bluuebunny/crossref_metadata_2025 huggingface dataset:
The Behavior of Sound in a Bounded Space
Authors: Berman J. M.
Published: October 2005

Consideration of the currently received theories of sound behavior in a room brought to light some severe anomalies. A concrete model of a rectangular room was constructed such that the number of boundaries could be varied. The steady-state and transient responses were investigated for different boundary configurations, and these were compared, firstly with predictions from the classical normal mode model, and secondly with digital computations from the impulse response, based on image model. The normal mode concepts were found to give a misleading picture of sound behavior, whereas the time-domain model was able to account for all results including those at frequencies comparable with the boundary dimensions where the normal mode model is usually substantiated. This model has also led to the prediction and verification of some unexpected phenomena in the fine structure of transient waveforms which, in the light of recent work on the hearing mechanism may well be responsible, in part, for our subjective response to an environment. [The material in this paper is shared with this session and the F. V. Hunt Memorial Session I.]
The Compleat Concert Hall: A Case Study in Concert/Recital Hall Acoustics
Authors: Kirkegaard R. Lawrence , Barrow C. W.
Published: October 2005

This paper presents subjective and objective aspects of the metamorphosis of a 750-seat concert hall. An example of spartan design and economic restrictions, this hall has undergone an extensive series of acoustical modifications to extend its ability to accommodate a wide range of musical programming.
Simple Mechanical Impulse Sound Source
Authors: Burgess J. C.
Published: October 2005

A 1-in.-diameter metal disk can be made to have two configurations of stable equilibrium and to jump suddenly from one to the other. The resulting acoustic pulse in air has a duration of approximately 2 msec and a peak sound-pressure level in excess of 103 dB re 2×10−5 N/m2. The power spectrum has a pronounced peak near 8 kHz and has power within 20 dB of its peak value at very low frequencies and in the range 3–14 kHz. An initial attempt to use cross-spectral analysis with direct and reflected pulses to measure the frequency-dependent sound-absorption coefficient of a surface produced anomalous results. These appear to be caused by a nonuniform source radiation pattern.
Results of the Graduate Workshop on Education in Acoustics
Authors: Oslac M. J.
Published: October 2005

At the Miami meeting of the Acoustical Society a special workshop was held on education in acoustics. This workshop was sponsored by the Education in Acoustics Committee with organization and participation coming from five graduate students in acoustics programs in various universities in the United States. The workshop attempted to identify, from the propsective graduate's point of view, those areas in acoustics which will be of major importance in the next decade and their relationship to incorporation into the academic community to fulfill the needs of the graduate. The consensus was that “acoustic specialization did not permit the more highly motivated graduate student to obtain the required breadth for entering tomorrow's fields of acoustics and that the required departmental regimentation be reevaluated to reflect this more diverse thinking.” The four major areas discussed at the workshop will be presented as well as the conclusions drawn from the discussion period.
Simulation of Schroeder's Integrable Model for Motion of the Basilar Membrane
Authors: Hall J. L.
Published: October 2005

Schroeder has recently developed an analytically tractable model for motion of the basilar membrane. The model is similar in form to earlier models based on the work on von Békésy (Zwislocki, 1950; Peterson and Bogert, 1950), but it is in close agreement with more recent measurements of basilar-membrane motion. We present here results from computer simulations of the model, including a motion picture showing the response to various signals.
Incremental Responses of VIIIth Nerve Units
Authors: Smith R. L.
Published: October 2005

Incremental responses of single units were studied in the auditory nerve of anesthetized, immobilized guinea pigs. The results confirm and extend earlier studies on the cochlear nucleus [R. L. Smith, J. Acoust. Soc. Amer. 52, 117(A) (1972)]. Positive and negative intensity increments were added to tone pedestals. Increments and pedestals always had the same sound frequency and phase and usually were at the unit's characteristic frequency (CF). The time delay from pedestal onset to increment onset was maintained at 150 msec. The change in firing rate at the onset of the incremental response served as a measure of incremental sensitivity. The pedestal intensity was varied, while the ratio between the incremental intensity and the pedestal intensity was held constant (constant decibel difference). The greatest incremental sensitivity was obtained for pedestals within 20 dB of the unit's threshold. If frequencies below CF were used the threshold became higher, and the region of maximum incremental sensitivity shifted to higher pedestal intensities. These results suggest that, for sufficiently high pedestal intensities, detection of intensity increments depends mainly upon units stimulated outside their CFs.
Exploration of the Range of Linear Response Activity of Cochlear Nerve Fibers
Authors: Littlefield Warren M. , Kim Duck On , Molnar Charles E. , Pfeiffer Russell R.
Published: October 2005

