bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement Dynamic Strain Vibrating Piezoceramic Bending Bars
Authors: Fox C. C.
Published: November 2005

The photostress technique of strain measurement was applied to piezoceramic bending bars, vibrating in air at their resonant frequency, in an effort to learn the actual instantaneous strain distribution that does exist on the surface of these bars. A polariscope, high-intensity short-duration strobe light, and strobe synchronizing system were used on several types of bending bars coated with 0.120-in. photostress plastic. Data from a specimen with a well-behaved strain pattern agreed fairly well with a strain function corresponding to a uniformly loaded simply supported beam. On another specimen, a case of combined bending and torsional strains was discovered. The relative ease with which these undesirable combined strain conditions and strain concentrations can be located constitutes a major advantage of the technique.
Eddy Current High-Frequency Reproduced
Authors: Rich Stanley R.
Published: November 2005

A free radiating diaphragm of thin aluminum toil is mounted parallel and close to, but does not physically contact, a fixed, long, rectangular, flat, spiral winding. Both are situated in an orthogonally directed flat magnetic field tailored to the coil and sheet geometry. Eddy currents induced in the aluminum foil react with the magnetic field causing the foil to provide useful output from 5000 to 30 000 cps. Theory of the transducer is discussed. Practical devices, results, and frequency response obtained are presented. Similarity to and differences from the Hewlett reproducer of the early 1920's are outlined.
Sound Isolation for Transducer-Threshold-Noise Evaluation
Authors: Powell John G.
Published: November 2005

Measurement of transducer electrical-noise threshold requires an extremely low ambient acoustic level. Conventionally, this measurement is accomplished by replacing the transducer with a “dummy” microphone. However, an accurate determination of the spectral distribution of system noise requires precise simulation of the sensing element. As an alternative, accurate measurements can be made with the complete microphone system placed in an acoustically quiet environment. A chamber has been constructed that, in our laboratory environment, provides an ambient spectrum level less than −15 dB (re 0.0002 dyn/cm2) at a frequency of 100 cps and less than −36 dB at 10 kc/sec. Since these acoustical thresholds are comparable to the electrical-noise levels of microphone systems currently being evaluated, considerable speculation exists regarding the minimum sound-pressure level that can be realized. Problems encountered in an attempt to measure the threshold noise are discussed.
Sound Attenuation between 200 and 10 000 cps Measured along Single Paths
Authors: Leroy C. C.
Published: November 2005

In the deep Mediterranean basins, the water is perfectly isothermal below 400 m, and the deep refracted ray gives clear signals up to 40 km, with a spreading loss free from any frequency-dependent effect. Exploiting this unique opportunity, a frequency analysis has been performed between 200 and 10 000 cps on the waveforms of acoustic signals from explosive sources, which had travelled along this path. Statistically, the change of spectrum with range is due only to absorption and internal spectral rearrangements of the shock-wave energy. Seven independent acoustic runs were analyzed and led to similar results. The average gives a detailed accurate curve of relative attenuation between 500 and 8000 cps. Among the possibilities of placing this curve in absolute scale, the one giving a best fit to a variation in f2 at low frequencies is found (a) to agree when extrapolated with values already published below 200 cps, (b) to be well-represented by a=Af2+Bf0f2/(f02+f2), where Af2 is the classical absorption and where f0=1.5 kc/sec. Some discussion follows about the interpretation of the results.
Ray-Tracing Program for Computing Transmission-Loss Contours
Authors: Norris A. B.
Published: November 2005

A computer program has been developed that allows a more economical approach to the problem of obtaining transmission-loss contours. Application of this program is limited to a medium in which the velocity structure is a function of the depth only and the boundaries are plane parallel. One of the bounding surfaces is assumed to be perfectly reflecting. The program computes transmission loss as a function of horizontal range and receiver depth for given source positions. Contours of constant loss are then obtained that provide a more complete quantitative picture of transmission than would otherwise be available. Results of sample computations are shown that illustrate many of the general features of sound transmission in the deep ocean. [Work supported by the Bureau of Ships, U. S. Navy Department.]
Vertical Coherence of Explosive Reverberation
Authors: Lund G. R. , Urick R. J.
Published: November 2005

The crosscorrelation of the outputs of hydrophones along a vertical array 15 ft long, suspended at depths of 60 and 300 ft from a surface ship, has provided information on the coherence and directional properties of reverberation in the sea. Correlograms of the clipped outputs of various hydrophone pairs in the band 1–2 kc/sec have yielded values for the correlation coefficient and the delay time, equivalent to arrival angle, for the return following the detonation of an explosive charge at a depth of 800 ft. The correlation coefficient is found to decrease with separation of hydrophones, as it should, and to decrease with time as volume reverberation replaces surface reverberation, until the arrival of the bottom reflection. Some correlograms show the presence of a deep scattering layer. The results may have application to the design of reverberation-suppressing arrays.
Neural-Information Processing in the Peripheral Auditory System of the Guinea Pig
Authors: Hanna George R.
Published: November 2005

