bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Transmission of Sound into Finite, Closed Shells: Statistical Energy Analysis, Modal Coupling, and Nonresonant Transmission
Authors: Pope Larry D.
Published: October 2005

An investigation of sound transmission into small enclosures considers the effects of acoustically induced coupling between shell modes. Using an integral equation approach, the transmission loss into a small rectangular box is computed and the level of cavity reactance examined. The noise reduction for a closed cylinder sitting in a reverberant acoustic field is computed. The transmission by resonant and nonresonant shell modes is examined, especially in relation to the statistical energy analysis approach. The nature of the predominance of one type of transmission over the other is considered in relation to shell and cavity configurations and structural damping levels.
Development and Application of Nearfield Techniques for In Situ Calibration of Sonar Transducers—A Survey
Authors: Baker D. D.
Published: October 2005

A review is presented of previous work at Applied Research Laboratories on development of underwater transducer calibration techniques based upon nearfield acoustical measurements. The Kirchhoff-Helmholtz formulation, with a simple approximation for the normal pressure gradient, was used to compute farfield transducer parameters from nearfield pressure amplitude and phase data. This technique was used successfully to calibrate several different types of practical transducers. In situ calibration of sonar transducers is the most fertile area for application of this nearfield “probe technique,” so called in distinction to the array technique pioneered by Trott. The philosophy of in situ measurements is discussed, as related to applications of the probe technique that are in progress. A description is included of the nearfield bearing and range accuracy calibration system (NEFBRACS), the only known application of nearfield calibration technology to a sonar transducer aboard ship. It represents a specialized approach closely related to the array technique. Much practical information was obtained during the NEFBRACS development that will be applicable to other in situ measurements.
Farfield Prediction of Time Dependent Signals
Authors: Murphy D. A. , Dunn F. W.
Published: October 2005

It has been previously shown [Horace G. Ferris, “Computation of Farfield Radiation Patterns by Use of a General Integral Solution to the Time Dependent Scalar Wave Equation,” J. Acoust. Soc. Amer. 41, 394–400 (1967)] that the formulation of the farfield pressure in terms of an integral formula proceeded from the time-dependent scalar wave equation and thus had no single-frequency assumption. Thus, the farfield prediction theory should be valid for broad-band, as well as single-frequency signals. Measurements made by Hughes Aircraft Company and others have demonstrated the validity of the prediction theory, as applied to single-frequency steady-state signals. It has remained unverified, however, in the realm of time-dependent broadband signals. Measurements have been made in the Hughes Test Tank driving a narrow-bandwidth transducer with white noise. The pulse shape, as measured in the farfield has been accurately reproduced from measurements made over a small surface in the nearfield of the source. No attempts were made to predict the magnitude since such a small portion of the nearfield was covered. This suggests that the theory can be applied to the prediction of broad-band signals from measurements made in the nearfield.
Computation of the Nearfield/Farfield Radiation from a Cylindrical Transducer Array
Authors: Scott V. D. , Smith D. A.
Published: October 2005

A computer model has been created to study the pressure field of a large, low-frequency cylindrical sonar array. The pressure at a field point was taken to be the superposition of the complex pressures of the individual transducer elements. The pressure field of an element was taken to be the farfield approximation of the element's free field weighted by an angle-dependent function that approximates the effect of the baffle. Array field points were not calculated in the nearfield of the elements. Both horizontal and vertical beam patterns were computed for ranges from the nearfield to the farfield of the array. By combining the data from many beam patterns, a contour plot of SPL as a function of range and bearing was constructed. By correcting the field for spherical spreading loss, another contour plot was generated that displays the nearfield/farfield transition region. The results indicate that single probe calibration might be made to useful accuracy at ranges much less than the classic farfield range.
Loudness Changes Resulting from an Electrically Induced Middle-Ear Reflex
Authors: Gunn Walter J.
Published: October 2005

An experiment was conducted in order to determine the changes in loudness brought about by electrocutaneous elicitation of the middle-ear reflex. Subjects were required to judge the loudness of the second of three consecutive 30-msec bursts of tone, the second tone being accompanied by an electrical shock to the external auditory meatus, capable of eliciting a contraction of the middle-ear muscles. The difference between these judgments and those of the control condition (shock on the arm) was taken to represent a measure of the attenuation provided by contraction of the middle-ear muscles. Test tones were 500, 1000, 2000, and 3000 Hz at levels of 70, 80, 90, 100, and 110 dB (SL). The results indicate that the middle-ear reflex decreases the middle ear's transmission mainly for low-frequency sounds. The results fail to lend support to the Loeb-Riopelle hypothesis that the middle-ear reflex acts as a limiter, rather than as a linear attenuator. In fact, there was a small, but significant, decrease in attenuation with increasing auditory stimulus intensity at the higher frequencies.
Spatial Patterns of Cochlear Difference Tones
Authors: Worthington Don W. , Dallos Peter
Published: October 2005