We have obtained experimental evidence that the response activity of spontaneously active cochlear nerve fibers is effectively linear over a certain range of parameters. These results were obtained by examining the Fourier transforms of period histograms of discharge activity in response to one- and two-tone stimulation. The following four bounds describe a range of parameters in which the statistical response patterns of a cochlear nerve fiber in all experiments to date (more than 75 fibers) are consistent with a linear hypothesis: (1) stimulus frequency <2 kHz; (2) SL (stimulus level) <40 dB SPL; (3) A < Amax = (8/N)12 (where N is the total number of spike discharges in the histogram and A equals 2/N times the magnitude of the appropriate Fourier component); (4) the two tones must satisfy the constraint that the absolute difference between each SL (Amax)<20 dB. Linear responses have been obtained well outside this range, but no statistically significant nonlinear behavior has been witnessed inside this range with histograms having N = 8000 to 16 000 spikes. On the basis of these results, for example, we can conclude that no essential nonlinearities exist in this range. The latter conclusion is also supported by other data from this study that show that all distortion components measurable, f2−f1, f1+f1, 2f1, 2f2, 2f1−f2, 2f2−f1, etc., have been observed to fall off with decreasing stimulus level faster than the primaries f1 and f2. [This work was supported in part by grants from the U. S. Public Health Service.]
Computer Simulation of a New Hair Cell Model
Authors: Hall J. L. , Schroeder M. R.
Published: October 2005

We describe digital computer simulations of a new model for mechanical-to-neural transduction in the auditory receptor. The model is based on the fixed-rate random creation of quanta of a chemical agent (“vesicles”) inside the hair cell and their migration into the intersynaptic cleft where they can cause action potentials (“neural firings”) in the attached afferent fiber. The probability of a vesicle appearing in the intersynaptic cleft is proportional to their number inside the hair cell and related in a simple manner to the instantaneous amplitude of the mechanical (“acoustic”) stimulation. The model is further characterized by an absolute and a relative refractory period. Computer simulations include the following experimental conditions: (1) spontaneous activity (interval histograms); (2) steady-state sinusoidal and noise band simulations (interval histograms and average firing rate as a function of stimulation level); (3) steady-state sinusoidal and multifrequency stimulation (interval and period histograms); (4) tone and noise bursts (PST histograms). Results of these simulation results agree closely with extant neurophysiological data.
Golgi Stains of the Cochlear Nerve Fibers
Authors: Smith Catherine A. , Haglan Betty J.
Published: October 2005

The terminal branching of the cochlear nerve dendrites within the organ of Corti of the guinea pig has been studied by means of the Golgi impregnation methods. Under fortuitous conditions, only a few nerve fibers are stained, so that the ramifications of a single nerve fiber can be studied. There appears to be some difference between the branching of the outer spiral nerve fibers in the basal coil and those in the upper coils. The cochlear nerve fibers which have been found in the basal coil either exclusively or predominantly supply a single row of outer hair cells. The nerve fibers in the upper coils generally supply two, and often all three rows of outer hair cells. In a previous report [Acta Oto-Laryngol. 75, 203 (1973)] we were uncertain if the latter were cochlear nerve dendrites or efferent olivo-cochlear axons. Electron microscopy has now supplied evidence that our previous assumption was correct, and that these nerve fibers are cochlear. The outer spirals studied thus far all course for some distance among the Deiters cells before branching. Their terminal ramifications cover a segment of basilar membrane which has varied from 70 to 280 μ in the fibers studied. [Supported by NIH Grant No. 08813.]
Reaction-Time Measures of Ear Advantage in Dichotic Listening
Authors: Springer Sally P.
Published: October 2005

Experiments employing a dichotic listening test to study hemispheric specialization for speech have typically used probability of recall as the response measure to assess ear asymmetry. Reaction-time (RT) measures can be shown to provide additional information about the underlying processes and to reveal asymmetries not found with the traditional paradigm. In the first experiment, subjects monitored a dichotic consonant-vowel (CV) tape for each occurrence of a designated syllable. Whenever that item occurred, subjects manually depressed a button. For right-ear responses, percent correct was higher and reaction times were shorter, with no significant interaction of ear and hand-used-to-respond for either response measure. A second study showed that manual and verbal RT responses to targets produced identical ear differences, suggesting that at least the terminal portion of the processing of each speech input takes place in the left hemisphere. That RT may be a more sensitive tool to study ear asymmetries is suggested by a third study in which manual RT responses were obtained to CV syllables in the presence of contralateral noise. Right-ear RT responses averaged 14 msec shorter than left-ear responses, although percent correct scores did not reveal any asymmetry.
Phonetic Errors in Dichotic Listening to Simultaneous and Time-Staggered CVs
Authors: Berlin Charles I. , Hughes Larry F. , Thompson Carl L. , Cullen John K. , Lowe-Bell Sena S.
Published: October 2005