A number of 1st- and 2nd-order neurons of the guinea-pig auditory system were studied extensively in an attempt to determine the method by which information is conveyed. Single-neuron electrophysiological techniques with anatomical controls were used in the study and, in response to several different stimuli, various response patterns were observed. Statistical methods of analysis, utilizing a digital computer, were employed. It appears that each fiber in the auditory nerve conveys only fragmentary information; the information carried by a number of fibers is required to extract all the information about a single signal. The data suggest that a pulse-density-modulation system of encoding is used, in which the “carrier” appears to be the irregular spontaneous background activity, the pulse density of which is actively increased and decreased to convey information about both pitch and loudness. The system appears to be much more sensitive to sound changes than to absolute values. For example, pulse density correlated far better with rate of change of stimulus intensity than with absolute levels of intensity. It was also found that, in addition to frequency and amplitude, the interval between successive stimuli may be an important parameter of stimulation.
Single Neural-Unit Response Patterns from the Auditory Cortex of the Guinea Pig
Authors: Parker Donald E.
Published: November 2005

Action potentials evoked by a variety of auditory stimuli were recorded with microelectrodes from single neural units in the auditory cortex of the guinea pig. Temporal characteristics of the action-potential response patterns were analyzed using a unique system that employs a digital computer. The computer is programmed to perform four types of analyses, which reflect various assumptions regarding the manner in which information may be encoded by the single neural unit. These programs include pulse histogram, pulse-rate pattern, interpulse-interval distribution, and average pulse position. A summary is presented of the various response characteristics that distinguish between the single neural units encountered in the present investigation. The response characteristics associated with the pulse-rate pattern are most useful for distinguishing different neurons, whereas the response characteristics associated with the interpulse-interval distribution generally fail to distinguish the neurons. Differences between auditory cortical neurons and those from (1) the somatic sensory system or (2) lower centers within the central auditory pathway are also most clearly manifested in terms of pulse-rate pattern-response characteristics.
Response Characteristics of Some Single Units in the Cochlear Nucleus to Tone-Burst Stimulation
Authors: Pfeiffer Russell R.
Published: November 2005

Spike discharges of single units in the cat's cochlear nucleus in response to repetitive tone-burst stimulation were recorded with metal microelectrodes; histograms of times of discharges relative to onset of stimuli were obtained on the TX-0 computer. The histograms of the responses of some units show several distinct peaks, that indicate that any one unit fires at preferred times during each tone-burst presentation. The time of the first peak (latency of response) and the time intervals between successive peaks change systematically with changes in intensity (tens of dB's), repetition rate (5–35/sec), and duration (10–100 msec) of the tone bursts (2–40 kc/sec). These time measurements decrease monotonically with increases in stimulus intensity and increase monotonically with increases in stimulus repetition rate and duration. They do not correlate with the frequency of tone to which the unit is most sensitive. [Work supported in part by the U. S. Army Signal Corps, the U. S. Air Force Office of Scientific Research, and the U. S. Office of Naval Research; the National Science Foundation (grant G-16526), the National Institutes of Health, U. S. Department of Health, Education, and Welfare (grant MH-04737-03); the National Aeronautics and Space Administration (grant NsG-496); and in part by research grant B-1344, National Institute of Neurological Diseases and Blindness, National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Frequency-Following in the Superior-Olivary Complex of the Cat
Authors: Boudreau James C. , Tsuchitani Chiyeko
Published: November 2005

Presentation of tonal stimuli to either ear of the anesthetized cat evokes wave activity in the superior-olivary complex (SOC) of the same fundamental frequency as the stimulus. “Following” of the potentials was observed to tones as low as 30 cps and as high as 2700 cps, with a maximum around 800 cps. Above 600 cps, the waveforms of the potentials approximate that of the stimulating tone. So faithful was the reproduction of the stimulus that spoken words were understandable when the potentials were led into an audiomonitor. Depth penetrations into the SOC while stimulating with an 800-cps tone revealed amplitude peaks in and around the accessory nucleus. With contralateral stimulation, an amplitude peak was observed at the ventromedial border of the accessory nucleus and another in the cell layer, whereas with ipsilateral stimulation a peak was seen in the cell layer and another at the dorsolateral border of the accessory nucleus. Phase measurements during penetration of the response to an 800-cps tone demonstrated large phase shifts accompanying the passage of the electrode from one peak to another. These findings support the hypothesis that the “following” response recorded in the SOC is primarily a product of dipole fields within the accessory nucleus.
Point-Jet Compressed-Gas Transducer
Authors: Rich Stanley R.
Published: November 2005