First-order intermodulation components in cochlear-microphonic potentials were measured with the differential electrode technique from all four turns of the guinea pig cochlea. Measurements were made with six pairs of primary frequencies and a wide range of primary signal intensities. The spatial patterns of the first-order difference tones were compared with those of the primaries, and with pure tones whose frequency was the same as that of the difference tone. The results indicated that at low and moderate primary intensity levels the distortion component was localized in the cochlea somewhat apical from the region of maximum excitation by the higher frequency primary. With increasing stimulus intensity, a general shift of the distribution pattern was observed, accompanied by the development of a second region of maximal difference tone activity. This second region, where the difference tone become more prominent as the intensity was increased, corresponded to the location of maximal microphonic elicited by a pure tone whose frequency was the same as that of the difference tone. These results further confirm that distortion of the cochlear microphonic is a two-stage process [Work supported by the National Institute of Neurological Diseases and Stroke.]
Acoustic Fountain Effect
Authors: Ingard U. , Ross James A.
Published: October 2005

An intense standing sound wave along the free surface of a liquid produces a static deformation of the surface and in certain cases stationary fountains. This phenomenon has been known for a long time [V. Dvorak, Ann. Physik 7, 42 (1876)]. We have measured the acoustic threshold of fountain formation in different liquids and propose an explanation for this instability. [This work was supported by the ONR, under contract.]
Acoustic Streaming as a Mechanism in the Treatment of Suspensions
Authors: Rooney James A.
Published: October 2005

Hydrodynamical shearing of droplets occurs when sufficiently high-velocity gradients exist [F. D. Rumscheidt and S. G. Mason, J. Colloid Sci. 16, 238–245 (1961)]. Theory for acoustic microstreaming near a gas bubble indicates that large velocity gradients can exist in the boundary layer. Comparison of such gradients with hydrodynamic theory leads to the prediction that acoustic streaming can be an important mechanism in the disruption of suspensions. For example hydrodynamic theory predicts that a velocity gradient of 2.5 × 104 sec−1 existing in a fluid with a viscosity of 20 cP is sufficient to shear a droplet of radius 10 μ and a surface tension of 10 dyn/cm. A velocity gradient of this magnitude exists near a resonant 20-kHz bubble oscillating with an amplitude of 20 μ. Under suitable experimental conditions, such amplitudes can be achieved using a single controlled oscillating bubble. Data obtained from such an arrangement substantiate aspects of the theory. [This investigation was supported by a National Institutes of Health Fellowship.]
Envelope Spectra of Ambient Sea Noise
Authors: Wilson O. B. , Whitney William
Published: October 2005

Ambient sea noise as detected with an omnidirectional hydrophone mounted at 300-ft depth on the R/P FLIP is analyzed by examining the low-frequency spectral character of the envelope of the noise in the 1–4 kHz band. A smoothed envelope of the noise as passed through a linear rectifier is sampled and digitized in a form suitable for fast-Fourier-transform processing. Spectral estimates from about 5 × 10−4 to 10−1 Hz are provided. Details of the method and some of the results are presented. A conclusion that seems to be indicated is that the spectrum of the fluctuations of the sea noise from the mean has about the same shape as does noise provided by a conventional noise generator, but the level is about 10 dB higher than that of generator noise having the same rms value. [Suported by the Office of Naval Research.]
Wide-Bandwidth Constant-Beamwidth Acoustic Array
Authors: Hixson E. L. , Au K. T.
Published: October 2005

A linear broadside array can be made to have constant beamwidth over wide frequency ranges by using logarithmic element spacing and the proper filtering and combination of signals from the elements. Such an array is achieved by choosing the array size and linear element spacing to give the desired beamwidth and side-lobe suppression at the lowest frequency of interest. An identical array at twice the frequency will be half as long with half the spacing. When the signals from these two arrays are properly filtered and combined constant beamwidth over an octave band results. When the arrays are superimposed, redundancy allows a reduction in the number of elements. This process can be continued to cover the desired bandwidth and a log spacing results. Results obtained from a five-element array covering 0.3 to 3 kHz are presented. [Partially supported by LTV-Electrosystems.]
Detecting Active Sonar Pulses Using Empirical Bayes Techniques
Authors: Spooner R. L.
Published: October 2005

In active sonar situations, one is confronted with a multiple decision problem in detecting the presence or absence of a signal in the multiple returns. For a rapidly fading channel, the problem is compounded in that the signal may vary from echo to echo. The purpose of this paper is to present some initial attempts to apply empirical Bayes analysis techniques to this problem. These techniques represent a compromise between the positions of Bayesians and non-Bayesians and appear to be especially suited to the varying multiple decision problem. In addition, some of the techniques of nonsupervised learning are also applied and comparisons made.
Approach to the Transient Sonar Equation
Authors: Sachs D. A.
Published: October 2005

