratories and of the helpful suggestions received from members of the Underwater Sound Laboratory at New London. [This development was undertaken as part of the Hughes company-sponsored acoustic-radiation-research program.]
Propagation Losses of Underwater-Explosion Shock Waves
Authors: Christian Ermine A.
Published: November 2005

At very great ranges from an underwater explosion, the propagation losses of discrete frequency components of the shock wave appear to follow acoustic laws. If a reference range near the charge is used, however, the high-amplitude source characteristics must be taken into account. A method of combining the explosion and acoustic propagation-loss functions is suggested. The “excess” losses in the shock wave are estimated for several experimental conditions.
Variance of the Bearing Angle of a Discrete Linear Difference Array in a Random Transmission Medium
Authors: Lord Gary E.
Published: November 2005

An approximate expression has been derived for the variance of the bearing angle, about the central null point, of a discrete, linear-difference array in a random transmission medium. The Chernov formulation for plane-wave propagation in a random medium, restricted to small absolute values of the phase and amplitude fluctuations, is used as a basis for the derivation. It is further assumed that the phase and amplitude fluctuations are normally distributed with zero means. Qualitatively, the variance is approximately proportional to the range and is nearly independent of the frequency. The dependence of the variance on the number of receiving elements n and their spacing d is more complex, although it can be stated that it decreases at least as rapidly as n−2 and d−2. [This work was supported by the Bureau of Naval Weapons, U. S. Navy, under contract NOw 62-0579-d.]
Signal Detection by Arrays with Arbitrary Processors and Detectors
Authors: Usher Theron
Published: November 2005

The signal-detection characteristics of local arrays of transducers used to detect the presence of a plane-wave random signal in an isotropic noise background are analyzed for the situation in which the transducers are followed by identical nonlinear processors. The resulting signals are summed and detected by a square-law device with a low-pass filter. The performance of this system is compared to that for a system with linear processors and a square-law detector. Also analyzed are the signal-detection characteristics of an array with linear processors and a non-square-law detector. The performance is also compared to that for the linear system with a square-law detector. Results indicate that, for maximum-output signal-to-noise ratio, the system with linear processors and a square-law detector is optimum for both situations considered above. The degradation in performance caused by deviations from the optimum is not great, however. On an output-signal basis, defined by the difference between “on-target” and “off-target” output, the linear processor provides an optimum system, if there is a choice of processor function. However, no optimum exists when the processor is linear and there is a choice of detector function.
Limitations on the Detectability of Targets by Passive Sonar Techniques
Authors: McDonald R. A. , Schultheiss P. M. , Tuteur F. B.
Published: November 2005

The paper considers basic limitationes on the ability of hydrophone arrays to detect the presence of directional signals in a very much stronger noise background. The design of the optimum-detection system and its performance clearly depend on knowledge of signal and noise properties. A fairly weak but often not unrealistic assumption is that both signal and noise are stationary, Gaussian, random processes, and are, therefore, characterized completely by total average power and spectral properties. The optimum detector can make use of these properties to achieve improvements in performance over the standard instrumentation, a simple power detector. Theoretical limitations on these improvements and practical considerations affecting their realization are discussed. When the target is a moving ship, the signal commonly has additional properties that can be used in detection. Thus, motion of propellers and other machinery introduces periodic signal components. Furthermore, one frequently finds that the propeller frequency appears as a periodic amplitude modulation on the high-frequency portion of the random signal components. On the other hand, if the hydrophone array is mounted on a moving ship, similar periodic components are contained in locally generated self-noise. The paper investigates what advantage can be gained from knowledge of these special signal and noise properties by use of data-processing techniques ranging from optimal procedures to procedures that are clearly suboptimal but fairly easily instrumented.
Signals Tailored to Specific Sonar and Radar Requirements
Authors: Rowlands Richard O.
Published: November 2005

