bluuebunny/crossref_metadata_2025 huggingface dataset:
Pitch Extraction and Display for the Deaf
Authors: Dolansky Ladislav , Ferullo Robert J. , O'Donnell C.
Published: September 2005

Because of the absence of auditory feedback, it is difficult to teach correct intonation to the deaf. This investigation is concerned with the problem of teaching iutonation patterns to deaf children by means of visual display obtained with the help of an envelope-type pitch extractor. The visual display itself consists of a storage oscilloscope so that the student's pitch pattern may be compared repetitively to the teacher's pitch pattern. Several deaf children took a limited number of brief instructional lessons, using the apparatus mentioned above. Their attempts to imitate the teacher's pitch patterns were recorded photographically and magnetically before and after the series of instructional lessons. The magnetic recordings were presented, in a raudomized order, to a group of judges. The summary of the judges' ratings with respect to the degree of imitation of the teacher's pitch pattern, examples of oscillograms of pitch patterns and other observations made during the experimeuts are presented. [Research supported by the U. S. Department ooe Health, Education, and Welfare, Office of Education.]
Effect of Head Movement on Speech Reception in the Presence of Noise
Authors: Olsen Wayne O.
Published: September 2005

The ability of 18 normal-hearing persons to hear and to understand speech in the presence of speech-spectrum noise was tested under monaural direct, monaural indirect, and binaural listening conditions in an anechoic chamber when (1) the subject's head was held immobile by a headrest and strap, (2) the listener was permitted slight head movement, and (3) the observer moved his head freely without moving the rest of his body to achieve best speech reception. The subject was seated equidistant between two loudspeakers located at angles of 45° to his right and left. Test materials consisted of spondaic words and monosyllables. Experimental results reflected the influence of the head shadow, regardless of whether the head was held immobile or permitted substantial movement. Binaural performance was slightly superior to that achieved in the best monaural condition. However, within each of the monaural and binaural conditions, ability to hear and to understand speech was influenced very little by head movement. [Research was supported by contract with Prosthetic and Sensory Aids Service, Veterans' Administration.]
Robust Two-Input Correlators
Authors: Wolff S. S. , Gastwirth J. L.
Published: September 2005

In the two-input polarity coincidence correlator (PCC), the two data channels are hard-limited before they are correlated. As a threshold detector for underwater acoustic signals, the PCC has the desirable property that (under certain assumptions) its false-alarm rate is independent of the noise-probability distribution, including the commonly occurring situation of time-varying average noise power. One disadvantage of the PCC is that it is not robust; that is, for a given noise distribution, its performance relative to the best-possible correlator for that distribution depends strongly on the distribution. In this paper, we derive the optimum two-input correlator for a given noise distribution and then propose two devices that are more robust than the PCC. These robust correlators have the property that their performance is relatively uniform over a large class of noise distributions. Implementation of these devices requires that the noise power be estimated. Sequential methods of accomplishing this are given. [Work supported by the U. S. Office of Naval Research.]
Computer Experimentation on Echo Detection, Using the Cepstrum and Pseudoautocovariance
Authors: Bogert Bruce P. , Ossanna J. F.
Published: September 2005

The cepstrum (power spectrum of the log power spectrum) and the pseudo-autocovariance (Fourier cosine transform of the log power spectrum) were proposed as a method to detect an echo in a time series, and for possible application as a substitute for autocorrelation to determine the depth of a seismic or acoustic source. The cepstrum and pseudoautocovariance are much more tolerant of the shape of the power spectrum of the echoed signal than is the autocorrelation. Computer-generated examples of white and colored echoed Gaussian signals in Gaussian noise are given that exhibit this property. [Work supported in part by the U. S. Navy Bureau of Ships.]
Scattering by an Array of Cylinders of Small Surface Impedance
Authors: Embleton T. F. W.
Published: September 2005

Plane waves are considered to impinge at normal incidence half-space containing a random array of cylinders whose axes are parallel to the wavefronts and to each other. The relevant multiple-scattering theory has been given by Twersky [N. Y. Univ. Rept. EM-59 (1953)]. The average attenuation per unit distance within the array is calculated for various sizes of scatterers, radius 0.1–10 cm, and surface impedances R/ρc=0, −2<X/ρc<2. It is found that attenuation is directly proportional to cylinder radius. In a relief map of attenuation versus X/ρc and ka (k being the wavenumber), the attenuation becomes infinite at the origin but is otherwise zero when ka=0. When X/ρc is a stiffness reactance, the function is a series of ridges radiating from the vicinity of the origin—these ridges are sharp and high close to the origin, becoming broader and lower further away; each ridge is curved, being convex to the ka axis. For any given value of X/ρc, the greatest attenuation is found at frequencies near to the value given by ka=X/ρc. When X/ρc is a mass reactance, no interesting features arise and the surface is a gently sloping plateau.
Acoustic Scattering from an Interface between Media of Greatly Different Density
Authors: Mitzner Kenneth M.
Published: September 2005

