bluuebunny/crossref_metadata_2025 huggingface dataset:
Decay of a weak shock followed by a tail of arbitrary waveform
Authors: Blackstock David T.
Published: October 2005

Weak-shock theory is used to find the decay of a shock that is propagating into a quiet fluid. The tail, or flow field behind the shock, is assumed to be smooth but otherwise arbitrary. Let the time wave-form of the pressure at the initial measurement point be given by p = P0g(t), where P0 is the initial pressure amplitude and g(t) is the arbitrary tail function normalized so that g(0) = 1. For plane waves the dependence of the shock amplitude P on distance x is found from the following coupled equations: Ax = [g(φb)]−2  ∫ 0φb g(λ)dλ and P = P0g(φb), where A is a constant and φb is the time-like parameter (for the shock) from the Earnshaw solution. For example, if G = exp(−at) (an exponential tail), the coupled equations yield P = (P0/Ax)[(2Ax + 1)−1/2 + 1], in agreement with P. H. Rogers' result [J. Acoust. Soc. Am. 62, 1412–1419 (1977)]. Solutions have also been obtained for the model tail functions described by J. W. Reed [J. Acoust. Soc. Am. 61, 39–49 (1977)]. For spherical waves replace x by r0 ln(r/r0) where r is radial distance and r0 is the initial measurement distance. [Work supported by ONR and AFOSR.]
Subharmonic response of ultrasonically driven liquid helium
Authors: Carey R. F. , Rooney J. A. , Smith C. W.
Published: October 2005

The subharmonic spectrum of liquid helium was studied using pairs of PZT-4 thickness mode transducers resonant at 1, 3, or 10 MHz. One transducer serves as the sound source and the acoustic response of the liquid is measured by spectral analysis of the signal detected by the second transducer. Above specific displacement amplitudes the subharmonic and its associated ultrahomonics can be detected. Measurements of the threshold amplitudes for these spectral components indicates at most a weak temperature dependence for temperatures well below the lambda point Tλ. Significant changes in subharmonic amplitude occur near Tλ. Specifically, for a sound amplitude of 75 Å using the 1-MHz transducers we observe that the amplitude of the subharmonic increases by at least 10 dB when the temperature is decreased from (Tλ + 5mK) to (Tλ − 5mk). In addition, analysis of the spectral broadening of the subharmonic provides information about the fluid and turbulent motions within the sample vessel. Observations will be discussed in relation to mechanisms for subharmonic generation. [Work supported in part by the Air Force Office of Scientific Research.]
Finite-amplitude standing waves in rectangular cavities with degeneracies and weakly-perturbed walls
Authors: Coppens Alan
Published: October 2005

It was observed and reported in an earlier paper [“Finite-amplitude standing waves within real cavities.” Alan B. Coppens and James V. Sanders, J. Acoust. Soc. Am. 58, 1133–1140 (1975)] that when there was a degeneracy involving any normal mode stimulated by finite-amplitude distortion of a driven normal mode, and a normal mode which could not be so stimulated, energy was coupled into the “forbidden” normal mode. At that time no quantitative explanation could be advanced. Subsequent work analyzing the effects of weak perturbations of the boundaries of an otherwise ideal rectangular cavity has shown that it is possible to stimulate “forbidden” degenerate normal modes through the perturbation corrections to the ideal normal modes resulting from the boundary irregularities. This coupling is important only when the eigenfrequencies of the normal modes in question are very close together. Under certain conditions the amplitude and phase of the “forbidden” normal mode can be obtained by a relatively simple calculation after the calculations for the finite-amplitude standing wave in the absence of the degeneracy have been obtained.
Lateralization performance in the presence of background noise
Authors: Cohen Marion F.
Published: October 2005

Interaural time just noticeable differences (jnds) were measured for a tonal signal in the presence of broadband noise, the interaural relation of which was either perfectly correlated, uncorrelated, or reversed in phase to one ear. Results indicate that lateralization performance deteriorates markedly when the interaural relation of the noise is changed from perfectly correlated to 180° out of phase. The presence of uncorrelated noise does not cause a similar increase in jnds. [Work supported by the University of Connecticut Research Foundation.]
The effect of interaural electroacoustic hearing aid properties on sound localization abilities in normal and hearing-impaired listeners
Authors: Wilson J. , Yonovitz A. , Campbell I. , Spydell J. , Thompson C. L.
Published: October 2005

The use and benefit of binaural amplification in the hearing impaired has generated considerable conflict. One easily measured benefit of binaural hearing includes improved sound localization. The normal binaural auditory system has the capacity to determine with considerable accuracy the azimuth of a sound source. Binaural hearing aid fitting procedures are typically accomplished with an independent concern for each ear. The interaural intensity, phase characteristics, and time of arrival cues processed by hearing aids undoubtedly affect the quality of the binaural fitting, The purpose of this study was to investigate the dependence between binaural hearing aids and in their electroacoustic functioning by determining minimal audible angles (MAA) and center position (CP) shifts in a sound localization task. Six normal and two hearing-impaired adults responded to tonal and click stimuli using four selected pairs of hearing aids. These pairs were selected for matched electroacoustic characteristics: interaural phase distortion, and interaural transient distortion. Results of this study revealed smaller MAAs and CP shifts with the hearing aid pair matched closely in electroacoustic characteristics, whereas dissimilar pairs had larger MAAs and greater CP shifts. The results of this study provide information concerning binaural interactions and hearing aid fitting procedures with implications for improved binaural hearing in the hearing impaired.
Binaural release from masking for speech: Validation of a model
Authors: Grossman J. E.
Published: October 2005