This paper reviews the various types of signals used for sonar and radar and discusses their limitations. Two conflicting requirements are (1) the desirability of being able to discriminate between stationary objects and moving targets, and (2) that of being able to detect the Doppler-shifted echoes with the minimum number of matched filters. Pseudorandom noise and Doppler-invariant FM represent extreme examples of signals that, respectively, meet the first and second of these requirements. Starting with an FM signal in which the instantaneous frequency is given by f = ktα, it is shown how the values of k and α may be chosen to satisfy any degree of compromise between Doppler invariance and moving-target indication.
Prediction of the Farfield Pattern of an Asymmetrical Radiator from Pulsed Nearfield Measurements at 30 kc/sec
Authors: Lubman David
Published: November 2005

This paper describes the results of an experiment in which the farfield-radiation pattern of an asymmetrical radiator was computed from pulsed measurements of complex pressure in the nearfield at 30 kc/sec. Choice of this frequency permitted both farfield and nearfield measurements in the same tank under similar conditions. Farfield-pattern computation was based upon an approximate form of the Helmholtz equation suggested by Baker. The transducer consists of six cylindrical elements stacked together and driven in phase in a radial mode. Nearfield measurements were made on lines parallel to the transducers axis and at various distances from its active face. The measured nearfield pressure was perturbed in the region around the second element in the stack, suggesting that the element was defective and would cause the transducer radiation pattern to be asymmetrical. This was confirmed by computations and measurements of the farfield. Perturbations around the defective element were greatest along the line spaced closest to the active surface and diminished with distance. Resolution of 0.1 dB in pressure magnitude, 1° in phase, and repeatability generally within 12 dB and ±2° was attained. [This experiment was undertaken as a part of the Hughes Acoustic-Radiation-Research Program.]
Experiments in Bone-Air Cancellation
Authors: Smith Ernest L. , Bowman Howard S.
Published: November 2005

An audiofrequency tone applied to the bones of the head can be completely cancelled by a tone of the same frequency supplied to the ears by air conduction, after proper adjustment of the amplitude and phase of the air-conducted tone. Experiments have been carried out on air-bone cancellation with bone stimulation applied to the forehead and binaural stimulation of the ears with no masking and also monaural stimulation with masking. Measurements of the amplitudes and phases of the impressed signals applied to the bone and air transducers were made.
On the Lack of Agreement between Earphone Pressures and Loudspeaker Pressures for Loudness Balances at Low Frequencies
Authors: Rudmose Wayne
Published: November 2005

The “missing 6 dB” has remained a problem for many years. The author has previously shown [W. Rudmose, in Proceedings of the Fourth International Congress on Acoustics, Copenhagen. 1962 (to be published)] that pressure thresholds and freefield thresholds, at 100 Hz, can be made to agree if the masking effect of physiological noise is minimized. In this paper, data and experimental techniques are presented to show that “pressure” and freefield” loudness balances, for 100 Hz, can also be made to agree. Three procedures, (1) monaural, (2) monaural using transfer earphone, and (3) binaural, are discussed, showing how the missing 6 dB can be attributed to certain experimental techniques. No single explanation fits all experiments. Some factors affecting judgments are (a) failure to occlude the nonused or transfer ear in monaural balancing, (b) the loudspeaker location (some subjects require different pressures for loudspeaker balancing if only the loudspeaker changes), (c) mechanical vibrations from the loudspeaker reaching the subject, (d) unexpected results, with some subjects from small amounts of distortion. What affects one subject may have no effect on another. [This work was done at Southern Methodist University and supported in part by the Callier Trust.]
Relation of Auditory and Middle-Ear-Muscle Thresholds in the Cat
Authors: Simmons F. Blair , Beatty Dana
Published: November 2005