The problem of acoustic scattering from an interface between two homogeneous media is formulated as two integral equations with coupling minimized. When γ, the ratio of the densities, goes to zero, the equations decouple, one becoming the equation of a soft-boundary problem, the other of a hard-boundary problem. For small γ, an approximate solution is constructed by perturbation methods from solutions to the related soft- and hard-boundary problems.
Interaction of Acoustic Waves with Solid-Gas and Liquid-Vapor Interfaces
Authors: Porter J. W.
Published: September 2005

Adsorption and condensation are presented as mechanisms for the interaction of acoustic waves with solid-gas and liquid-vapor interfaces, respectively. Interface boundary conditions are derived and are used, in turn, to derive equations that describe normal reflection of one-dimensional acoustic waves at infinitely rigid solid-gas and liquid-vapor interfaces. Results show that, as the frequency of the incident wave goes from zero to infinity, the velocity-amplitude reflection ratio decreases monotonically from unity to a limiting value, which may be as small as 0.42, and the phase shift of the reflected velocity wave goes from zero through a maximum and back to zero. Significant absorption of the incident wave may begin at frequencies as low as about 1.0 cps (for solid-gas interfaces exhibiting chemisorption and for liquid-vapor interfaces) or as high as about 10 Mc/sec (for solid-gas interfaces exhibiting monomolecular physical adsorption). The interaction mechanism presented in this paper should prove useful in investigating the effects of acoustic disturbances on (1) heterogeneous chemical reactions between adsorbed gaseous species and (2) water-vapor condensation on small solid or liquid nuclei.
Loudness as a Function of Sound Intensity and Duration: An Analysis
Authors: Zwislocki Jozef J.
Published: September 2005

According to empirical evidence, loudness is nonlinearly related to sound intensity, but loudness level grows linearly with stimulus duration up to about 100 msec. The interaction between the two functional relationships could easily be explained by assuming that temporal summation in the nervous system occurs prior to the nonlinear transformation. However, such an assumption is contrary to results of physiological and psychophysical experiments that indicate that temporal summation follows the nonlinear transformation. It is shown how the auditory system can act as an integrator of sound energy in the time domain in spite of the intervening nonlinearity. The analysis combines data obtained by both psychophysical and physiological means.
Critical Bands and the Discrimination of Intensity Relations in Two-Tone Complexes
Authors: Chaves John F. , Scharf Bertram
Published: September 2005

The intensity relations within a two-tone complex were varied by setting one tone 0.5 to 4 dB below 70 dB SPL and the other the same number of decibels above. 25 subjects, listening monaurally through earphones, tried to distinguish these complexes from complexes with both tones at 70 dB. The main variable was the frequency separation ΔF between the two tones. It was usually more difficult to detect an intensity difference within the complex when the two tones were close or far apart in frequency than when they were at some intermediate distance, roughly equal to the critical bandwidth. The effect of ΔF was clearest when the lower-frequency component was more intense than the higher-frequency component. Measures were also made with the intensity of the two components changed in the same rather than opposite directions. Here detectibility was independent of ΔF. These findings held up best at center frequencies of 1000 and 2000 cps, less well at center frequencies of 500 and 4000 cps. [Research supported by the Public Health Service, U. S. Department of Health, Education, and Welfare.]
Rôle of Stimulus Frequency in the Apparent Location of Tone Bursts
Authors: Butler Robert A. , Naunton Ralph F. , Roffler S. K.
Published: September 2005

Loudspeakers were concealed behind a drape arranged in a semicircle with a radius of 5 ft. Listeners, seated at its center, were asked to repeat the location of tone bursts By giving the number on the drape behind which the sound appeared. Stimulus frequency ranged from 0.5 to 8 kcps; burst duration was 10 msec; rise-decay time was 5 msec. Head movements were minimized by a device attached to the listener's chair. The results showed that the apparent location of the intermediate frequencies (2–4 kcps) were displaced toward the midline. The magnitude of displacement increased with increases of the azimuth of the sound source. Augmented interaural intensity differences by partially occluding the ear opposite the sound source served to decrease the constant error of location, but did not eliminate it. When bands of noise bursts instead of tone bursts were used, listeners still displaced toward the midline that band consisting of the intermediate frequencies. The adequacy of interaural tone and intensity difference cues in accounting for these data is discussed.
PSE Tracing Method for Subjective Harmonics Measurement and Manaural Phase Effect on Timbre
Authors: Kuriyagawa Mamoru , Kameoka Akio
Published: September 2005

Simutaneous measurement was made of both sound-pressure levels and phases of subjective harmonics, by adopting a PSE tracing method based on successive-pair comparisons. The conclusions reached are as follows: (1) The new method measured the subjective harmonics about 20 dB down against the best beat method. The second subjective harmonic of a fundamental 440 cps 80 dB SPL, for example, was 34 dB down and the sine phase angle 262°, while Fletcher's result is 17 dB down. (2) The vector-addition law is applicable when summating external tones on the subjective harmonics. (3) The MPE depends largely on the subjective harmonics. (4) By adjusting intensities and phases of external harmonics, observers recognized the possibility to produce subjective pure tones. (5) Those suggest a hypothesis that the MPE is due to harmonics amplitude changes by interactions on the subjective harmonics. The phase rule seems of no truth for actual ears with non-linearity.
Performance of a New 100 000-cu ft Reverberation Room
Authors: Eldred Kenneth McK. , Spice B. J.
Published: September 2005