A model for predicting binaural release from masking for speech was presented recently [H. Levitt and L. R. Rabiner, J. Acoust. Soc. Am. 42, 601–608 (1967)]. The validation of this model was carried out. Speech stimuli were presented against a background of −6-dB/octave flat and +6-dB/octave sloping noise in homophasic (SONO) and antiphasic (SπNO) configurations under three different signal-to-noise ratios. Qualitative predictions were made, in accordance with the model, for each testing condition. The analysis of the obtained data demonstrate the validity of the model over a wide range of spectrum slopes and signal-to-noise ratios.
Effects of leading and trailing tones on frequency discrimination of signal tones
Authors: Ebata M. , Sone T. , Nimura T.
Published: October 2005

The effects of leading and trailing tones (interference tones) on frequency discrimination of a brief tone are investigated and auditory response to the unsteady sounds is discussed. Changes in frequency discrimination were measured as a function of frequency difference between the interference and signal tone, and interval between the two tones (Δt). The results show that frequency discrimination deteriorates as Δt decreases, and the performance is significantly affected by the interference tone especially for Δt less than 20 ms, and they also show that frequency discrimination of test tone accompanied with the interference tones of the same frequency as the test tone is almost the same as in the case without the interference tones. Frequency discrimination becomes worse, however, in the presence of interference tones with the frequency slightly different from the test tone, and when the frequency of the test tone is 1000 Hz, the effect of the interference tone is maximum for the frequency difference of 50 Hz. But frequency discrimination is little affected by interference tones when the difference in frequency between test and interference tones is greater than 100 Hz. The relation between temporal masking and frequency discrimination is discussed.
Complex beats
Authors: Warren Richard M.
Published: October 2005

Superimposing two complex tones mistuned slightly from unison (for example, 199 and 201 Hz) produced a harmonic sequence of beat rates or a “complex beat.” The multiple heat rates (2, 4, 6, 8, … beats/s) were not perceived, and only the fundamental beat rate (FBR) or 2 beats/s was heard. When the FBR was deleted (leaving 4, 6, 8, … beats/s), the missing fundamental remained the only beat rate heard. Other experiments produced complex beats by superimposing three to five pairs of beating sinusoidal tones. Any desired beat rate was produced by choice of frequency difference between sinusoids of a tone pair, and this beat rate was sent to any desired place along the basilar membrane by choice of the tone pair's center frequency. The FBR was dominant for all such complex beats regardless of the loci selected for individual beat rates and regardless of whether the FBR and lower beat rates were present. These observations demonstrate integration of neural periodicity information from different cochlear loci. Implications for perception of multiple periodicities in the pitch range were noted. [Work supported by NSF and NIH.]
Physiology and bioacoustics in reptiles
Authors: Turner R. G.
Published: October 2005

Hearing in reptiles is of particular interest because of the diversity in the anatomy of the reptilian auditory system. This diversity is best illustrated in the lizard, where there is significant variation in cochlear anatomy across families. This review of the auditory physiology of reptiles will begin with a detailed discussion of the extensive physiological data available for the alligator lizard (Anguid family). These data include measurements of basilar membrane motion, intracellular hair cell responses, and single-unit activity of primary auditory-nerve fibers. Single-unit data from an Iguanid lizard will be compared to that for the alligator lizard and discussed in terms of the differences in cochlear anatomy of these two families. In addition, single-unit data for other lizards and other reptiles will be reviewed. The presentation will conclude with a comparison of auditory processing in the reptile and the mammal and will consider issues such as the tuning of individual fibers and the relationship of anatomical structure to physiological response.
Physiological aspects of the glottal sound generator
Authors: Hirano M.
Published: October 2005

This paper describes the function of laryngeal muscles in regulating the glottal sound generator. The glottal sound generator, i.e., the vocal fold, has a layered structure. From the anatomical point of view, one can differentiate five layers, all having different mechanical properties [M. Hirano et al., J. Acoust. Soc. Am. 58, S13 (1975)]. From the physiological point of view, the layers may be divided into two major categories: the outer layer, i.e., the mucous membrane, which receives only passive regulation of the mechanical property, and the inner layer, i.e., the vocalis muscle, which has both active and passive regulations for the mechanical property. The ratio of the stiffness of each layer during normal phonation is estimated based on the measurement of the degree of elongation of each layer of an excised fresh human vocal fold. Then, the effect of laryngeal adjustment on the change in stiffness of the entire vocal fold is investigated by simulating the contraction of each of the cricothyroid and the vocalis muscles in dogs' larynx. The results are examined in reference to behavior of each layer during normal vibration of vocal fold observed with ultra-high-speed photography.
On estimating the shape of a time-varying vocal tract
Authors: Sondhi Man Mohan
Published: October 2005