Transient forms of the sonar equation have been formulated in terms of the time-averaged intensity by Urick [R. J. Urick, Principles of Underwater Sound for Engineers, McGraw-Hill Book Co., New York, 1967, pp. 23–27] and the peak intensity by Marsh [H. W. Marsh, J. Acoust. Soc. Amer. 34, 1789 (1962)]. Our formulation, conforming to Marsh's, is to consider the peak pressure as the observable quantity. Assuming that the transducer produces a step-function pressure pulse, its propagation to the vicinity of the scattering target is treated with an approximate form of the wave equation including viscosity. The propagation of the scattered pulse back to the transmitter is handled with the same equation. The pulse backscattered from a general target is calculated using an asymptotic high-frequency technique, which should yield an accurate prediction of the peaks produced by specular reflections. The technique used is an extension of Freedman's theory [A. Freedman, Acustica 12, 10 (1962)] to transient pulses. [Work supported by ONR Acoustics Programs.]
Changes in Subglottal Air Pressure Associated with Changes of Fundamental Frequency
Authors: McGlone Robert E. , Shipp Thomas
Published: October 2005

Subglottal air pressure was recorded with the aid of an intratracheal catheter as three young adult males produced an upward and downward glissando. From a graphic display of both the pressure and the phonation, changes in pressure (ΔPs) and fundamental frequency (Δfo) were determined. The mean Δfo/ΔPs ratio for both phonatory activities was 7.67 semitones per centimeter of water. This is considerably larger than reported by previous investigators. Moreover, when only the range of fundamentals most often used for speech was considered an even larger ratio was found. Even though the importance of subglottal pressure to the generation of a laryngeal tone cannot be denied, the present data suggest that changes in the fundamental of that tone are probably more directly related to laryngeal adjustments such as changes in mass and length of the vocal folds.
Intensity Variations during Vocal Pry Phonation
Authors: Murry Thomas , Brown W. S.
Published: October 2005

Investigations indicate that as one approaches the lower limit of the modal phonational register, the range of vocal intensities decreases until no variation is possible. Such results in modal and falsetto phonation led to predictions of the mechanics of intensity changes. No data are available relating frequency/intensity changes in vocal fry. The purpose of this study was to determine the relationship between fundamental frequency and vocal intensity in vocal fry. Subjects sustained fry for 3 sac at three points in their total fry range as intensity was recorded. Thereafter, they sustained fry at the three recorded intensities, previously obtained, while the frequency was recorded. Results indicate that vocal intensity during vocal fry is relatively low compared to other phonational registers. As subjects increased fundamental frequency, intensity also increased. Subjects did not always produce a particular frequency at a given intensity; however, when asked to increase or decrease intensity only, frequency also increased or decreased. These data and previous studies suggest that vocal fry frequency/intensity changes are primarily regulated aerodynamically.
Acoustical Consequences of Lip, Tongue, Jaw, and Larynx Movement
Authors: Lindblom B. , Sundberg J.
Published: October 2005

In the past, numerous attempts have been made to develop quantitative models of the human vocal tract. The present paper describes such a model and some of its acoustic properties. It has been constructed with a view towards finding a set of parameters that are physiologically “natural.” Thus it differs from earlier schemes in that the mandible has been incorporated as an independent parameter. Other novel features can be interpreted to represent larynx height, the rounding-spreading action of the lip musculature, and “genioglossal,” “styloglossal,” and “hyoglossal” components of tongue shape. The paper describes the acoustic effects of varying these parameters systematically. The model is capable of generating most of the vowel qualities known to occur in the languages of the world. In general, well-known vowel sounds are found along the extreme contours of the total acoustic space characteristic of the model. They are not necessarily located at acoustic “plateaus” or regions insensitive to articulatory imprecision. The model specifies the notion of “possible vowel articulation” in terms of parameters that are not in a one-one relation with distinctive feature dimensions such as open, close, high, low. A discussion of the implications of these results for universal phonetic and phonological theory concludes the paper. [This work was supported by a research grant from The National Institutes of Health.]
Electromyographic Investigation of the Articulatory Basis of Vowel Duration Differences before Voiced and Voiceless Consonants
Authors: Raphael Lawrence J.
Published: October 2005

It has often been observed that English vowels are of greater duration before voiced than before voiceless consonants. This durational difference has been shown to be a significant perceptual cue to the voicing characteristic of word-final consonants. Little, however, has been done to specify the articulatory mechanisms underlying the observed differences in vowel duration. Spectrographic evidence can supply only inferences in this regard. Electromyographic techniques provide a more direct way of investigating articulatory muscular activity and of determining which of the potential factors governing vowel duration are at work in the voiced-voiceless context. This study investigated minimal CVC pairs, in isolation and in stressed, sentence-final position, in which the articulators producing the initial consonant and vowel were independent of those which produced the final consonant. Electromyographic procedures were used to measure the muscular activity controlling the two sets of articulators in order to determine the differences in the relationship between vowels and final consonants. The only consistent effect found was a greater duration of muscular activity for vowels preceding voiced consonants. [This research was supported by the National Institute of Dental Research.]
How Evoked Slow Wave Can Influence the Shape of PST Histogram of Neurons' Spike Activity
Authors: Nahvi M. J.
Published: October 2005

