bluuebunny/crossref_metadata_2025 huggingface dataset:
Whole-Nerve Action Potentials as an Index of Severity of Cochlear Injury in Chinchilla
Authors: Eldredge D. H.
Published: October 2005

The N1 peak voltage of the AP response to a wide-band click is proving to be a sensitive index to injuries following exposures to noise. Over a wide range of injury, changes in magnitude and sensitivity of N1 responses correctly rank ears with respect to amount of loss of hair cells. With loss of 100–300 hair cells, the voltages are one to two standard deviations below normal means at all levels of the input-output function. The voltages are down two to three standard deviations with 300–800 missing cells. With greater losses the input-output functions are also shifted to a lower sensitivity. A small response can still be elicited 70 dB above normal visual detection levels when an estimated 6800 out of 9100 (75%) hair cells are missing. Differential masking of the N1 responses with selected bands of noise provides additional information concerning the locations of the injuries.
The Channel Capacity of the Ear as a Function of Frequency
Authors: Corliss E. L. R.
Published: October 2005

The channel capacity of the ear as a function of frequency can be computed by a technique similar to that in an earlier paper [E. L. R. Corliss, J. Acoust. Soc. Amer. 50, 671–677 (1971)]. The legitimacy of this computation rests upon the justification that sufficient variables are involved to permit replacement of actual statistical distributions by normal distributions. This legitimacy is tested by comparing the predicted growth of intelligibility of individual phonemes as a function of level above threshold with experimental results. The channel capacity of the ear shows a broad maximum in the frequency range of 3–6 kHz. Taking into account the duration of speech sounds as a function of frequency, one finds that each phoneme tends to convey the same number of bits over the range from 300 Hz to 4 kHz. However, many more phonemes are uttered per unit time at the higher frequencies, so that the rate of information transfer is higher. This explains to some extent the empirical observation that the high-frequency limit necessary for accurate communication depends upon redundancy of the material. One ought to reconsider the convention that the spectrum above 3 kHz is relatively irrelevant for speech communication when unfamiliar speech material must be recognized.
Further Investigations of Reaction Time to Clicks in Sentences: Linguistic Structures Emerge with Extended Processing
Authors: Abrams K. H.
Published: October 2005

This study reports an experimental and theoretical resolution to two seemingly contradictory findings in the literature of attentional strategies of sentence processing. Abrams and Bever (1969) reported that reaction time (RT) to brief tones located at the linguistic boundary between major sentence constituents was slower than reaction time to tones near the major break within major constituents. Holmes and Forster (1970), using different sentences and different tone locations within constituents found that RT to tones between constituents was relatively fast. The present study used practiced subjects and a frequency balancing technique that equalized the conditional probability of a tone occurring in each of four locations given that a tone had not occurred previously in the sentence. In Condition I, the instructions emphasized fast reaction time and the results looked like the findings of Abrams and Bever. In Condition II, the instructions stressed written recall accuracy and the results replicated the Holmes and Forster findings.
Amplitude Compression. I. Speech Intelligibility in Quiet with Normal and Pathological Hearing Groups
Authors: Vargo S. , Carhart R.
Published: October 2005

The theoretical contribution of amplitude compression to the enhancement of speech intelligibility for pathological hearing groups remains unresolved. Previous investigations by Caraway and Carhart [J. Acoust. Soc. Amer. 41, 1424 (1967)] and Burchfield et al. (1971) have shown contradictory findings on this topic. Although this study essentially replicates the two previous investigations, it employs a more advanced compressor system with an instantaneous attack time (100 nsec); moreover, word triplets are delivered to listeners at three sensation levels (SLs), 10, 20, and 30 dB. The findings are discussed in terms of previous studies as well as in the usability of amplitude-compressed phonemic information at low SLs. [Supported by Special Research Fellowship Grant of NINDS.]
Acoustic Alterations of Speech When Processed through Air Force Aircraft Communication Systems
Authors: Gasaway D. C.
Published: October 2005

The acoustic composition of voiced speech signals received at a distance of 1 m (normal speech) is compared with those picked up by standard Air Force lip microphones that are transmitted via standard electroacoustic communication systems. The acoustic composition of speech used in Air Force ground and airborne operations is significantly different from that associated with normal live voice communication. Many voiced and voiceless speech components that constitute minimal acoustic amplitude in normal speaking situations undergo significant amplitude alterations when picked up by lip microphones. The author noted that pilots and other rated personnel frequently report that several transition flights are required before the speech communication messages are fully intelligible. This phenomenon has been studied and analyses of actual airborne speech communications are used to identify and define acoustic alterations that necessitate learning a new (or altered) type of speech. Voice prints of English vowels, diphthongs, and consonants are used to illustrate acoustic changes that exist between normal conversational speech and speech picked up by lip microphones. The results of this research suggest that the acoustic alterations created by picking up speech at the lips may increase intelligiblilty after the listener has learned how to process the signals accurately.
Word Intelligibility of U. S. Navy Aircraft Radios
Authors: Webster J. C.
Published: October 2005