Tonal thresholds and middle-ear-muscle reflex thresholds were concomitantly and serially measured in normal-hearing and then in sound-damaged cats [Ann. Otol. Rhinol. Laryngol. 71, 767 (1962)]. Normal, recovery, and postdamage comparisons were made between the two, showing that (1) in normal animals, the relation between reflex and auditory threshold is generally unpredictable (36−>65 dB difference), (2) reflex thresholds in any one animal can be maintained with stability, and (3) under the conditions of autocorrelation of pre-post damage comparisons, a predictable pattern emerges that is dependent upon slope and severity of the auditory loss, evidencing reflex “recruitment” with auditory losses isolated to low frequencies (500–2000 cps), and little or none for losses above about 4000 cps. Reflex measurements obtained during the post sound-damage recovery period suggest that the middle-ear-muscle reflex can be used as a satisfactory indicator of sound damage without requiring time-consuming behavioral measurements on a clay to day basis.
Some Relations of the Cortical-Evoked Response to the Intensity of the Acoustic Stimulus
Authors: Davis H. , Yoshie N.
Published: November 2005

Averaged evoked responses, led from the vertex relative to ear lobe, were obtained from waking human adults in response to tone pips at various intensities, delivered in pairs. The intrapair interval was 0.5 sec.; interpair was 4.5 sec. Both pips (A and B) of the control pair were constant at 60 dB SL. The intensity of either the first (C) or the second (D) member of the variable pair was also 60 dB SL, and all four were of the same center frequency: 300, 600, 1200, 2400, or 4800 cps. Conclusions are based on the ratios of peak-to-peak (100 and 180 msec) voltages of the responses, averaged over three subjects and four frequencies. (4800 cps omitted: responses systematically small.) The input-output relation, C/A relative to decibels, is nearly linear with a slope of 1.7% per decibel. Measurable responses were regularly identified at 20 dB SL and often at 10 dB SL. Recovery of amplitude is nearly complete at 4.5 sec, but is only about 50% at 0.5 sec, for pips of equal intensity. A weaker first pip (C) causes less depression (D/A or D/B) than a stronger one. The depressing effect of a first pip (C) at 20 dB SL on a test response (D) at 60 db SL is regularly seen. For the second response (D) after 0.5 sec to be as large as C, the pip must be 15 dB stronger. [Supported by grant B-3856 from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, U. S. Department of Health, Education, and Welfare; and contract N6onr-272(05) with the U. S. Office of Naval Research.]
Vibrational Relaxation in Dry and Moist Oxygen
Authors: Clark Anna Vincent , Henderson Malcolm C.
Published: November 2005

Using the pressure resonance tube developed in this laboratory, the relaxation frequency of oxygen has been measured as a function of water-vapor content, ranging from bone dry up through 140 ppm to 5500 ppm M. The mixture's composition, always at 100% relative humidity, was established by controlling the temperature and total pressure of oxygen in the tube, which always contained free water, or a water-glycerine mixture to reduce the vapor pressure. The relaxation frequency at one atmosphere is given in kc/sec⋅atm by f=0.003+1.66 h+14.5 h2, h, in mole percent. (Least-square solution, but the dry-oxygen relaxation frequency is actually 9 cps/atm.) This expression overlaps and extrapolates to fit the Knötzel's and Knudsen's data satisfactorily, but there is an outstanding discrepancy with the data for air of Evans and Bazley and of Harris, who used the reverberant-chamber method, and obtained a power law: e.g., f=kh1.6. The method of mixture control through total pressure is being extended to other volatile substances. [This work was supported by the U. S. Office of Naval Research under contract Nonr 2249(02).]
On the Molecular Theory of Sound Propagation in Liquids
Authors: Wilson Wayne D.
Published: November 2005

A short review is given on the molecular theory of sound velocity in solids, liquids, and gases, with particular attention paid to liquids. A simple rudimentary theory is presented to explain the manner in which sound is propagated in the primary alcohols. This theory assumes that the velocity between molecules is different from the velocity within the molecules. Computations of these velocities indicate that both are finite and of the same order of magnitude as the observed sound velocity in the liquid. Comparisons at a temperature of 0°C with other molecular data appear to substantiate the results obtained.
Elastic Constants of Benzene
Authors: Heseltine James C. W. , Elliott Donald W. , Wilson O. B.
Published: November 2005

