bluuebunny/crossref_metadata_2025 huggingface dataset:
Human Auditory Thresholds During Deep, Saturation Helium-Oxygen Dives
Authors: Thomas W. G.
Published: October 2005

Pure-tone air conduction thresholds and Sensory Acuity Levels were measured on 33 different divers during eight saturation dives ranging from 300 to 1000 ft in a hyperbaric helium-oxygen environment. A total of 366 audiograms were performed at 26 different depths between surface and 1000 ft, as well as pre- and postdive audiograms at surface. All divers showed a progressive conductive hearing loss related to depth, reaching a maximum of around 30 dB at 1000 ft. The greatest hearing loss occurred in the low frequencies during the first 100 ft of the dives, with smaller increases with additional depth. During decompression, hearing levels were slower to return, with significant amounts of hearing loss remaining at 2 ft from surface. Hearing for the higher frequencies, especially 6000 Hz, became better than surface values as surface was approached. All thresholds returned to predive levels upon reaching surface. No change was noted in the SAL for any depth.
A Discrimination Test for Nonspeech Signals
Authors: Bienvenue Gordon R.
Published: October 2005

Coal miners, while they are exposed to excessively high levels of noise, must be able to listen for roof talk or sounds created by stress release in the mine roof, which is indicative of an imminent cave-in. Any device that interferes with the ability of the miner to hear these roof-talk signals would constitute a safety hazard to the miner. It has been suggested that the use of ear protectors might constitute such a hazard. A set of roof-talk tapes has been assembled to assess this possible hazard. These consist of one listening tape for training subjects in listening to roof talk and a set of test tapes for testing subjects' abilities to identify the presence of roof-talk warning signals in the presence of varying amounts of noise. Six subjects were tested using these roof-talk test tapes and speech discrimination materials. Aspects of test development and test results will be discussed in detail. [This research was supported by contract with the U. S. Bureau of Mines.]
Behavioral and Anatomic Manifestations of Acoustical Overstimulation
Authors: Trahiotis C. , Ades H. W. , Kokko-Cunningham A. , Averbuch A.
Published: October 2005

The data to be discussed represent preliminary attempts to investigate further the relations between acoustic overstimulation, cochlear pathology, and behavioral indices of auditory discriminability. Monaural chinchillas served as subjects and were tested by traditional avoidance techniques to detect pure tones in “quiet” and in various levels of broad-band noise. Stimuli producing acoustic overstimulation included various levels of 4-kHz pure tones and bandpass noise whose greatest spectral levels occurred between 1 and 2 kHz. Both “quiet” and masked postexposure thresholds will be compared to the cochleograms obtained six months following stimulation. [Supported by grant from NASA.]
Audiometric and Histological Effects of Exposure to 40-μsec High Level Impulses
Authors: Henderson Donald , Hamernik Roger P. , Sitler Ronald W.
Published: October 2005

Monaural chinchillas (15) were exposed to 50 impulses of either 158, 615, or 175 dB peak SPL. The impulses were generated by a spark-gap source, which produced an impulse with a 40-μsec A duration. Quiet thresholds were measured at 0.25, 0.5, 1, 2, 4, and 8 kHz, using the averaged evoked response technique. Recovery was monitored for 31 days and then the animals were sacrificed and their cochleas were analyzed using the surface preparation technique. The three exposures produced virtually no permanent threshold shifts (PTS) with the exception of 10–30 dB PTS in one animal in each of the 165- and 175-dB groups. However, hair cell losses were seen in all three groups. The cochleagrams varied from low level scattered losses to lesions of the OHC that spanned a 4-mm stretch in the base of the cochlea. The IHC losses were considerably smaller and more restricted. The audiograms do no necessarily reflect the state of the cochlea.
Resonant Stresses in Structures Based upon Experimental Response Data
Authors: Mitchell L. D. , Todd M. C.
Published: October 2005

A combined experimental and analytical approach to the problem of resonant stresses is presented. The approach is formulated so that the mechanical dynamic eigenvalue-eigenvector analysis can be used with a single-point mechanical mobility measurement on the structure to predict the resonant stresses at any point in the structure.
Transient Response of Multi-Degree-of-Freedom Linear Systems to Forcing Functions with Inequality Constraints
Authors: Michalopoulos C. D.
Published: October 2005

Optimal control theory is employed to analyze the transient response of discrete linear systems to forcing functions whose dependence on time is not known, but which lie within specified bounds. Attention is focused on the complete determination of the forcing function that will induce (a) maximum displacement of any specified mass element; (b) maximum relative displacement of any two adjacent masses; and (c) maximum acceleration of a given mass. Undamped mechanical systems with an arbitrary number of degrees of freedom are considered wherein only a single forcing function acts. In general, the desired forcing function is found to be a bang-bang type function, that is, a function which switches from the upper to the lower bound and vice versa at certain instants of time. The general procedure for finding these switching times is presented.
Approximate Fundamental Frequency of Noncircular Ring Membranes
Authors: Eastep F. E.
Published: October 2005