In this talk we will be concerned primarily with acoustical methods for estimating vocal tract shapes. These fall into two general categories: (i) methods that estimate the shape from the speech signal and (ii) those that require external measurements. Methods in the first category are based on several tacit assumptions. The validity of these assumptions is not easily tested, and the effects of departures from these assumptions are quite significant, yet difficult to quantify. Of the methods in the second category, the one based on periodically measuring the impulse response at the lips [Sondhi and Gopinath, J. Acoust. Soc. Am. 49, 1867–1873 (1971)] will be shown to be potentially the most reliable. This method recovers the cross-sectional area functions exactly for a lossless vocal tract under the single assumption of plane wave propagation. We will briefly review this method and present evidence that departures from the basic assumptions do not drastically affect the reconstructed shapes. We will also review the algorithms presently available to take account of distributed losses. Finally, we will suggest that much useful information would be gained if the impulse response measurements are made simultaneously with an x-ray movie of the midsagittal plane.
Formant frequencies for incrementally varying vocal tract
Authors: Wakita H.
Published: October 2005

In order to gain a better understanding of the relationships between vocal tract configurations and their corresponding acoustic characteristics, the formant frequencies for an incrementally varying vocal tract were investigated by use of a vocal tract model. A transmission line analog of the vocal tract was simulated on a digital computer, taking all the losses within the vocal tract and the lip radiation effect into account. A vocal tract configuration for a vowel was represented by a 34-section area function, and the difference in the area functions for two vowels were linearly interpolated to represent the dynamics of the vocal tract. Between the two neighboring interpolated area functions, the formant frequencies were computed by changing two contiguous sections at a time. Dependence of the formant frequencies on particular parts of the vocal tract and the sensitivity of the formant frequencies to the change in the vocal tract shape were investigated.
Speech synthesis from text with an articulatory model
Authors: Coker C. H.
Published: October 2005

In a film, a talking articulatory model describes itself, and its way of generating spoken English from text. Topics that may be considered include physical properties of the model, articulatory dynamics, sequencing of articulatory commands, relationships between articulatory commands and linguistic properties of sounds, and intermediate- and higher-level prosodic effects, including segment duration, allophonic variation, boundary marking, stress, and intonation.
Computer model for predicting reverberation from ocean boundaries following a large underwater explosion
Authors: Goertner J. A. , Blatstein I. M.
Published: October 2005

Following detonation of an underwater explosion, sound reverberates from the ocean surface and bottom and from scatterers within the medium itself. In addition, the ocean basin and obstructions within it, such as seamounts and islands, reradiate the acoustic energy incident upon them. This paper describes a computer model developed to predict the sound level that will ensue following detonation of a large underwater explosion as a result of this latter basin boundary reverberation. Experimental data from 10-ton shots fired a number of years ago in the North Atlantic were used in the development of the computer model. The model has now been tested by comparing predictions with results obtained from CHASE XXI, a 660-ton North Atlantic shot. This simplistic model has proved adequate for matching available experimental measurements in the North Atlantic Basin. Since the parameters on which the model is based are simply defined and applicable to any geometric configuration, the computations are expected to apply to other ocean basins as well. [Work supported by DNA.]
An experimental study on noise similarity law of centrifugal fan rotors
Authors: Odaka K. , Ikawa K.
Published: October 2005

On the basis of the general theoretical development of aerodynamic noise mechanisms, sound power radiated from fans operating at low tip Mach numbers is deduced by Chanaud as follows: PWL = 10 logn6D28 + K, where PWL is the sound power level, n the rotor revolution rate, D2 the rotor diameter, and K constant. To confirm the equation, experiments were conducted on three kinds of uncased centrifugal fan rotors with diameters of 368,528, and 800 mm. Rotors were driven at tip Mach number from 0.05 to 0.24 by means of a variable-speed motor in a 503-m3 unechoic chamber. The overall PWLs calculated from the measured sound pressure levels show that the Chanaud's equation is perfectly correct. Moreover, the spectra with dimensionless frequencies (e.g., real frequencies devided by the rotor revolution rates) are quite similar for a fixed shape of rotors over the whole range of frequencies. The spectrum has a peak frequency, but it does not correspond to a blade passing frequency.
Low-frequency combustion noise and its abatement
Authors: Nishiwaki N. , Mori T.
Published: October 2005

Noise of low-frequency type, 1–40 Hz, will be generated from cupola furnaces or from a duct of a hot gas producer in a steel factory. These low-frequency noises will induce secondary noises of glass windows of residential houses, near noise sources. Frequencies of these noises from cupola furnaces A and B are 32 and 47 Hz respectively, and that of a hot gas producer is 7 Hz. It seems that the wave-length λ. of these noises is approximately connected with length or height L of burning parts. λ. ≑ 4L or ≑ 2L. With the use of adequate silencing method for low-frequency noise, it is shown that considerable decrease of SPL is expected by model tests.
A study on the sound radiation characteristics of the sound insulation box (An experimental study on vibration damping. IV.)
Authors: Yasuda Hiroyuki , Matsui Masayuki
Published: October 2005