The elastic coefficients of benzene have been determined from sound velocities measured with the use of an ultrasonic-pulse technique over a temperature range of 170° to 250°K. At 250°K, the results are (in units of 1010 dyn/cm2): C11=6.14; C22=6.56; C33=5.83; C44=1.97; C55=3.78; C66=1.53; C12=3.52; C13=4.01; C23=3.90. These elastic coefficients generally increase as the temperature is lowered. The observed absorption coefficients are relatively large, thus confirming data reported by L. N. Liebermann. However, it was found that the absorption is not isotropic and that the absorption for shear waves is comparable with that for longitudinal waves. Some of the experimental techniques used are described. [Supported by the U. S. Office of Naval Research.]
Attenuation of Guided Waves in Viscoelastic Plates
Authors: Coquin G. A.
Published: November 2005

Wavepropagation in an infinite, isotropic, elastic plate with tractionfree faces is governed by the Rayleigh-Lamb frequency equations. As is well-known, an analysis of the equivalent viscoelastic problem shows that the frequency equations for an isotropic. viscoelastic plate may be obtained from the Rayleigh-Lamb equations by replacing the two independent elastic constants with complex functions of frequency. The propagation wave-numbers corresponding to modes that propagate unattenuated in an elastic plate are complex in a viscoelastic plate, the imaginary parts being attenuation constants. In this paper, an approximate method is developed for obtaining roots of the viscoelastic frequency equations from known roots of the Raleigh-Lamb equations with comparatively little additional calculation. The approximate method is applicable when the attenuation per wavelength is small. Calculations have been carried out for the lowest three longitudinal and flexural modes in plates with Poisson's ratios of 0.17 and 0.35, and curves are presented that show the contributions to the over-all attenuation due to dissipation associated with dilatational and shear deformations separately. In addition, the variation of attenuation with frequency in a Voigt solid has been calculated and plotted for two ratios of dilatational-to-shear losses.
Some Features of the Army Channel Vocoder
Authors: Phyfe Douglas L. , Toffler Jerome E.
Published: November 2005

A new channel vocoder has been developed jointly by the Hughes Aircraft Company and the U. S. Army Electronics R & D Laboratory as an integral component of a tactical communications system. The technical features of this vocoder include an improved voicing indicator, a pitch extractor in which the analog representation of the pitch frequency is stored during unvoiced intervals, and a spectrum-flattening technique that is based on schemes that have been used in the design of voice-excited vocoders [E. E. David, Jr., et al., IRE Trans. Inform. Theory 8, (1962)]. Preliminary results of performance tests, conducted by an independent organization, indicate PB word-intelligibility scores in excess of 90% for 2400 bits/sec digital operation and scores near 95% for analog operation. In order to illustrate the relative value of the above-mentioned technical features, test results for other modes of operation are also presented.
Quality Improvement in the Channel Vocoder
Authors: Steele Robert W. , Cassel Lawrence E.
Published: November 2005

Recent progress in channel vocoder engineering has resulteed in word-intelligibility scores in excess of 90%. No longer can intelligibility be indicated as the limiting factor in vocoder acceptance. This being the case, what is the criterion for wide vocoder acceptance? Most often it is expressed as the unnaturalness and/or lack of quality of the synthesized vocoded speech personified in the expression that “it sounds like a vocoder.” Considerable engineering effort has been applied to improving the quality of the synthesized vocoded speech. Primarily, this is a study of the synthesizer section of the vocoder, voiced and unvoiced excitation, modulation techniques, and filter characteristics. A few additional areas are discussed. The techniques are explained and tape recordings are used to demonstrate the effect of various synthesis techniques. [This work was supported by U. S. Air Force Contract AF19-628-586.]
Introduction of Fundamental Frequency and Timing Information into Speech Synthesized from Stored Data
Authors: Kerby H. R. , Enke G. G.
Published: November 2005