An exact solution for the frequency of a ring membrane can be obtained when the inner and outer boundaries are concentric circles or confocal ellipses. If either boundary has some other shape, approximate methods must be used. This paper presents a simplified approximate method for determining the fundamental frequency of ring membranes whose boundaries deviate only slightly from circular. This method was initially used by Rayleigh in his investigation of simply connected membranes. The radii of both bounding curves are approximated by a truncated Fourier series. The membrane transverse motion, which is written as a superposition of the modes of a circular ring membrane, is forced to vanish on the approximated boundaries. A characteristic equation is obtained from which the approximate frequencies may be found. This technique is used to determine the fundamental frequency of the following: (1) Elliptical ring membrane with the inner and outer ellipses being confocal; (2) square membrane with a centered circular hole; (3) square ring membrane; and (4) an eccentric annulus. Comparisons with exact solutions, when known, are given.
Response of a Helical Coil to a Step Impact Load
Authors: Haines D. W. , Chang N.
Published: October 2005

A theoretical solution is presented of a one-turn elastic helical coil of small pitch with one end fixed and subjected to a step impact load applied tangentially to the other end. Previously derived one-dimensional equations [Paper H8, 83rd Meeting of the Acoust. Soc. Amer.] are taken as the governing equations of motion. The Mindlin-Goodman method is applied to solve these equations with the boundary conditions as indicated. The solution demonstrates the effectiveness of the coil as an impact absorber. [This work was supported by the National Science Foundation.]
On Modeling the Vibration Characteristics of a Chain Saw
Authors: Reynolds D. D. , Soedel W.
Published: October 2005

The vibration response characteristics of a chain saw were modeled, treating the saw as a rigid body supported by a system of springs and dampers at the two handle locations of the saw. The arrangement and values of the coefficients for the springs and dampers were experimentally selected to result in the same dynamic response as if human hands were clasping the chain saw handles. The saw was modeled as a 7 df (degree of freedom) system—three translational directions, three rotational directions, and one to describe the rotational motion of the slider-crank mechanism of the I.C. engine of the saw. The kinematic and dynamic properties of the slider-crank mechanism were exactly modeled. The analytical results of the model for the fundamental forcing frequency agreed very well with the experimentally measured results, often within 10% of each other. Because of structural resonances of the saw body, which were not incorporated into the model, the agreement between the analytical and experimental results at the harmonic frequencies of the fundamental forcing frequencies was not as good.
Ambient Noise Generation at the Arctic Ice-Water Boundary
Authors: Diachok O. I. , Winokur R. S.
Published: October 2005

Quasi-synoptic measurement were made to determine the spatial variability of ambient noise at the Arctic ice-water boundary over a frequency range from 100 to 1000 Hz. The results of this investigation show that the ice-water boundary acts as a spatially well-defined source of ambient noise with measured noise levels near a compact edge about 12 dB higher than open water levels and about 20 dB higher than levels far in the ice field. Measured noise levels near a diffuse ice edge were about 4 dB higher than open water levels, and about 10 dB higher than levels far in the ice field. The relatively high noise levels are probably generated by wind-wave interactions with ice floes. Specific mechanisms of noise generation are suggested, and the measured data are compared to ambient noise data in the central Arctic.
Speaker Recognition and Verification using Linear Prediction Analysis
Authors: Sambur M. R.
Published: October 2005

The speaker recognition and verification effectiveness of a set of 92 measurements was examined. These measurements included the formant structure of vowels, the duration of certain speech events, the dynamic behavior of the formant contours, various aspects of the pitch contour throughout an utterance, formant bandwidths, glottal source “poles,” and pole and zero locations during the production of nasals and strident consonants. Linear prediction methods were employed in the analysis, and a probability of error criterion was devised to evaluate the speaker-characterizing potential of the measurements. The experimental speech data were collected during five different recording sessions, the last session being 312 years after the original recordings. The measurements that were found most useful were related to the nasals, certain vowel resonances, certain temporal attributes, and average fundamental frequency. A speaker identification experiment using only the five “best” measurements resulted in only one error in the identification of 11 speakers for 320 test “utterances.” [This work was part of a doctoral thesis at the Massachusetts Institute of Technology.]
Techniques for Objective Speaker Identification
Authors: Hair Geroge D. , Rekieta Thomas W.
Published: October 2005

A technique has been developed and tested for identifying from voice recordings which, if any, of a number of possible speakers corresponds to a particular object speaker recording. Segments of the same set of selected phonemes by the object speaker and all suspect speakers are Fourier transformed. These phoneme spectra, and features derived therefrom, are utilized to make measures of voice similarity. Experiments with voice recordings by 140 men have yielded estimates of the probability of correct identification as a function of the number of suspects for both forced-choice and open-choice tests. Identification reliability has also been related to number of phonemes, number of utterances, and number and type of features. Open-choice decision reliability of 99% or better for small numbers of suspects was demonstrated. Another decision procedure, whereby decisions are made in only 95% to 99% of cases, can reduce error probabilities essentially to zero.
The Use of Prosodic Features to Derive Word and Syllable Boundaries
Authors: Willems Y. D. , Allen J.
Published: October 2005