A high-intensity point-jet whistle is presented. A pointed pin on the axis of a high-velocity gas stream acts as a vortex and shock-wave-initiating mechanism to excite the gas in a resonator cavity to high-intensity elastic-wave output. Point-jet transducers for industrial applications of elastic-wave energy have been constructed in the frequency range 10 000–50 000 cps. The point jet operates without requirement for dimensional adjustment whether driven by compressed air, carbon dioxide, nitrogen, vinyl chloride, or dry steam over the pressure range 5–60 psig. In a focusing point-jet transducer operating at 60 500 cps, a level of 186 dB has been measured at the focus. Increased efficiency inherent in the design results in reduced compressed-gas consumption. Principles of operation are discussed. Design of the point jet, results obtained, and practical applications are presented.
Echo-Ranging Device Used to Measure the Size of a Well at Camp Century
Authors: Mullineaux O. Charles
Published: November 2005

The echo-ranging device used to determine the size of a heat-sink well at Camp Century, Greenland, is briefly described. A rotating, barium titanate, narrow-beam transducer served as both transmitter and receiver. Short 500-kc/sec acoustic pulses were generated at the transducer by shock excitation. The device was designed to operate to a maximum range of 500 ft when suspended from a 1200-ft cable. A graphic recorder presented the echo time as a horizontal cross section of the well. The configuration of the well was determined by repeating the horizontal scan at successive depths. Tests at Camp Century revealed that the well was approximately 200 ft in diam, with a water depth of approximately 100 ft. Good repeatability and an accuracy of less than 6 in. was demonstrated. The volume of the well was determined to be approximately 2 million cu ft. [Work supported by the U. S. Army.]
Mechanical Impedance Today
Authors: Belsheim R. O. , Remmers G. M.
Published: November 2005

During the past several years, there has been considerable interest in the study and use of mechanical-impedance techniques. A number of workers concerned with shock or vibration problems have recognized the inherent potentialities of this approach. However, the practicing engineer has seen but few results that aid in solving his problems. At least in part, this is because of some misconceptions of what these techniques can do; also, there exist certain limitations and uncontrolled variables that restrict the accuracy and/or usefulness of impedance measurements. Even though slow, there is significant research in progress that either utilizes impedance methods or expands the knowledge base required before the engineer can use the procedures with confidence. This paper reviews some of these research results and attempts to identify problem areas that require further study.
Role of Synthetic Speech in Speech Research
Authors: Lawrence Walter
Published: November 2005

The Parametric Artificial Talking Device is described, and the purposes for which it was designed and for which it may be used are discussed. Human speech may be studied either as a sequence of articulatory events, or as an acoustic disturbance freely propagating through air, or as an auditory sensation. The concepts underlying the design of the artificial talking device serve to unify and correlate these three aspects of speech. The parametric signals used for controlling the device constitute a precisely defined descriptive terminology for the specification of speech utterances. This is of especial value in interdisciplinary discussions, and by this means phoneticians, psychologists, speech and hearing pathologists, and communication engineers can find a common language for talking about speech. Machines of the type considered were first conceived as part of a speech-band-width-compression system; the problems raised in the optimum design of such a system provide a motivation for the investigation of many diverse aspects of speech, and, hence, contribute to the establishment of a unified and inclusive science of speech.
Frequency Multiplex System for a 10-Spectrum-Channel Voice-Excited Vocoder
Authors: Golden R. M. , MacLean D. J. , Prestigiacomo A. J.
Published: November 2005

A prototype frequency-multiplex system has been completed for use with a 10-channel voice-excited vocoder. The VEV and multiplexer can transmit a 3-kcps bandwidth speech signal within a bandwidth of 1.38 kcps, thereby realizing a bandwidth-compression ratio of at least 2:1. The inputs to the transmitter portion of the multiplexer are the low-frequency spectrum channels from the vocoder. These low-frequency signals amplitude-modulate 10 separate carriers. The modulated carriers are added together, band-limited, and then combined with the base-band signal for transmission. At the receiver, separating filters are used to recover the base-band signal and spectrum channel signals from the composite waveform. The recovered spectrum-channel signals and base-band signal are then connected to the vocoder synthesizer. This multiplex system combined with a VEV provides a practical means for transmitting a reduced bandwidth signal over existing speech-communication channels
Bandpass Compressor
Authors: Gold B. , Rader C. M.
Published: November 2005

A new speech compressor is described. We have named this device the bandpass compressor (BPC) because it is based on the idea that the output of a narrow-band filter can be adequately described by means of two slowly varying parameters, the amplitude envelope, and the instantaneous frequency. In the BPC, amplitude information is conveyed as in a channel vocoder, but, instead of detecting and transmitting pitch and voicing information, a slowly varying instantaneous frequency is derived from each band-pass channel by means of a limiter, frequency discriminator, and low-pass filter. At the synthesizer, a frequency-tracking loop regenerates a square wave of the appropriate instantaneous frequency. This wave is modulated by the transmitted amplitude information and applied to a final bandpass filter. The compressed speech is the sum of the outputs from a bank of these bandpass filters. We estimate that a 16-channel BPC uses 800-cps bandwidth. If the BPC is used solely for recovering the base-band speech, which is then used to excite a voice-excited vocoder, we estimate that 525-cps bandwidth is needed. More testing must be done on the BPC (which has been simulated on a digital computer) before definitive statements can be made about its advantages and shortcomings. Preliminary results are quite encouraging.
Studies on a Computer-Programmed Formant Vocoder
Authors: Coker Cecil H.
Published: November 2005