As one of the noise controls, the noise sources can be covered with the sound insulation boxes. They are usually made up of the frame constructed by steel beams, and the steel panels or the others. In this study, we excited the sound insulation box by different methods, and measured the vibration acceleration distribution of the steel panel surfaces and the sound pressure at points normal to the radiating surface. From the measured values, the radiation efficiencies [L. Cremer, M. Heckl, and E. E. Ungar, Structure-Borne Sound (Springer-Verlag, New York, 1973), Chap. 6, pp. 459–461] of steel panels was obtained.
Control of industrial noise using ceramic sound absorber
Authors: Koketsu M.
Published: October 2005

This paper introduces the acoustic characteristics of the sound absorptive ceramics and their application for outdoor barriers. The developed sound absorptive ceramics, a kind of porous plates, are produced by binding the particles of hard porcelain with glaze. They have excellent weather-durability and water- and fire-resistant characteristics in striking contrast with conventional sound absorptive materials, such as glass wool and rock wool. The sound absorption coefficient curves of the ceramic show the combined characteristics of resonant-type and porous-type absorbers. The ceramic sound barriers constructed for transformer and other equipments noise sources showed the superior effect of noise reduction than that predicted by Maekawa's formula. The ceramics are also applicable for the acoustic treatment of ventilating ducts, steam-exhaust silencers, machine rooms, and barriers for roads and railways, etc.
Response properties of avian auditory-nerve fibers and cochlear nucleus neurons
Authors: Sachs M. B. , Woolf N. K. , Sinnott J. M.
Published: October 2005

Because of their appeal as a model animal communication system, birds have become the subject of many studies of stimulus encoding in the auditory system. Our approach to the study of this encoding has been to characterize in detail the transformations which occur at various levels within the system. Because this approach is similar to that which we and others have taken in studying the mammalian auditory system, we can now make some quantitative comparisons between these two classes. Thus far our studies have been largely limited to the auditory nerve, and nucleus magnocellularis and nucleus angularis, the avian homologues of the mammalian cochlear nuclei. Response properties of avian auditory-nerve fibers are generally quite similar to those in mammals. However, average discharge rates (both spontaneous and driven) are considerably higher in birds than in mammals. Although the sharpness of tuning in the “tip” region of avian auditory-nerve tuning curves is quite similar to that in mammals, low-frequency “tails” occur only at higher sound levels than in mammals, if at all. Response properties of cells in nucleus magnocellularis and nucleus angularis bear a relation to auditory-nerve patterns which is similar to that of their mammalian homologues. Cells in nucleus magnocellularis exhibit properties which closely resemble those in the auditory nerve, whereas those in nucleus angularis show a similar increase in complexity to that which is found in mammalian posteroventral and dorsal cochlear nuclei. [Supported by Grant No. NS 12112 from NIH.]
Strategies for sound localization in birds
Authors: Knudsen Eric I.
Published: October 2005

The ability of an animal to localize sound is correlated with its ethological niche. Birds face a particularly difficult task in sound localization, since they must localize well in both azimuth and elevation: The azimuth of a target is of no use to an airborne predator unless it can also determine the target's elevation. Furthermore birds must perform sound localization with access to only a limited range of low sound frequencies (<12 kHz), with heads that provide little sound shadow, and with ears that have no pinnae and are close together. However behavioral, physiological, and anatomical data suggest that the auditory systems of birds are capable of extremely fine time resolution. Also, birds have elaborated a large, patent air canal connecting their two middle ears that might improve the directional properties of their ears. Finally, some birds have developed asymmetrical ears that cause interaural time and interaural intensity cues to assume different axes of symmetry. It is proposed that these adaptations permit birds to achieve a high level of sound localization ability, the best of which rivals, and may exceed that of man. [Work supported by NIH.]
A color display system of connected speech for the deaf
Authors: Watanabe A. , Kisu S. , Isayama M. , Matsuno O.
Published: October 2005

The system is composed of a computer for processing speech, digital memories for temporarily storing speech parameters, and a color coder for converting the parameters into composite color video signals. The video signals are transmitted from an antenna and received by conventional color TV sets. In voiced segments of connected speech, three formant frequencies are made to correspond to signals of three primary colors as follows: blue, EB = F2/3F1; the red, ER = 5F1/F3; green, EG = 3F3/5F2. The pitch signal controls the brightness of the colors. In unvoiced segments, as in brightness changes, only black and white stripe patterns appear on the TV screen. The patterns of connected speech flow from the bottom to the top of the TV screen. According to visual tests using connected vowels, the following results caused by simultaneous contrast effects in color can be shown. (1) The transition bands between two vowels judged using colors are much narrower than those determined by acoustical parameters. (2)The colors of adjacent vowels are emphasized with respect to each other so that it is possible that the influence of coarticulation on speech parameters can be compensated visually.
Design of condenser microphone using back plate electret
Authors: Imai Tsutomu
Published: October 2005

