bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation of Sound by Surface Waves
Authors: Cook Richard K.
Published: November 2005

Travelling surface waves on natural bodies of water can radiate sound power into the atmosphere, although the phase velocity for surface waves is subsonic relative to the sound velocity in the atmosphere. The mathematical analysis for radiation by such waves is summarized. The analysis leads to relationships between point, line, and plane sources having travelling subsonic waves. The results for radiation from various configurations of travelling waves—e.g. circular patches, standing waves, etc.—will be presented. Those atmospheric waves whose velocity is subsonic have a “nonradiative” sound power associated with them. The results show the relationship between this latter power and the total radiated power. The corresponding analysis for surface waves having a supersonic phase velocity leads to parallel results. For surface waves travelling at exactly sonic velocity in the atmosphere, only finite wave trains are amenable to analysis.
Basic Mechanisms in Aerosol Production
Authors: Smith C. W.
Published: November 2005

The production of capillary waves and aerosols has been examined to gain some insight into the rôle played by capillary waves in the production of aerosol. Vibration-amplitude measurements have been made which suggest two things. First, viscosity is an important factor in the thresholds for the formation of capillary waves and for the production of aerosol. Second, at the threshold for the production of aerosol, one is exciting the second as well as the first unstable solution zone of Mathieu's equation, the controlling equation for capillary waves. The wavelengths in these two zones are nonintegrally related and it is proposed that this fact is basic to the production of aerosol. Cavitation effects are also observed to be present. In liquids with large viscosity indices, such as castor oil, capillary waves are not observed; one sees only the cavitation effects. It is suggested, then, that the basic controlling mechanism (capillary waves or cavitation) is determined by which threshold is reached first as one increases the vibration amplitude. [Work sponsored in part by U. S. Army, Edgewood Arsenal, Maryland.]
Some Neuronal Response Patterns in the Cochlear Nucleus of Kangaroo Rat
Authors: Rupert Allen L. , Moushegian George
Published: November 2005

Neurons within the cochlear nucleus of kangaroo rat have best frequencies that range between 200 cps-23.0 kcps. The greatest percentage, however, exhibit best frequencies below 2.0 kcps and, in terms of interval and PST-histogram analyses, may be tentatively categorized as “frequency followers” and “non-frequency followers.” The frequency followers show recurrent peaks in the interval histograms that are multiples of the stimulus period for all combinations of frequency (below 2.0 kcps) and intensity. The non-frequency followers also show peak activities, but the intervals that appear are not frequency related. Changing the parameters of the stimulus produces changes in the peak intervals, but no distributions are ever produced that show frequency-related firing patterns. This classification is only a first-order categorization; the response activity of cochlear-nucleus neurons is so varied that such a classification is too simple. [Research supported by National Science Foundation.]
A Model Study of Phase Effects on Neural Firing Rates
Authors: Kletsky Earl J. , Fraioli Anthony J.
Published: November 2005

Electronic-analog neuron models have been used to explore the dependence of neural firing rate on phase, frequency, and intensity of excitatory inputs. Results demonstrate that phase difference between two excitatory inputs can either reduce or increase firing rate without requiring an inhibitory input. Two model neurons driven with low-frequency signals (below 500 Hz) of adjustable phase were used to provide excitatory inputs to a third neuron model. The firing rate of the input units was approximately proportional to voltage except where the ratio of firing rate to frequency was 1:2, 1:1, or 2:1. In these regions, small changes in level resulted in no change in firing rate, producing a small plateau. The firing rate of the third unit depended strongly on phase only when the driving neurons were operating at the plateaus. The detailed variation of firing rate is complex but can be predicted on the basis of temporal coincidence among excitatory postsynaptic potentials (EPSP's). [Research supported by the National Institute of Neurological Diseases and Blindness.]
Electrical Stimulation of the Crossed Olivocochlear Bundle—Its Effect on Responses of Auditory-Nerve Fibers to Tone Bursts
Authors: Wiederhold M. L. , Swift S. H.
Published: November 2005

In anesthetized cats, spike responses of single auditory-nerve fibers during tone-burst stimulation were recorded for tones at different sound-pressure levels (SPL). Every other tone burst was preceded by a train of shocks to the crossed olivocochlear bundle (COCB). For each fiber two curves of number-of-spikes vs SPL were plotted, one with and one without shocks to the COCB. The two curves are nearly parallel in the region where they are rapidly changing, the curve obtained with shocks to the COCB being effectively shifted to higher SPL. The size of this shift varies considerably among fibers even within a single preparation and has been plotted against characteristic frequency, threshold, and rate of spontaneous discharge. [Supported in part by the Joint Services Electronics Program, the National Science Foundation, the National Institutes of Health, Department of Health, Education, and Welfare, and the National Aeronautics and Space Administration; and in part by a research grant and a predoctoral fellowship (to MLW) from the National Institutes of Health, Public Health Service.]
Cortical Responses of Unanesthetized Cat to Brief Tone Bursts Masked by Narrow-Band Noise
Authors: Glaser Edmund M. , Suter Charles M.
Published: November 2005