A computer-programmed formant vocoder is being used as a “breadboard” for testing possible vocoder features. Recent studies include an informal evaluation of a controllable pole-zero pair for approximation of the glottal-source spectrum and nasalization in a serial resonance synthesizer. Currently, forms of nonlinear smoothing of formant signals are being tried. These studies are discussed and demonstration tapes are played.
Performance of a Code-Operated Speech Synthesizer
Authors: Olson Harry F. , Belar H.
Published: November 2005

A syllable synthesizer is required to complete a voice-to-voice communication system in which the sender speaks one syllable at a time into a microphone and in which transmission to the receiver takes place in the form of a syllable number. The merit of such a system is the extremely small communication-channel capacity. Speech synthesized from prerecorded syllables has been proven highly intelligible. To determine the possibility of synthesizing speech from segments of spoken syllables, a 200-syllable synthesizer was used as an investigative tool. Statistical studies were made in order to find the smallest recognizable particle of a spoken syllable that can be segmented by machine, recognized by machine, and from which speech can be synthesized by machine from prerecordings. This particle has been tentatively given the name “Syblet,” a contraction of syllablet. The design of the 200-syllable synthesizer is described, the results of listening tests presented, and a demonstration of speech from prerecorded syblets is given.
Approximation to the Diffraction of Sound by a Circular Aperture in a Rigid Wall of Finite Thickness
Authors: Wilson George P. , Soroka Walter W.
Published: November 2005

An approximate solution for the diffraction of a plane sound wave incident normally on a circular aperture in a plane rigid wall of finite thickness is obtained by postulating rigid, massless, infinitely thin plane pistons in each end of the aperture, whose motions simulate the movement of the air particles at these positions under acoustic excitation. Plane longitudinal waves are assumed inside the aperture. Numerical solutions obtained on an IBM-7090 computer very closely coincide over a wide range of frequencies with those of much more-complicated existing exact solutions. Furthermore, extensive experiments were conducted on the transmission of reverberant sound through steel pipes of various lengths and diameters inserted individually into a heavy wall between two concrete chambers of 1750 cu ft each. Measured values of reverberant sound-transmission loss through these apertures were found to agree within experimental error with those calculated from the approximate theory. The assumption of plane-wave propagation in the aperture was found to give valid experimental results up to values of d/λ exceeding unity, where d is the pipe diameter and λ is the wave length of incident sound.
Impact-Noise Measurements for Some Floated-Floor Construction
Authors: Hehmann H. W.
Published: November 2005

An impact-noise test was conducted in the laboratory, comparing results of using the standard tapping machine and real hard-heeled foot traffic for impact excitation. Tests were made on a bare 4-in. thick concrete floor and on the same floor reenforced with a floated wood floor applied both directly and on several isolation materials. Constructions that yield improvements as large as 20 dB in “Impact Noise Rating” [see Federal Housing Administration Bulletin 750] are found to produce in the underlying room loudness of football equal to that obtained with bare concrete.
Objections and Suggestions on Impact and Airborne-Insulation Measurements
Authors: Fuchs G. L.
Published: November 2005

Present standard measuring methods condensed in ISO recommendation R.140 are discussed and changes proposed, based on our experience. Our own standard tapping machine has been checked against controlled subjective appraisals and found in good agreement with objective rating methods, once adjusted by our proposed changes. Airborne insulation is evaluated in the form of “Q” (quality) factors derived from standard tests that we believe express the insulation properties of partitions more accurately than TL. NRC, or speech-privacy computations used to date.
Simulated Background Noise to Improve Acoustical Privacy in Buildings
Authors: Curtis J. A. , Figwer J. J.
Published: November 2005

In many existing buildings where the construction provides a low degree of sound isolation between rooms, complaints concerning a lack of acoustical privacy most frequently arise where the ambient-background-noise levels are low. In most cases, the adequate improvement of the construction is either impractical or too costly. An increase of the ambient-background-noise level, on the other hand, can often provide the desired improvement of privacy. Sometimes this can be achieved by modifying an existing ventilating system. Where this cannot be done, background noise duplicating the characteristics of ventilation-system diffusers and other types of air distribution devices can be simulated electronically and distributed by means of loudspeakers. The instrumentation and technique as used in a few recent building installations is described.
Pitch Change of the Stopped French Horn
Authors: Pyle Robert W.
Published: November 2005