Two types of in-flight recordings were made: (1) actual radio/intercom voice messages on operational flights and (2) standardized word lists read by flying observers on routine test flights. An experienced civilian listener who lacked any experience or knowledge of air operations transcribed 34% of the operational recording, an experienced U. S. Navy Chief Petty Officer Air Controller 68%, and an experienced U. S. Navy aviator 90%. The standardized word lists were listened to by typical U. S. Navy enlisted men. The lists included the 1000 phonetically balanced (PB) words, the Fairbanks rhyme test (FRT), the modified rhyme test (MRT), the Voiers diagnostic rhyme test (DRT), Clarke's medial vowel rhyme test (VRT), and a specially developed brevity code—phonetic alphabet word test (BREV). Scores on the FRT, MRT, and BREV words were equivalent and therefore the easier-to-administer standardized tests (FRT or MRT) can be considered valid alternatives to words actually used operationally. Scores on the PB tests were low, and scores on the VRT and DRT were high. Analysis of the diagnostic words showed the most frequent consonant pair confusion on aircraft radios to be V/B; the vowel EE (beat) was the worst “carrier” vowel, while EH (bet) was the best. Nasality was an intelligible attribute at good speech-to-noise (S/N) ratios but very bad under bad listening conditions. Voicing and sibilation were the more intelligible attributes when listening at low S/N ratios.
Intelligibility of Initial versus Final Consonants in Monosyllabic Words
Authors: Byers V. W.
Published: October 2005

The intelligibility of 10 consonants [/p/, /t/, /k/, /b/, /d/, /g/, /m/, /n/, /l/, and /s/] in two-vowel environments, /l/ and /ae/, were studied in the initial and final positions of monosyllabic words. A closed set of 88 words was constructed such that the consonants were transposed within the same vowel environment, e.g., pat-tap. Three randomized lists were presented at 60 dB HL to subjects in a counterbalanced order of three signal-to-noise ratios, +4 dB, 0 dB, and −4 dB. Results indicated that the initial consonant is more intelligible than the final consonant. Additionally, significant differences were found among the subjects, vowel environment, and individual phonemes. The identification of a monosyllabic word is a complex process in which the distinctive features that serve as perceptual cues for the initial and final consonant may not be processed in a similar manner.
Intelligibility of Alternated Speech
Authors: Trooien T. T. , Speaks C.
Published: October 2005

The intelligibility of interaurally alternated speech was measured by two methods: shadowing and subjective rating. The first of two experiments used speech spoken at a normal rate; the second experiment used fast-rate speech. With normal-rate speech, shadowing scores and estimates of intelligibility by eight subjects were nearly 100% for eight different rates of alternation between 1 and 10 aps. Estimates of intelligibility for fast-rate speech were depressed slightly from 100% and shadowing scores were near 70% for most rates of alternation. No particular alternation rate or region of alternation rates produced significantly depressed shadowing scores. The results convince us that interaural alternation of speech does not affect intelligibility unless the speech is spoken at a very rapid rate. Even with fast-rate speech, however, intelligibility is not dependent in any meaningful sense on the rate of alternation.
Relative Effects of White and Speech-Correlated Noise on Speech Quality
Authors: Sen T. K. , Dennis T. M.
Published: October 2005

An experiment was designed to study the effects of speech and noise levels on speech quality using white and speech-correlated noise (SCN). Two types of speech signals were used: (1) flat with respect to frequency (flat speech), and (2) flat below 1 kHz, and with frequency emphasis of 9 dB/oct above 1 kHz (shaped speech). Both speech and noise were bandlimited between 150 and 3600 Hz. The speech level ranged between 54 and 100 dBt SPL and the noise spectrum level between 2 and 33 dBt/Hz. A total of 45 noise and speech level combinations were used as test stimuli. Each test condition consisted of a pair of phonetically balanced sentences in the presence of one of the 45 test stimuli. The subjects were required to rate the speech quality on a 5-point scale. Averaged over all conditions, the shaped speech was preferred over flat speech. For shaped speech, SCN was preferred over white noise. For flat speech the same was true for speech levels of about 80 dBt and higher, and the reverse was true for speech levels lower than 80 dBt,
Ultrasonic Energy Measurement by Optical Diffraction Technique
Authors: Cook Bill D.
Published: October 2005

Optical methods are often proposed for the precise determination of the energy density of an ultrasonic area. Several measurement techniques have been developed to yield certain optical parameters. However, the difficulty remains in interpreting the results in terms of the local parameters of the sound field. This paper reviews the basic concepts of ultrasonic light diffraction, the parameters used to describe these concepts, methods of measurement, and limitations on interpretation.
Far Noise Field of a Subsonic Air Jet
Authors: Yu J. C.
Published: October 2005

Far noise field survey was made for a 2-in. circular subsonic cold air jet. The exit velocity range investigated varied from 350 to 800 ft/sec. The experiment was conducted in the open field. The contoured converging nozzle used had a contraction ratio of 50. In order to eliminate possible upstream acoustic contamination of the jet noise, blown-down technique was used to generate jet flow with a large acoustically treated settling chamber. Experimental results obtained are presented in the form of overall and spectral directivity, power spectrum, total power radiated, and their dependence on mean flow parameters. The experimental findings were correlated with the existing theories of subsonic jet noise. [This study has been sponsored, by the NASA-Langley Research Center.]
Long-Term Sound Propagation Studies in the Bristol Channel
Authors: Weston D. E.
Published: October 2005