Responses of the primary auditory cortex of the unanesthetized cat have been obtained from chronically implanted epidural electrodes. The tone-burst envelopes were Gaussian in shape with a bandwidth equal to approximately one quarter the critical bandwidth for the particular stimulus frequency employed. The masking stimulus was narrow-band Gaussian noise whose bandwidth was variable in steps from several hertz to several kilohertz. The center frequency of the noise was adjustable but generally set to the same frequency as that of the tone burst. The noise power was maintained constant while bandwidth was varied from much narrower to much wider than the critical bandwidth. Stimulation was binaural in a free field. Average response techniques were employed. The cortical responses obtained tend to conform to predictions based upon critical-band theory. There are, however, some interesting dependencies of masking effectiveness on noise bandwidth which do not seem explainable by this theory. [Work supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Response of Cells in the Cerebellar Cortex to Clicks
Authors: Nahvi M. J. , Shofer R. J.
Published: November 2005

Poststimulus-time histograms of cerebellar single-cell responses to click stimulation were obtained in locally anesthetized or nembutal-treated cats. Commonly, an early sharp peak was followed by an interval during which the firing level falls below the level of spontaneous activity (inhibitory interval). The response latency varies from 8–40 msec for different cells. The inhibitory interval, which is sometimes followed by a rebound, may last up to several hundred milliseconds. Pairs of clicks were also used to investigate increases or decreases in the probability of firing to a second click for variable intervals after presentation of the first click. Double-click response patterns correlate with the characteristic latency and time course of unit firing and suggests at least two different classes of unit behavior are found in these studies. [Work was supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare, the Joint Services Electronics Program, the National Science Foundation, and the National Aeronautics and Space Administration.]
On Wave Propagation in an Elastic Plate with Nonmixed Edge Conditions
Authors: Miklowitz Julius
Published: November 2005

Within the framework of the “exact” linear theory, an important class of wave-propagation problems in elastic waveguides, involving nonmixed edge conditions (like stress or displacement), have remained unsolved. Basically, this is because known separation methods (classical or integral transforms) do not “ask” in a natural way for the given edge (and corner) information. A means for solving some problems in this class for the semi-infinite plate is presented here. In the method a Laplace transform is used on the propagation coordinate, say x. Exploitation of the boundedness condition of the solution, at χ→∞, generates two coupled integral equations for the edge (and corner) unknowns (displacements and strains), which depend, parametrically, on those complex wave-number roots of the governing Rayleigh-Lamb frequency equation representing unbounded waves. In some cases, these equations can be reduced to a set of algebraic ones with the aid of plate-thickness-eigenfunction expansions for the edge (and corner) unknowns. Numerical solution for the eigenfunction coefficients then determines the transformed solution of the problem, which can be inverted through known techniques. The problem of a plate with a built-in edge, subjected to symmetric face loadings, is treated as an example.
Studies in Articulatory Coordination
Authors: Öhman Sven E. G.
Published: November 2005

The present paper summarizes certain recent results of research in speech production. A model of coarticulation is outlined in which vowel and consonant production is represented by independent parameters in such a way that simultaneous vowel and consonant gestures may be reproduced quantitatively. The model is found to compare well with cinéradiographic data of real speech. A set of acoustic measurements on vowel target undershoot in consonant-vowel-consonant utterances due to variations of speaking tempo can also be accounted for in terms of a simple extension of the model. In this version, the parameter specifications corresponding to the phonemic constituents of an utterance are rectangular pulses. The physiological plausibility of the discrete-instruction theory implicit in this modeling work is discussed in relation to data obtained from electromyographic measurements. It is found that this theory leads to certain assumptions about neural inhibition, adaptation, and feedback in speech production. The discussion of these assumptions terminates the paper.
New Facilities for Transmission-Loss Measurement on Massive Materials
Authors: Stekman William
Published: November 2005

Four interconnected reverberation rooms have been added to the existing facilities at the Riverbank Acoustical Laboratories. All the rooms have adequate dimensions and diffusion mechanisms to meet the revised ASTM designation E 90-66 T. The justification for this addition was the need to study the effects of aging on massive specimens. Samples up to 150 lb/ft2 can be handled within portable frames somewhat larger than 14×9 ft in size, and floors up to 14×20 ft in size can be measured in situ. Measurements are validating the suspicion that both size and curing must be considered when examining test results. Heavier specimens are particularly prone to yield optimistic data when smaller sizes are examined.
Footstep Noise Through Wood Joist and Concrete Floors in Buildings
Authors: Olynyk D. , Northwood T. D.
Published: November 2005