Hand-stopping is a technique employed in horn playing to obtain a particularly pungent and biting tone quality. To stop a horn, the player blocks its bell as completely as possible with his right hand. With the length of the horn fixed, the notes sounded are not the same with the bell stopped as with the bell open. There has long been controversy over the relation between the stopped and open notes. One group contends that a stopped note is the next lower note that has been raised in pitch by stopping; another group holds that it is the next higher open note that has been lowered. It is the purpose of this paper to show that hand-stopping is equivalent to truncating the horn near the position of the hand and terminating it with a lumped resonator. The natural frequencies of the coupled horn and resonator are found. Comparison of these with the natural frequencies of the separated horn and resonator reveal the reasons for the confusion and show that both the falling-pitch and rising-pitch theories are at least partially justified, depending on whether or not the resonator is considered an integral part of the horn. Experimental data confirm these conclusions.
Resonance in Violins
Authors: Caldwell C. L.
Published: November 2005

The acoustical characteristics that make each violin an individual are rooted in the frequencies and amplitude of the resonances. Saunders showed that these resonance data could be obtained from the harmonic analysis of the tone. By the same reasoning, those characteristics of the tone quality not under the control of the player are due to the resonances. A method is described for determining whether a given resonance is due to the belly, the back, or the air within the instrument, without taking the violin apart. An electromagnetic driver causes the bridge to vibrate. The acoustical output is measured at each different frequency. Next, the violin is placed face up in a shallow box of sand, which damps out all resonances in the back, and the measurements are repeated. The differences between these two sets of readings give the response of the back. Sound from a public-address driver is then conveyed into the violin through a tube and a hollow-tailpiece holder. In this way, the air response is obtained. Those resonances in the original readings not as yet accounted for must be due to the belly.
Temperament Habits and Preferences of Professional Musicians
Authors: Stauffer Donald W.
Published: November 2005

Equal temperament has been widely used for the tuning of fixed-pitch instruments throughout the Western World for nearly 200 years. Nevertheless, some artist musicians remain highly critical of equal temperament, implying that there is a superior scale of some sort that is more perfect for artistic purposes. The question of the temperament habits of professional musicians has never been satisfactorily determined by experimentation. Such a task is fraught with many uncontrollable factors. It is felt that reliable conclusions can be arrived at only through statistical averages of a large number of cases. In this second of a series of experiments, a large number of highly selected professional musicians are asked to pass judgment on a series of isolated major thirds. These intervals are tuned at random as follows: pure, equally tempered, and sharpened (above equal temperament) major thirds. In addition to preferences, the reliability of individual judgment is studied by comparing random repeated answers to the same interval.
Methods for Analyzing the Radiation Loading of Finite Cylindrical Transducers
Authors: Junger M. C. , Greenspon J. E.
Published: November 2005

Methods are presented for analyzing radially pulsating finite cylinders, no restriction being imposed on fluid circulation around the transducer ends. The solid cylinder and two free-flooding configurations (the “squirter” and the array of coaxial, spaced ring transducers), are discussed. Numerical results are given for the “squirter.” The customary approach to this type of problem is to formulate the unknown potential in terms of the Helmholtz-integral equation over the radiating surface, use being made of the free-space Green's function. By constructing suitable Green's functions, the integral equation in the present analysis is transposed from the radiating surface to the two cylindrical surfaces extending the transducer, where the potential is weaker. Consequently, the accuracy of results is less sensitive to inaccuracies in the solution of the integral equation. Four techniques for solving this equation are presented. The corresponding numerical results are compared. The most economical approach, which eliminates matrix calculations, is a variational technique. [Work supported by the U. S. Office of Naval Research, Acoustics Programs.]
Acoustic Pressure-Release Techniques for Transducers
Authors: Toulis W. J.
Published: November 2005

The acoustic stiffness of a liquid within a small enclosure may be altered greatly with the introduction of mechanical structures in the form of compliant tubes. This is due in part to the added compressibility of the compliant tubes and in part to volume resonance. The mixture can be tuned or detuned by changing either the number of compliant tubes or the type of liquid in the fill. Such a combination within an acoustic transducer provides a satisfactory pressure-release mechanism and at the same time permits the resonant frequency to be altered to a considerable extent. The mechanical Q may be altered also to a degree that depends critically upon the stiffness of the transducer diaphragms and the radiation load on them. Moreover, compliant-tube mixtures provide linear and uniform acoustic pressure release within a transducer as long as the stresses lie within the yield-strength limit of the compliant-tube walls. Additional investigations demonstrate that a simple liquid fill can also be employed successfully if the compliance of the transducer is designed to be comparably small. The results may be analyzed in terms of an equivalent circuit with either lumped or transmission-line parameters.
Broad-Band Hydrophone
Authors: Merrill J. A.
Published: November 2005