Sound propagation has been studied for several years in the shallow waters of the Bristol Channel. The measurements central to this account have involved repeated transmissions of a sequence of tone pulses, with frequency varying from 0.3 to 4.5 kHz, the arrivals building up into a simple display. The signals were transmitted and monitored by fixed bottom-laid transducers, with path lengths up to 137 km. The investigations have been supported by other time-series measurements: in long-range echo ranging on fish and other reverberators, in ambient noise, and in oceanography. As a result of prolonged detective work, 11 different mechanisms causing signal fluctuation have been identified, eight of which would not have been revealed in the absence of long time-series results. Four reasons for the importance of long-term fixed-transducer multiple-frequency studies are given, as follows, each illustrated by one of the fluctuation types: (a) Many effects need relatively long studies if they are to be seen at all, e.g., the diurnally changing attenuation due to fish. (b) Some effects may only be understood by their behavior over long periods, e.g., fluctuations due to internal waves and their tidal dependence. (c) Some effects occur at random times, to be observed only by patient waiting, e.g., storms. (d) Understanding of the absolute transmission levels involves a knowledge of the variations in level, especially the variations with season.
Fluctuations of Sound Transmission in the Straits of Florida
Authors: Steinberg John C.
Published: October 2005

Sound waves transmitted across the Florida Current between fixed transducers are used to investigate relationships between acoustic and environmental variations. Year-long measurements of the amplitude and phase of 420-Hz sound waves reveal fluctuations with periods from seconds to weeks and longer-term trends. The variations of phase correspond to changes in the medium and increase in magnitude with increase in period. The amplitude fluctuations are not readily identifiable. The slowly changing phases of the multipath arrivals result in varying patterns of amplitude interference and fading which have noiselike spectra. The Florida Current is characterized by a cross-stream temperature-depth structure related to the transport of water. Variations of transport from tidal and wind forces induce fluctuations of temperature, sound speed, and phase. Temperature and phase are also modulated by internal waves and components of current parallel to the sound path. The observed characteristics of the amplitude and phase variations appear in computations with ray-propagation models in which plane parallel boundaries and measured time variations of sound speed versus depth are used.
Surface-Duct Propagation-Loss Measurements
Authors: Cummins James
Published: October 2005

The surface duct is the mixed-layer underwater sound channel generally bounded by the ocean surface and the thermocline. In a recent experiment, abundant measurements of surface-duct propagation loss were made concurrently with detailed environmental sampling. The experiment requiring three ships was designed to fill a gap in the knowledge of surface-duct propagation at frequencies below 8 kHz that has not been addressed. Propagation loss was measured at frequencies from 0.4 to 20.0 kHz, at depths from 20 to 600 ft, over ranges of 0–18 miles. The experiment was novel because for the first time adequate environmental measurements were made over the entire acoustic field. Three different instruments measured sea surface roughness. Sound speed profiles were continuously sampled both in space and time: every 50 ft along the track by a towed thermistor chain, every 10 sec by a string of thermistor buoys spaced along the propagation path. The accuracy of these systems was ±0.02°C or ±0.06 m/sec in terms of sound speed. The purpose of the experiment was to provide data required for evaluating several theories of surface duct propagation loss.
Scattering Function Measurements for a 7-NM Propagation Range in the Florida Straits
Authors: Deferrari H. A. , Nghiem-Phu Lan
Published: October 2005

A pulse received after transmission through the ocean will be spread in time owing to multipath and shifted in frequency owing to scatter from the ocean wave surface. If the time spread is small compared with the period of the surface waves, a Doppler spectra may be measured for each successive part of the received signal. The resulting scattering function is a three-dimensional description of the transmission (intensity, frequency, and delayed time of arrival). Scattering functions for the 7-NM range show that energy arriving via SRBR paths has Doppler spectra with sideband components at surface wave frequencies. A large fraction of the total received energy is transmitted by RBR paths and is not influenced by surface waves. Measurements are presented for some environmental conditions typical of the Florida Straits. Results are compared with predictions from combined propagation and scattering models that include the effects of multiple scattering along the propagation paths.
Binaural Processing in the Cat. II. Detection
Authors: Robinson Donald E. , Wakeford Onslow S.
Published: October 2005

Detection of diotic and dichotic tones partially masked by noise was studied in the cat. The continous noise masker was always diotic. The single gated tone bursts had frequencies of 0.5, 1.0, and 1.5 kHz and were presented in phase (N0S), 180° out of phase (N0Sπ), and monaurally (N0SM). The transducers were held in a fixed spatial relation to the auditory canal by means of “pinna inserts” and leather helmets. An avoidance response in a shuttle box was used as the dependent variable. In contrast to human observers the cat displayed as large a release from masking at 1.0 and 1.5 kHz, as at 0.5 kHz. At 1.5 kHz, the cat shows a significantly greater release from masking than the human.
Curvature Effects on Side and Aliasing Lobes of Transparent Arrays
Authors: Smith P. W. , Berkman E. F.
Published: October 2005