The neurons' electrical activity recorded by a microelectrode often contains a slow wave on which the spikes are superimposed. To evaluate the PST histogram of spikes in response to stimuli such as acoustic clicks [to be called p(t), o < t < T], one passes the signal through a threshold device. Choosing a high threshold level ensures that only spikes are counted but will cause some occasional omission. Under certain conditions the omission of spikes influences the shape of PST histogram. By using a mathematical formulation, conditions under which the PST histogram resembles the average of evoked slow wave [to be called r(t), o < t < T] are discussed. When the spike activity is not correlated with stimulus and slow wave is very small compared with the height of the spikes, the threshold level p(t) = A + Br(t), where A is proportional to the level of spontaneous activity of neuron and B is inversely proportional to standard deviation of slow wave. Thus, with some distortion, p(t) resembles r(t). Results are illustrated by simulation on a digital computer. [Supported by Aria-Mehr University.]
Comparison of Cochlear Nerve Fiber Responses to Cochlear Microphonics
Authors: Pfeiffer R. R. , Molnar C. E.
Published: October 2005

The Fourier analysis of period histograms of spike discharges of single cochlear nerve fibers in response to continuous, single sinusoidal stimuli reveals properties that are remarkably similar to those of the cochlear microphonic (CM) as measured in individual turns of the cochlea. We compare phase shift, as a function of stimulus frequency, for the fundamental component of response of single fibers (as obtained by us) to that for the CM from different turns of the cochlea (from the literature). Curves from both sets of data can be closely approximated by two straight lines. The changes in slopes, and the positions of the break points of the straight line segments behave similarily with changes in characteristic frequency (CF) of the fibers (0.37–5.4 kHz) and changes in the frequency of maximum sensitivity of the CM. For both sets of data, intercepts of extrapolations of the straight lines depart from the origin; for one, as CF increases; for the other, as turn number decreases. Relative amplitudes of the fundamental and second and third harmonics versus stimulus level and versus stimulus frequency also behave in a manner similar to the corresponding CM measurements. These data, resulting from single sinusoidal stimuli, suggest that CM is closely associated with the mechanisms affecting the structure of the spike discharge trains sent to the brain. [This investigation was supported by PHS research grants from the National Institutes of Health.]
Augmentation of Masked N1 to Loud Clicks by Crossed Olivocochlear Bundle (COCB) Stimulation in Guinea Pig
Authors: Nieder P. , Nieder I.
Published: October 2005

With a masking stimulus of low-level room noise present, stimulation of the COCB reduces the cochlear neural response to low-level clicks; high-level click responses increase. At the crossover point—about 60 dB above detection level—high-frequency noise that further decreases the response by an amount equivalent to a 10-dB signal reduction can be partially counteracted by COCB stimulation at 400/sec for 100 msec, and the response increased the equivalent of 8 dB. When a 65-dB click response is almost obliterated by responses to 400/sec clicks at 45 dB, it can be made clearly visible by COCB stimulation, which decreases responses to the lower clicks and increases that to the higher. Responses to high repetition rate clicks at low-level are reduced proportionately more than single-click responses. COCB firing thus appears to block selectively low-level excitation processes; afferent neurons freed from responding to low-level periodic excitation become available for response to higher-level signals. This efficient mechanism would serve to improve both periodicity and place coded signals. [Supported by NINDS.]
Computational Methods for Nonlinear Acoustic Absorbers
Authors: Zorumski William E.
Published: October 2005

Computational techniques are presented for high-intensity sound transmission through and reflection from a nonlinear absorber. The absorber is made of a thin sheet of porous material with a nonlinear pressure-velocity relationship and a backing of arbitrary impedance. It is shown that the spectral analysis approach reduces the physical problem to the solution of infinite sets of nonlinear algebraic equations, while real-time analysis reduces to the solution of a nonlinear integral equation. In special cases, the integral equation reduces to a nonlinear algebraic functional equation for which exact solutions are given. The frequency-domain formulation is solved by a steepest descent iteration for arbitrary nonlinearity and by a perturbation method for small nonlinearity. Numerical solution methods for the integral equation are given. Qualitative merits of each method are discussed, and numerical results of each method are compared to the exact solutions.
Zero and First-Order Differential Equations in the Perturbation Parameter for the Stochastic Boundary Theory
Authors: Bugnolo D. S.
Published: October 2005

A theory recently introduced as a possible new approach to the rough surface problem in the ocean [D. S. Bugnolo, “On the Effects of Stochastic Boundary Perturbations on Acoustic Wave Propagation,” J. Acoust. Soc. Amer. 45, 1560–1562 (1969] has been applied to the case of an ocean characterizable by two homogeneous layers. The perturbation method has been used to generate a set of differential equations for the radial eigenfunction to order l in the surface parameter, Δh. Particular results are presented for the first two equations.
Derivation of the Stochastic Helmholtz Equation from First Principles
Authors: Neubert J. A. , Lumley J. L.
Published: October 2005