This paper describes the design requirements for and performance of a 100 000-cu ft reverberation room designed and built by Wyle Laboratories in Huntsville, Alabama. The walls were designed to withstand a 165-dB sinusoid at the resonant frequency expected to give maximum stress and fatigue. The fundamental resonance of the room occurs at 9.6 cps. Above this frequency, the modal density increases, averaging and increasing approximately with the square of frequency above 25 cps. The paper reviews the frequency response characteristics, spatial correlation in various bandwidths, and the amplitude distribution in the room for both high- and low-intensity sound.
Forced Oscillations of a Liquid in a Cylindrical Tank at Low Gravity Environments
Authors: Yeh Gordon C. K.
Published: September 2005

This paper presents a solution to the forced liquid-sloshing motions in a circular cylindrical tank at low gravity environments owing to an arbitrary horizontal translational motion. Conventional methods of analysis apply to normal or high-gravity conditions only, in which the undisturbed liquid-gas interface can be taken to be flat and the surface tension effects can be neglected. At low-gravity environments, the curved static interface shape, the liquid-to-solid contact angle, and the surface-tension effects must be taken into account. A solution to the corresponding free-vibration problem has been obtained by H. M. Satterlee and W. C. Reynolds [Stanford Univ. Dept. Mech. Eng. Tech. Rep. No. LG-2 (1 May 1964)] by means of a variational procedure. In this paper, the forced-motion problem is solved by first expanding the velocity potential, the interface waveheight, and the forcing functions in terms of the normal-mode shapes obtained in free-vibration analysis and then solving the resulting pairs of simultaneous ordinary differential equations for the generalized coordinates. Representation of the liquid motion by a dynamically equivalent spring-mass mechanical system is also given.
Perceived Noisiness of Pure Tones: A Status Report
Authors: Pearsons K. S. , Bishop Dwight E.
Published: September 2005

Paired-comparison tests investigating the effect of pure tones superimposed on broad-band noise spectra are described. Harmonically and nonharmonically related tones and amplitude- and frequency-modulated tones are being utilized in current laboratory judgment tests. Results from the current judgment tests are presented and compared with the results of previous studies. Difficulties arising from test methodology and other possible pitfalls are discussed, and an outline of work planned for the near future is presented. [Research supported by the National Aeronautics and Space Administration.]
Accuracy Considerations in Fan Sound Measurements
Authors: Baade Peter K.
Published: September 2005

Existing fan-sound power data appear reasonably adequate for air-conditioning system design purposes, provided that the fan does not generate any discrete frequency sound. One of the main reasons for conducting fan-noise tests is, therefore, to get accurate data on any discrete-frequency components. Such measurements tend to be subject to large errors owing to standing waves in the duct. Longitudinal standing waves not only affect the pressure field in the duct but also the sound-power output of the fan and must be eliminated by an anechoic termination. Crosswise standing waves pose problems for in-duct measurements, which can be overcome by averaging over the duct cross section or by the use of an acoustic wattmeter. Accurate measurement of the broad-band component is much simpler. Microphone windscreens for in-duct measurements differ greatly in their ability to reject near-field turbulence created by the fan. For this, too, an acoustic wattmeter should be of great help.
Further Investigations of Pitch Discrimination of Pulse-Train Bursts
Authors: Rosenberg Aaron E.
Published: September 2005

Previous results have indicated that discrimination of pulse-train bursts, identical except for polarity pattern, with pulse separations of the order of 10 or 15 msec is associated with the magnitude of the difference in the number of polarity transitions between stimuli [J. Acoust. Soc. Am. 39, 1233(A) (1964)]. This interpretation of the result is not adequate for pulse separations less than 10 msec. In discussing the previous experiment, it was hypothesized that discrimination is based on distinct pitch sensations associated with homopolar and heteropolar pulse pairs. Then, the pitch sensation associated with a pulse-train burst is some additive combination of the pitch sensations of constituent pulse pairs. In the present experiment, this hypothesis is given further support. Moreover, it is shown that for pulse separations less than 10-msec pitch discrimination for some pulse-train bursts may be accounted for by simple extension of this hypothesis. Attaching greater weight to pulse pairs occurring latterly in a burst and admitting pitch sensations associated with pulse pairs formed from nonadjacent pulses are extensions suggested by the results.
Auditory Afterimages in Gated Noise
Authors: Lummis Robert C. , Guttman Newman , Bock Donald E.
Published: September 2005