Performance characteristics of sound recording and reproduction components have been improved greatly in the past decade. This has created a great demand for high-performance, popular-priced microphones. Sony successfully developed an electret condenser microphone (diaphragm electret) ten years ago. Its sound quality was just that of a condenser microphone, and its price was cheaper. But after ten years, Sony has developed a new high-quality electret condenser microphone, such as the back-electret condenser microphone (back-plate electret). We claim that a back-electret condenser microphone exceeds a conventional electret condenser microphone (diaphragm electret). This paper tries to describe the present development. The environmental stability of the electret microphone requires a back-plate electret method. The higher sound quality requires a diaphragm of suitable thickness, material and frequency characteristics. Finally, less stray capacity is required for a low-distortion condenser microphone.
Environmental effects and concepts for use on electret microphone
Authors: Miura K.
Published: October 2005

The most important thing to be considered in manufacturing electret microphones is their endurance in all environments. Research so far has mainly considered the materials for the electret and their poling methods. There seems, however, to have been little study of the protection of the electret from actual environments. Viewed from the standpoint of us manufacturers, the matter to be considered is how to protect the electret from bad conditions and make them stable over a long time. Things that we should consider in connection with this problem are the structures fitting the objects in use, i.e., back-electrode electret, protection from dust, safety from humidity; optimum treatment; poling methods, and manufacturing processes to provide excellent durability. These questions are considered simultaneously. By these methods we have produced some electret microphones as commercial products. The above-mentioned methods are adopted for microphones of professional use; hand-free interphones; small hearing aid used under such bad conditions as sweat, high temperature, and shocks; and built-in microphones used in high temperature and high humidity. Thus we have found from the data of the market that by the methods outlined above, we can make electret microphones sufficiently stable.
Piezoelectric high-polymer film transducers for fetal phonocardiograph and monitor
Authors: Kobayashi K. , Yasuda T. , Suzuki K.
Published: October 2005

Piezoelectric polyvinylidene fluoride (PVDF) film has many remarkable properties, and various applications to medical transducers can be considered. Those transducers may be designed to have simple structures fitting on the body and capable of impedance matching. In this paper, the use of a fetal phonocardiographic transducer for the heart-rate monitor is described. The transducer is made of PVDF film, with transverse effect due to d31 constant and silicon rubber. One surface of the rubber is convex and covered with PVDF film, while the other is flat, for receiving vibrations from the body surface. This prototype structure is nearly a disk of diameter about 50 mm and thickness 5 mm, Data of signal-to-noise ratio in clinical use has been obtained. Furthermore, this type of transducer can be utilized not only as a detecter but also a vibration excitor. Hence, the array of receiving and transmitting transducers can be fabricated on one film surface, so that a functional transducer sheet on an abdominal in-term pregnant patient can be realized.
Noise criteria for outdoor living
Authors: Lawrence Anita
Published: October 2005

Many community noise criteria were derived on the basis that acceptable sound levels for sleeping and general daily living activities, such as speech communication, should not be exceeded inside bedrooms and living rooms of conventional domestic construction. However, in warm climates many of the daily living activities, including sleeping in some cases, take place outdoors, thus the attenuation assumed to be provided by a building is often lacking. Not only are the sound levels higher outdoors, but their frequency spectra may be significantly different from those received indoors. As an example, spectra of vehicle noise measured inside and outside domestic buildings will be presented, and the implications for determining acceptable outdoor A-weighted noise criteria discussed.
Factors other than noise that precipitate a community response—some case histories
Authors: Pelton Howard K. , Carnes Ted N.
Published: October 2005

In today's society the awareness that noise can be controlled in the community has been heightened by various governmental actions. A community's response to noise may often be precipitated by a cause other than noise. While it is usually assumed that established noise criteria would describe a satisfactory environment, this paper demonstrates this is not always true. Such criteria should not be the only means used to judge the community's response to noise. Many complaints about noise sources have been a result of, but not limited to, some of the following: (1) the noise source's visibility, (2) its permanence in the community, (3) communication gaps between community and industry, (4) money to be gained through litigation, (:5) higher utility rates from REA because of a power plant next door, and (6) general awareness of noise. Some case histories, which include power plants and water pumping stations in residential and recreational settings, large transformer substations, and field compressor station, will illustrate that these items can be more important than the noise levels of the source.
Acoustic microscopy at cryogenic temperatures
Authors: Heiserman J. , Rugar D.
Published: October 2005