Spoken integers between 0 and 999 (e.g. “three hundred and seventy two”) were recorded by four speakers. For each utterance, a measure of the waveform amplitude (called the envelope) and pitch period estimates were recorded and plotted. It is shown that these two correlates can be used to predict word and syllable boundaries within each spoken integer. These junctural correlates also reflect the semantic structure of the integers, so that both multiplication and addition operations are represented in the spoken number. Each boundary is also assigned a likelihood factor. These junctural determinations are determined without any use of segmental information (such as spectral estimates), and are directly related to the structure of the utterance.
An Experimental Technique for Establishing Lexical Variants by Rule in Automatic Recognition of Continuous Speech
Authors: Tappert C. C. , Dixon N. R.
Published: October 2005

The primary task in phonetic-to-lexical translation is to develop procedures which, from a pragmatic point of view, provide the necessary paths for changing an acoustic-continuum reality into a series of discrete standard-orthographical forms, which, at the present time, exist only as theoretical abstractions, Implicit in this problem is the assumption that words exist acoustically, even though complexly, in a many-to-one mapping. For automatic recognition, a technique is required that will provide the variety that is to be accounted for in this many-to-one mapping. Since words are known to be highly variable with regard to their phonetic constituents, it is necessary to tie a representation system to some unit which is smaller than the word itself, but larger than the individual phonetic unit. In the present system, it was tentatively decided to attempt variant generation based on units generally corresponding to the syllable. While present results are not conclusive, it appears viable to continue the development of this approach. Whether or not a within-word unit can be used to characterize all interword phenomena has yet to be determined.
A Theory on the Characteristics of Pitch and Formant Frequency Transitions in Human Speech
Authors: Doublier R. M.
Published: October 2005

Perceptual experiments have shown that the characteristics of fundamental frequency (pitch) and formant frequency variations usually represent a more important acoustic cue than those of the formant amplitudes. Unfortunately, however, the exact nature of these frequency transitions is far more subtle. If the speech production process is viewed as a closed-loop feedback control system, application of modern control theory techniques yields a rather interesting model for the vocal-tract control function. This system may be viewed in terms of the familiar phase-locked loop. The loop filter model, which appears to fit both theoretical considerations and the empirical (sound spectrograph) results, is the so-called “imperfect integrator,” with transfer function F(s) = (s+a)/(s+b). A discussion of this proposed model, including samples of synthetic speech, is presented.
Preliminary Model of Tone, Intonation, and Segmental Duration in Serbo-Croatian
Authors: Purcell Edward T.
Published: October 2005

The paper will describe a 600 statement FORTRAN IV subprogram for the synthesis-by-rule of simple statements in Serbo-Croatian, a Slavic tone language. The model receives an input phoneme string, calculates the duration of each segment in the string, computes a set of fundamental frequency values corresponding to the sentence intonation, and then modifies these fundamental frequency values to reflect the influence of word tone. Several factors affect the calculation of segmental duration, e.g., number of segments in the string, number of syllables in the word, accented versus unaccented syllable, type of accent, voicing characteristics of adjacent consonants, and others. Word tone is calculated as a deviation from the previously defined sentence intonation. The paper will be accompanied by slides and tape-recorded samples.
Computer-Assisted Phonetic Analysis Techniques for Large Recorded Corpuses of Natural Speech
Authors: Malécot André
Published: October 2005

A system of computer programs has been developed for creating, from surreptitiously recorded conversations, data files containing phonetic transcription, intonation and stress patterns, allophonic variations, grammatical functions, demographic information such as the age and occupation of each speaker, psychological factors such as degree of formality, emotional state and intellectual level of subject matter, and paralinguistic factors such as syllabic rate, loudness, etc. The system also includes programs for locating phonetic patterns, expressed in a language readily understood by phoneticians with no computer training, and for analyzing them statistically, either for the corpus as a whole or as functions of any of the nonlinguistic or paralinguistic variables mentioned above. These techniques have initially been applied to 50 half-hour recordings of conversations with members of the Paris “establishment,” revealing a number of phonetic laws hitherto unsuspected. The method is now ready and available for the study of the phonology of other languages, and other applications have appeared. One particularly promising possibility is the establishment of patterns of phonetic habits for a given number of individuals for voice verification purposes.
Equivalent Sound Pressure Levels of Different Pressure-Gradient Hydrophones at Low Frequencies due to Turbulent Flow
Authors: Lee S. P.
Published: October 2005

Assuming turbulent pressure fluctuations near a hydrophone to be a substantial contributor to the acoustic low frequencies, the low-frequency response of a pressure-gradient hydrophone with different shapes and sizes is studied. It is demonstrated that the predicted equivalent sould pressure level at low frequencies can be reduced by changing the shape and/or size of the hydrophone. The result of the study shows that a pressure-gradient hydrophone with spherical shape exhibits 4–10 dB reduction in the equivalent sound pressure level as compared with a cylindrical shape at a frequency of 10 Hz.
A Reverberant Water Tank for Underwater Measurements
Authors: Watters B. G.
Published: October 2005