These data represent further analyses of experiments previously reported [C. I. Berlin, C. L. Loovis, S. S. Lowe, J. K. Cullen, Jr., and C. L. Thompson, J. Acoust. Soc. Amer. 48, 70–71 (1970)]. Analysis of the errors made by normal subjects reveal that at simultaneity unvoiced consonants are better perceived than voiced consonants, especially when the unvoiced compete with the voiced consonants. When two voiced consonants compete, the V-V competition yields intelligibility about as good as the U-U competition; however, when U and V compete, then the intelligibility of the unvoiced syllable goes up while the intelligibility of the voiced syllable drops. As time asynchronies are introduced, the intelligibility of the unvoiced consonants remains constant while the intelligibility of the voiced consonant in the competing pair increases until, by 90-msec temporal offset, intelligibility of both voiceless and voiced CVs are the same. A preliminary hypothesis on switching during analysis time will be presented.
Interference by Speech and Nonspeech Signals
Authors: Speaks Charles , Kuhl Patricia , Trooien Terry , Marth Suzanne , Rubens Alan , Podraza Bonnie
Published: October 2005

Temporal-lobe patients provide a useful vehicle for exploring the “speech-nonspeech” dichotomy. Berlin et al. [J. Acoust. Soc. Amer. 52, 702–705 (1972)], for example, reported reduced intelligibility for the ear contralateral to the lesion when speech competed in the ipsilateral ear but only a slight reduction in intelligibility when noise competed. Our results on one patient were similar. We have also extended our observation to other competing signals: speech, backward speech, foreign language, voice babble, white noise, and a noise envelope. The message was synthetic-sentence identification (SSI). With SSI to the ear ipsilateral to the side of suspected lesion and any competing signal to the contralateral ear, SSI scores were high. With SSI to the contralateral ear and competing “speech” (normal, backward, or foreign language) to the ipsilateral ear, SSI scores were severely reduced. SSI scores were unaffected with noise (babble, white, or envelope) to the ipsilateral ear. All competing signals seemed clearly dichotomous as either “speech” or “nonspeech.” Our interest is to determine the properties of “speech” signals, linguistic or other, that are responsible for this interference.
Aural Protection for Utility Employees
Authors: Teplitzky Allan M.
Published: October 2005

Compliance with occupational noise exposure standards requires a period for program development and implementation. The time period for compliance with noise standards by engineering methods varies from industry to industry. Consistant with the U. S. Labor Department Bulletin No. 334, an employee hearing-conservation program includes identification of noise-exposed personnel, audiometric examination, inclusion of noise-control techniques by engineering methods, education programs, and personal hearing protection. The type of personal hearing protectors selected for use during the interim period when noise-control devices are engineered and installed depends upon the amount of noise reduction required, environmental conditions in which the protectors will be worn, and compatibility with existing safety equipment and industry safety standards. An aural protector for power plant employees was developed. This earmuff is made with no metal parts to insure a dielectric strength of greater than 30 000 V. It is approximately 33% lighter than earmuffs with metal bands, and is inexpensive and designed to be worn with safety caps. Noise attenuation provided by these earmuffs compares favorably to protection provided by alternate methods. Development and continued refinement of this “metal-less” muff has provided a viable means of personal hearing protection for power plant employees.
Polyphase Induction Motor Noise and Its Control
Authors: Brozek Bob
Published: October 2005

A plethora of sources have arisen over the years that have made noise control desirable and mandatory. The growing national concern of “the environment” has culminated in many studies in the acoustical arena dealing with noise-related hearing loss, worker inefficiency, and many other physiological and psychological areas. The result of this noise awareness has been to effectuate a wealth of noise limitations. These range from federal, state, and local municipal ordinances to those found in the specifications of the motor buyer. The motor manufacturer has not been immune from this onslaught of noise restrictions. Whether the motivating agent is to meet a specification or simply remain competitive, the motor supplier has had to suddenly add a third dimension to motor design. Where previously only electrical and mechanical parameters were considered, sonance properties must now also be deliberated. In this paper, the gravitation towards the quiet motor will be presented. Of all the possible motor noise sources, only two have been found to have a major impact on the motor's airborne noise level, these being air movement (fan and ventilation passages) and magnetic (slot combination) in nature. While abatement of the former is possible by source, enclosure and/or acoustical treatment, magnetic noise is controllable solely through source diminishment. In summary, motor noise sources are enumerated, distinction as to whether peculiar to high- or low-speed machinery is explained, and means of abatement are discussed. Both calculations and test data are also presented to verify the assertions made. Finally, it is suggested that reforms necessary to reduce motor airborne noise levels were not as debilitating as first imagined. Some related areas of further investigation are delineated at the conclusion of the paper.
Steam Turbine Noise
Authors: Bannister Ronald L. , Niskode Padamakar M. , Carey John H.
Published: October 2005

The heavy demand for electrical energy has required turbomachinery manufacturers to design and build steam turbine-generator units which can produce over 1000 MW. Based upon numerous field surveys and experimental programs conducted in the laboratory, this paper identifies the major sources of sound produced by large fossil and nuclear steam turbines. Basic differences in operation between the two types of machinery are explained. Typical sound spectra are reviewed and measurements are used to show how the sound level varies as a function of such parameters as rotor unbalance, unit size and load, steam flow, and structural resonances. Basic sound mechanisms are discussed and general guidelines are given for designing quiet steam turbines, including such components as valves and piping systems. Additional measurements show that the sound level on the main turbine floor depends not only on the sound radiation characteristics of the turbine-generator unit, but on the building architecture and plant layout. Measurement problems associated with predicting steam-turbine sound levels are also discussed.
Steam Turbine Control Valve Noise
Authors: Heymann Frank J. , Staiano Michael A.
Published: October 2005