Resolution in the scanning acoustic microscope is determined by acoustic wavelength which is in turn limited by attenuation in the acoustic medium. In heated water, the liquid most commonly used, the acoustic frequency is currently limited to 3 GHz, giving a wavelength of 0.5 μm [V. Jipson and C. F. Quate, Appl. Phys. Lett., 32, 739 (1978)]. In order to make use of the low attenuation found in cryogenic liquids we have developed an acoustic microscope suited for use at low temperatures. Images of various objects have been obtained in liquid argon with an acoustic wavelength of about 0.45 μm, and work is underway to improve this figure. Even shorter wavelengths and hence better resolution are expected in superfluid helium at 1.95 K. [Work supported by ONR.]
Reflections from microparticles in a flowing liquid
Authors: Abts L. R. , Beyer R. T. , Richardson P. D. , Galletti P. M. , Karlson K. E.
Published: October 2005

A 5-MHz pulsed ultrasonic system has been designed which can detect microparticles in a free-flowing liquid, monitoring particles between 10 and 400 μm in diameter. As in an earlier version by the same authors [J. Acoust. Soc. Am. 60, S53–S54(A) (1976)], the transducer is mounted in the plexiglass wall of a cylindrical dielectric cell (interior diameter 1.27 cm) so that a thin section of plexiglass of plano-concave shape exists between the transducer and the liquid stream, serving as an acoustic lens and focusing the ultrasonic beam at a point 1.36 cm from the surface of the lens. The return reflections from density discontinuities within the liquid are converted to digital signals by use of a 100-MHz A-D converter. This information is then analyzed by means of a PDP-11/40 computer. Both the video signal and the RF signal from the ultrasonic transmitter-receiver are used to provide information on the size and type of particle detected. Air bubbles return a symmetric pulsed echo, while various solid particles examined return asymmetric pulses. The RF signal can also be used to provide phase information, thus distinguishing particles with acoustic impedance less than that of the flowing liquid from those with higher acoustic impedance.
Numerical technique for analyzing laser cavity acoustics and its application to a real laser design
Authors: Yaeger Larry S.
Published: October 2005

Pulsed chemical laser devices require a high degree of fluid homogeneity to meet electrical discharge and optical beam-steering requirements. However, the lasing initiation process generates relatively large pressure and temperature (and thus, critically, density) disturbances which propagate upstream and downstream at fluid and acoustic velocities. These disturbances can interact with each other and with other system components and later return to the cavity to degrade subsequent lasing pulses. A quasi-one-dimensional numerical fluid analysis program has been developed, using the “discrete element” technique, which permits examination of the various forms of acoustic attenuation being considered for use in such systems. This technique has been used to establish fluid supply system characteristics for an actual 1000-Hz pulse rate lasing system. A design was arrived at that could supply adequate acoustic attenuation within the required 1 ms. Some details of the numerical technique and correlation with experimental data will be presented. Major emphasis will be on the application of the technique to at least one particular laser system, and a generally applicable convective/acoustic design philosophy, which developed as a result of parameterization studies carried out using the numerical model.
Acoustic drying of carbohydrate
Authors: Otsuka T. , Seya K. , Yamane H.
Published: October 2005

The specimens were cubes having the size of 1.5 am on one side, made of compressed granular sugar, and the drying rate was measured with and without ultrasound. The frequency used was 20 kHz having the sound pressure level of 160 dB. The study was divided into two cases: (1) use a cylindrical horn to produce the sound field in a small chamber, and (2) use flexural vibrating plates located in the tube, 6.6 cm in diameter, to produce the sound field, and the specimens on the continuous belt were moved in this tube. It was found that the introduction of acoustic energy was very effective to increase the drying rate under low temperature surrounding air.
Ultrasonic assist in reducing smog with electrostatic precipitation
Authors: Nakane T. , Otsuka T. , Seya K.
Published: October 2005

The purpose of this experiment was to study the effect of reducing smog by ultrasonics with electrostatic precipitation (E.P.). The ultrasound was produced by a vibrating plate, 33 by 7 cm, having the frequency of 20 kHz with 145–160 dB, and the voltage of the E.P. was about 20 kV. Two cases of studies were used: (1) E.P. and the sound source were connected in series, and (2) both were operated at the same time. The intense sticks were used to produce smog, and the flow rate was about 25 1/min. It was found that when E.P. and ultrasound were operated at the same time, the collection efficiency was better than only E.P. or ultrasound used.
Defining optimum electrode arrays for multichannel cochlear prostheses; electrophysiological studies
Authors: Vivion M. C. , Merzenich M. M. , Leake-Jones P. A. , White M.
Published: October 2005

Electrophysiological experiments were conducted to determine “optimum” intracochlear locations for bipolar elements of multichannel cochlear prostheses. Brainstem evoked response (BSER) mapping procedures were employed to define the spread of excitation across the auditory nerve array, as a function of current level, evoked by intracochlear electrodes having different configurations and locations. Experiments were conducted in dissected cochleas of anesthetized neomycin-deafened cats. In cochlear regions with few or no dendrites, optimum excitation was effected with longitudinally arrayed electrodes positioned along the medial margin of the spiral lamina. With dendrites present, discrete low-threshold excitation was effected with longitudinally or transversely arrayed electrodes positioned anywhere across the spiral lamina. Excitation was elicited even when few dendrites and ganglion cells survived. We concluded: (1) The bony lamina apparently offers little impedance to brief biphasic electrical pulses; (2) threshold excitation occurs in myelinated portions of dendrites or somata; (3) distance between dendrites or somata and electrodes is a critical factor in effected excitation patterns. [Work supported by NIH Grant ♯NS-11804, NIH Contract ♯N01-NS-7-2367, and Hearing Research, Inc.]
Properties of electrical stimulation relevant to the design of a cochlear prosthesis
Authors: Pfingst Bryan E. , Spelman Francis A.
Published: October 2005