In a study of the auditory afterimage [E. Zwicker, J. Acoust. Soc. Am. 36, 2413–2415 (1964)], normal-hearing subjects listened to conditioning noise in which the band from 1900 to 3350 Hz was eliminated. The noise was switched on and off repetitively at rates from 0.1 Hz up, with variable duty factor. At a favorable spectral-density level (e.g., 20 dB re 0.0002 dyn/cm2/Hz), tonal afterimages were heard by some subjects at switching conditions as extreme as TON=0.5 sec, TOFF=9.5 sec. For other subjects, such a small duty factor produced no afterimage; as the duty factor was increased, a noisy afterimage was heard first. With further increase, the image acquired a tonal component that became dominant at large duty factors. The range of switching parameters capable of producing a tonal afterimage varied more among subjects than between the two ears of any one subject. Other experiments showed that, for some subjects, partially filling the frequency gap of the conditioning noise with either a sinusoid or noise was surprisingly ineffective in obliterating the afterimage. When located at the normal after image pitch, such a sinusoid sometimes shifted the afterimage pitch appreciably.
Nonlinear Distortion and Battery Life in Hearing Aids
Authors: Lotterman Stephen H. , Kasten Roger N. , Revoile Sally G. , Majerus Diane
Published: September 2005

This study examined the alterations in nonlinear distortion in hearing aids that resulted from normal battery-voltage variations over useable battery life. New hearing aids of several types were selected for study. Initially, the gain of each instrument was adjusted to a level 6 dB below maximum at 1000 Hz. The gain was readjusted to this value for all subsequent measurements until battery voltage dropped below a level adequate to maintain that gain, even at a maximum setting. Nonlinear distortion was recorded at 500, 600, 700, 900, and 1250 Hz, utilizing 70-dB-SPL (sound-pressure level) input signals. The hearing aids were operated for 8 h daily and distortion measurements were made at regular intervals until gain dropped below −10 dB reference the initial test value. The results indicate that for some hearing-aid/battery-type combinations disproportionate increases in distortion accompany decreases in battery life. Results are considered both as a function of battery life and voltage. Implications of these findings are discussed.
Effect of Hearing-Aid Gain Control on Acoustic Gain
Authors: Kasten Roger N. , Lotterman Stephen H. , Revoile Sally G.
Published: September 2005

It is generally accepted that a hearing aid should not operate at or near the maximum setting of the gain control where distortion is usually highest. This investigation examined the effect that the physical movement of this gain control has on the acoustic gain of hearing aids. Using a large group of commercially available aids, the gain-control knob of each instrument was divided into eight increments of 1212% and acoustic gain was measured at 500, 1000, and 2000 Hz at each increment. The input signals to the hearing aids were maintained at 70 dB SPL (sound-pressure level), an intensity compatable with acoustic levels encountered in every day situations. It was found that, under the conditions employed in this investigation, a nonlinear relationship was most often observed. For the body aids, average gain exceeded 50% with a 25% rotation of the gain control and exceeded 78% at the 50% setting of the control. Corresponding control settings for ear-level aids yielded 47% and 72% acoustic gain.
Measures of Human-Tursiops Sonic Interactions
Authors: Lilly John C. , Truby H. M.
Published: September 2005

It has been shown [J. C. Lilly, Man and Dolphin (Doubleday & Co., Garden City, N. Y., 1961); Science, 15 (1965)] that Tursiops truncatus can be induced to produce airborne sounds in response to human utterances. These responses [“humanoids”: J. C. Lilly, Proc. Am. Phil. Soc. 106, 520 (1962)] bear certain acoustic and visual-acoustic resemblance to the vocal stimuli. Under effective operant conditioning, the number of Tursiops humanoid emissions in a given response train precisely matches the number of human vocal emissions in the corresponding stimulus train. Tabulations based on the analysis of hundreds of such sonic interchanges demonstrate that Tursiops is capable of accurate matching of number of events for runs of over 40 stimulus-response interactions, in which the number of events in each train ranged as high as 10. In some experiments, the human was replaced through the use of tape-recorded stimuli and an automatic fish-dispenser, and, in some, the food reward was eliminated entirely to prevent its function as a signal. The incidence of either interpolation or overlap of response events with respect to stimulus events disappears with training. Differing vowel color and intonation contour of stimuli are reflected in humanoid variations of structure and contour. The correlation of humanoid and stimulus utterance is evident in acoustigraphic form. Tape-recorded examples are given, and apparent errors and inter-species considerations are discussed. [Work supported by the National Institute of Nervous Diseases and Blindness and the National Institute of Mental Health, National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Efficient Coding of Vocoder Pitch Periods, Using Variable-Length Coding
Authors: Crowther William R. , Rader Charles M.
Published: September 2005

The pitch signal derived from a good pitch extractor is a time function that sometimes varies very rapidly, but usually varies very slowly. Using a pitch extractor that produces an 8-bit linear code proportional to pitch period at a rate of 150 times/sec, it is possible to transmit the entire message (ostensibly 1200 bit/sec) with approximately half the total number of bits by making use of the slowly changing parts of the function. The basic principle is to transmit a short code when a probable pitch period occurs and a long message when an improbable period occurs. The probable messages are those representing little or no change from the last period. The rate reduction achieveable this way is better than two to one with exact preservation of the message, but this requires a considerable delay and buffer storage. Instead of this approach, we tried to optimize our code for a given bit rate, keeping the required delay as small as possible. We found that, at a rate of five-eighths or 750 bit/sec, we could choose code words so that a buffer length of 144 bit was sufficient, corresponding to a delay of 60 msec in a 2400-bit/sec vocoder. We use seven codes to indicate small changes, i.e., 0, ±1, ±2, ±3, and an eighth code to indicate that a large change has occurred, followed by the new pitch value. If the buffer is near overflow (an event that occurs on the average of only once in 10 min of an active monolog), the 0 change code is sent, and this represents the only possible deviation from a perfect reproduction of the pitch message.
Nonlinear Time Compression and Time Normalization of Speech
Authors: Hanauer Suzanne L. , Schroeder M. R.
Published: September 2005