Although noise problems with steam turbine control valves have existed before, they have become more prominent with nuclear turbines, whose valves range to 20 in. in diameter. Our first-generation nuclear control valves were unacceptably noisy when operating under chocked conditions. These noise levels have been ameliorated by incorporation of a valve cage with numerous small holes. Rational design rules for this “dispersive muffler” have been developed from published multiple-jet noise data, and improved through our own tests. However, we are also evaluating other low-noise valve configurations which are consistent with turbine requirements. The approach we are developing is to investigate the internal aerodynamic noise generation in small air model tests, and to combine this with measurements of pipe-wall transmission characteristics (being reported separately) to predict externally radiated noise. These predictions will be checked in a new steam test facility for complete scale-model valves. The small air tests show that acoustic efficiencies of throttling valve flows tend to vary with third power of Mach number when exhausting into space, and with a lesser power when enclosed in a downstream pipe. At some pressure ratios, narrow-band spikes appear in the spectrum, and for some configurations, step changes in sound power are associated with transitions in flow regimes.
Blowdown Noise-Analysis and Control
Authors: Anderson Ronald E.
Published: October 2005

The severe noise generated during the expansion of gas or steam under high pressure to an atmospheric pressure through a valve is investigated. Empirical equations based on field data are presented as a means for predicting unsilenced sound power levels and spectrum shapes. Design parameters for equipment to control this noise are discussed, with references made to regenerated noise. The application of electronic data processing to define the problems and solutions and comparison with field data is also presented.
On the Relationship Between Surface Backscattering Strength at Low Frequencies and the Ocean Gravity Wave Spectrum
Authors: Saenger R. Alfred
Published: October 2005

A theory employing the Kirchhoff approximation and other physical assumptions has been used to obtain a theoretical expression for bistatic surface scattering strength 10 log s(φi,φs) appropriate for the case of a vertically suspended separated source and receiver. In backscattering only one grazing angle φ is involved, and s(φi,φs) reduces to s(φ,φ′) = g2k42π2l2⋅2P(F̃)Ω̃3, where 2P(F̃) is the ocean wave amplitude spectrum density at frequency F̃ = Ω̃/2π, Ω̃2 = 2g k cosφ, and l is unit length. At steeper grazing angles where surface shadowing effects are relatively unimportant, the formula provides a good description of the relation between experimental values of 10 log s(φ,φ) and 2P(F) recently reported by Brown and Saenger [J. Acoust. Soc. Amer. 52, 944 (1972)]. Low-frequency s(φ,φ) data of other investigators will be discussed in light of this theoretical relation. [This work was supported by the Office of Naval Research.]
Can Acoustic Volume Scattering be Predicted from Net-Haul Data?
Authors: Batzler W. E. , Friedl W. A. , Reese J. W.
Published: October 2005

Explosive volume-scattering measurements made in widely separated areas in the Pacific and Indian Oceans exhibit a similarity in frequency pattern over the range 1–20 kHz. Typically, column scattering strength (for columns extending from the water surface to a depth of 1000 m) increases sharply in the range from 1 kHz to about 6 kHz and is fairly constant or decreases slowly thereafter. The similarity, from area to area, in the shape of this pattern suggests a mechanism common to all these areas even though the individual scatterers vary, from area to area, in size and depth distribution. We believe that this characteristic pattern is produced by resonant scattering from an assemblage of several species of mid-water fishes, principally myctophids, which vary in size within the rather narrow limits characteristic of these mid-water fishes. (Myctophids, for example, have swim-bladder radii falling within the limits 0.5 to 5 mm.) Tests of this hypothesis using a fictitious but plausible assemblage of fishes have produced patterns similar to those measured acoustically. Further comparisons in which column strength measurements in a given area are compared with column strengths which were calculated from net-haul data giving the sizes and depth distribution of the mid-water fishes in that area also give considerable support to our hypothesis. Refinement of the calculations, provided by a better knowledge of net-haul efficiency and more exact information on target characteristics (resonance frequency, Q, and target strength), is expected to provide further support for this hypothesis.
Sound Pulse Propagation in a Statistically Anisotropic Medium
Authors: Hadden W. James , Mintzer David
Published: October 2005

Amplitude and phase correlation coefficients for spherical-wave pulses propagating in a statistically anisotropic medium were obtained using a single-scattering approximation. Particular attention was given to the cases in which the receivers were equidistant from, or colinear with, the source. The range of validity of the resulting expressions for the correlation coefficients, as characterized by the Fresnel parameter r/ka2, extends from the ray-theory region to the wave-theory regime. The contrasting dependence on Fresnel parameter and relevant scatterer populations in the two cases will be discussed. Contrasts with previously reported results will also be noted.
Surface Waves of Rayleigh and Whispering Gallery Type
Authors: Dickey J. W. , Frisk G. V. , Überall H.
Published: October 2005