For cochlear prostheses, environmental stimuli can be translated into electrical currents in a variety of ways. This study explores some of the variables relevant to prosthetic stimulation using psychophysical and biophysical techniques in an experimental animal model. Macaque monkeys trained to perform a simple reaction time task were used to test thresholds and dynamic ranges for sinusoidal, pulsatile, and white noise electrical stimulation via prostheses implanted in the scala tympani. In addition, biophysical techniques were used to examine current spread and electrode damage in relation to these variables. Results show that stimulus frequency, pulse duration, and stimulus intensity have major effects on threshold and suprathreshold measures while pulse repetition rate, electrode spacing and location, and stimulus waveform have relatively less effect. Limits within which these variables can be usefully manipulated will be discussed. [Supported by NIH grants NS13056 and RR00166.]
Autoradiographic delineation of brainstem auditory pathways after intracochlear injection of tritiated amino acids
Authors: Silverman M. S. , Clopton B. M. , Hendrickson A. E.
Published: October 2005

The orthograde transport of tritiated leucine and proline from the cochlea into the brainstem auditory system was investigated in guinea pigs using standard autoradiographic techniques. With scala tympani injections of leucine, the neuropil of all regions of the ipsilateral AVCN and PVCN were heavily labeled. The label in the DCN was lighter and differentially distributed with the central field showing the highest labeling and the molecular layers showing little labeling. No labeling was seen in other areas of the brainstem auditory system with the use of leucine. With intracochlear proline injections, the regional distribution of silver grains in the CN was similar to that obtained with leucine, with cell somas being labeled as well as the neuropil. Unlike leucine, proline injections resulted in heavy labeling in various regions of the brainstem auditory system more central to the CN. Heavy bilateral labeling of the MSO was seen whereas only ipsilateral labeling of the LSO and contralateral labeling of MNTB the DNLL and VNLL and the IC. The ipsilateral IC showed light and regionalized labeling. No labeling was seen rostral to the IC. These observations are compared to those obtained in normal and developmentally sound deprived rats. [Supported by grants NS 13052-02 and EY 0128.]
Effects of visual attention on the frequency following response
Authors: Oatman L. C. , Anderson B. W.
Published: October 2005

Frequency-following responses were recorded from unanesthetized cats with electrodes chronically implanted in the cochlear nucleus and round window. Tone bursts of different frequencies (irrelevant stimuli) were presented continuously (85 dB SPL, 1/s) before, during, and after the presentation of the visual discrimination task (relevant stimuli) which was used to alter the attentive state of the animals. The mean peak-to-peak amplitudes of the frequency-following responses from the cochlear nucleus were significantly reduced during attention to the visual discrimination stimuli when compared to the pretest and post-test control periods, but no significant changes were found at the round window (cochlear microphonic) for the same periods. These data suggest that, during attention to a visual stimulus, the frequency-following responses are attenuated presumably via the olivocochlear bundle.
Effects of high-pass masking on the scalp-recorded FFR in humans and cats
Authors: Gardi J. , Merzenich M. M.
Published: October 2005

Low frequency tone burst stimuli were used to elicit the scalp-recorded frequency following response (FFR) in the presence of high-pass maskers (with variable low frequency cutoffs) from normal hearing human subjects and anesthetized cats. Threshold shift and binaural loudness balance procedures, conducted with similar masking stimuli, were administered to compare psychophysically derived masking curves with the FFR curves. Among the results were the following: (1) At moderate to high probe-tone levels, the amplitude of the FFR masked with a 2-kHz cutoff ranged from a mean value of 75% for humans to a value of 55%–75% for cats. (2) At probe-tone stimulus levels near FFR threshold, the amplitude of the FFR masked with cutoffs of 1.5, 1.8, and 2.0 kHz was equivalent to the amplitude of the unmasked FFR. (3) The FFR masking curves did not correspond with the psychophysically derived curves except at low probe-tone stimulus levels. Although the area of stimulation (along the basilar membrane) for the FRR is broad, the most powerful input arises from the apical aspect of the cochlea (below 2 kHz). Except for lower stimulus levels, the responding area was apparently wider than the critical band around a low frequency signal. [Research supported by the Coleman fund and Hearing Research, Inc. San Francisco, CA.]
Review of acoustic research for telecommunication in Japan
Authors: Yoshikawa S.
Published: October 2005