This paper describes a digital-computer technique used to introduce fundamental frequency and timing data into synthetic speech generated from stored phonetic data. The phonetic data are obtained from a library of synthesizer control signals. Entries from the library, each roughly corresponding to the synthesizer parameters necessary to generate a consonant-vowel or vowel-consonant pair, are assembled in accordance with the desired phonetic sequence of an utterance. Fundamental-frequency patterns can be handled independently, i.e., stored in the computer and selected in a manner similar to the phonetic library data. The patterns can be of any specified shape and length and can be placed at any position along the phonetic-data train. Timing data are introduced by extending the vowel portion of the vowel-consonant entries appropriately to the phonetic environment and in accordance with the stress desired. The system as a whole is general enough to permit extensive investigations of the role of fundamental frequency in controlling intonation and the role of vowel duration in controlling stress. Initial experiments will be directed toward obtaining the fundamental frequency and timing data necessary to produce natural declarative intonation and grammatically relevant stress. Preliminary results of these experiments are given.
Design and Construction of a Convertible Anechoic/Semianechoic Chamber
Authors: Lang W. W.
Published: November 2005

An anechoic chamber has been constructed in which the floor wedges can be removed in less than 30 min to convert it to a “semianechoic” chamber. Measurements in a free-field above a reflecting plane are also important for many noise-control studies. The size and shape of the single, 30-cm-thick, bare, concrete shell were selected to permit power-level measurements on machines with major source dimensions up to 1.5 m. A cutoff frequency of about 90 cps is provided by glass-fiber wedge units 87 cm long on a 60 × 60-cm2 base backed by a 9.5-cm air space. The working area with all wedges installed is 5.0 × 6.3 m2 by 6.1 m high. Access to the working level of the anechoic chamber is provided by a wire mesh (2.5-mm-diam wire, 5-cm spacing) suspended 2.3 m above a reinforced-concrete floor poured on undisturbed earth. Each wire is tensioned to 90 kgf and supported by an I-beam frame behind the wedges. For measurements in the fully anechoic environment, machines can be hoisted to the working level through a 2.4-m-diam hole in the wire mesh by a hydraulic lift. Temperature, humidity, and internal-noise levels are carefully controlled.
Performance of a Convertible Anechoic/Semianechoic Chamber
Authors: Nordby K. S.
Published: November 2005

The performance of the chamber described in another paper [W. W. Lang, Paper Y1, this meeting] is presented. The background-noise levels of the chamber with and without the air-conditioning system in operation are given. With the system in operation, the background-noise levels are just below the normal threshold of hearing. For the site selected, a double-shell construction was proved to be unnecessary. The nine-frequency sound-transmission loss of the single-shell structure exceeds 55 dB. A monitoring system was installed to warn the experimenter if the background-noise levels in the chamber should exceed normal values, due to external noise. The pressure-reflection coefficient of the wedges for normally incident sound was first determined in a standing-wave tube measuring 0.6 × 0.6 × 4.9 m3 and then compared to the over-all pressure-reflection coefficient obtained by the reverberation technique in the anechoic chamber. Draw-away experiments were made to determine how well the chamber approaches a free field. The performance of the “semianechoic” chamber was studied by measuring the interference pattern above the reflective floor.
Annoyance Judgments of Sonic Booms
Authors: Pearsons Karl S.
Published: November 2005

Judgment tests have been conducted to determine the relative noisiness of sonic booms as compared to sounds produced by aircraft flyovers or to bands of filtered, random noise. The sonic booms tested were those that one might experience outside or inside a woodframe dwelling and ranged in overpressure from 0.5 to 5 lb/ft2. The booms were either simulated by a special waveform generator or played back from FM tape recordings of actual booms. According to test results, a sonic boom such as might be experienced outdoors at a peak overpressure of 2.8 lb/ft2 was judged equal in noisiness to jet flyovers with over-all sound-pressure levels in the range of 85–90 dB. On the other hand, a sonic boom such as might be experienced indoors at a peak overpressure of 0.5 lb/ft2 was equated in noisiness to jet flyovers in the range of 80–85 dB. It is to be noted that a boom in the test chamber caused no structural vibrations as there would be in a house; also, there was no appreciable startle effect because of the test procedures used. [Work was jointly supported by the National Aeronautics and Space Administration and the Federal Aviation Agency under contract NASr-58.]
Thresholds of Audition for Three Species of Monkeys
Authors: Fujita Shiro , Elliott Donald N.
Published: November 2005