The basic stochastic wave equation is derived from first principles (as represented by the continuity equation, the Navier-Stokes equation, and an appropriate equation of state). It is shown that, for very low turbulent Mach numbers and monochromatic transmissions, sound propagation in a turbulent fluid can be adequately represented by the stochastic Helmholtz equation (∇2p+k02μ2p=0) only if the acoustic wavelength does not exceed the Taylor microscale divided by the square root of the turbulent Mach number times the Prandtl number. The comparison of similar turbulent flows in air and in water, in regard to estimating their acoustic frequency limitations, is illustrated by contrasting: (1) the Baerg and Schwartz experiments with the Stone and Mintzer experiments and (2) the turbulent lawyer atmosphere with the turbulent upper ocean.
On the Ability of the Glace-Holmes Synthesizer to Produce High-Quality Speech
Authors: Wathen-Dunn Weiant , Soron Henry , Michaels Sheldon
Published: October 2005

Formant speech synthesizers are important on two counts. The signals controlling them are related to meaningful articulatory events and are likewise very compact descriptions of speech. They are thus important for experiments on speech generation, perception, and synthesis-by-rule, and for reduced-data-rate communications. However, before such synthesizers can be used for fully meaningful investigations, it is necessary to know the inherent capability of the synthesizer to produce high-quality speech. This paper reports attempts to maximize the quality of speech produced by a Glace-Holmes synthesizer. Talkers produced utterances ranging from vowels to entire sentences. These were carefully recorded and spectrum analyzed at 10-msec intervals. The resulting data are used as a base for optimizing synthesizer output in an attempt to replicate the original speech. Speech quality judgments are made both informally and by formal listening tests. These data should prove useful in setting a standard against which the performance of communications systems or the results of speech experiments utilizing the Glace-Holmes synthesizer can be judged.
Some Techniques for Hologram Interferometry of String Instruments
Authors: Stetson Karl A.
Published: October 2005

While hologram interferometry is proving very useful in determining the plate resonances of string instruments such as guitars, viols, and violins, there are definite technical difficulties involved. Many of these relate to the extreme sensitivity of any interferometer to dimensional changes such as produced by wood expanding with humidity, or seismic noise. Others relate to mode combinations that often occur owing to close spacing in frequency of relatively low Q modes. This paper discussed hologram interferometry from a practical point of view, explaining those techniques which are most helpful in overcoming these difficulties. They include use of liquid gates and in-place development of holograms to speed up real-time measurements, 35-mm film for recording time average holograms rapidly and in large numbers, the positioning of excitation points to separate combining modes, and laser speckle interferometry as an alternate to real-time hologram interferometry. The measurement of Q values for vibration modes via hologram interferometry is also discussed.
Negative Resistance in the Bowed String
Authors: Schelleng John C.
Published: October 2005

The action of the bowed string is discussed from the viewpoint of negative resistance and illustrated by oscillograms of string motion that are obtained by an electromagnetic rather than an optical method. Effects of string rotation are discussed. Consequences of different bow pressure in relation to bow velocity and position are summarized in a diagram significant to the player.
Study of Flow Resistance, Including Nonlinearity, in Sintered Fibrous Materials
Authors: Bies D. A.
Published: October 2005

An empirical equation has been found that collapses onto a single line most flow resistance data for many sintered metal fibrous materials. The data collapse extends well into the nonlinear regime. The flow resistance, expressed in dimensionless form, is found to be a function of Reynolds number based on the fiber diameter and on the effective density of the material. The expression consists of two terms, one being a linear term, which is a function of gas viscosity, and the other being a nonlinear term, which is a function of gas density and particle velocity. An application of the empirical equation is given to provide some insight into the requirements for linearity of materials exposed to high-particle velocities. [This work was sponsored by the Aircraft Division, Douglas Aircraft Company, McDonnell Douglas Corporation, Long Beach, California.]
Some Consequences of the Masking Produced by Combination Bands of Different Types
Authors: Greenwood D. D.
Published: October 2005

Data reported earlier [D. D. Greenwood, 78th Meeting of the Acoust. Soc. Amer. (Nov. 1969)] demonstrated the existence, and masking effects, of combination bands of the same form as combination tones given by (n+1)FL−nFH, where FL, FH are the frequencies of the primaries. Combination bands could be generated by a pure tone and a band of noise, by two bands of noise, or by only one band of noise. In the latter case, the combination bands (n=1,2,3,⋯) overlap and form the combinational aggregate. A relationship of combination tones, or bands, of this type to critical bandwidth has been shown: when two primary stimuli are separated by one critical bandwidth, the first (n=1) combination tone or band stands at a frequency locus coinciding with the low-frequency foot of the masked audiogram produced by the lower primary. Several considerations lead to the inference that critical bandwidth extends downward from the lower primary tone, and support further the view of critical bandwidth as a resolution, and integration, interval. These experiments also reveal the role of combination bands (and the combinational aggregate) in remote masking and permit the demonstration of difference bands corresponding to the difference tones, (FH−FL) and 2(FH−FL). Other data indicate that combination components can be generated iteratively in situations where three external primaries are used.
Simulated Sound Fields Programmed from Acoustic Model Data
Authors: Klepper D. L. , Kirkegaard R. L. , Terroux P. , Watters B. G.
Published: October 2005