In a study of the effects of different speaking rates on articulator dynamics [J. E. Miller, J. R. Pierce, and M. V. Mathews, J. Acoust. Soc. Am. 34, 1978(A) (1962)], it was found that, when talkers were instructed to speak faster, they shortened the “steady-state” vowel portions while keeping the phoneme transitions approximately constant in duration. Thus, in speaking faster, humans use nonlinear time compression. In the present nonlinear time-compression scheme, speech is separated into contiguous narrow frequency bands, for each of which signals representing amplitudes and instantaneous frequencies are derived [J. L. Flanagan et al., J. Acoust. Soc. Am. 38, 939(A) (1965)]. The sampling rate of these signals is made proportional to the total temporal derivative of the logarithmic short-time spectrum. As a result, the sampling rate is higher during phoneme transitions than during “steady-state” portions. Nonlinear time compression is achieved by applying these nonuniform time samples at a constant rate to a speech synthesizer. Thus, speech can be time-compressed in a manner resembling human speech at increased speaking rates. Results are compared with linear time compression for the same average compression factor. Also, the application of nonlinear time compression to time normalization for automatic speech recognition is discussed.
Some Spatial and Temporal Variations in Pacific SOFAR Propagation Paths
Authors: Northrop John
Published: September 2005

Hydroacoustic signals from a series of 752 explosions detonated off Cape Mendocino, California, were monitored at SOFAR depth hydrophones of the Pacific Missile Range at Oahu, Midway, Wake, and Eniwetok Islands. A 15-cps low-pass filter was used prior to recording. The time interval between shots was about 1 min, and variations in signal level for individual shots were coherent between the local and distant hydrophone data. None of the shots were received at Wake, due to blocking by intervening topography of the Hawaiian Arch. A saddle in the arch NW of Lisianski Island permitted good reception at Eniwetok. A 212-h periodic peak in signal level, amounting to 10 dB at Eniwetok, is apparent in the data. These results are compared with those from shallow seismic shots of the Scripps FLORA expedition 350 miles south of Cape Mendocino.
Precision in-situ Measurements of Relationship between Temperature, Salinity, Pressure, and Sound Speed
Authors: Mackenzie K. V.
Published: September 2005

The relationship between temperature. salinity, pressure, and sound speed has been studied in situ through water columns to depths of 4000 ft in several diverse areas near San Diego. Measurements were made on DEEPSTAR DS-4000, using ACF TR-4 and TR-3 velocimeters. Temperatures are measured by three thermistors. Pressures are measured with vibratrons. Salinity is determined with Hytech model 6007 salinometer. Fjarlie bottles with two protected and two unprotected thermometers each can be tripped at will. Data are recorded on a multichannel tape recorder for automatic analysis ashore. The dive is stopped at equilibrium points and sensors directly counted. After all the readings have been obtained at each equilibrium point, a bottle is tripped to get a water sample for laboratory analysis and to obtain protected and unprotected temperatures. Four of the equilibrium points on each dive are: (1)—DEEPSTAR 50 ft deep to obtain measurements in the surface channel; (2) and (3)—two different distances above but near the bottom; and (4)—on the bottom. The craft can hover ±1 m. When more-turbid waters were observed, data were obtained in these as well as the clearer waters while maintaining a course and speed of 12 kt (knot) to determine sound-speed anomalies. A special bottom probe was used to measure the temperature 1 ft below the bottom, at the bottom, and 1, 2, and 4 ft above the bottom to complete thermal-gradient information.
Possible Subjective Significance of the Ratio of Height to Width of Concert Halls
Authors: West J. E.
Published: September 2005

For positions along the center aisle of a rectangular hall, the ratio of travel times of early reflections from the ceiling and walls is approximately equal to 2H/W, where H is the height and W is the width of the hall. This ratio was determined for 38 concert halls and opera houses and the results were compared with the subjective categories compiled in Beranek's extensive investigation [L. L. Beranek, Music, Acoustics and Architecture (John Wiley & Sons, Inc., New York, 1962)]. The correlation coefficient for 2H/W and a numerical scale of the subjective categories is 0.71. Thus it appears that this ratio, which determines the relative arrival times of early lateral and vertical reflections, accounts for a major portion of the subjective ratings. The importance of lateral versus vertical reflections has been substantiated by laboratory experiments conducted in an anechoic chamber, using delayed speech and music signals played through loudspeakers.
Rôle of Model Testing in the Acoustical Design of Auditoria
Authors: Watters B. G. , Kirkegaard R. Lawrence , Schultz Theodore J.
Published: September 2005