The design and development of a hydrophone with a flat response from 100 cps to 60 kps and to operate at hydrostatic pressures up to 1500 psi is described in this paper. The acoustic design to achieve relatively high sensitivity, flat response, and stable performance with pressure is discussed, as well as the mechanical-packaging considerations necessary to obtain high-performance reliability for years of operation in unattended underwater acoustic arrays where maintenance is impossible. Considerable emphasis is placed upon the high-reliability packaging, including a discussion of various material investigations, consisting of acoustical evaluation and compatibility tests with sea water and other materials used in the hydrophone, that led to the final hydrophone design. The assistance of a number of Navy laboratories was obtained to utilize all available experience in achieving high reliability, and the final approval of this broad-band hydrophone by these same laboratories is now pending.
Backward Enhancement of Binaural Fusion
Authors: Guttman Newman , van Bergeijk W. A. , Harmon L. D.
Published: November 2005

When a proximal pair of clicks in one ear is “probed” by a single contralateral click, with all clicks of the same amplitude, the probe produces two types of binaural fusion: (1) direct fusions with the individual clicks and (2) fusion with an aftereffect of the first click occurring roughly 1 msec after the direct first-click fusion. The second type is remarkable because it exists even though the second click occurring perhaps more than a millisecond after the aftereffect-fusion time cannot produce fusion. The interval of masking of the second click decreases with increasing triad-repetition rate. A neurophysiological model was recently proposed to account for this, but it did not account for the aftereffect fusion. In an attempt to test an improvement of the model, an experiment was run to secure more data on the aftereffect fusion, particularly with respect to its dependence on repetition rate. The results indicate that the aftereffect fusion rarely attaches to an unpaired click, regardless of repetition rate. Detection improves greatly if a second click occurs within a few milliseconds of the first, and probability of detection improves somewhat further with increasing repetition rate. Thus, a second click, itself not fusable, enhances an aftereffect fusion of an earlier click.
Role of Stimulus Frequency in the Phenomenon of Localization Shifts
Authors: Butler R. A. , Naunton R. F.
Published: November 2005

The apparent location of a sound in space can be influenced by the monaural presentation of a second auditory stimulus. The extent to which the localization shift occurs has been shown to be related to the frequency and intensity relations between the two auditory stimuli [R. A. Butler and R. F. Naunton, J. Acoust. Soc. Am. 34, 1100 (1962)]. The results of additional experiments have described in greater detail the importance of frequency relations between the two stimuli. In these experiments, the sound in space (signal) was either 0.5, 1, 2, 4 or 8 kc/sec and the frequency of the monaural stimulus (interference) ranged from three octaves below to one octave above that of the signal. Three loudness-level relations between signal and interference were also employed: 40:80, 10:50 and 10:20 phons. The results demonstrated that the signal localization shift is greatest when the frequency difference between signal and interference is least, and increases as the loudness level of the interference stimulus is increased. [Work supported by funds provided under contracts NB 04508-01 and NB 03815-03 with the National Institutes of Health, U. S. Department of Health, Education and Welfare.]
Pitch Extractor, Using Clippers
Authors: Toffler Jerome E. , Wade Fred B.
Published: November 2005

Several previous pitch extractors have been constructed, based on the principle of nonlinear operations on the input-speech wave. Typical schemes have included envelope detectors, full-wave linear rectifiers, and square-law devices. This paper described a new experimental pitch extractor in which the nonlinear elements are amplitude limiters, or clippers. Advantages claimed for the system are the following: (1) operation over a wide dynamic range of input amplitude due to the clipping employed, (2) wide frequency range suitable for male and female speakers, and (3) regeneration of the fundamental pitch frequency from its harmonics. Test results are presented showing the performance of the pitch extractor with a variety of speech signals.
Pitch-Period Reiterating Speech-Compression System
Authors: Megna Joseph J.
Published: November 2005

In this paper, the performance of a speech-compression system, in which certain pitch periods are eliminated and replaced by the latest transmitted pitch period, is studied. The pitch-period representations are digitized and various bit rates and quantizing combinations may be used. Using the various combinations, the experimental results, based on listening tests and intelligibility scores, are presented.
Note on Buzz-Hiss Detection
Authors: Gold Bernard
Published: November 2005

Speech sounds can be approximately divided into two categories, buzz or periodic sounds and hiss or aperiodic sounds. Vocoder buzz-hiss detectors have discriminated between the two classes by comparing the high-frequency and low-frequency portion of the spectrum. This technique succeeds during most of the input speech because most voiceless sounds contain a preponderance of high-frequency energy whereas the voiced sounds emphasize the lows. However, voiceless sounds such as aspirates and plosives often contain large amounts of low-frequency energy. Also, microphone distortions can produce low-frequency aperiodic sounds. This paper describes a periodicity meter that processes the output from six pitch detectors to produce another measure appropriate for buzz-hiss detection. Preliminary results are presented.
Speech Recognition by Formant Pattern Matching in N-dimensional Space
Authors: Campanella S. J. , Coulter D. C. , Engler P.
Published: November 2005