Surface waves on smooth curved boundaries consist of an infinite number of modes, the lowest of which may be classified as of “Rayleigh type,” since it tends towards the Rayleigh wave in the limit of vanishing curvature. The others, which correspond to the “Whispering Gallery” modes of Lord Rayleigh, combine to form the lateral wave(s) in the zero-curvature case. For an elastic cylinder imbedded in a fluid, we have developed a computer program, combined with an analytic approach, in order to compute these modes and their dispersion curves. The results may be compared with asymptotic forms for a cylinder in a vacuum given by Brekhovskikh [Sov. Phys. Acoust. 13, 462 (1968)]. The mentioned surface waves play a role in scattering and target strength calculations, and these aspects of the problem are now being studied. [Supported in part by the Office of Naval Research.]
High-Frequency Vibrations of Crystal Surfaces, Plated with Electrodes
Authors: Dökmeci M. Cengiz
Published: October 2005

In a recent paper (M. C. Dökmeci, to be published in J. Math. Phys.), we established a variational theorem for linear piezoelectricity and then constructed a theory of piezoelectric crystal surfaces. This theory is now extended to include the effects of the elastic stiffness and inertia of the electrodes in crystal shells completely coated with electrodes on both faces. Each of the electrodes may have different thickness and material properties, and each is assumed to be perfectly conducting. Starting with the local equations of linear piezoelectricity and using an averaging procedure, we establish the two-dimensional dynamical theory of plated crystal surfaces for the case when the mechanical displacement and electric potential fields are taken to vary linearly with respect to the thickness coordinate. The interactions between the crystal shell and its electrodes are taken into account. Further, we study some special cases of practical importance such as very thin electrodes and crystal plates [cf. R. D. Mindlin, in Progress in Applied Mechanics (Macmillan, New York, 1963), p. 73, and H. F. Tiersten, Linear Piezoelectric Plate Vibrations (Plenum, New York, 1969)], and present the theorems of uniqueness in this theory. [Work supported by the U. S. Office of Naval Research.]
Dependence of Middle-Ear Parameters on Body Weight in the Guinea Pig
Authors: Funnell W. R. J. , Laszlo Charles A.
Published: October 2005

The dependence of several anatomical and functional parameters of the guinea-pig middle ear on body weight, and thus on age, has been investigated. In particular, the volumes of the tympanic and epitympanic cavities are found to increase with age, with the tympanic cavity growing somewhat more slowly. The acoustical impedance of the passage between these two cavities also varies with age, while the weight of the incus appears to be independent of body weight. These results are important for establishing the values of parameters used in mathematical models of the middle ear. They are also relevant to theoretical considerations of the significance of middle-ear resonances. [Supported by the Medical Research Council of Canada.]
Successful Conditioning of the Stapedius Muscle
Authors: Yonovitz A. , Harris J. D.
Published: October 2005

The question of the conditionability of the stapedius muscle has not been satisfactorily answered. Some studies report positive though weak results in both cat and man. More typically, however, negative results have been reported. In all previous reports a loud acoustic stimulus served as the unconditioned stimulus (UCS). In the present study electrocutaneous stimulation of the external ear canal was used to elicit the stapedius muscle in humans. Contraction of the muscle was assessed by impedance changes within a delayed conditioning paradigm. The conditioned stimulus (CS) was a 1-kHz pure tone presented at a 30-dB hearing level. Thirty CS-UCS pairings were given each subject and then the CS was delivered alone until any conditioned responses (CR) which occurred had been extinguished. Latency measurements of the CRs were also recorded. CRs were readily obtained in eight of 10 subjects. Temporal conditioning was also demonstrated. Reference will be made to the close parallel between pupillary and stapedius muscle conditioning with regard to the relative ineffectiveness of light and sound, respectively. In addition, the effectiveness of mild electrocutaneous stimuli as the UCS will be discussed.
A Flexure Mode Piezoelectric Transducer for Driving the Ossicular Chain of Research Animals
Authors: Cook R. O. , Royster L. H. , Thomas W. G. , Prazma J. , Beckham J.
Published: October 2005

This paper describes the development rationale and some of the operating characteristics of a piezoelectric transducer for ossicular chain activation. By utilizing a very thin, bimorph-type, flexure-mode piezoelectric transducer in a cantilevered configuration, relatively large displacements can be generated by very low activating voltages, typically less than 1 V to produce displacements corresponding to normal communication levels. Measurements of transducer activating voltage necessary to produce various levels of round-window cochlear microphonic (CM) are compared with tympanic-membrane sound-pressure levels necessary to produce equal round-window CM in response to pure-tone waveforms. Umbo displacements produced by the transducer are compared with umbo displacements produced by pure-tone sound fields down to displacement levels less than 10 Å, through the medium of constant round-window CM in guinea pigs. Other investigations have concerned the ability of the transducer to deliver complex signals to the ossicular chain.
Dynamic Response of Freestanding Lateral Line Organs in Necturus maculosus
Authors: Oman C. M. , Frishkopf L. S.
Published: October 2005