The flow of sound from the stage of an auditorium to the audience is controlled both by the gross auditorium shape and by the architectural treatment of the interior surfaces. Both of these are, of course, primary architectural as well as acoustical elements. We have found acoustical testing of a scale model to be a valuable aid in achieving an architecturally acceptable design that yields “sound patterns” that have the desired frequency and amplitude characteristics and the appropriate times of arrival. Test data and instrumentation techniques are described; typical auditorium-design problems are illustrated.
Acoustical Modeling in the Design of the Saratoga Performing Arts Center Pavilion
Authors: Veneklasen Paul S. , Christoff Jerry P.
Published: September 2005

The development of a balance of clarity, envelopment, and reverberance by the use of acoustical modeling is described for the design of the 5100-seat pavilion for the Saratoga Performing Arts Center. Unusual problems were associated with the extreme size, the wide fan shape, and the largely open walls. Echograms are illustrated for the component surfaces and the complete array of enclosure.
Pressure Radiated by a Point-Excited Plate in the Presence of a Coating
Authors: Feit David
Published: September 2005

In a previous paper [D. Feit, “Pressure Radiated by a Point-Excited Elastic Plate,” J. Acoust. Soc. Am. (to be published)], the farfield pressure radiated by an infinite elastic plate excited by a time-harmonic point force in the presence of fluid loading was obtained. Here, the effect on the pressure radiated of a low-impedance coating, applied uniformly to the radiating surface, is determined. This analysis differs from previous analyses in that it takes into account wave effects within the coating. These are important since the sound-reduction capabilities of the coating are altered by their presence. These waves produce high-frequency resonant amplification in addition to the familiar low-frequency resonance between the coating and the mass of the elastic plate. This corresponds to the decrease in vibration isolation properties of mounts resulting from wave effects in the mounts [Mark Harrison, A. O. Sykes, and M. Martin, J. Acoust. Soc. Am. 24, 62–71 (1952)]. [Work sponsored by the U. S. Bureau of Ships General Hydromechanics Research Program administered by David Taylor Model Basin.]
Directional Characteristics of Slotted Piezoelectric Ceramic Tubes
Authors: Devine John A.
Published: September 2005

The acoustic performance of longitudinally slotted thin-walled tubes was investigated at the U. S. Naval Air Development Center under its Foundational Research Program. Single-element and line transducers of various dimensions were fabricated from radially polarized, slotted piezoelectric ceramic tubes. Their acoustic properties were measured over a frequency range of 3–80 kHz. The tubes exhibited multiple directivity characteristics, in a plane normal to the axis of the tubes, at certain discrete frequencies. The shape of the directivity patterns and the frequencies at which they occurred were explained in terms of circumferential extensional vibrations with geometrically determined nodal positions. In addition, unidirectional response patterns were found at frequencies that were below the fundamental breathing mode of the tubes. These patterns had front to back ratios of 10 dB or greater. The experimental data and an analysis of the results are presented.
Pratt & Whitney Aircraft Experience in Compressor-Noise Reduction
Authors: Sofrin Thomas G. , McCann John C.
Published: September 2005

This paper summarizes the Company's research and development activity in studies of compressor noise and means for its reduction. Correlation between theory, small-scale-rig tests, and full-scale-engine data are discussed. Special rig and instrumentation systems helpful for diagnosis of compressor noise are described, and illustrations are given of several techniques for reducing noise and the extent to which these techniques worked in rigs and engines. The paper concludes with a discussion of the noise characteristics of possible future high bypass ratio turbofan engines.
Effects of Increased Inlet-Guide-Vane/Rotor Spacing on Compressor-Noise Reductions
Authors: Copeland W. L. , Crigler J. L.
Published: September 2005

One of the sources of compressor noise is the fluctuating aerodynamic loadings resulting from interaction between the fixed and rotating blades. Studies involving a model single-stage compressor have shown that an increased axial spacing between the components of the compressor resulted in substantial reductions of the pure-tone noise. Based on the above experience, the inlet guide vanes of a turbojet engine in the 2000-lb-thrust range were relocated forward about six chord lengths, with the objective of reducing noise. Comparisons are made of the noise characteristics of the above simply modified engine with those of the unmodified engine. The compressor-noise levels for the modified engine are shown to be greatly reduced, for all frequencies, with no measurable performance loss.
Noise Control of On-Board Auxiliary Power Units for Aircraft Use
Authors: Callaway Vernon E.
Published: September 2005

The APU-equipped commercial jet transport is a relatively new addition to the typical busy airport. Its introduction into service has provided many operational advantages for the airlines, but it has also created many noise-control problems for the aircraft designer. Special acoustical materials and installation techniques that fulfill high-temperature requirements and stringent fire-safety demands are needed to control the three principal noise sources: the inlet, the case, and the exhaust. In addition, practicable noise criteria are required for the APU installation. Fulfillment of these requirements for installations on the existing Boeing model 727 and for the new model 737 aircraft are discussed in this paper.
Detection Performance and Two Parameters of the Auditory Stimulus
Authors: Nichols Thomas L. , Jeffress Lloyd A.
Published: September 2005