A transparent array, either continuous or discrete, is located on a spherical surface. Its sensitivity is spatially constant in magnitude and phase, compensated for maximum signal in the direction of the main lobe. A stationary-phase analysis shows that a sufficiently large continuous array has large sidelobes in a direction dependent on array size. A discrete array has aliasing lobes (grating plateaux) at a lower frequency than does a similar flat array.
Information Derivable from the Doppler Polar Profile Spectrum
Authors: Spooner Ronald L. , Nitsche Jude R.
Published: October 2005

There has been considerable interest recently in the use of Doppler shifted signal information as a technique for passive acoustic localization. An investigation of this phenomenon using conventional techniques, however, rapidly becomes complicated by the large number of parameters and geometrical configurations that must be considered. In particular, it is especially difficult to determine the sensitivity of the technique to measurement errors. As an alternative, this paper treats the Doppler profile in terms of its inherent information content and indicates how such information may be utilized to obtain both qualitative and quantitative results. By invoking Fourier transform and sampling techniques, the limitations of Doppler localization are viewed in terms of conventional filter bandwidth and aliasing problems. Furthermore, measurement sensitivity is treated as a generalized S/N ratio enhancement problem. Utilizing the methods of this paper, a more generalized and complete understanding of the Doppler phenomena is achieved when compared to the specialized results of conventional methods.
Covariance Structure of Surface Reverberation
Authors: Swarts Robert L.
Published: October 2005

An analytical expression for the covariance function of underwater sea surface reverberation is obtained from the FOM model. Certain powerful results based on the properties of Fourier transforms are demonstrated. The expression is then evaluated by computer for several hypothetical Doppler density functions. Plots of the resulting covariance functions are compared with functions obtained empirically from experiments at 28 kHz in Puget Sound, Washington. Ensemble averaging techniques are used. Effects of data nonstationarity are also illustrated.
Characterizing Volume Reverberation Signals Using Level Crossing Information
Authors: Spindel R. C. , McElroy P. T.
Published: October 2005

A point scatterer model is used to formulate expressions for the expected number of level and zero crossings of backscattered volume reverberation signals. It is shown that zero crossing measurements on narrow-band transmitted signals can yield quantitative estimates of scatterer population density in oceanic deep scattering layers. Level crossing data can be used to estimate scattering strengths. For wide-band transmitted signals, level crossing information can provide a relationship between scatterer Q and resonant frequency. Some features of using crossing data are (a) level and zero crossing systems are relatively simple to implement; (b) scattering strength measurements are independent of transmitted signal waveshape; and (c) since zero crossings are unaffected by the general time dependent decrease in reverberation level, zero crossing measurement systems do not require time-varying gain compensation. An experiment east of Bermuda compares scattering strength determination through level crossings to more conventional measurements. Also, the experiment gives scatterer density as a function of depth through a scattering layer. Peak densities of between 10−3 and 2 × 10−3 scatterers/m3 are found.
Vibration Measurement by Laser Interferometry: Homodyne and Heterodyne Techniques
Authors: Eberhardt F. J.
Published: October 2005

The theory of typical homodyne and heterodyne laser interferometers for vibration amplitude measurements is reviewed. For the former, methods of absolute measurement by analysis of the harmonic series with Bessel coefficient amplitudes is presented. These methods are applicable for measurements from less than 1 Å up. Limitations and noise problems are discussed. For the typical heterodyne system the detection technique and calibration required are discussed in detail. A description is given of the noise and bandwidth limitations on the range of amplitude and types of waveforms to be measured. Advantages and limitations of the two techniques are discussed in relation to each other and to other optical approaches to vibration measurement. Applications that have already been found or proposed, both for air and underwater measurement, are pointed out.
Noise Propagation in the Open Atmosphere
Authors: Piercy J. E.
Published: October 2005

This contribution to the review of our present understanding of outdoor noise propagation, and the way in which it may be brought to bear on current problems, will include all effects other than those due to the presence of the ground or other surfaces. Included will be geometric spreading caused by source configuration, as well as absorption and refraction by the atmosphere. The fluctuations of sound level due to atmospheric conditions will also be discussed. The importance of bringing into engineering use the knowledge obtained in recent years in related fields such as meteorology, propagation of light in the atmosphere, and vibrational relaxations in gases will be emphasized.
Reverberation for Multipath Propagation in Urban Areas
Authors: Lyon Richard H.
Published: October 2005

The propagation of urban noise combines the transmission phenomena of reflection, scattering, and shielding to produce sound levels that are substantially different from those that would exist in an open terrain situation. When the source is elevated, the number of important contributing paths is generally less than four or five, and the reverberation phenomenon is simply a combination of these. For street level sources, corridor propagation is dominant, complicated by the scattering that occurs on the building faces. Sound level patterns in streets, therefore, have significantly different forms than the propagation in a smooth corridor as several field experiments have shown. This paper plays a series of results from both experimental and territorial studies that demonstrate the phenomenon involved in urban propagation in addition to some of the unsolved problems that are apparent from the results.
A Climatology of Distant Airblast Propagations
Authors: Reed Jack W.
Published: October 2005