A technique was developed for directly stimulating individual freestanding cupulae in the lateral-line organs of Necturus maculosus, a common aquatic salamander, by means of a small wire hook. Afferent and efferent nerve responses were recorded from one organ on the tail while another organ of the same stitch was stimulated. Afferent units were direction sensitive and appeared to respond at a rate proportional to cupula velocity, rather than to displacement. Instantaneous spike frequency averaged over periods of constant hook velocity was a linear function of velocity. Sensitivities typically varied between 0.1 and 0.2 spikes/second per micron/second. Efferents did not appear to play an active role in rendering the organs sensitive to cupula velocity. The cupula was found to contain a structurally distinct outer sheath and an inner core of longitudinal fibers. The stiffness of the cupula was measured experimentally. Cupula displacement dynamics in response to uniform local water-flow velocity were predicted to approximate those of a second-order overdamped dynamic system. Since the afferent fibers are sensitive primarily to the transient component of cupula displacement, it appears that the system as a whole transduces primarily flow acceleration at low frequencies and flow velocity at higher frequencies.
Phase-Locked Response of the Noctuid Acoustic Receptor
Authors: Adams William B.
Published: October 2005

Phase-locked responses were studied in the simple auditory receptor of the noctuid moth. In this receptor, there are no synapses in the periphery and no interactions between receptor units. The mechanical properties of the eardrum normally preclude responses to acoustic stimuli that have frequencies below 10 kHz. However, if the eardrum is set into motion with vibrating probes, responses can be obtained for stimulus frequencies as low as 100 Hz. Extracellularly recorded spike responses are phase-locked for frequencies below 500 Hz, but to a lesser extent than reported for mammalian auditory nerve fibers. The only exception was found in deteriorating preparations; after the spontaneous activity had ceased, firings were restricted to a quarter cycle of a 100-Hz sinusoidal stimulus. The poor phase locking, as compared with mammalian auditory fibers, suggests several interpretations, including the following: (a) the membrane time-constant of 1 msec in the moth receptor is much longer than in mammals; (b) the transduction process in the moth receptor is full-wave rather than half-wave; or (c) the moth receptor lacks an active alternate half-wave inhibition that is present in mammals.
Sonic Excitation of an Air Bubble in Gel
Authors: Storm D. L.
Published: October 2005

Entrapment of an air bubble in gel provides an easy means of isolating a single bubble and allows observation of its volume pulsation and surface instabilities. A large bubble was injected into gel and driven by a low-amplitude sound field with frequency near that for volume resonance, about 1 kHz. Typically, the bubble is ellipsoidal initially. At driving pressure amplitudes A in the range 0.1 to 10 mbar, zero-order vibrations of the surface S are visible through a low-power microscope. The amplitude of the displacement is nonuniform, being greater where the curvature of S is greater. In addition, there is a steady displacement of S, inward where the curvature is greater and outward where it is less. As A is increased beyond about 10 mbar, a surface mode of higher order suddenly appears. For still larger A unstable cusps protrude into the gel. Eventually a cusp may be sufficiently extended that a microbubble is pinched off from its tip. If A is increased beyond about 20 mbar, the cusps no longer form as the surface waves grow to large amplitude. In a separate experiment, the threshold for a one-half-order subharmonic component in the pressure spectrum is found to be very dependent on driving frequency, varying from as low as one-half the surface wave threshold to much higher. [Supported in part by NIH Grant GM-08209.]
Thermal Factors in Ultrasonic Tissue Destruction
Authors: Hsu W. L. , Lele P. P.
Published: October 2005

A purely thermal mechanism of tissue destruction by focused high-intensity ultrasound has previously been postulated in the following two ways. One is that there is a fixed threshold temperature which describes the threshold of damage. The second is that the threshold is time dependent and that the threshold is described by a temperature-time history curve. In experiments on cats, the threshold temperatures for damage in brain tissue during irradiation were measured. Data were taken with miniature thermocouples at 0.1-mm intervals. The ultrasound was delivered at powers of 6–20 acoustic watts, at several frequencies from 1.8 to 4.5 MHz, with single and multiple pulses and with variation of base conditions of the animal (e.g., base temperature, intracranial tissue perfusion). Lesion diameters were correlated with temperatures at various radial distances from the irradiation axis to determine threshold temperatures. Results for irradiations under varied values of irradiating parameters were analyzed. The threshold temperatures observed at different frequencies and under different irradiation conditions will be reported with comparisons made of data on time-temperature histories of lesion thresholds. Studies to test the extrapolability of a previously reported theoretical model using a purely thermal analysis to predict lesion dimensions will be discussed.
Effect of Practice on Intelligibility of Masked Speech
Authors: Tobias Jerry V.
Published: October 2005