In a previous paper, a technique was described for rating floors for impact-sound insulation by subjective observations of the level of tailored random noise required to mask transmitted footsteps. The objective was to compare subjective ratings with impact machine ratings. The initial study was done on variations of a reinforced concrete-slab floor under laboratory conditions. Further observations have now been made in typical buildings, with special emphasis on wood-joist floors. For the whole study, the correlation between subjective ratings and machine ratings is poor if the FHA type of reference contour is used. The effect of this contour is to make the results, especially for concrete floors, quite dependent on the high-frequency noise produced by the machine. A better correlation is obtained by altering the present FHA reference contour to a flat one, thus reducing the emphasis on high frequencies.
Effective Directivity Pattern of a Violin Played by a Standing Performer
Authors: Crabtree John B. , Watters B. G.
Published: November 2005

The directivity pattern of a violin played by a standing performer has been measured. The instrument was played throughout its frequency range and on each of its strings, and data were taken for a number of directions of radiation. The levels were averaged over third-octave bands. The effective directivity pattern measured in this way can be understood in terms of a substantially nondirective source that is acoustically shielded by the body, head, and arms of the performing violinist.
Loudness Functions Transformed by Inhibition
Authors: Stevens S. S. , Guirao Miguelina
Published: November 2005

In both vision and hearing, a masking or inhibiting stimulus increases the slope (exponent) of the power function that relates sensation to stimulus [J. Acoust. Soc. Am. 39, 725–735 (1966)]. The power transformation applies only to the inhibited part of the function, where the signal is fainter than the masking noise. Where the signal equals the noise, the function shows a discontinuous knee. Experiments were undertaken to see whether the loudness of a tone of 1000 Hz in a white noise would follow a model based on a simple principle concerning the signal-to-noise ratio (S/N) at two locations on the masked-loudness function. The model assumes a constant S/N both at the effective threshold and at the knee where the inhibited function meets the uninhibited function. The data accord with the slopes (exponents) generated by the model. The same model gives a fairly good account of the recruitment functions for ears suffering from cochlear involvement (e.g., Ménière's disease). Regardless of degree of hearing loss, loudness recruitment reaches normal when the tone (1000 Hz) is about 30 dB above the affected threshold.
Several Experiments on Central Factors in Auditory Fatigue
Authors: Smith Richard P. , Loeb Michel
Published: November 2005

Experiments were performed to assess the influence of attentive or alerting factors on temporary threshold shifts (TTS) with exposure times, frequencies, and alerting factors different than those employed in previous experiments. When subjects were exposed to a 1 kHz, 90- or 100-dB tone for ten minutes, while engaged in either mental arithmetic or reverie, no significant differences in TTS at 1 kHz were observed. Similarly, there was no significant difference in a subsequent experiment in which exposure time was 15 min and the computations were performed with pencil and paper. When subjects tracked their thresholds for a 1000-Hz tone in one ear and exposed for 15-min to a 90- or 100-dB, 1,000-Hz tone in the opposite ear, TTS was significantly greater than it was following exposure in a reverie condition; this effect was subsequently replicated. Finally, subjects were administered a placebo, a dose of 0.21-mg/kg d-amphetamine sulphate, or 1-mg/kg secobarbital during a similar 15-min exposure; differences were nonsignificant.
Effect of Auditory-Cortex Ablation upon Discrimination in the Monkey
Authors: Elliott D. N. , Frazier L. A.
Published: November 2005

Using a 2-AFC procedure, rhesus and cynomolgus monkeys were trained on a battery of discrimination tests. Bilateral ablations of either the classical or the classical and accessory auditory areas were then created. Following this, postablation discrimination performance was determined and compared with preablation performance. Not all types of discrimination tasks suffered equally, and there appears to be a low correlation between initial ease of learning a discrimination and the extent to which that discrimination suffered from the ablation. [This research supported by grant from the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
An Investigation of Some Possible Behavioral Correlates of Rasmussen's Efferent Olivocochlear Bundle
Authors: Trahiotis Constantine , Elliott Donald N.
Published: November 2005

Although reliable anatomical and electrophysiological data have established the inhibitory nature of the efferent olivocochlear bundle (OCB), sparse attempts to explicate their contribution to the hearing process have been unsuccessful. This study was concerned with the possible rôle that the crossed OCB may play in the determination of absolute threshold, effective masking, and temporary threshold shifts (TTS). Six cats with their right ears destroyed were utilized in a double-blind experiment. Absolute thresholds were determined at octave intervals from 125 to 16 000 Hz. Spectral levels of broad-band noise were adjusted to produce 20, 30, and 40 dB effective masking for pure tones of 500, 1000, and 2000 Hz. TTS was induced by a 107-dB broad band noise of ten-minutes duration. Two independent Latin-square designs were used to evaluate TTS at 1000, 2000, 4000, and 8000 Hz twice after each exposure. Each animal was exposed on four different occasions. The anatomical and behavioral results are discussed and compared to the extant literature.
Unconditioned Galvanic Skin-Response Magnitude as an Index of Frequency-Intensity Relationships in the Hearing of the Mouse
Authors: Gill Alan J. , Berlin Charles I.
Published: November 2005