Microbarograph data from Nevada atmospheric nuclear tests of 1951–1962 and some recent large chemical explosives tests are presented to show climatological patterns for long range propagation to about 225 km. Amplitudes are normalized to 1-kiloton yield, free airburst, and corrected for height-of-burst effects. Propagations under early morning temperature inversions often showed double the amplitudes expected for standard hemispherical explosion wave expansion at 30-km ranges. With sound velocity-height gradients, propagations may be reduced to 0.2× of standard amplitude at 10- to 30-km ranges. Strong upper winds, at 6- to 10-km altitudes, occasionally gave as much as 5× magnification at 50–150 km. Ducting by the high stratosphere, near 50-km altitude, is seasonally directed eastward in winter, westward in summer. Amplitudes in the sound ring, near 225-km range show as much as 3× magnification downwind and 0.006× reduction upwind. [This work was supported by the U. S. Atomic Energy Commission.]
Mapping of Ultrasonic Fields with Conventional Light Diffraction
Authors: Cook Bill D.
Published: October 2005

A theory is proposed from which a cross-sectional mapping of a progressive beam can be obtained by conventional light diffraction techniques, i.e., by passing a parallel beam of light through the sound field. To obtain sufficient information, the sound field must be rotated around its major axis for a series of optical measurements. These measurements, along a line perpendicular to the sound beam axis, are to yield the strength and phase of the effective phase grating. As an extensive amount of data is needed to compute one map ultilizing two-dimensional Fourier transforms, a data acquisition system and digital computer are required. However, in the constraint of linear acoustics, one set of measurements will permit the calculation of the sound field in all space.
Generalized or Adjoint Reciprocity Relations for Electroacoustic Transducers
Authors: Yaghjian A. D.
Published: October 2005

The “equations of motion” of a linear electroacoustic transducer are written in the alternative forms L+X = 0, L−X = 0, where the matrices L± are linear differential expressions, X = (E,H,u) represents electroacoustic fields, and the superscripts distinguish selected normalizations of the equations of motion. To each operator L± corresponds a mathematically defined adjoint operator (L±)a and an associated adjoint transducer, whose material tensor parameters are given by certain transpositions and interchanges of the parameters of the given transducer. Dissipative characteristics (lossiness, losslessness, or “gaininess”) of the material of the given transducer are preserved pointwise in the adjoint transducers. A generalized reciprocity lemma leads to relations of reciprocal type between external properties of the given and the adjoint transducers. In the self-adjoint cases, the conventional electroacoustic reciprocity and antireciprocity relations are obtained and the derivation of those relations is critically confirmed. The generalized or adjoint reciprocity relations have been applied in the plane wave scattering-matrix formalism developed for electroacoustic transducers by Kerns (Abstract BB3). Corollaries of the adjoint reciprocity relations, analogous to conventional reciprocity theorems, but involving properties of adjoint pairs of transducers, are readily derivable.
A Scanning System for the Measurement of Beam Profiles of Ultrasonic Therapeutic Transducers
Authors: Harris Jerry , Stewart Harold F.
Published: October 2005

A system for measurement of the intensity distribution across the beams of ultrasonic therapeutic transducers is described. The system consists of a mechanical positioner, a small receiving hydrophone, electronic signal processing circuitry, and an X - Y plotter. The positioner gives manual control over the location of the hydrophone within the beam. The signal from the hydrophone is fed to the electronics, which gives an output proportional to both the spatial intensity and the integrated intensity as the hydrophone is scanned across the beam. These outputs are fed to the Y axis of the plotter. The X axis is driven by a voltage proportional to the position of the hydrophone. The resulting plots are used to determine how the energy radiated from the therapeutic transducer is distributed within the beam.
A Differential Microcalorimeter for the Measurement of Ultrasonic Powers at the Milliwatt Levels
Authors: Sokollu Adnan , Guvenc Serpil
Published: October 2005

A microcalorimeter system has been developed to evaluate ultrasonic power outputs, especially of pulsed diagnostic transducers. The system is composed of two basically identical calorimeters, interwoven by an extensive network of thermocouples serving as an averaging temperature comparator. Borh calorimeters are mounted into a common housing with heavy aluminum walls so geometrically as to ensure a well-balanced thermal equilibrium. Either calorimeter may be used as an energy recipient, while the other serves as a temperature reference. Their filling consists of a silicon oil that matches the acoustical impedance of water. Each calorimeter contains a heating wire for calibration and a cooling system to achieve a fast temperature equilibrium following the measurement. The thermocouple battery is formed by 30 pairs of junctions, made of 20-μ-diam copper and constantan wire. It permits temperature evaluations at the millicentigrade level. The overall sensitivity of the system is approximately 0.08°C per calorie. Transducers to be measured are inserted into one of the calorimeters and are energized for about 30 sec and then pulled out to prevent the heat created in the transducer from reaching the area of measurement. Both pulsed or CW diagnostic transducers have been measured to ultrasonic power levels as small as 1 mW and with an accuracy of about ±4%.
Self-Reciprocity Calibration of Echo Ranging Transducers
Authors: Reid John M.
Published: October 2005