In the past we have found the impulse responses of auditoriums to be useful indicators of qualities such as clarity or reverberance for speech and music. We have also used impulse responses measured in acoustic models of halls in the design stage to predict these qualities in the finished building. A further development, now under way, is to simulate the three-dimensional sound field expected in a finished hall, using simulation equipment described in this session. The impulse response of the simulator is programmed to correspond to that of an acoustic model of the hall. Speech and music recordings are then played through the simulator so that the basic acoustic qualities of the design may be previewed. We will describe a set of experiments involving a well-known existing concert hall, an acoustic model of the hall, and a simulation of the hall acoustics based on model and hall objective data.
Speech Absorption Coefficient (SAC)
Authors: Pirn Rein
Published: October 2005

A single-number rating is proposed for evaluating the sound absorption of an acoustical material for use in applications where the control of speech sounds is of primary importance, such as in open-plan offices and schools. The development and application of the speech absorption coefficient are described, and its use is compared with the familiar noise reduction coefficient (NRC).
Approximate Theory of Torsional Wave Propagation in Elastic, Composite Cylinders
Authors: Haines D. W. , Lee P. C. Y.
Published: October 2005

One dimensional equations of motion are obtained for axially symmetric torsional deformation in elastic, composite cylinders. Under consideration are cylinders composed of two materials: a circular inner core surrounded by an annulus of different material properties. These approximate equations were obtained from the variational equations of motion of a linear elastic medium by assuming a set of simple, orthogonal displacement functions. These functions were chosen to give the first two branches of the dispersion diagram for torsional waves in the composite cylinder. The slope of the first branch at the origin of the dispersion diagram is identical with the corresponding slope obtained from the “exact” analysis. Two correction factors are introduced in the approximate equations in order for the second branch to match the exact analysis at two particular points. The dispersion relations obtained from the resulting corrected equations are very accurate through a wide range of frequencies for real wave numbers. Conditions at the end of finite cylinders, sufficient to provide a unique solution, are provided.
Variational Principles and Techniques
Authors: Ingard U.
Published: October 2005

A survey is given of general variational principles in physics and the specific variational techniques that have emerged for solving radiation and scattering problems in acoustics and related areas. The various techniques are elucidated by simple examples. [This work was supported by the Office of Naval Research, under contract.]
Prosodic Model for Orthographic-to-Phonetic Conversion of English
Authors: Vanderslice R.
Published: October 2005

The subset of prosodemic features that occur within sense groups (excluding grammatical pauses and shifts, which occur between sense groups) comprises accentuation and intonation. “Prosodemic” designates grammar-expounding as opposed to indexical features—a crucial distinction for reading machines in that text-sensitive assignment of indexical features is a cardinal requirement for fictive texts (including poetry), but can be omitted for straight factual prose, whose conversion to speech requires only that prosodemes (and, of course, segmentals) be appropriately assigned. Modeling accentual phenomena in terms of the binary features ACCENT and EMPHASIS eliminates degrees of “stress.” The correct assignment of these features requires two kinds of information: syntactic (ultimately semantic) considerations govern which words in a sentence are accented (or emphasized); and orthoepic considerations determine which syllables in a word are weak and which strong—and, of the latter, which ones may receive the accents if the word is accented. Final disposition of accents and emphases is mediated by surface rules, contingent on the rate and style of speech, which produce, e.g., “rhythmic” recessions and suppressions of accents. Two intonational features—CADENCE, or postnuclear fall, and ENDGLIDE, or terminal rise—provide the four standard contours falling, rising, fall-rise, and sustained.
Laterality Factors in the Recall of Sentences Varying in Semantic Constraint
Authors: Jarvella R. J. , Herman S. J. , Pisoni D. B.
Published: October 2005

The role of the left and right ears in listening to undistorted speech was evaluated in a short-term memory task. Twenty-four normal right-handed subjects listened to sentences with the same syntactic structure but varying in semantic integration [e.g., “The brave soldier fought the cruel war” (well integrated) versus “The glad soldier owned the tiny chair” (poorly integrated)]. All sentences were presented monaurally. Listeners were required to count backwards after each sentence (to block rehearsal) and then after 5 sec to repeat back what they could remember. For both levels of semantic integration, sentences presented at the right ear were recalled faster and with fewer errors than sentences presented at the left ear. These results indicate that laterality factors related to cerebral dominance for language functions influence short-term memory for sentences heard monaurally.
Direct Comparison of Detection and Lateralization under the Condition N0SM
Authors: Hafter E. R. , Shotland R. M. , Carrier S. C. , Stephan F. K.
Published: October 2005