Method and results are presented for the application of statistical pattern-recognition techniques to automatic classification of words and talkers using formant-tracking data as the input. The method employs the expression of an entire formant pattern as a single n-dimensional vector. Each vector component represents a sample of one of the formant functions at a giventime. Thus, the dimensionality of the n space is determined by the product of the number of formant parameters sampled and the number of observation epochs. A computer program processes these data in two steps. In the first step, called a “learning” program, separate statistical categories are established by the computation of the mean vector and covariance matrix describing a normal distribution function for the set of vectors that define each category. In the second step, called the “recognition” program, an unknown is recognized by computing the statistical distance to all possible categories and selecting the category for which this distance is minimum. Results, in the form of confusion matrices, are presented for word recognition of the first ten letters of the alphabet as spoken by 10 talkers and for recognition of the talkers.
Solutions for Nonlinear Plane-Wave Equations of Acoustics by the Method of Functional Interrelationships of Dependent Variables
Authors: Raelson Verner J.
Published: November 2005

A general formulation of the theory of propagation of fine-amplitude waves in a non-linear, viscous, heat-conducting and heat-radiating medium is solved by the device of imposing one additional relationship upon the dependent variables. This approach is interpreted as an extension of the more usual one, which ignores viscosity, heat conduction, and heat radiation and which leads to commonly used formulations of nonlinear acoustics. Solutions are offered for two different choices of the additional condition on the dependent variables. The first of these leads to a complete solution in finite form but does not reduce to the nonviscous formulation upon setting viscosity equal to zero. The second solution that fulfills this latter condition is presented in the form both of an infinite-series representation and graphically. [Work supported by the U. S. Air Force Systems Command.]
Theoretical Analysis of Propagation of Sound Waves Containing Shocks
Authors: Blackstock David T.
Published: November 2005

Analytical methods for treating propagation of continuous finite-amplitude waves are well-known. In the present work, waves having both continuous and discontinuous parts are considered. A useful approximation, valid for waves of up to moderate amplitude (that is, maximum-particle-velocity Mach number somewhat less than unity), is that waves containing shocks may be treated as purely progressive. In other words, no reflection takes place at the shocks. It follows that signals in the continuous section of the waveform travel with speed co+βu, where β=12(γ+1) for perfect gases and β=1+B/2A for other fluids. Because the discontinuities are weak, they travel with speed co+12β(ub+ua), where ub and ua are the particle velocities just behind and just ahead, respectively, of the shock. General rules for the change in waveform are derived. Of particular interest is the way in which shock strength and the relative spacing between shocks (or between shocks and zeros) varies with distance (or time). Examples considered are N waves, imperfect N waves, and originally sinusoidal waves. The analysis is given first for plane waves and then extended to cover spherical and cylindrical waves. [Work supported by the U. S. Air Force Office of Scientific Research, Office of Aerospace Research, contract AF49-(638) 1320.]
Parameter of Nonlinearity for Liquids
Authors: Coppens A. B. , Seiden M. B. , Beyer R. T.
Published: November 2005

The ratio of B/A in the adiabatic expansion for pressure p as a function of the density ρ, p=po+A (ρ−ρo)/ρo+B (ρ−ρo)2/2ρo2 is reported for a number of organic liquids. A detailed comparison of these values, obtained from measurement of the sound velocity as a function of the hydrostatic pressure and the temperature, is made with measurements reported by other observers from finite amplitude measurements. Possible reasons are advanced for the rather wide discrepancies. [Work supported in part by the U. S. Office of Naval Research.]
Acoustic Streaming near an Undulating Surface
Authors: Nyborg Wesley L.
Published: November 2005

Theory is given for steady circulation near waves on a gas-liquid interface; thin boundary-layer approximations are made similar to those used by Schlichting and Longuet-Higgins. Such circulation is important in some aspects of stable cavitation. In accounting for this motion, the first-order (ac) boundary layer in the gas is of particular significance; here, high values exist for the nonlinear “driving term” in the streaming equation. In the case of standing waves at a plane interface, a row of eddies is predicted in both gas and liquid. Comparison with a result of Longuet-Higgins shows that the speed of streaming along the boundary predicted by the present theory is far greater than would be expected if effects of the gaseous boundary layer were negligible. Some experimental observations by Elder and Gould on spherical surfaces and by Brand on plane surfaces indicate speeds equal to and greater than those predicted here. Occurrence of the higher speeds suggests that special properties of the gas-liquid boundary should be considered. [Work supported in part by the U. S. Air Force Office of Scientific Research grant AF 62-63 and in part by National Institutes of Health, U. S. Department of Health, Education, and Welfare grant GM 08209.]
Audio-Visual Aids for the Study of Musical Sounds
Authors: Kent Earle L. , Hall Jody C.
Published: November 2005

This lecture demonstration is primarily for music students and music educators. It covers the use of a number of audio visual aids in studying musical sounds and in teaching music.
Distribution Of Internal Friction
Authors: Benson R. W. , Chapman J. R.
Published: November 2005