Two experiments on the CBA-J mouse demonstrate that the unconditioned galvanic skin-response (GSR) magnitude elicited by tones ranging from 2 kHz to 40 kHz were largest between 5 kHz and 20 kHz. This orderly relationship held at intensities of 60, 70, 80, 90, and 100 dB SPL. The growth of response magnitude with intensity followed a power law (100.17–0.22, depending on frequency), and is probably related to the nature of the mouse's vocal output under stress, which has its peak intensity at 10 kHz. [Supported by grants from the National Institute of Neurological Diseases and Blindness.]
Research towards Improved Machine Recognition of Syllables with Initial /l/, /m/, /n/, and /r/
Authors: Jamison Walter H.
Published: November 2005

Previous work in the field of machine recognition of speech has shown that syllables can be categorized into groups based on similar characteristics and difficulty of detection. This paper discusses research aimed at finding improved means of separating syllables with initial /l/, /m/, /n/, or /r/. A study of the liquids /l/ and /r/ and the semivowels /m/ and /n/ was carried out utilizing a Sonagraph, and a Visicorder in conjunction with a multichannel filter set. An analyzer system has been constructed that provides for intercomparison of frequency channels and for logic schemes that separate /l/, /m/, /n/, and /r/ from other initial sounds and from one another. Contained in the analyzer system is a spectrum shaper consisting of contiguous 13-octave filters covering the audio spectrum. The outputs from these filters can be combined in any manner to provide various frequency channels. Each channel contains a logarithmic converter, envelope detector, summing amplifier, threshold circuit, and relay driver. A relay memory provides logic and a digital output from the analyzer.
A Limited-Vocabulary Adaptive Speech-Recognition System
Authors: Ross Paul W.
Published: November 2005

This paper describes a recently developed adaptive speech-recognition system. The system quantizes the spectrum of the speech signal in respect to frequency, amplitude, and time. A 20-bit binary feature matrix is obtained for each utterance. Each feature matrix, identified as to the word spoken, may be stored in a disk memory. With the system in its present form, up to 256 reference samples for 10 classes of words may be accumulated. When the desired number of reference samples have been obtained, the system may be used for the recognition of speech. Test words are spoken and quantized as before. The new feature matrix is compared serially with the contents of the disk memory. The degree of difference between each reference sample and the test sample is determined. If this difference is sufficiently small, the identifying information on the reference sample is decoded and a visual display actuated. This system, with the aid of the operator, adapts itself in an optimum manner to the characteristics of the speaker “training” the system. The contents of the memory may be readily changed for a different speaker or vocabulary.
Performance of a 200-Syllable Communication System
Authors: Rogers Edward S. , May Everett G.
Published: November 2005

A 200-syllable communication system has been built and tested that automatically analyzes, recognizes, and encodes speech at the transmitter. At the receiver, the digital code is used to synthesize speech from prerecorded speech elements. The result is highly intelligible speech transmitted at the extremely low bit rate of 8 bits/sec. This system is the result of several years of research on speech processing directed toward discovering the useful, invariant information-bearing portions of the acoustic signal. The analyzer processes speech spoken one syllable at a time and transmits an eight-bit code for each syllable. The features used to derive the code include intrasyllabic pauses, voiced-to-unvoiced sound transitions, rate of growth and decay, duration, and relative spectral information. The entire communication system has been completed and the memories have been charged to store the codes for 200 syllables. An overall performance evaluation has been made using four speakers over a ten-day period with a 24 000-voicing-test sample. The system responded to 91% of the voicings with an accuracy of 80%.
Extraction of the Spectrum Envelope for Voiced Speech Segments
Authors: Mermelstein Paul
Published: November 2005

A previously suggested method for smoothing the narrow-band spectra of voiced speech segments by “low-pass filtering” the logarithm of the power spectrum [M. R. Schroeder and A. M. Noll, “Recent Studies in Speech Research at Bell Telephone Laboratories. I,” Paper A21 in Proceedings of the Fifth International Congress on Acoustics, Liége, Belgium, 1965, D. E. Commins, Ed. (Georges Thone, Liége, 1966)] has been found inadequate for high-pitched female voices. Low-pass filtering, with a cutoff “quefrency” (independent variable in the Fourier-transform domain of power spectra) below the pitch-period value, may result in elimination of peaks due to the formant structure. An approximation to the spectrum fine structure (due to the quasiperiodic excitation of the vocal tract) is generated by requiring its Fourier cosine transform to match that of the log power spectrum of the speech signal in the immediate neighborhood of the pitch peak, but to have no other significant quefrency components. By subtraction of this approximation to the fine structure from the log power spectrum of the speech signal, an improved spectrum envelope is obtained. A formant-tracking algorithm, operating on spectral-envelope data so derived, yielded correct results where otherwise serious errors would have been committed. Several examples for male and female speech are given.
Differential Sound Spectrograph
Authors: Lawrence Walter
Published: November 2005