This paper describes the water-filled tank used at BBN for measuring the radiated-noise power of underwater sources. The rank has centerline dimensions of 32×23×14 ft and contains 11 000 ft2. Its lowest resonance frequency is 220 Hz; the lowest usable 13-oct band is centered at 320 Hz—low enough for direct measurements on full-size torpedoes. The tank can accommodate a large torpedo, full-scale sections of sonar domes and similar constructions, and suitably scaled models of larger structures. The ambient noise is low, near Knudsen SSO. The wall absorption coefficient is small (less than 5% at 1 kHz), producing very long reverberation times (up to 5 sec). A sound-absorbing treatment was developed to adjust the reverberation time to about 34 sec at all measurement frequencies. A multiple-hydrophone incoherent array is used to reduce the sampling error. The residual error due to the finite number of samples and to finite tank volume has been evaluated and compared to theoretical estimates. The facility is also used for ordinary pulsed “free-time” measurements.
A Low-Frequency Technique for the Underwater Calibration of the Individual Elements of a Line Hydrophone Array
Authors: Zalesak J. F. , Trott W. J.
Published: October 2005

The calibrator consists of three coaxial internally radiating piezoceramic cylinders with their ends and outside surfaces shielded. These piezoceramic cylinders terminated with coaxial metal tubes form a feed-through calibrator when suspended in an open, water-filled trough. The two outer piezoceramic cylinders produce the sound which is monitored by the central piezoceramic cylinder. The calibration procedure consists of comparing the output from a line hydrophone element located inside the central piezoceramic cylinder with the output of the piezoceramic cylinder. The purpose of the water-filled metal tubes is to provide sufficient mass reactance in order to retain a usable sound pressure level at low frequencies. The upper frequency at which this procedure is valid is determined by the lowest resonant frequency of the piezoceramic cylinders. Pertinent design considerations of the calibrator are presented, and the technique for measurement is evaluated using a calibrator as described above.
Transducer Sound Dome Interaction
Authors: Pond H. L. , Hoy R. W.
Published: October 2005

The acoustic interaction of a transducer and a surrounding sound dome is analyzed by a modified separation of variables method. The theory is described for transducer and dome of general shape. If they arc concentric spheres, the method reduces to classical separation of variables. Perhaps the simplest crumple that uses the general theory in a significant way is obtained if transducer and dome are concentric spheres but the thickness of the dome varies with position. Numerical results are given for this case. For the calculations the velocity at the transducer is phased to a plane wave and its magnitude multiplied by a constant to adjust for a fixed transducer power output, which is taken as that for the no-dome case. The results show that, with a dome that has a thickness increasing uniformly from a minimum value A in the direction of the main radiated beam to a maximum value in the opposite direction, the directivity index and main beam magnitude are increased several decibels in comparison with results for a dome of constant thickness equal to the average of A and B.
The Effect of a Biphase Lubricant on Induction Motor Bearing Noise and Stability
Authors: Muster Douglas , Beauchamp Jeffery O.
Published: October 2005

A specially constructed single-phase induction motor was used to study the effect of a biphase (liquid-solid) lubricant on the stability of and noise from its bearings. It is shown that the stability of a full-film bearing was improved when a biphase lubricant was used. The biphase lubricant was an SAE 20 oil with from 5% to 20% (by volume) to l-μ fluorinated ethylene propylene (FEP) particles in suspension. A small reduction in bearing noise was observed. This was associated with the corresponding stabilizing effect of the FEP-loaded lubricant.
The Radiation Resistance of a Simply Supported Beam
Authors: Chung J. Y. , Crocker M. J.
Published: October 2005

Convenient approximate solutions for the modal radiation resistance are presented for a baffled simply supported beam that is acoustically narrow. The results compare very well with those obtained by numerical integration, which are considered to be exact. The results calculated from the equations presented have been compared with the existing approximate solutions [R. H. Lyon and G. Maidanik, “Power Flow Between Linearly Coupled Oscillators,” J. Acoust. Soc. Amer. 34, 623–639 (1962)]. It is seen that in most frequency ranges the results presented offer better accuracy than those referenced. The approximate solutions presented are derived from an exact series solution of the modal radiation resistance. Three equations are derived for three different regions, namely, above-coincidence, below-coincidence, and about-coincidence regions. For mode numbers higher than six, the equations for above and below coincidence practically cover the entire frequency range.
First Steps toward Noise Reduction of a Fly Shuttle Loom
Authors: Emerson Paul D. , Georgopoulos George
Published: October 2005

Several simple and inexpensive loom modifications were evaluated as means of reducing noise at the source in fly shuttle looms. Noise from a Draper model X loom 40 in. wide and running at 160 picks per minute was analyzed before and after modification. Spectra were determined both with and without a shuttle. Reductions of 2 dB in all weighted scales were achieved.
Organization of the Posterior Colliculus
Authors: Adams Joe C. , Teas C.
Published: October 2005