The technique of reciprocity calibration, which allows the absolute determination of sound quantitaties, has been effectively used for many years at low frequencies. The self-reciprocity modification of this technique requires fewer measurements and has higher accuracy. Present day pulse echo systems have been used to perform this calibration on their own transducer. These transducers are available with wide bandwidths and can be used to measure both peak and average fields. The technique is discussed from the standpoint of energy density, from which the self-reciprocity conditions and derived in a convenient form. The choice of auxiliary measurements of impedance or open-circuit voltage is also discussed. No acoustical standards are required. The technique appears to be suitable for average power measurements on pulsed and CW systems. Corrections for short-pulse operation of typical medical systems require further investigation.
Further Experiments with Impediography: A New Ultrasonic Technique with Biomedical Implications
Authors: Jones Joie Pierce
Published: October 2005

A new technique suitable for medical diagnoses and nondestructive testing was recently introduced [Papers NN7 and NN8, 83rd Meeting, Acoust. Soc. Amer.]. Termed impediography, this method employs time-domain deconvolution of appropriately shaped acoustic impulses and their echoes to produce a temporal waveform that can be related to physical parameters such as impedance. Thus, impediography allows us to measure accurately the specific acoustic impedance at an arbitrary position within a test object. In preliminary experiments using a spark source to illuminate the test object, analysis of the reflected signal gave the impedance as a function of the acoustic travel time. This acoustic “picture” is termed an impedogram. In this paper, two particular experiments will be discussed in detail. In the first, impedograms of a soft rubber test object were obtained under various degrees of tension. Changes in impedance were clearly observed as the sample was stretched. I n a second experiment, a two-dimensional impedogram was obtained of a rabbit's hind limb. This impedance profile showed excellent correlation with the actual biological structure: bone, bone marrow, skin, and even fascia were clearly distinguished.
Piezoelectric Ring and Spherical Transducers Designed to Vibrate in a Dipole Mode
Authors: Chervenak John
Published: October 2005

Free-flooding piezoelectric ring transducers have good efficiencies, are capable of radiating high acoustic power, are of simple design, and have the mechanical strength required for deep underwater submergence operation. However, the omnidirectional acoustic radiation in the plane of a ring transducer is undesirable for applications where directional beams are required. Directional acoustic beams may be obtained from nondirectional transducers by the use of reflectors that are bulky, costly, and difficult to maintain for large low-frequency arrays or by using volume arrays in which the transducer elements are spaced and phased in such a manner that acoustic radiation from all transducers adds in the direction along the acoustic axis of the array and cancels in the opposite direction. Since the technique used to get directionality from biplanar or volume arrays controls acoustic radiation only along the 0° and 180° but not the 90° and 270° directions associated with beam pattern charts, the system works best when transducers with dipole (figure-eight type) beam patterns are used. The design of a dipole ring and spherical transducer will be discussed and measurement data presented.
The STL-Ionophone Transducer
Authors: Fransson F. J. , Jansson E. V.
Published: October 2005

The STL-ionophone consists of a dc discharge in air. The discharge emits sound when an ac current is superimposed on the dc current. It represents a small sound emitter with high internal impedance and constant source strength from low to ultrasound frequencies. It can also register air motions as a superimposed voltage and works in this function from zero to ultrasound frequencies. It has been employed as a sound source for measurements on woodwind instruments and models of the human vocal tract. As a receiver, it has been employed to study the sound field at the embouchure of flutes. Fundamental properties registered and applications will be discussed.
Preliminary EMG Investigation of Certain Intrinsic and Extrinsic Laryngeal Muscles in Patients with Spasmodic Dysphonia
Authors: McCall G. N. , Colton R. H. , Rabuzzi D. D.
Published: October 2005

EMG studies were conducted on eight patients with nontremor related spasmodic dysphonia. Bipolar hook-wire electrodes were inserted into the cricothyroid, sternothyroid, and throhyoid muscles of each patient. The electromyographic activity from each muscle was recorded along with the voice of each patient on a multichannel FM data recorder for subsequent writeout and analysis. Data were obtained during quiet respiration, as well as during each patient's utterance of a standard sequence of isolated vowels, CV syllables, words, and contextual speech. Data analyses revealed that the characteristic intermittent voice stoppage episodes exhibited by patients with spasmodic dysphonia occur in association with sharp, burst-like increases in EMG activity in the cricothyroid and in some instances the sternothyroid and thyrohyoid muscles. Patients with spasmodic dysphonia tend to show prolonged contraction of the muscles under study prior to and following phonation. The postphonatory time data provide evidence suggestive of a problem in muscle relaxation. Implications of these preliminary observations will be discussed and directions for further investigation suggested.
Fundamental Frequency Characteristics of Young Deaf Adults During Oral Reading
Authors: Horii Yoshiyuki , Bishop Milo E.
Published: October 2005