In the normal form of the sound spectrograph, the density of the marking of the spectrogram is controlled by the rectified output of the heterodyne filter. In the differential spectrograph here described, the rectifier is replaced by a discriminator, or frequency demodulator. The density of marking of the spectrogram is then a function of the differential coefficient of the spectral power with respect to frequency. Positive values of the coefficient are indicated by normal marking; negative values are distinguished by an identifying modulation. The spectral maximum appears as a narrow white line separating the positive from the negative regions. The device has been found useful for the precision determination of formant frequencies in speech.
Experimental Investigation of a Sub-Bottom Reflecting Layer in the Deep Ocean
Authors: Fox G. R.
Published: November 2005

The existence of a subbottom reflecting layer is indicated by acoustic measurements made about 50 miles south of Bermuda, in the vicinity of moored hydrophones several hundred feet above the bottom. A transducer located on the bottom at a range of 2400 ft generated acoustic signals in the frequency range 400–1000 Hz. Interference effects were observed in the reception at the various receivers. Interpretation of the data in terms of a simple model indicates that there is a subbottom reflecting layer more than 100 ft below the nominal ocean bottom. [Work was supported by the U. S. Naval Electronic Systems Command.]
Backscattering from the Deep Sea Bed at Small Grazing Angles
Authors: Buckley J. P. , Urick R. J.
Published: November 2005

Measurements have been made of the backscattering of explosive sound from the sea bed with both source and receiver located at a great depth in the deep sea. Standard U. S. Navy Mk-59 sound signals detonating at depths near 14 000 ft, together with a deep nondirectional hydrophone, were employed. The measured levels of backscattering were converted to backscattering strength by the appropriate conversion formula [J. Acoust. Soc. Am. 34, 1721 (1962)] and compared with the Lambert's “law” expression found by Mackenzie [J. Acoust. Soc. Am. 33, 1498 (1961)] to hold for the deep sea bed at larger grazing angles. A computer program was developed to allow for the fact that the explosive charges and hydrophone were offset horizontally and vertically.
Use of Selective Equalization for Feedback Suppression
Authors: Boner C. P.
Published: November 2005

The paper summarizes results of measurements and observations made in about 200 rooms with sound re-enforcing systems. Behavior of sine-wave room response near major feedback modes is described. The effect on feedback of broad-band equilization is shown. The role of narrow-band filters relative to control of ring modes and excessive reverberation is set out. The existence of a limit to system gain before feedback, set by the geometry of the situation and other parameters, is discussed, along with the concomitant change in the nature of the feedback modes as the limit is approached. The observed effect of temperature on the frequency of feedback and ring modes is reported. The degree of nonlinearity between the irregularity of room response at these modes and the insertion loss of a filter to eliminate the irregularity is described.
Digital Geoacoustic System Technology
Authors: Burg Kenneth E.
Published: November 2005

A geoacoustic system consists of acoustic sources, sensors, and data processors. High-explosive sources such as dynamite are being replaced by mechanical, electrical, hydraulic, and thermal sources. Data are now recorded directly on computer-compatible digital tape with 1-msec sampling of 32 channels, and in some cases as many as 56 channels. Principles of statistical-information theory are applied by high-speed solid-state computers, to develop an acoustic signal in the presence of noise. Multiple-channel filters and arrays of sources and detectors making use of the noise coherence are also used to improve signal-to-noise ratios. Computer processes, such as deconvolution, dereverberation, etc., are designed and applied within the computer from analysis of the acoustic data. Auto- and cross-correlations, power spectral estimates, and coherence and covariance are used in filter design using Weiner least-mean-square-error concepts. Adaptive filters are a newer and promising approach to signal-to-noise improvement and signal enhancement.
Analog System for Analyzing Infrasonic Signals Monitored in Field Experimentation
Authors: McGahan L. C. , Fehr Uri
Published: November 2005

Large quantities of ultralow-frequency acoustic data, accumulated over long periods of time, can be analyzed by several methods. Preliminary analysis of the analog waveform determines specific areas of primary interest prior to digital-computer analysis. Data of no consequence can be discarded, or their worth graded, to scale their importance for computer processing. This technique also provides a means of expediting initial findings and primary conclusions can be deduced. This study was conducted by the University of California, Los Angeles and entitled “Ionospheric Disturbance Experiment.” The raw tape-recorded data are played back through an electronic system. Some important parts of this system are narrow-bandpass filters and a Missalyzer (sound spectrograph). Some sample results are summarized.
VLF Adjustable Acoustic Band-Pass Filter Microphone System
Authors: Beavers Bob R. , Meyer Norman J.
Published: November 2005