Four subjects were run in a conventional YES-NO psychophysical experiment in auditory masking. The stimulus consisted of a 250-msec burst of wide-band white noise. On 50% of the trials, a 500-Hz sinusoidal signal was added to the noise burst. On each trial, a record was made of the stimulus (N or SN), the subject's response (YES or NO), his response latency, and two physical measures of the stimulus. These were obtained by using an electronic-ear model consisting of a narrow-band filter (simulating the subject's critical band), followed by a rectifier and two measuring devices. One of these determined the magnitude of the largest envelope peak occurring during the stimulus interval, and the other the average voltage of the stimulus envelope. A series of multiple linear regression equations was constructed to determine the independent contribution of each of the electrical measurements to predicting the nature of the stimulus (N or SN), and the subject's response. The average voltage of the envelope was found to be the more efficient predictor of both stimulus and response. The maximum amplitude was a poor predictor, and added little to that furnished by the average voltage. [Work supported through a contract with the U. S. Navy Bureau of Ships and a grant from the National Aeronautics and Space Administration.]
Effects of Vibrator Types and Their Placement on Bone-Conduction Threshold Measurements
Authors: Weston Peter B. , Gengel Roy W. , Hirsh Ira J.
Published: September 2005

Monaural bone-conduction threshold measurements in the quiet were obtained for 10 normally hearing young adults at both forehead and mastoid positions using two hearing-aid-type vibrators of different manufacture. Physical calibration data for the vibrators were obtained by other laboratories, using different Beltone artificial mastoids. Bone-conduction force thresholds (in root-mean-square dynes) are reported, along with measures of both intra- and inter-subject variability. [Work supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Corrected String Lengths to Compensate for Tension and Damping
Authors: Burchett O. J. , Eaton R. R.
Published: September 2005

The fact that the diatonic scale cannot be used on a fretted instrument is shown. The derivation of the chromatic scale is also shown and the results are compared to the diatonic scale. A testing device that simulates the stretching of a string when fretted was used to obtain the necessary string lengths to produce the desired vibration frequencies. The desired vibration frequencies are determined by the chromatic scale. Nylon guitar, steel guitar, and banjo strings were tested.
Duration of Flyover Noise Level during Takeoff and Landing
Authors: Ilkcagla Edward A. , Marsh Alan H.
Published: September 2005

Corrections to flyover perceived-noise level (PNL) are required to account for varying durations of aircraft flyover noise signals. The magnitude of the duration of takeoff and landing flyover noise signals has been determined for two turbofan-powered jet transports, the DC-8 airplane with JT3D short fan-discharge duct engines and the DC-9 airplane with JT8D long fan-discharge duct engines. Recordings of actual flyover noise signals from these two aircraft over a range of altitudes were analyzed in 13-oct bands using digital techniques. Instantaneous PNL's and over-all sound-pressure levels (SPL) were determined and plotted by a machine under program control. For altitudes greater than 800 ft, maximum values of the PNL and the over-all SPL did not occur simultaneously, and the time between the 10-PNdB down points was considerably shorter than the time between the 10-dB down points on the over-all SPL. The duration of the top 10 PNdB of both DC-8 and DC-9 noise signals correlated well with the altitude of the aircraft.
Theory and Computer Simulation of a Self-Adapting Echo Canceler
Authors: Sondhi Man Mohan
Published: September 2005

The problem of eliminating echoes becomes increasingly difficult with increasing roundtrip delay in long-distance telephone communication. This paper discusses the theory of a new kind of self-adapting echo canceler proposed at Bell Telephone Laboratories. Various simplifications and improvements of this new echo canceler are described. The results of computer simulation of such echo cancelers are presented.
Subjective Effects of Noise and Loss in Telephone Transmission
Authors: Sen Tapas K.
Published: September 2005

Voice transmission through telephone channels usually encounters a number of impairments that degrade the transmission quality. Two common impairments are loss of speech energy (known as “loss”) and noise. To maintain a high standard of transmission quality, it is therefore necessary to know the extent to which specific amounts of noise and loss degrade circuit quality. This paper describes an experiment concerned with this problem. 60 subjects took part in the experiment in which a range of 20 dB of loss and 40 dB of noise was used in actual telephone conversations made within the Murray Hill PBX (Bell Telephone Laboratories). The subjects' telephones were connected to a system that automatically introduced an experimental condition during calls made by the subjects. Talker volumes were measured with a volume indicator, and at the end of each call the subjects gave a rating of the transmission quality by dialing one of four predetermined digits. The results show that loss affected talker volume more significantly than noise, but influenced the ratings as significantly as noise over the range of those impairments considered.
Further Rhyme-Test Modification for Diagnostic Articulation Testing
Authors: Griffiths John D.
Published: September 2005