A total of 18 young deaf adults read a 181-word passage, and distributional characteristics of fundamental frequency (f0) were investigated using a period-by-period f0 analysis program. The results of analysis showed significantly higher f0 means and smaller standard deviations and mid-90% range than those for normal-hearing subject. Deaf speech was characterized, furthermore, by significantly less skewness of fundamental frequency distribution. In addition, bimodality or multimodality of f0 distributions commonly observed in speech of normal-hearing subjects were also less clear in the deaf speech samples. The results indicate limited, monotonous pitch variability and almost constantly strained type of phonation in deaf speech. [This research was supported in part by Air Force Cambridge Research Laboratories, OAR, and by National Institute of Dental Research.]
Observations on a Multiple Harmonic F-Tracking Program
Authors: Snow T. B. , Montgomery Allen
Published: October 2005

This paper presents some special features of an F0 tracking algorithm that proceeds logically to examine the harmonic structure of speech signals. The results of the procedure are F0 contours suitable for such purposes as intonation studies, synthesizer inputs, statistical studies of vocal frequency, etc. Characteristics of the system include a very low error rate and a conservative treatment of segments whose spectra are not clear. This treatment is based on continuity and whole-number ratio constraints on harmonies detected from short-time spectra. Error rates as low as one discontinuity in a 10-see sample have been achieved, with errors generally being simple multiples of the true fundamental, and therefore easily detectable. Comments on the relationship of this approach to human pitch detection will be made, and the potential application of aspects of this method to the output of other F0 extraction systems as a refinement procedure will be discussed.
“Tone” and Pitch Perception
Authors: Lancker D. Van , Fromkin V. A.
Published: October 2005

Research has demonstrated that while many aspects of language processing are lateralized to the left cerebral hemisphere in man, perception of pitch differences is not. We have conducted experiments in the dichotic listening paradigm to determine whether speakers of tone languages show a right ear advantage in processing contrasting “tones.” Three sets of stimuli were used: randomly paired combinations of five Thai words differing only in tone; paired lists of five Thai words contrasting only in initial segment; the five Thai tones hummed to contrast only in pitch level and direction. Thai speakers were used as subjects. The preliminary results show that for Thai speakers, there is a right ear preference for pitch stimuli only when the contrasting pitches represent linguistic “tones.” Consonantal discrimination and “hums” were processed as expected: a right ear preference for consonants, a left ear preference for nonlinguistic pitch. [This research was supported in part by a U. S. Public Health Services (NIH) Grant, and in part by an Office of Naval Research Contract.]
SKAT: An Automated, Self-Administered Preschool Auditory Screening Test
Authors: Berry R. C. , Katz S. J. , Schaefer T.
Published: October 2005

SKAT is part of an automated, self-administered preschool screening battery for vision, IQ, and readiness. SKAT was designed to detect educationally significant hearing and discrimination problems. Sixteen CVC words were selected for familiarity to preschoolers. The words were grouped into sets of four. All words in a given set had the same vowel; consonants differed. The four pictures for a set were displayed together on a rear-projection screen. A response button was located beside each picture. Words were presented through TDH-49 earphones. To reduce testing time, conditioning was limited to naming each picture once. When testing began, the S was instructed to press the button next to, e.g., “pot.” A new display and new word were presented when S responded, or after 6 sec. Twelve words per ear were presented at varying intensities: four each at 55, 50, and 45 dB SPL, randomly. Standard puretone (Malco Audiometer) screening was administered to 61 Ss, K-2. Each S self-administered SKAT in 3.5 min, average time. Six Ss (10%) failed both procedures. Three (5%) failed SKAT, but passed pure tone. In similar studies, more false negatives and false positives have been reported for the VASC and Fading Numbers Test.
Replication of Frequency Response Aspects of Hearing Loss for Use in Communication Studies
Authors: Prout James H. , Bienvenue Gordon
Published: October 2005

In studying the problems of communication among coal miners, it was desirable to replicate electronically certain aspects of their hearing abilities so that one group of normal-hearing subjects could be used for the entire study. Tests were designed to determine the ability of miners to hear speech and nonspeech signals in noise and quiet, with and without ear protectors. Since miners cover a wide range of ages with varying amounts of hearing loss, the literature dealing with hearing of noise-exposed miners was surveyed and collated to obtain audiograms of three representative subgroups. From this threshold data, a linear transformation was used to obtain equal loudness contours for bands of noise. Three electrical filters were then developed from this data to approximate the frequency response aspects of the miners' hearing loss. The derivation of the filters and some results of tests involving their use will be described. [This research was supported by a contract with the U. S. Bureau of Mines.]
The Interaction of Continuous and Impulse Noise: Audiometric Effects
Authors: Crossley James J. , Salvi Richard J. , Hamernick Roger P. , Henderson Donald
Published: October 2005