A series of studies has been made in an attempt to determine the selection of the proper independent variable that will allow for the prediction of the distribution of internal friction in mechanical vibrators of various geometries. Previous studies of cylindrical vibrating bars have indicated that the loss is a sole function of the longitudinal strain. The choice of a material for use in a generating or receiving system based upon its internal friction, can be misleading when practical geometries are used rather than the cylindrical geometry used for laboratory measurements. Impedance discontinuities caused by the selection of shape or the use of disimilar materials can lead to internal friction, in addition to that anticipated on a longitudinal-strain basis. The results of numerous measurements of losses and corresponding theoretical calculations are presented to indicate the complexity of the problem. Preliminary conclusions are presented to indicate the application of these findings.
Coupled Mode Theory Applied to Ultrasonic-Light Diffraction
Authors: Cook Bill D.
Published: November 2005

One approach to the theory of the diffraction of light by plane, periodic, ultrasonic waves is to solve Maxwells' equations, using a method of plane waves. These plane waves give rise to the Fraunhofer-diffraction orders. This approach yields a set of difference-differential equations describing the amplitudes of the plane waves. A physical interpretation of these equations can be obtained by using coupled mode theory where the periodic change of refractive index produced by the ultrasonic waves provides the coupling between light waves. The amount of energy transfer between the light waves is dependent on the degree of synchronization of these waves, which are travelling in different directions. It is this degree of synchronization and the consequent energy transfer that determines the nature of the diffraction.
Light Diffraction by Ultrasonic Waves as a Multiple-Scattering Process
Authors: Hance Harold V.
Published: November 2005

Past theoretical studies of light diffraction by ultrasound have for the most part been severely limited in scope by the complexities of the analytical methods employed and by the consequent need to use simplifying restrictions in order to obtain useful results. Recently, however, a new analytical approach has been devised that yields valid quantitative results for arbitrarily specified conditions. This method, developed initially at the Physics Department of Michigan State University by Hargrove, has been extended at the Lockheed Research Laboratories. It treats the diffraction phenomenon as a multiple-scattering process, with the elementary scatterers considered as a series of layers formed by subdividing the ultrasonic beam along planes parallel to its direction of propagation. The layers are taken thin enough that the diffraction in any one is accurately described by the Raman-Nath theory; and the cumulative effect of all of the layers is obtained by an iterative process carried out on a digital computer. Hargrove's analysis yielded results in very good agreement with existing experimental data and covered the range of conditions appropriate for such a comparison. This paper presents the results of a study of the case of normal incidence but for a range of conditions extending far beyond those previously considered. In addition, the case of oblique incidence has been studied for incidence angles between zero and the Bragg angle for the second diffraction order and for a wide range of other pertinent parameters. Based on results of the theoretical phase of this study, a new physical interpretation is given of the diffraction process and of the widely used criteria for so-called “normal” or Raman-Nath diffraction and for strong Bragg diffraction. [Work supported by the Independent Research Program of Lockheed Missiles & Space Company.]
Engineering Approach to Prediction of Space-Vehicle Acoustic Environments
Authors: Gruner William J. , Johnston Garland
Published: November 2005

Precise estimation of the acoustic environment of space vehicles during the static firing, liftoff, and transonic/maximum-dynamic-pressure domains of the vehicle lifetime is made mandatory in order to optimize dynamic qualification of the structure and operational systems. Engineering methods of estimating the acoustic environment during these critical areas of the vehicle lifetime are presented and comparison is made for the predicted and measured data of the Saturn I Block I and the Saturn I Block II vehicles. Specific direction is indicated for future analyses and research projects.
Sonic Boom Assessment
Authors: Richards E. J.
Published: November 2005

The difficulties of assessing the significance of sonic booms and the public's reaction to them is causing great concern. The paper describes some recent researches carried out at the University of Southampton on the relevant reactions of persons to transient sounds of the sonic-boom type, in which the various characteristics of the boom are altered. Some comments are made regarding the significance of this work and its relationship with other work of a similar kind.
Study of Noise and Other Factors in Conference Telephony
Authors: Gardner Mark B.
Published: November 2005

In view of the increasing interest in broad-band voice communication between conference groups who may wish to meet at different inter- or intra-city locations, a study of the various factors that affect such transmission has been undertaken. For purposes of the study, a flexible multichannel transmission system has been set up between experimental conference rooms at the Murray Hill laboratory. The system provides a selection of various microphone and loudspeaker displays, a choice of mono or stereo transmission and provision for adjusting the noise level, noise spectrum, bandwidth, room constant, etc. The present paper includes a brief description of the system, together with a summary of some of the results obtained in the initial stages of the study. Primarily, these include the effect of noise on preferred levels of the incoming speech signals and on indication of the reliability of various types of noise ratings for predicting such preferences. Noise levels well beyond those generally acceptable for conference telephony are considered in view of other areas of possible application.