Using various conditioning procedures, three species of monkeys have been conditioned in order to determine their audiograms. Squirrel monkeys have been conditioned in a double-grill cage, using shock as the reinforcement, while squirrel monkeys, Rhesus monkeys, and Cynamolgus monkeys have been conditioned in a single-bar reward and a single-bar avoidance situation. In general, the audiograms obtained for the various species, and using the various conditioning procedures, agreed quite well. The audiograms of the individual animals, as well as the average performance for each species, are reported.
Short-Tone Exploration of Hearing Impairment
Authors: Boomsliter Paul C. , Powers Samuel R.
Published: November 2005

Development of a method of using a class of short-duration tonal stimuli for exploring auditory perception indicates that the method measures some factors not measured by conventional audiometry. While a normal listener perceives tonal quality in a pure-tone stimulus of 10 msec duration, impaired subjects require much longer (in this study, up to a full second), perceiving the shorter duration stimuli as clicks. Additional dimensions, such as the size of the gap between ascending and descending test scores, also appear significant. On humans and dogs, the test has shown that adequacy of blood supply to the brain stem relates to these dimensions. Surgical relief of stenotic arterial lesions limiting brain-stem circulation in humans improves these scores, independent of pure-tone audiograms. Four dogs trained to respond only to a sensation of tone were subjected to ligation of the basilar artery. A 5-fold increase of the stimulus duration necessary to elicit the response was seen in three animals.
Auditory Masking in the Rat
Authors: Gourevitch George
Published: November 2005

Masked thresholds in rats were measured with an operant tracking method [Science 131, 1046 (1960)] at four frequencies between 1000 and 8000 cps and at three to five levels of wide-band noise. Critical ratios calculated from the masked thresholds were found to be greater than those found in cat and in man. The mathematical function derived by Greenwood [J. Acoust. Soc. Am. 33, 1344 (1961)] relating critical bandwidths to position on the basilar membrane was shown to fit reasonably well the data collected in this experiment. [Work supported by grants from the National Institutes of Health, U. S. Department of Health, Education, and Welfare (NB-02484), and from the Alfred P. Sloan Foundation, Inc.]
Diffraction of a Plane Compressional Wave by a Spherical Cavity in an Elastic Medium
Authors: Yeh Gordon C. K.
Published: November 2005

A spherical cavity in an infinite homogeneous and isotropic elastic medium is enveloped by a plane compressional shock wave whose front propagates with a constant velocity. The displacement and stress fields produced by the diffraction of the wave by the cavity are formally determined by means of an integral transform technique. Expressions for the transforms of the various components of the displacements and stresses are derived. The rigid-body component motion of the cavity boundary is also extracted. The problem is considered for compressional waves with a step distribution in time. The results may be used as influence coefficients to determine by means of Duhamel integrals the displacement and stress fields produced by stress waves with time-varying intensity. [Work performed under contract No. AF29(601)-5132 (Project No. 1080, Task No. 108007) for the U. S. Air Force Special Weapons Center, Kirtland AFB, New Mexico.]
Multiple Scattering of Waves by a Forest
Authors: Embleton T. F. W.
Published: November 2005