Internal organization of the posterior colliculus cut in the coronal plane is demonstrated in silver-stained material in a variety of species. Within the central nucleus, predominant fiber paths cross dorsolateral to ventro- medial with another group crossing at right angles directed in the dorsomedial to ventrolateral plane. Electrophysiological investigations in the chinchilla indicate that penetrations made with a microelectrode in the dorsolateral to ventromedial direction successively encounter neurons whose temporal patterns are quite similar. Tonotopic organization corresponds to that previously described in the cat. Penetrations made in the dorsomedial-to-ventrolaterai plane reveal little consistent progression as the electode moves through the central nucleus. Results are described in view of previously described input to the colliculus.
The Effect of Interaural Phase at Different Frequencies on the Discharges of Cells in the Posterior Colliculus of the Chinchilla
Authors: Teas D. C. , Adams J. C.
Published: October 2005

Some cells in the posterior colliculus with discharge latencies between 7 and 10 msec (presumably in the central nucleus of the colliculus) show variation in their discharge rates with changes in interaural phase of the acoustic stimuli. These cells may show a characteristic interaural delay since their response rates can reach a maximum (or minimum) at the same interaural time difference for different acoustic frequencies. However, for frequencies about Z oct below an optimum characteristic delay frequency, optimal delays may produce opposite effects. That is, delays that were inhibitory at the higher frequencies may produce excitation at the lower frequencies, and delays that produced excitation at the higher frequencies may produce inhibition at the lower frequencies. Although our data support the idea of a temporal regularity in changes of discharge rate with interaural phase changes, the label, characteristic delay, may be too limited a descriptor for cells that respond to interaural time or phase differences.
The Effect of Stimulus Intensity at Different Interaural Phases on the Discharges of Cells in the Posterior Colliculus of the Chinchilla
Authors: Teas D. C. , Adams Joe C.
Published: October 2005

Binaural intensity functions for cells in the posterior colliculus can vary in slope and sensitivity depending upon the phase relations of the stimuli at the two ears. Interaural phase differences that produced low and high discharge rates were chosen as locations on a cell's phase function at which to examine its response to binaural intensity. The inhibitory or excitatory effect of phase angle is maintained across a wide range of intensity.
Variation of Excitability of Neurons in Primary Auditory Cortex in the Unanesthetized Macaque Monkey; Effects of Sleep and Body Movement
Authors: Merzenich M. M. , Brugge J. F.
Published: October 2005

Microelectrode mapping experiments have been conducted to determine the position, size, and internal organization of the primary auditory field in the macaque. These experiments have revealed: (1) The primary field is strictly tonotopically organized, and the entire cochlear partition is represented within it. (2) The boundaries of the primary field can be defined on cytoarchitectonic as well as physiological bases. (3) The primary field is bounded by four other representational areas, and there is evidence for fields beyond these. Several of these secondary fields can also be delimited on cytoarchitectonic bases, and several appear to be tonotopically organized. Studies have been made of the responsiveness of single neurons in several of these regions in unanesthetized monkeys during stages of wakefulness and sleep. The state of the animal was monitored by the EEG and by close inspection over dosed-circuit television. When the animal was awake and sitting quietly, neurons could be very responsive to pure tones though the number of spikes evoked could vary from one stimulus to the next. The responsiveness of many neurons was dramatically reduced during corpuscular body movement. Similarly, a neuron's responsiveness was often very much reduced during both slow-wave and REM sleep.
A Comparison of Averaged Evoked Potentials Recorded from Auditory Nerve Region and Brain Cortex in Waking Monkeys
Authors: Wilpizeski Chester R. , Maioriello Richard P.
Published: October 2005

Squirrel monkeys were fitted permanently with rigid depth electrodes having tips localized in the auditory nerve region and with screw-type electrodes fixed on the surface of the parietal brain area (“vertex”). Summed records of pure-tone evoked potentials were recorded from both electrode sites using either a digital or an analog signal averager. Compared with cortical AERs, nerve evoked potentials showed greater amplitudes, greater resistance to habituation, less test-retest variability, and were characterized by less ambiguous waveforms at near-threshold levels. Acuity functions based on nerve AERs generally show greater sensitivity (lower detection levels) than those based on brain cortex responses.
Human Brainstem Electrical Responses to Acoustic Signals
Authors: Galambos R. , Hecox K. , Hillyard S. , Picton T. , Furman G. , Leigh M.
Published: October 2005

Jewett and Williston [Brain 94, 681 (1971)], nsing conventional EEG scalp electrodes, recently demonstrated click-evoked electrical responses that appear during the first 10 msec post-stimulus and evidently reflect activity in the auditory nerve and progressively higher brain stem structures. We will describe experiments aimed toward developing a clinical audiometric test based upon these electrophysiological responses. Using clicks delivered at rates of 20–75/sec, and computer averaging of 2000 to 6000 responses, we have shown in 10 normal subjects that the wave labeled V by its discoverers increases in latency from 6 + 0.5 msec at a click intensity of approximately 60 dB SL to 8 or 9 msec at levels around 10 dB SL. The amplitude of wave V also declines as a function of decreasing intensity. Brief tones generate similar functions. Evidence that these responses are generated by the brain, not by muscle contractions or other antifactual sources, will be presented.
Effects of Long Onset Ramp on Auditory Evoked Patentials (AEP)
Authors: Williams K. N. , Elfner L. F. , Bothe G. G.
Published: October 2005