A microphone system has been designed and tested for use in measuring VLF atmospheric-pressure variations. The system is a cylinder of over-all dimensions 5 in. in diam and 6 in. long, containing an inlet tube, two volumes connected by a bypass tube, the microphone, and its electronics. Essentially, a capacitor microphone (with very low self-noise electronics) has an acoustically transparent back electrode. Each surface of the membrane is exposed to an acoustic low-pass filter, i.e., a tube and a volume. Fixed parameters are: the 1-in.-diam 0.25-mil-thick stainless-steel diaphragm that resonates around 1 kHz; the low-frequency volume of 1000 cm3, and the high-frequency volume of 50 cm3. The variable parameters are the tube diameters (10 to 20 mil) and lengths (up to a few inches) that serve to establish the bandpass range. The system has been pistonphone calibrated at LTV Research Center and UCLA, with a nominal sensitivity (adjustable) of −58 dB re 1 V/μbar. The operational range can be selected within 0.001 to 100 Hz. The system has been packaged in a weather-resistant configuration.
Approaches to the Design of a Temperature-Independent Adjustable Fluid-Flow Resistor
Authors: Bedard A. J.
Published: November 2005

Flow resistors are used in many designs of infrasonic instrumentation. Changes in temperature will cause equipment response variations resulting from changes in flow resistance. Approaches to the design of a temperature-independent adjustable fluid-flow resistor are reviewed. Results of measurements at laminar flows, on a prototype resistor are presented.
Theory of Light Scattering in Doubly Relaxing Liquids
Authors: Nichols W. H. , Carome E. F.
Published: November 2005

The theory developed by R. D. Mountain [J. Res. Natl. Bur. Std. U. S. 70A, 207 (1966)] to describe the scattering of monochromatic light from density fluctuations in a liquid where a singly relaxing internal degree of freedom is weakly coupled to the translational modes has been extended to the case of a liquid exhibiting double relaxation effects. The predicted spectral distribution of the scattered light and velocity dispersion are presented. The applicability of the results in current experimental studies of benzene and other liquids is considered. [Research supported in part by the Office of Naval Research.]
Combination Tones and Auditory Nonlinearity
Authors: Goldstein J. L.
Published: November 2005

A psychophysical study of the combination tones that are perceived with a two-tone stimulus suggests that cochlear mechanics may contain an essential nonlinearity. The amplitude and phase of various combination tones were measured with a pitch-cancellation method. The most prominent combination tone obtained with a two-tone stimulus, f1 plus f2, has a frequency 2f1−f2. Its relative amplitude decreases sharply with increasing stimulus frequency interval and depends primarily upon the ratio of the levels of the two stimulus tones, but not upon their absolute levels. At frequency intervals of 10%, the relative level of this combination tone was typically 15%–20%. Combination tones with frequencies in the third harmonic region of the stimulus tones were not perceived, and their absence could not be attributed to masking by the stimulus tones. These results are similar to the distortion that is produced by loading a tuned circuit with a peak detector. Therefore, the possibility that the cochlear employs a mechanical peak detector is supported.
Underwater Hearing Thresholds
Authors: Brandt John F. , Hollien Harry , Thompson Carl
Published: November 2005

The audibility threshold performance of the human ear submerged in water at eardepths of 12 and 35 ft is compared to its performance in air. Threshold SPLs at 125, 250, 500, 1000, 2000, 4000, and 8000 Hz from five male and three female divers wearing open-circuit SCUBA equipment were obtained by the Békésy technique. Differences between water- and air-conduction thresholds ranged from 18 dB SPL re 0.0002 μbar at 125 Hz to 56 dB at 8000 Hz. Water-conduction thresholds ranged from between 58 and 74 dB SPL with maximum sensitivity around 500 Hz. Maximum sensitivity for air-conduction thresholds was obtained at 2000 Hz. Slightly higher thresholds were obtained at the 35-ft depth than obtained at the 12-ft depth (about 1 dB at 250 Hz and 10 dB at 8000 Hz). Threshold SPL for male divers was lower than female divers below 1000 Hz but higher than female divers above 8000 Hz in both air and water. [Research supported in part by Office of Naval Research, Code 454, and National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Auditory Thresholds in Adrenal Cortical Insufficiency
Authors: Henkin Robert I. , Bartter Frederic C. , McGlone Robert E. , Daly Robert L.
Published: November 2005

It has been previously shown that patients with untreated adrenal cortical insufficiency (ACI) exhibit decreased detection thresholds for taste and smell. These thresholds return to normal after treatment with carbohydrate-active steroids (CAS) is instituted. The purpose of the present study was to compare auditory detection thresholds in eight patients with ACI, aged 14–57, with those in 25 normal volunteers, aged 18–61. Sinusoidal tones of different frequencies were presented by a calibrated oscillator, attenuator, earphone system, and thresholds determined by the method of limits. Auditory detection thresholds in patients with ACI were significantly lower than those in normal subjects over most of the frequency range, but especially in the region 1000–2000 Hz. Increased detection sensitivity was found in all patients, irrespective of age; it appeared independent of changes in extracellular sodium or potassium. Decreased auditory thresholds returned to normal in all patients after CAS therapy was reinstated. Results indicate that CAS play a significant role in control of auditory sensitivity.
Relation between Cerebral Blood Flow and Time Required for Tonal Sensation in Conditioned Rhesus Monkeys
Authors: Creel Warren , Powers Samuel R. , Boomsliter Paul C.
Published: November 2005