Theoretical expressions due to Twersky [New York Univ. Rept. EM-59 (1953)] for waves multiply scattered by an array of cylinders have been recast in a form suitable for numerical calculation and, hence, comparison with experiment. This theory affords sufficient explanation of the magnitude of the attenuation observed in forests, 7 dB/100 ft [T. F. W. Embleton, J. Acoust. Soc. Am. 35, 1119 (1963)], provided that the scattering cylinders are assumed to have surfaces of finite impedance. The resistive component of the bark on trunks and branches at 500 cps needs to be about 10 ρc to obtain agreement; values close to this have been obtained from impedance-tube measurements. The S-shaped curve of attenuation vs frequency, observed in certain parts of the forests, may be related to the “resonance” of the cylindrical surfaces as their reactive impedance changes sign.
Absorption of Upholstered Chairs as Related to Their Spacing
Authors: Delsasso L. P.
Published: November 2005

Progressive measurements of the reverberation times were obtained during the construction of three similar lecture rooms. Two of these rooms have identical shape. Each has 106 seats. The third differs only in its width and has 158 seats. The three rooms have essentially flat reverberation characteristics of slightly less than 1 sec. The reverberation characteristics were measured just after the rooms had been plastered, when the acoustical treatment had been placed on the walls, and then progressively as the seats were added. The rows of seats were installed in the following sequence: 1st, 3rd, 5th, 2nd, 4th, 6th, and 7th. From these observations, the absorption per seat and per unit area are calculated for the different configurations. These values are compared with values measured on identical seats in a reverberation room.
Ratio of “Early” to “Delayed” Sound Energy in Halls
Authors: Watters B. G. , Schultz T. J. , Klepper D. L.
Published: November 2005

The ratio of “early-arriving” sound energy to “delayed” sound energy has long been recognized as an important property affecting speech intelligibility and the quality of music heard in auditoriums. We have recently measured this ratio as a function of frequency in several concert halls where there has also been the opportunity to listen and judge the “liveness” during performances of orchestral music. We have also listened to various types of music with simulated sound fields, where the ratio and spectral balance of “early” and “delayed” sound components could be adjusted. The results of these measurements and listening tests are discussed.
Digital-Computer Method of Measuring Concert-Hall Acoustics
Authors: Schroeder M. R.
Published: November 2005

A digital-computer method for measuring sound transmission and diffusion in concert halls is described. Specially shaped tone bursts are generated on the computer and recorded on magnetic tape. These tone bursts are radiated in the hall and recorded at various locations, using omnidirectional and directional microphones. The recorded sound-pressure responses are first “cleaned” by the computer, using a matched-filter technique, and then squared and integrated over various time intervals to obtain (1) the total energy for each frequency band, location in the hall, and microphone condition; (2) the “early” energy (direct sound and that arriving within the following 50 msec); (3) the energy of the direct sound; (4) the energies of various early reflections (ceiling, walls, etc.); and (5) the ratio of early-to-total energy. These energies and ratios are converted to decibels and plotted as functions of frequency by a special microfilm plotter attached to the computer. Frequency averages of these data as functions of location in the hall and spatial averages over all or certain selected locations are also computed and plotted. For more-detailed analyses, “echograms” are plotted on both linear and logarithmic scales. The computer also time-averages the sound-pressure responses and plots smoothed decay curves on a logarithmic scale, together with one or more straight lines fitted to the decay curves. Measures of time-varying sound diffusion are computed from the outputs of directional microphones. Results obtained by this method in Philharmonic Hall (New York) are discussed in a companion paper. Parallel studies are aimed at assessing the subjective significance of the measurements.
Acoustical Measurements in Philharmonic Hall (New York)
Authors: Sessler G. M. , Atal B. S. , Schroeder M. R. , West J. E.
Published: November 2005