Human event related potentials (ERP) were taken using averaging techniques to tonal pulses with systematically varied onset ramp. The rate at which the tonal pulse grows to full amplitude (ramp) was linear on both signal onset and offset. Auditory evoked potentials (AEP), were taken on seven naive college sophomores, with demonstrated normal hearing (ISO, 1964), for onset ramps of 50, 150, 500, 1500, and 5000 msec and a no-signal condition. Offset was 50 msec for all signal conditions. Equipment, calibiation, between-subject variation, and noise considerations required that 64 trials be averaged to achieve useful (approx. 8:1) SIN ratios. Trials consisted of 5.05-sec signal condition to 45-dB sensation level full amplitude and 9.95-sec intertrial interval. Visual analyses indicate that onset ramp affects offset AEP progressively less for all signal conditions as ramp duration increases. Onset ramp associated AEP is not apparent beyond the 150-msec condition. Stepwise correlational analyses are being performed to clarify the apparent dichotomous onset/offset results.
Sound Absorption in Dimethyl Sulfoxide-Water Mixtures
Authors: Madigosky W. M.
Published: October 2005

Ultrasonic attenuation was measured in dimethyl sulfoxide mixtures over the frequency and temperature range 5–200 MHz and 25°C to − 80°C. At the higher temperatures the quantity α/f2 was found to be independent of frequency and in excess of the value calculated from the classical Stokes equation for shear viscosity. The excess attenuation can be attributed to a volume viscosity, which is two-thirds of the shear viscosity. At the lower temperatures α/f2 was found to be highly frequency dependent and less than that predicted by the Stokes equation. Furthermore, the data indicate that both shear and volume viscosities are relaxing with a single relaxation time. The low value of the excess attenuation observed at high tempeatures suggests that there are no specific hydrogen bonded complexes being formed. The dramatic decrease in α/f2 with increasing frequency at low temperatures seems to indicate the onset of a glassy state.
Origin of the Relaxational Sound Absorption in Sea Water below 1 kHz
Authors: Fisher F. H. , Yeager Ernest , Bressel Robert , Miceli John
Published: October 2005

From long-range sound transmission data, Thorp [J. Acoust. Soc. Amer. 42, 270 (1967)] concluded that sea water has a relaxation at 1 kHz (τr≃1.6×10−4 sec) in addition to the magnesium sulfate relaxation at ∼100 kHz. Laboratory measurements with the temperature-jump relaxation method confirm the existence of a relaxation of the proper time (τr = 1.5×10−4 at 9.7°C) and identify this relaxation with the boric-acid-borate system in sea water. No relaxation has been observed in the range 10−5–10−2 sec in synthetic sea water, made up without borsres or boric acid. Pressure shock measurements in boric-acid-borate solutions also reveal a relaxation in the proper time domain. The slow relaxing process is believed to involve the B(OH)3-B(OH)4− reaction coupled to fast reactions involving the other buffer systems (e.g., CO32−-HCO3−) in the sea water. The complete analysis of this relaxation in sea water is complicated by these faster chemical processes. [Supported by Office of Naval Research.]
Ultrasonic Absorption Measurements in Single Organic Crystals
Authors: Victor A. E. , Altman H. E. , Beyer R. T.
Published: October 2005

Two sets of measurements are reported of the ultrasonic absorption coefficient in single organic crystals. In benzene, the measurements were made with longitudinal waves in the frequency range 6–38 MHz and over the temperature range 170°–250°K. Similar measurements over the same temperature range are reported for crystalline nitrobenzene for frequencies 6–62 MHz. A newly designed seedholding crystal growth tip greatly aided the growing of the single crystals of nitrobenzene. Present absorption theories predict absorption proportional to the square of the frequency, over the ranges covered in these experiments. In the case of benzene, however, there appears to be a relaxation peak in the range 15–20 MHz for propagation along the a, b axes. The propagation along the c axis is more complex. The experimental results for both crystals are compared with pertinent theory. [This work was supported in part by the Advanced Research Projects Agency, Department of Defense, and the National Science Foundation.]
Improved Perceived Noise Computational Algorithm
Authors: Gruner W. J.
Published: October 2005

An improved algorithm for the computation of the perceived noisiness of an acoustic pressure stimulus has been developed. The algorithm is presented along with the development logic and fit criterion. Coefficient determination is achieved using a constrained least-squares method. A statistical analysis of fit is presented for the derived algorithm as well as previously available methodology. The new algorithm is shown to improve accuracy from 26% to 36% depending upon amplitude and reduces computational storage requirements by 15%. Improved accuracy is achieved at every applicable 13-oct band. This algorithm was derived during psychophysiological criteria development for space shuttle system launch and static firing sites. [The development was funded under contract under the cognizance of the George C. Marshall Space Flight Center.]
Effect of Noise on Sleep
Authors: Thiessen G. J.
Published: October 2005