Three rhesus monkeys were conditioned to respond to bursts of 500-cycle tone and ignore bursts of white noise. They also ignored tone bursts of 10 msec and under, a duration that would be heard as noise by a human subject. After surgery to alter cerebral circulation by producing a subclavian steal (arterigrams are presented), they showed a many-fold increase in time required to produce tonal response, comparable to abnormal time requirements found in human patients with confirmed impairment in vertebral artery circulation. Before and after subclavian steal, measurements were made of blood flow in specific brain areas of conscious monkeys using permanently implanted double-thermistor probes. Results are presented. Evoked potentials before and after subclavian steal are presented. After surgery to correct the subclavian steal, the time requirements for tonal sensation returned to near normal. [Supported in part by the National Institutes of Health, U. S. Public Health Service, Department of Health, Education, and Welfare.]
Determination of Hearing Aid Specifications for Each Instrument User
Authors: Wallenfels Herman G.
Published: November 2005

Presented is a method of determining the amount of amplification necessary to reach the optimal hearing level of each individual case of hearing loss. The basis for the calculation is the conventional audiogram as drawn by every otologist and audiologist—augmented by a narrow-band noise tolerance study which indicates the upper limit of amplification for each year. This paper is the outcome of a 3-yr study of the actual sound levels at which hearing-aid users were operating their instruments—both successfully and unsuccessfully. All measurements were made at the tip of the users' personal earmold at his actual listening level. These measurements were then compared with the audiometric findings in each case. This evolved into a formula which is useful for presetting a hearing aid on the exact level at which the user will feel comfortable and function best. This is most important in fitting cases of pure sensorineural involvement when the patient is not able to judge the optimum level himself. The chief beneficiaries are the aged and the congenitally deaf children. Also presented are guidelines by which those cases can be spotted which are either completely unfittable with a hearing aid or in which only partial or limited success can be expected. The paper is amply illustrated with slides made of the measurements of actual cases.
Aeolian Tones Associated with Resonant Vibration
Authors: Leehey Patrick
Published: November 2005

Experiments were conducted on taut wires stretched normally across an open jet test section of a low turbulence wind tunnel at various subsonic wind velocities. Measurements were taken of radiated sound-pressure level, lateral spatial correlation of wake velocity fluctuation, end-support acceleration, wire damping, and oscillatory lift on the wire for various ratios of vortex shedding frequency to wire resonant frequency for the first four wire-resonant frequencies. The radiated sound was essentially dipole at the Strouhal frequency of vortex shedding. Its intensity increased as U20 as the Strouhal frequency approached a wire resonant frequency from below. This is markedly in excess of the U6 dependence predicted by Phillips [J. Fluid Mech. 1, Pt. 6 (1956)] for rigid cylinders. The difference results from the influence of resonant vibration upon the root-mean-square sectional lift coefficient and the correlation length of vortex shedding. [Work carried out under General Hydromechanics Research Program administered by the David Taylor Model Basin, U. S. Navy.]
Response of a Simply Supported Beam to a Three-Dimensional Reverberant Acoustic Field
Authors: Crocker Malcolm J. , White Robert W.
Published: November 2005

A study of the expression for the response spectral density of linear systems to random pressures shows that the response problem essentially reduces to evaluating the joint acceptance of the system with the pressure field. A novel method using a coordinate transformation is presented. This method enables the joint acceptance for a simply supported beam with a pressure field, which has a spatial pressure correlation function which is easily described mathematically, to be determined in a simple manner. The joint acceptance for a beam in a reverberant acoustic field as a function of mode number and nondimensionalized frequency parameter (beam length/wavelength) has been computed for the first 16 modes. An engineering approximation for the joint acceptance for a simply supported flat plate in a reverberant acoustic field may be obtained from the beam results. The method can also be used to determine beam and flat-plate joint acceptance with a turbulent boundary-layer pressure field and with acoustic waves in a very simple manner.
On the Effect of Spin on the Vibration Characteristics of Cylindrical Shells
Authors: Kurzweil Leonard , Shulman Yechiel
Published: November 2005

The phenomenon of the rotation of the node lines of the vibratory modes of a spinning cylindrical shell, at a rate different from the spin rate, has been known for some time. Previous investigators, however, have studied different aspects of this problem utilizing various degrees of approximations. In studying all the effects of spin on the vibration characteristics of such shells, this paper isolates the separate centripetal and Coriolis effects on the various modes, determines their nature and severity, and provides some useful closed-form expressions for the vibration frequencies and nodal rotation rates. The results of the present study indicate that the effect of the spin is most important for the flexural modes and is insignificant for the tangential, axisymmetrical and beam modes of the shell. The effect of the centripetal acceleration, as expected, is to stiffen the shell in all its circumferential deflection modes while the Coriolis acceleration is identified as the cause of the phenomenon of the rotation of the node lines. The effects of this phenomenon are most pronounced for modes of low circumferential mode numbers and diminish rapidly with increasing mode numbers.
Dynamical Interaction Across the Common Boundary of a Hemispherical Shell and a Cylindrical Shell, Smoothly Joined. Extension to General Axisymmetric Shells
Authors: Schipper J. F.
Published: November 2005