Acoustical measurements in Philharmonic Hall have been performed according to the computer method described elsewhere [Paper C6, this meeting]. The measurements were taken before, during, and after alterations of the Hall in 1963. The following improvements were noted. The total and early energies are increased by about 5 dB in the octave band 80 to 160 cps and by 2 dB in the octave band 120 to 240 cps. As a result of the realignment of the suspended acoustical reflectors (“clouds”), the reflected energy in the frequency range 120 to 400 cps has increased by about 7 dB. Particularly noteworthy is the lack of low frequencies in the direct sound at the seats. This deficiency (probably common to many halls) has been traced to wave interference due to multiple reflections from the regularly spaced rows of seats. The stage enclosure shows a good low-frequency reflectivity. Echoes from the rear wall were noticeable on stage and in the front part of the Hall. A directional loudspeaker was used to measure these reflections. They were found to be attenuated by about 7 dB after absorptive and diffusive treatment of selected surfaces of the rear wall and balcony fronts. The sound decay was found to be nonexponential for many locations. This characteristic, which may account for the subjective “dryness” of the hall, can be attributed to a lack of diffusion. More diffusion would also improve the feeling of envelopment by sound and eliminate any remaining echo problem.
Evaluating the Acoustics of a Completed Auditorium
Authors: Klepper David L. , Watters B. G.
Published: November 2005

Techniques using prerecorded tapes and ordinary rubber balloons have been developed to measure the factors affecting hearing conditions, with the minimum time and equipment, in a completed auditorium. With the tapes and balloons and a sound-level meter, octave-band analyzer, portable tape recorder, and microphone and calibrator, the engineer can measure the following factors in the field: (1) background-noise levels; (2) reverberation time; (3) sound-system frequency response; (4) uniformity of speech intelligibility; and (5) ratio of reverberant to early sound energy. Certain of these data require further laboratory analysis. The specific techniques are discussed with reference to evaluating the completed Branscomb Memorial Auditorium, a modest-budget 1800-seat multipurpose auditorium on the Florida Southern College campus. Nils Schweizer and Associates are the architects.
General Definition of Transducer Coupling Coefficient and Some Applications
Authors: Mohammed A.
Published: November 2005

In studies of transducers, the coupling coefficient serves as a measure of the interaction between the parts of a coupled system and its value is an indication of transducer quality. The literature reveals many definitions of coupling coefficient, the majority of which are consistent but not reconciled. A general definition due to Hersh applicable to mechanical, electrical, and electromechanical systems, tuned and untuned, reciprocal and antireciprocal, is presented. It is shown that this definition leads to the other forms in common use. Several familiar examples of its application to electromechanical systems are considered, and, in particular, the expression for the coupling coefficient of a compound bar resonator is derived.
On the Properties of Segmented Ferroelectric Ceramic Systems
Authors: Martin Gordon E.
Published: November 2005

This paper considers the properties of segmented systems of longitudinally polarized ferroelectric ceramics, including the effects of the cement joints between segments. The theory for such a system of alternate ceramic and cement segments is summarized. It is shown that the system can be described in terms of effective parameters that combine the effects of the ceramic and cement joints. Unfortunately, the IRE Standards do not discuss the effective parameters of segmented systems; nevertheless, these are the parameters that must be used in transducer design. A technique for the direct evaluation of the effective parameters of large cemented systems is discussed. Experiments are described that have been used to evaluate the compliance of the cement joints and both the actual and effective parameters of the ceramic. The experimental properties of ceramic transducer materials are summarized.
Dumiload: A Variable-Radiation-Impedance Simulator
Authors: Hanna Dean A.
Published: November 2005

A wide range of radiation load impedances for a transducer element has been created by a laboratory device. This range included all the radiation impedances that exist for any of the transducers of a large planar array of over 400 elements. The device is called DUMILOAD, which is a contraction of DUmmy Mechanical Impedance LOAD. The DUMILOAD consists of a transducer terminated with an electrical impedance. A purely passive electrical impedance is sufficient to create positive radiation resistances. The DUMILOAD transducer is cemented face to face with a test transducer. The radiation impedance of the test transducer is controlled by adjusting the electrical impedance terminating the load transducer. The DUMILOAD is an existing research tool and has been of great value for high power transducer testing at NEL. The procedures necessary to create a desired radiation impedance are presented and a simple but precise method for measuring directly the radiation impedance achieved is described.