An earlier paper demonstrated a direct relation between lateralization and the binaural-masking condition N0Sπ. This work extends the technique to the binaural condition N0SM. Signals were monaurally presented (500 Hz, 100-msec tones; the masker was a diotically presented (continuous wide-band noise). Test intervals were marked by a 100-msec light; signals were randomly presented on half of the test trials. Subjects were instructed to lateralize the acoustic image occurring simultaneously with the test light and to indicate the laterality on a 12-in. rating scale. The scale was designated to represent intracranial auditory space. Trials that contained signals produced responses more toward the periphery of the scale than those that contained noise alone; for more intense signals, subjects showed a lateral bias toward the side receiving the signal. Receiver Operating Characteristics (ROCs) were drawn for each signal-level tested by computing likelihood ratios across the rating space, and then re-ordering the response data by descending likelihoods. The areas under these ROCs compared favorably with detection data obtained for the same levels, supporting the notion that signal detection under N0SM is of a lateral shift in the acoustic image. [This work was supported by a grant from the National Institutes of Health.]
Feasibility Study of Self Calibration of Audiometric Earphones
Authors: Joscelyn Edwin R.
Published: October 2005

For clinical accuracy, it is important that verifiable information about the sensitivity of earphones used in conjunction with audiometric equipment be made obtainable to the user in the field. A form of reciprocity calibration has been examined and evaluated for 100 pairs of TDH-39's. The two earphones of one headset are alternately used as transmitters and receivers acoustically coupled in a small cavity. The electrical, acoustical, and mechanical constants of the transducers are lumped together by taking the absolute averages of the sensitivities of 100 pairs of earphones, where the absolute sensitivity is traceable to the NBS, and by integrating these sensitivity averages with the transmitter-receiver voltage transfer characteristic. A calibrating K factor is thus obtained and made available by the TDH-39 manufacturers laboratory. With this factor, the average sensitivity of a pair of earphones may be determined in the field from the relation Sav=K−(V1−V2), where V1 is the driver voltage and V2 the reeciver voltage. By using a third earphone, it is possible by an extension of the above analysis to determine the absolute sensitivity of any one of the three units.
A Design to Evaluate Low-Frequency Amplification for Habilitating Preschool Deaf Children
Authors: Asp Carl W.
Published: October 2005

An experimental design was utilized that permitted a teacher to speak simultaneously through two different amplifying systems, a low-frequency auditory training unit (SUVAG I) and a conventional one (Warren, T-2). The microphones of both units were held securely in one fixture. Preschool deaf children were “matched” and assigned to either unit. The teacher utilized the verbo-tonal method for habilitation. Each training unit could independently excite five headsets and five bone vibrators. The same type of headset and vibrator was utilized for all the children. The electrical response of the low-frequency training unit extended from at least 20–20 000 Hz (± 2 dB), and the response of the conventional unit was 330–9000 Hz. With the same earphone, the acoustic response of both units was similar for high frequencies; however, the low-frequency unit produced a greater response below 500 Hz. Two hearing aids were selected that produced frequency responses that were similar to the training units. The Mini-Suvag was assigned to children on the low-frequency unit and the Zenith Vocalizer II was assigned to children on the conventional unit. The Mini-Suvag is capable of simultaneously driving a vibrator and a headset, and it can be utilized as a training unit. [Work supported by the Office of Education, U. S. Department of Health, Education and Welfare.]
Slow Evoked Cortical Responses and Auditory-Shock Interactions
Authors: Rothman H. H. , Davis H. , Hay I.
Published: October 2005

Slow evoked cortical responses are known to have a recovery period of several seconds. A second stimulus of the same modality presented within this period shows a diminished response. Theoretically, a second stimulus presented in a different, independent modality should show no response diminution. This principle was used to test for independence between shock and auditory stimuli, separated by a 200-msec interval. Simultaneous interaction between these two modalities was also investigated, using a special method to separate the simultaneous responses in the two modalities. Results for most subjects show that simultaneous stimulation enhances responses.
Spectral Analysis of the Averaged Auditory Evoked Response During Learning of Speech and Nonspeech Stimuli
Authors: Greenberg Herbert J.
Published: October 2005