Anecdotal evidence often is used to illustrate how people who live or work in noise can hear and understand signals that are inaudible or unintelligible to others. Following a procedure previously used to test the ability to learn to understand distorted speech, learning curves were generated for six untrained listeners. The speech materials were imbedded in enough white noise that well-trained listeners averaged 80% intelligibility. In their first minute of listening to this masked speech, the experimental subjects' scores ranged from 5% to 29%. After approximately 25 minutes, subjects reached plateaus ranging from 48% to 90% intelligibility; the plateau value was correlated with the score from the first minute of listening. The learning curves show a somewhat shallower slope than that for distorted signals. One unexpected but interesting piece of information that derives from these data is that speech-reception thresholds for masked signals are not necessarily similar from listener to listener. This finding is particularly pertinent in the development of valid audiometric tests for those who work in noise.
Forward and Backward Masking of Short Vowels
Authors: Dorman M. , Kewley-Port D. , Brady-Wood S. , Turvey M. T.
Published: October 2005

The processing of vowels of brief duration was studied in a series of experiments using a masking paradigm. The target stimuli were real speech vowels (/i/, /ɛ/, /ʌ/) computer truncated to 15.5-, 20-, or 30-msec duration, and equated for peak-to-peak amplitude. The masks were 125 msec in duration and were either a steady-state two-formant speech-like stimulus or an /o/. In one condition the target and mask were equated for peak-to-peak amplitude; in another, the mask was 20 dB more intense. The stimuli were presented binaurally, with the mask either preceding or following the target offset at intervals from 0 to 500 msec. Forward masking was found to be insignificant. In the backward masking conditions, the subjects divided into two groups; the majority showed no masking, while the remainder evidenced some masking of the 15.5- and 20-msec vowels at interstimulus intervals up to 200 msec. Performance was unaffected by type of mask or by differences in target-mask amplitude. The minimal masking obtained for 15.5- and 20-msec vowels contrasts sharply with the findings of Massaro (1972). A vowel duration of approximately 30 msec appears to be sufficient for subjects to derive a phonetic representation. [;This research was supported in part by NICHD Grant No. HD01994.]
A Non-Verbal Analog to the Verbal Transformation Effect
Authors: Lass Norman J. , West Linda K. , Taft Diane D.
Published: October 2005

The verbal transformation effect, the phenomenon in which continued listening to recorded repetitions of a stimulus produces perceptual illusory changes in normal listeners, has been elicited by a variety of speech stimuli, including isolated vowels, consonant-vowel nonsense syllables, words, phrases, and sentences. The purpose of this investigation was to determine the effectiveness of non-speech sounds as auditory stimuli in eliciting a non-verbal analog to this perceptual phenomenon. A total of five stimuli, three pure tones (250, 1000, and 4000 Hz), white noise, and a five-note musical motif, were repeatedly presented for a five-minute period to each of 25 adult listeners. Results indicate that the transformations elicited by the non-speech sounds are similar to those produced by speech stimuli in number of forms elicited, specific forms, and types of transformations. However, listeners usually require more repetitions of the non-speech stimuli before perceiving transformations. Implications of these findings for the proposed theory that verbal transformations represent skilled reorganizational mechanisms which aid in speech perception are discussed.
Temporally Segmented Speech III: Does Intelligibility Depend on Duration or Speech Content of the Speech Intervals?
Authors: Huggins A. W. F.
Published: October 2005

Earlier work [J. Acoust. Soc. Amer. 52, 176(A) (1972)] showed that when 200-msec silent intervals were used to temporally segment continuous speech, intelligibility decreased from 90% to 10% as the duration of the speech intervals was reduced from 200 msec to 30 msec. Other work [J. Acoust. Soc. Amer. 36, 1055 (1964)] suggests that the speech content (i.e., the number of speech events) rather than the duration of the speech intervals should be their critical attribute. Therefore, two experiments have been performed in which these two variables were separated, in one case by pitch-synchronous time-compression of the speech intervals by a factor of 2, and in the other by simply increasing the playback speed of the speech intervals by a factor of 1.5 (which also resulted in a frequency shift). Preliminary results, while not conclusive, point towards the speech content of the speech intervals as being their critical attribute. [This work was supported by NIH Grant No. NS 04332.]
The Active Control of Higher-Order Modes in Cylindrical Ducts
Authors: Harrington W. , Oslac M. J. , Reethof G.
Published: October 2005

Higher-order modes in a cylindrical duct were generated by an planar array of electro-mechanical sound drivers (Spinning Mode Synthesizer) by appropriate phase and amplitude control of the array. Predictions of the sound field generated show excellent agreement with measurements. Active control of the sound field was achieved by the introduction of a properly phased second coplanar array of sound drivers resulting in substantial reduction in the primary sound field. The analytical models agree well with experiment and furthermore clearly delineate the limitation on the complexity of the higher-order modes that can be controlled as a function of the number of drivers in the arrays and the driver frequency. Although substantial reduction of the primary modes was achieved, both analysis and experiment show that secondary higher-order modes are generated, again, depending on the number of drivers in the array and the frequency of excitation.
Investigation and Reduction of the Noise from Sulzer Weaving Machines
Authors: Bolleter U. , Chen Y. N.
Published: October 2005