The modified rhyme test has been shown by House, Williams, Hecker, and Kryter [J. Acoust. Soc. Am. 37, 158–166 (1965)] to be a highly repeatable, stable test that is easy to score and administer and, as a diagnostic tool, contains some representative minimal pairs that differ in only one speech feature (place or manner of articulation or voicing). The modification reported here increases the number of these initial and final consonantal minimal-feature pairs to include all those occurring naturally in English, while at the same time shortening the complete test to five lists of 50 words each. Since confusions in place, manner, and voicing may be regarded as independent, any confusion may be regarded as the sum of its minimal-feature-pair confusions. The test has been validated in the same fashion as the original test and was found to be stable and without learning effect. It does not replace the original test for normal articulation testing, but is designed as an easily administered and interpreted tool for speech-communications diagnosis.
Spatial Coherence of Sonar Reverberation
Authors: Meharg Louis S. , Hixson E. L.
Published: September 2005

This paper describes experiments performed to determine some of the spatial characteristics of reverberation signals as encountered in pulsed echo-ranging sonar systems. A sonar system operating at 112 kHz was set up in a tank and used to obtain reverberation signals from smooth sand surfaces (particle sizes≪λ). Backscattered signals for small grazing angles (4°–12°) and narrow beamwidths (8°, 15°, and 22°) were recorded. Spatial correlations of the reverberation fluctuations were plotted for various spatial translations of the transducers relative to the scattering surface. The correlations of the fluctuations became small for lateral displacements (displacements normal to transducer axis) on the order of a wavelength and longitudinal displacements (displacements parallel to transducer axis) on the order of a pulselength. Further analyses of the recorded signals indicated that the average reverberation pressure diminished as a function of range as r−2.7 for one grade of sand and as r−21 for another grade of sand. Amplitude analyses of the recorded signals indicated that with 95% confidence the amplitudes were Rayleigh-distributed. [Research was conducted at Defense Research Laboratory, The University of Texas.]
Influence of Beamwidth and Multiple Transmissions on Reverberation-Limited Sonars
Authors: Cole B. F. , Hanrahan J. J.
Published: September 2005

Previous work on the discrimination of transducers against reverberation has been extended to include the influence of beamwidth and multiple transmisisons. The directivity index against reverberation is expressed in terms of an ideal searchlight beamwidth that is defined as having a response of unity within the region bounded by its beam and a response of zero elsewhere. This ideal beamwidth is found by considering the total received reverberation power from a specific projector-receiver combination. Two situations are treated: namely, a single transmission and several transmissions. For a single transmission, various transmitting and receiving beamwidths are considered in order to determine the degradation in system performance when transmitting beam dimensions differ from those of the receiving beams. The sensitivity of these results to minor-lobe levels is demonstrated. The findings are then generalized by expressing the multiple-transmission case in terms of an equivalent single transmission. The consequences of the theory are compared with observed sea data and are shown to depend upon reverberation decay rate, and hence upon water depth. Finally, the relation between search rate, beamwidth, and system performance is developed.
Specular Scattering of Underwater Sound from a Wind-Driven Surface
Authors: Medwin H.
Published: September 2005

A wind-driven water surface possessing the characteristics of a simple sea (near Gaussian distribution of slopes and a realistic ratio of the upwind-downwind slope to the cross slope) has been studied acoustically by analyzing specular scattering at normal incidence (surface roughness g=16π2σ2cos2σ/λ2 ranging from 0.32 to 26). Theory, based on Kirchhoff approximation, is used to estimate the root-mean-square surface height and the root-mean-square slope. Theory and experiment agree far beyond the restrictions of the Kirchhoff assumption. The acoustically determined value of the root-mean-square slope is 17% less than the optically measured value. As predicted, the form of the distribution of scattered sound varies from Gaussian to Rayleigh for increasing surface roughness. At any instant, the relative specularly scattered intensity decreases monotonically with increasing frequency to a minimum value at g≃3, from which it is possible to get a second estimate of the root-mean-square surface height; above g≃3, the instantaneous scattered intensity is a nonstationary function of frequency. [Hudson Laboratories, Columbia University Informal Documentation No. 114. Work supported by U. S. Office of Naval Research.]
Excitation and Detection of Plane Shear Waves by a Quartz Transducer with an Electrode Array
Authors: Coquin G. A.
Published: September 2005

The response of a rotated Y-cut quartz transducer with an electrode array on the surface to a sheer wave incident at an arbitrary angle is found by a perturbation method. Numerical results are obtained for the case of quartz bonded to fused silica for various choices of transducer and array parameters. Due to reciprocity, the solution can be used to determine the amplitude of a shear wave generated by an alternating voltage applied to the electrode array.
Design of an Ultrasonic Whistle
Authors: Karplus Henry B.
Published: September 2005

A departure of the Hartman whistle has been evolved that produces high intensities with less audible noise than the standard Hartman-type whistle. The design consists of a straight jet of air impinging on a resonator cavity set at an angle to the flow. Operation seems to be intermediate between the jet-edge type and the straight Hartman. Mounting the whistle at the focus of a spherical reflector coupled to the throat of an exponential horn yields high performance at low line pressures, permitting applications in which economy of operation coupled with low initial cost are important. Immediate applications for scaring birds, rodents, and insects have been successful. Other applications to the whole field of airborne ultrasonics are discussed. [Work partially supported by Bird-X, Inc., Chicago, Illinois.]