A composite shell configuration consisting of hemisphere and cylinder—of identical thicknesses, mean radii, and material properties—smoothly and rigidly joined at the common boundary, is considered. The system is assumed to be vibrating, not necessarily periodically. The five force equilibrium equations for each shell are compared at their boundary, subject to four stress and moment “matching” conditions there plus equality of displacements u (longitudinal), v (circumferential), w (radial), and longitudinal derivative of w. By some intricate arguments one infers that: u and the longitudinal derivative of v vanish at the common boundary (for both shells), while the longitudinal derivative of w is a function only of time (axisymmetry is inferred). Invoking the thin shell assumptions in an approximation, additional (proximate) results are obtained: v, w, and the longitudinal derivative of u also vanish at the common boundary. The possibility of considering the shells as vibrating independently is considered: it is neither (fully) justifiable nor refutable here. More general composite configurations—two vibrating shells of revolution with identical principal curvatures in the circumferential direction and unequal curvatures in the longitudinal direction—are considered. The first three results above (cylinder-sphere configuration) are re-obtained. Additional results require further approximations.
Energy Method for Determining Natural Frequencies and Associated Mode Shapes of Truncated Conical and Parabolic Shells
Authors: Soo P. P.
Published: November 2005

An energy method is presented for calculating natural frequencies of thin, truncated conical shells or parabolic shells of revolution. Extensional and inextensional vibrations are treated separately, and the corresponding (approximate) mode shapes determined. For the inextensional case, the vanishing of the middle surface strains yield solutions for the displacement field in the three principal directions. The displacement expressions are used in the appropriate energy integral, together with Lagrange's method, to obtain an algebraic equation for the oscillatory frequencies for each mode. For the extensional vibrations, the displacements are written as orthonormal series of functions, selected to match the boundary conditions imposed. The (unknown) series coefficients are obtained by minimization of the energy integral (Ritz procedure), and a set of algebraic equations for the frequencies is obtained. Convergence of the orthonormal series is discussed. Finally, the square root of the sum of squares of corresponding inextensional and extensional frequencies, regarded as a measure of the correct natural frequencies for the shell, is examined.
Near-Field and Far-Field Radiation from an Experimental Electrically Steered Planar Array
Authors: Martin Gordon E.
Published: November 2005

Current interest in electrically steered transducers has led to new experimental and theoretical work. Several years ago extensive measurements were made on a large planar broadside array. Experimental results in the near and far fields agreed to excellent accuracy with theory based upon the assumption of an infinite, plane rigid baffle. This paper includes new experimental results for a similar transducer array which was electrically steered to seven different angles from broadside to endfire. These results are compared with theory based upon the infinite baffle assumption. It is demonstrated that both near-field and far-field errors increase as the steering angle approaches the endfire case. It is concluded that the effects of a finite baffle must be considered in any theory that is to be used for arrays steered to large angles from broadside. This observation is also important relative to radiation impedance computations.
Effect of Baffle Width on Beam Patterns of Planar Arrays
Authors: Douglass Richard E. , Gruber George J.
Published: November 2005

Beam patterns of close-packed arrays of rectangular pistons mounted in a rigid planar baffle are investigated for various array and baffle widths. Computed results are obtained from a model in which the array is positioned in a ribbon- or striplike baffle, i.e., the baffle has finite width but is infinite in height and infinitesimal in thickness. The array is steered by element phasing to direct a beam in given directions in the plane perpendicular to the infinite dimension of the baffle. Beam patterns are computed in this plane. For each array considered, the finite-baffle beam pattern is compared with that for the same array in an infinite baffle. The computed results demonstrate that the beam pattern of an array steered to broadside is not strongly dependent on the baffle width. However, as the array steering approaches endfire, the baffle width has an increasing effect on the directivity of the array.
Design of Optimal Transducer Arrays
Authors: Suchman D. F. , Waren A. D.
Published: November 2005

A generalized approach to the design of practical transducer arrays using recently developed mathematical optimization techniques is presented. The method generates the optimal array configuration and sets of element excitations to produce simultaneously a number of different three-dimensional patterns, which may be specified in any arbitrary planes. To ensure a practical design, the procedure is not limited to isotropic sources; it can also accommodate measured directivity characteristics of individual radiators. In addition, realistic bounds for all parameter values can be included. These variables are the location of the individual modules comprising the array and the excitation (amplitude and phase) of each module for each pattern. A computer program was written to implement this method, and two examples and of its use are presented: The first example treats the design of a linear array of eight isotropic radiators and shows that improvement over Dolph-Chebychev shading is possible; the second deals with a 12-element planar array required to produce, simultaneously, three patterns, each of which is specified in three planes.