When appropriate account is taken of duration of the stimulus the present data on interference of sleep by noise seem to present a consistent picture. This picture indicates a “threshold” of interference which varies inversely with the duration of the stimulus, while for a given stimulus length the probability of a shift in sleep level is proportional to the stimulus level. The slope of this line seems approximately independent of stimulus duration. Thus, when all the available data are combined, they appear to contradict previous statements that for sonic booms and other acoustic stimuli of short duration there is practically no dependence on intensity once the threshold of sleep disturbance is exceeded. There is still no evidence that any appreciable habituation exists.
In-Ear Monitoring of Noise Exposure
Authors: Brammer A. J. , Piercy J. E.
Published: October 2005

The device described at the last meeting has been used to obtain a continuous record of the sound field at the base of the concha. When the data are transformed into an equivalent diffuse field that would exist at the center of the head, an individual's exposure to noise can be directly compared with existing criteria for hearing conservation that include effects resulting from intermittent exposure (CHABA). A record of sound level as a function of time, obtained during a representative work cycle, coupled with a knowledge of the noise levels generated by similar machines enables a decision to be made on economic grounds as to whether to modify the work cycle or the machine. The method has been applied to operators of skidders who were found, in general, to experience an exposure considered unacceptable by either CHABA or OSHA. The use of quieter than average skidders and minor restrictions in the work cycle produces a noise exposure that would be acceptable to CHABA.
Survey of the Noise Environments of 300 Small Industries in North Carolina
Authors: Royster L. H. , Creel W. C. , Thomas W. G. , Scott C. E.
Published: October 2005

A total of 300 industries were surveyed with respect to their respective noise environments. These industries generally employed less than 100 employees. The surveys were conducted by the North Carolina Department of Labor Staff. Pertinent information concerning number of employees exposed, percent of employees exposed in different company size ranges, etc., was also obtained during the survey. These results are presented.
A Parallel between Degree of Encodedness and the Ear Advantage: Evidence from a Temporal-Order Judgment Task
Authors: Day Ruth S. , Vigorito James M.
Published: October 2005

Some speech sounds are more highly encoded than others. In acoustic terms, this means that they undergo more restructuring as a function of neighboring phonemes. In psychological terms, it may mean that special processing is required to perceive them. Stop consonants appear to be the most highly encoded speech sounds, vowels the least encoded, with other sounds falling in the middle. Stops, liquids, and vowels served as target phonemes in tests of dichotic temporal-order judgment (TOJ). A different syllable was presented to each ear with one leading by 50 msec, e.g., BAE(50)/GAE. Subjects reported which syllable began first. Ear difference scores were obtained by taking percent-correct TOJ on trials where a given ear received the leading stimulus and subtracting percent-correct TOJ on trials where the other ear led. Stop consonant pairs yielded a right-ear score, liquids a reduced right-ear score, and vowels a left-ear score. A right-ear advantage in dichotic listening is usually interpreted as reflecting the operation of a special speech processing mechanism. The present data suggest that the highly encoded speech sounds required the services of this mechanism to a greater extent than did the less encoded sounds.
Dichotic Right Ear Advantage in Males and Females—Ages 5 to 13
Authors: Berlin C. I. , Lowe-Bell S. S. , Hughes L. F. , Berlin H. L.
Published: October 2005

A total of 150 right-handed children (15 boys and 15 girls in each age group: 5, 7, 9, 11, and 13) listened dichotically to 60 pairs of precisely aligned nonsense syllables. All children had normal peripheral pure-tone sensitivity and monotic syllable intelligibility. A right ear advantage was seen even in children 5 years of age with no differences between the sexes as a function of age. The size of the right ear advantage and the nature of the phonetic errors, as well as the interactions between ear, age, sex, and phonemes will be presented. All effects will be discussed in terms of double corrects (where both items of the pair were correctly perceived) and single corrects (where only one item of the pair was correctly perceived).
The Effect of Memory Load on the Right Ear Advantage in Dichotic Listening
Authors: Yeni-Komshian Grace , Gordon Joel , Sherman Paul
Published: October 2005