Changes during learning and cortical hemispheric comparison of the averaged auditory evoked response (AER) to speech and nonspeech auditory stimuli were investigated. Right-handed subjects were required to learn ensembles of eight CV syllables and five piano notes by the process of association while electroencephalographic (EEG) activity was being recorded from right and left temporal lobe electrode placements. Fourier analysis of the AERS was performed at 60%, 70%, 80%, 90%, and 100% performance levels. The first 24 spectral components were examined in terms of variation of the largest amplitude spectral component and amplitude variation of the 24 components divided into three frequency bands. A progressive decrease in the amplitude of the AER spectral components occurred during the learning of the speech and nonspeech stimuli. These variations were similar for both ensembles of stimuli and were viewed as reflecting increased cortical activation. Hemispheric differences were found in the AER spectrums that were related to the type of stimulus. Although confounding activity may have been introduced by the language-oriented learning task, indications were that the right hemisphere plays a dominant role in nonspeech discriminations, with the left hemisphere being responsible for speech learning.
Some Experiments With a Shock-Excited Magnetostrictive Impact Transducer
Authors: Semmelink A.
Published: October 2005

The usual ultrasonic machining processes use transducers operating at resonance and with a sinusoidal motion of the tip. Magnetostrictive transducers can be designed, however, with excitation applied sequentially along their length at a rate equal to the velocity of sound in the material. In this case, a steadily increasing strain pulse is produced, which travels in the direction of excitation. The motion of the tip has a large amplitude, short rise time, and is almost nonringing. The displacement can reach a few mils and large forces are generated if the tip is held against a solid object. The amplitude of the output and the repetition rate can be precisely controlled. The transducer was studied for applications such as rivetting, metal forming, and rock drilling. Another important use for this transducer with its short duration nonringing output signal is as a transducer in nondestructive testing. Two 7-in. transducers and one 5-ft-long transducer were built. The 5-ft transducer was used for dimpling metal disks and in a rock drilling experiment.
Acoustic Method for Post-Treatment of Fibers
Authors: Greguss P. , Nagy S. B. , Erdie I. , Toth L.
Published: October 2005

An acoustic method is presented the purpose of which is to improve the mechanical characteristics of synthetic fibers of organic compounds, e.g., polyamide fibers, such as tensile strength, wear resistance, and readiness for dyeing. The approach is to remove the monomeric content before stretching the fiber in such a way that it can then be reused for making polyamide fibers. Costs are reduced both with respect to machinery construction and the required area for them. The machinery requires very little electrical and thermal power and its maintenance is simplified to the replacement of used compounds, e.g. vacuum tubes. Some technical details are discussed.
Stability of Ocean Propagated Acoustic Signals
Authors: Williams E.
Published: October 2005

The time stability of acoustic signals propagated over long ocean paths of 145 to 670 NM has been measured. Unusual stabilities were found on selected RSR and completely refracted paths. This experiment differed from other temporal coherence experiments by using a broad-band, repeated, hyperbolic FM waveform, rather than a continuous-wave signal. The signals were received on a vertical array of hydrophones moored to the ocean bottom, so that a separation of multipaths by vertical angle could be made. The received signals were cross-correlated with a replica of the transmission not only to measure time coherence but also to achieve a time separation of multipaths. This resolution of the acoustic arrivals in angle and time permitted a detailed study of individual propagation paths, and also allowed a comparison of stabilities on individual paths with the stability of the interference pattern representing the multipath composite. A large acoustic transducer was suspended from a ship allowed to drift freely during each 3-min transmission. The effect of source drift upon the changing phase of the correlation carrier, after processing, was removed by calculating the expected phase change from the ship's navigational track, established by smoothed LORAN C readings.
Technique for the Generation of Range Dependent Sound-Velocity Fields
Authors: Cornyn J. J.
Published: October 2005

A conceptually straight-forward technique useful for the generation of range dependent sound velocity fields with exact ray path solutions is described. The method involves a transformation to a rotated coordinate system. The rotation is performed on a hyperbolic cosine profile and several rays are traced through the resulting field using a revised version of the Hudson Lab Ray Tracing Program [Hudson Lab. Tech. Rep. No. 150 (June 1968)]. In this program rays are iterated from one position in the field to the next by use of coefficients in a Taylor's series expansion of the velocity field and an increment in the arc length of the ray. The program also uses control parameters that adapt the iteration increment to follow the velocity field structure. The resulting ray paths are then compared with the exact solution. The technique serves as a useful criterion for determining the ability of the program to handle horizontal gradients.
Selective Data Processing in a Large Data Bank
Authors: Roberts Bertie G.
Published: October 2005

A problem that has arisen since the advent of the computer is the retrieval of a small number of data points from a large data bank. A compacted version of the Naval Oceanographic Data Center tapes is an example of such a data bank. These consist of four magnetic tapes, which contain approximately 350000 entries or “stations.” This paper discusses the method of retrieving selected data along a proposed acoustical ray path. A computer program was written in 3800 Fortran to achieve the above objectives. A great circle route and the appropriate Marsden squares are computed between two points of interest, and acceptable stations are unpacked; the range from the origin to the station is computed and the velocity profiles are placed in ascending order. They may be print plotted for cost efficiency or written on an output tape for use in other programs, such as a contour program, which contours the velocity profiles, temperature, and salinity. These measures afford a fast access to, and a quick evaluation of, the data prior to introduction into acoustical-ray programs.