Using time- and frequency-domain analysis, the various noise sources in the high- and middle-frequency regions of a test machine installed in the anechoic chamber were determined. The results showed that a large number of sources contribute almost equally to the overall noise level. Among the machine operating parameters, it was found that speed was of major influence, the sound power following a power law with an exponent of about 5.6. The effects of added damping, of using parts made from plastic, and of other means to reduce the noise were investigated. This led to the conclusion that reductions beyond about 4 dBA would require major design changes of the machine. Alternately, partial or complete enclosures could be used; these have, however, inherent drawbacks in regard to operation and maintenance.
Precision In-Situ Sound-Speed Measurements Aboard DEEPSTAR-4000 and Comparisons with Extant Equations
Authors: Mackenzie Kenneth V.
Published: October 2005

Accurate measurements of in-situ sound speed, temperature, salinity, and pressure have been achieved during numerous replicating dives aboard Westinghouse DEEPSTAR-4000 to depths of 1200 m. Manned deep submergence vehicles offer optimum methods for observing the actual ocean environment. Advantages of submersibles include: capabilities of mounting multiple equipments with short cables, visually monitoring instruments during data acquisition, and controlling proximity to the seafloor—significant improvements over suspending sensors with miles of cables from rolling, pitching surface craft. Instrument packages have consisted of three precision velocimeters (two NUS TR-4's and one TR-5), two Dymec temperature sensors, one Bissett-Berman salinometer, one or two Vibrotrons, and four Fjarlie bottles with four reversing thermometers each. Accuracy is enhanced by meticulous calibrations before and after dive series, delicate handling of all equipment, intercomparison of several instruments, consistently careful measurements, and correct assessments of thermal lags and pressure effects. Results are compared with existing equations for sound speed versus temperature, salinity, and pressure.
New Methods in Architectural Acoustic Investigations for Evaluating the Acoustic Qualities of Concert Halls
Authors: Plenge G.
Published: October 2005

In recent years efforts in architectural acoustics investigations have concentrated upon correlation between the physical data of a concert hall, on the one hand, and hearing events and judgments in the hall on the other hand. Contrary to earlier investigations in this field, these efforts do not concentrate upon finding the subjective correlate to an individual physical characteristic, e.g., reverberation time versus frequency, early decay time, “Deutlichkeit,” and so on; nowadays, instead, the total hearing impression of an observer in a concert hall—the “Hörsamkeit”—is correlated with the total set of physical data measured in this room. L. Beranek, who started his work in architectural acoustics with exact calculations and measurements of rectangular rooms at the laboratory of F. V. Hunt, Harvard University, described the first important effort in this direction about 10 years ago. A deficiency of this and similar trials is the uncertainty of the subjective observations and judgments. In this respect in recent years, a great improvement has been attained by refining the collection of subjective judgments and by the aid of improved electro-acoustic transmission systems. A survey of these systems—especially head-related stereophonic systems—will be given and preliminary results will be reported.
Low-Frequency Propagation in the Composite Region of a Wedge and Two Parallel Plates
Authors: Ahner J. F.
Published: October 2005

Propagation in the composite region of a wedge which leads into a duct is considered where mixed boundary conditions are imposed. The problem is reformulated as an integral equation where instead of the free-space Green's function being used as the kernel function, the Green's function for the wedge region is used. This permits considerable simplification and a Fredholm integral equation of the second kind is obtained where the region of integration is merely a plane and is valid for any value of the wavenumber. For small values of the wavenumber the boundary integral equation may be solved iteratively and the solution is given as a Neumann series. The results for different sources will be discussed.
The Lateralization of the Residue for Preselected Interaural Phase Disparities
Authors: Young Lamar L. , Carhart Raymond
Published: October 2005

Three signal types were employed binaurally as stimuli on a lateralization experiment: a 200-Hz pure tone, a 2400-Hz sinusoid, and an AM waveform created by modulating 2400 Hz with 200 Hz. The latter signal type gave rise to a low-pitched residue. The subjects were required to achieve a midline image by altering the intensity of the signal at one ear to compensate for preselected phase delays in the stimulus routed to the contralateral ear. When statistical comparisons were made between the results for (1) the AM signal (residue) and the 200-Hz tone, (2) the AM stimulus (residue) and the 2400-Hz signal, and (3) the 200-Hz sinusoid and the 2400-Hz pure tone, the residue and the 200-Hz signal required similar compensatory intensity changes for the interaural phase difference to achieve a centered tone image, whereas the disparate phase conditions did not affect the intensity relationship required for a midline experience for the 2400-Hz binaural signals. The fact that both time and intensity alterations shift the perceptual location of the residue and the 200-Hz tone in the same way implies that the moment of neural excitation is mediated for the residue by the same rules that govern a comparable low-frequency sinusoid.