The right ear advantage for reporting speech signals observed in dichotic listening tasks was further investigated to examine the effects of memory load on this phenomenon. The time interval between stimulus presentation and response was varied. In all experiments subjects went through a no-delay condition (immediate recall) and different delay conditions that sampled intervals between 5 and 15 sec. Normal adult listeners were stimulated with dichotic triads composed of one-syllable common English words. The first experiment consisted of a free ear-order recall task, while in the second experiment subjects were cued as to which ear to report from. The results from both experiments show an overall right ear superiority, which was most pronounced in the longest delay condition. There was a sharp drop in accuracy for both ears at about 5–6 sec delay. With increasing delay times, the number of correct responses for the left ear stimuli continued to decrease, while the number of correct responses for the right ear stimuli either leveled off or showed an increase. A third experiment investigated the effect of reducing memory load by providing the subject with a chart listing all the stimuli (chart condition). The effect of delay on the right ear advantage with no chart was replicated, but the right ear effect was not observed in any of the chart conditions. The absence of a right ear effect in the chart conditions was due to an increase in the accuracy of the left ear scores while the right ear scores remained at the same level of accuracy under chart and no chart conditions. These findings are interpreted to demonstrate that the right ear advantage is not solely a perceptual phenomenon but that the recall of verbal material is also lateralized and complements the perceptual asymmetry. [Supported by PHS Post Doctoral Fellowship and research grants from NINDS.]
The Verbal Transformation Effect: A Comparative Study of the Verbal Transformations of Phonetically Trained and Nonphonetically Trained Listeners
Authors: Lass Norman J. , Gasperini Richard M.
Published: October 2005

Continued listening to recorded repetitions of a stimulus has been found to produce perceptual illusory changes in normal listeners. This phenomenon was labeled by Warren [Brit. J. Psychol. 52, 249–258 (1961)] as the verbal transformation effect. The purpose of this investigation was to compare the reported verbal transformations of phonetically trained and nonphonetically trained subjects in terms of the number of forms and transitions elicited, number of repetitions of the stimulus prior to the subject's first verbal transformation, types of transformations reported, and exact forms employed. A total of seven auditory stimuli, representing variations in meaningfulness and phonetic complexity, were presented individually to 28 phonetically trained and 28 nonphonetically trained listeners. Results of their responses to the stimuli indicate that there are both similarities and differences between the two groups. The differences that exist are quantitative, but not qualitative, in nature. The phonetically trained group reported more forms and transitions, and required fewer repetitions of the stimulus prior to their first verbal transformations, than the nonphonetically trained subjects. However, both listener groups reported the same types of verbal transformations and, in many instances, the identical forms as well. Implications of these findings for future research are discussed.
A State-of-the-Art Report on Aeroacoustic Testing in Conventional Wind Tunnels
Authors: Arndt R. E. A. , Boxwell D. A.
Published: October 2005

The increasing attention given to aerodynamically generated noise brings into focus the need for quality experimental research in this area. To meet this need, several specialized anechoic wind tunnels have been constructed. In many cases, however, it is desirable to use conventional wind tunnels. Two basic problems are inherent in conventional facilities; high background noise and strong frequency-dependent reverberation effects. This paper reviews the known acoustic characteristics of several existing tunnels and presents new data obtained in a conventional 7 × 10 wind tunnel and a smaller 4 × 5 wind tunnel, which is convertible from a closed-jet to an open-jet mode with an anechoic test section. The data from the smaller tunnel serve as a guideline for evaluating design techniques involving a closed-jet and sandwich-wall construction. Model scaling parameters and data reduction techniques are also considered. It is concluded that existing conventional wind tunnels can be utilized for aeroacoustic measurements. The overall technique, however, will require a careful balance of acoustic treatment, selection of proper model scaling, experimental technique, and data reduction schemes. Several suggestions are offered that are pertinent to a relatively large, low-speed wind tunnel facility.
Some Effects of Modal Coupling in the Transduction of Turbulent Pressure Fluctuations into a Closed Cavity
Authors: Strawderman W. A.
Published: October 2005

The transduction of turbulent boundary layer pressure fluctuations into a closed, rigid walled, rectangular cavity via a flexible, thin plate is theoretically treated from a model approach. The turbulence-excited vibration of the flexible plate induces pressure fields in the fluids internal and external to the cavity, which react on the plate and cause coupling of the plate modes. Since the plate modes excite the cavity modes, coupling of the plate modes results in coupling of the cavity modes. The forces on the plate resulting from coupling with the cavity may be interpreted as additional inertia or bending stiffness, and those resulting from coupling with the free field may be interpreted as additional inertia and resistance. The coupling forces cause changes in both the mode shapes and natural frequencies of the cavity.
Infrasound of 1 through 16 Hz Associated with Clear Air Turbulence
Authors: Posmentier Eric S.
Published: October 2005

1- through 16-Hz infrasound detected by a four-element array of microphones was recorded six times daily from April through June 1971. Four records were selected as representative of extremely low-amplitude conditions. Four other records were chosen as representative of highly coherent, strong-amplitude records. These latter four records all exhibited very high horizontal phase speeds, implying near-vertical incidence. A search was made for meteorological parameters which varied consistently with the acoustic data. It has been found that all four low-amplitude records were from periods during which nonturbulent conditions probably existed between altitudes of 6 and 12 kin. The four strong-amplitude records coincide with times of high probability of clear air turbulence. The turbulence judgments are based on the wind speed, the directional shear, and Richardson's number, calculated from nearby radiosonde data. It is concluded that 1- through 16-Hz infrasound may be radiated by clear air turbulence, and may be a basis for a remote passive detection system. If confirmed, this conclusion would have significant implications for both practical and theoretical problems associated with clear air turbulence.