Continuous and impulse noises, considered “safe” by existing damage risk criteria (DRC), were combined to model more realistic noise environments. Monaural chinchillas (23) were exposed to one of the following conditions: (a) 95 dB SPL continuous noise at 2–4 kHz for 1 h; (b) 50 impulses with a 40-μsec A duration at 158 dB SPL peak pressure; (c) interrupted combination of the continuous and impulse noise with the continuous noise off for 2 sec during the impulse delivery; (d) superimposed combination of the continuous and impulse noise. Quiet thresholds were measured before and after exposure at 0.25, 0.5, 1, 2, 4, and 8 kHz using the averaged evoked response technique. Recovery was monitored for 31 days. The median recovery from the 95 dB SPL continuous and 158 dB impulse was complete by 30 h. The interrupted combination produced temporary threshold shifts (TTS) of 50–60 dB at 2, 4, and 8 kHz that required four days to recover. The superimposed combination produced, 30 dB TTS at 0.25, 0.5, and 1 kHz, 70–90 dB TTS at 2, 4, and 8 kHz, and a final median audiogram typical of noise induced sensorineural hearing loss with 30–40 dB PTS at 2, 4, and 8 kHz.
Evaluation of Low-Frequency Amplification, Time in Therapy, and Testing Conditions for Preschool Deaf Children
Authors: Asp C. W. , French E. H. , Berry J. S. , Keller J. E.
Published: October 2005

Fifty-five deaf children were tested at four-month intervals with 27 test words. The factors under test included: (1) type of amplification (wide band versus narrow band); (2) testing times; (3) auditory versus visual and auditory clues; and (4) testing with amplification versus testing without amplification. Records were kept on the familiarity of the test words and the number of responses. Length of enrollment in the program was based on the availability of each child over the five-year period of this study. The verbo-tonal method was utilized to habilitate all the children. For the third, fourth, and fifth years, an experimental design [C. W. Asp, J. Acoust. Soc. Amer. 48, 87(A) (1970)] permitted the teacher to speak simultaneously through two different amplifying systems, a wide-band auditory training unit (Suvag I) and a narrow-band unit (Warren T-2). For one criterion measure, 20 656 speech samples were recorded, randomized, and judged on a 9-point scale. Preliminary statistical analyses suggested the following: (1) in general, children assigned to the wide-band unit improved at a faster rate than those assigned to narrow-band units; (2) significant improvements were detected over the testing times, (3) the scores were better when both visual and auditory clues were available and also when amplification was available. Data for additional criterion measures are being processed for future reports. [Work supported by U. S. Office of Education. Acknowledgment is offered for the many staff members associated with this project.]
Nonlinear Transverse Vibrations of Inhomogeneous Beams
Authors: Nayfeh Ali H.
Published: October 2005

The method of multiple scales is used to analyze the nonlinear transverse vibrations of inhomogeneous beams including the effects of transverse shear and rotary inertia. First-order uniform perturbation expansions are derived for the displacements, shear force, and frequency in terms of the ratios of maximum transverse displacement to cross-sectional radius of gyration and cross-sectional radius of gyration to wavelength.
Free Oscillation of Thin-Walled Open-Section Circular Rings: A Conventional Approach
Authors: Maddox N. R. , Rentzepis G. M.
Published: October 2005

A theoretical study of the eigenfrequencies for a complete thin-walled open-section circular ring with one plane of symmetry in the plane of the ring is conducted. The analysis consists of a conventional theory incorporating St. Venant torsion, Timoskenko warping, torsional inertia, and, for the first time, the shear center eccentricity from the center of gravity for out-of-plane free oscillations and extensionality for in-plane free oscillations. This approach, including all the effects mentioned above, yield four coupled equations of motion for the free oscillations. With the plane of symmetry lying in the plane of the ring, this system of equations splits into two coupled sets; one for the in-plane oscillations, the other for the out-of-plane oscillations. The complete ring eigenfrequencies correspond to eigenmodes of four or more nodes resulting from the values available in the literature even for slender rings; this is attributed to the incorporation of the shear center eccentricity—an effect that has been previously ignored. The out-of-plane ring equations have been found to reduce to ring equations of motion available in the literature by elimination of various parameters. Studies of these various systems of equations of motion have shown that the effect of the shear center eccentricity on the natural frequencies of rings with radii ratios as low as 1:50 is not negligible. Hence, a vibration study involving monosymmetric rings should include the eccentricity of the shear center if a reasonable prediction of natural frequencies and/or the response of a system to a given forcing function is being sought. If, in addition, one neglects the warping, the results are completely erroneous for thin-walled rings.
Vibration and Sound Radiation of a Plate
Authors: Hannon R. J.
Published: October 2005

Because of resonances, plates are acoustically soft. The experimental evaluation of the acoustic properties of plates is difficult since they are usually supported at points which act to clamp the plate. To eliminate this, a plate was placed on a cushion of open-cell plastic foam, and the velocity amplitude due to a point force was determined with a record player cartridge and a microphone in the near sound field. The results show that the many modes that are excited interact to generate “hot spots” on the plate. The attachment of ribs and supports disturbs the vibration field and leads to localized area of sound radiation.