Various acoustic researches for telecommunication are performed in the Electrical Communication Laboratory, NTT. Among these, researches on acoustic standard apparatus, acoustic measurements, electroacoustic transducers, vibrating systems, acoustic materials, room acoustics, and telephone networks are included. A new 12-in. standard condenser microphone has been developed for precise sound measurement and sensitivity calibration of telephone sets. This new standard microphone, made of titanium alloy, has high sensitivity (−54 dB re 1 V/mgr;bar, high reliability, and wide frequency range (∼35 kHz). A precise calibration method using standard couplers, as well as a simplified calibration method using active coupler, are established. Research of room acoustics is important for telephone systems in the future, because the acoustic transmission characteristics of rooms may take an important place in the system. Transmission characteristics and the spatial correlation coefficients of various rooms are investigated. The results of these researches are especially useful in telephone loudspeaker design. Based on the results of various researches, several types of new telephone sets and systems are now being developed.
Experiments with partial damping treatments in multilayer beam type and rod type structures
Authors: Curreri J. R. , Kirschner F.
Published: October 2005

Rapid developments in new materials helped to achieve superior performance in sports equipment. The art of manufacturing skis, tennis racquets, vaulting poles, and fishing rods benefited from many of the so-called space age materials. Better material properties and light weight contributed to superior achievements by sports enthusiasts, but also gave rise to injuries to the human body or other qualitative deterioration for which damping can be a useful parameter for safety and performance. Experiments describing damping on skis and fishing rods will be shown, indicating how the amplitude of vibration can be reduced without impairing weight and structural performance and, in some instances, improve the quality associated with good performance.
The TMC 0280 speech synthesizer (Part II)
Authors: Brantingham Larry
Published: October 2005

The TMC 0280 is a single chip speech synthesizer based on the technique of linear predictive coding. The problems of producing high quality synthesized speech at very low cost are discussed and the solutions implemented in the 0280 are presented. The computational core of the unit is a single multiplier, single adder implementation of the two-multiply lattice filter. All othe required auxiliary functions such as excitation generation, parameter decoding and interpolation, oscillator, interface logic, and 200 mw D/A are also incorporated on this 44 000 mil2 P-channel MOS bar. Mask programmable options for varying data rate and excitation and filtering characteristics are discussed and features of the companion 131072 bit PMOS ROM are summarized.
Simplified techniques for range dependent sound channels
Authors: Cox Henry
Published: October 2005

Simple techniques are presented for treating sound propagation for situations in which the sound velocity profile and depth vary gradually with range. The goal is to obtain clear insight and useful quantitive estimates for quantities of interest without resort to a large computer. The basic approach involves developing local Approximate Ray Angle Diagrams (ARADs) for the source position, receiver position, and intermediate positions of interest. These are obtained simply and directly from the local sound velocity profiles. Depth-angle contours on different ARADs are related using the action integral which is an adiabatic invariant for the ray characteristics. The action integral is written in a modified form to permit simplified numerical integration. Techniques for obtaining averaged transmission loss, coherence properties, and effective horizontal velocity are discussed in the context of a specific range dependent channel.
Classical geometric construction of multipaths
Authors: Floyd E. R.
Published: October 2005

For a bilinear sound-speed profile, geometric construction by straight edge and compass of the multipaths is developed for the symmetric (i.e., both source and receiver at the same depth) first-convergence-zone cases for a given range.
Oceanographic mapping by use of low frequency acoustic attenuation measurements
Authors: Browning D. G. , Kibblewhite A. C.
Published: October 2005

It is well known that low frequency sound waves can travel long distances in the ocean via the deep ocean channel (SOFAR propagation) and thus sample a large region. At low frequencies two attenuation mechanisms are dominant; a chemical absorption process due to boron, and scattering from oceanographic inhomogeneities. Hence attenuation can be related to the physical and chemical properties of the medium, and a characteristic attenuation can be attributed to a specific water mass. Data from long range propagation experiments in the Pacific Ocean is analyzed to determine the extent of particular water masses and to locate their boundaries (fronts).
Environmental considerations applicable to numerical acoustic modeling studies across ocean fronts
Authors: Hashimoto E.
Published: October 2005

A systematic approach towards an understanding of the basic acoustical effects of ocean fronts can be accomplished by the use of numerical acoustic models. A fundamental prerequisite for this approach is an understanding and precise definition of the ocean environment. Physical characteristics of ocean fronts that may be important to ocean acoustics are therefore discussed. Also, definitions, types, and the horizontal/vertical extent of various fronts are presented in the context of their possible acoustical impact. Special attention is devoted to the Labrador-Gulf Stream and Sargasso Sea water mass provinces. [Work supported by CND/NORDA.]
Statistical distribution of noise levels in open plan educational facilities
Authors: Walsh David P.
Published: October 2005

The two major acoustical problems in open plan educational facilities are the average levels of the activity noise and the noise level fluctuations. The average noise level can be accurately predicted from a knowledge of the number of students, grade level, and floor area. Correlation between the subjective impressions of “annoyance” and “acceptability” in these spaces are reviewed with respect to their measured statistical distribution curves. A simplified method is discussed which provides a comparison of direct A-scale measurements of class noise made in the field to previously developed criteria of acceptability.