bluuebunny/crossref_metadata_2025 huggingface dataset:
Perceptual learning of acoustic patterns: Mirror-image versus direction-of-glissando pairs
Authors: Grunke M. E.
Published: October 2005

In natural speech prevocalic stop consonants are roughly the mirror image in time of their postvocalic counterparts. Are mirror-image acoustic patterns in general perceptually related? In a perceptual learning paradigm subjects were required to map four nonspeech acoustic patterns into two response categories. The acoustic patterns consisted of one, two, or three sinusoidal tones with frequencies corresponding to formants of the syllables /ba/, /da/, /ab/, and /ad/. Each component tone contained a rapidly rising or falling frequency glissando that either followed or preceded an interval of constant frequency. Stimulus mapping in which mirror-image pairs were assigned to the same response were easier to learn than mappings based on direction of the frequency glissando. In a second experiment subjects attempted to match the acoustic patterns to either phonetic labels—“ba,” “da,” “ab,” and “ad”—or to acoustic labels representing pitch change— ↽, ↼, ⇁, ⇀. For single- and double-tone patterns acoustic labels were more accurately matched than phonetic labels, but phonetic categorization was more accurate for triple-tone patterns. A third experiment identified a configural aspect of the nonspeech patterns, overall frequency or pitch, as the salient perceptual property accounting for the advantage of mirror-image mapping. [Work supported by NIMH.]
Effect of modest sidetone delays in modifying talker rates and articulation in a communications task
Authors: Schmidt-Nielsen A. , Coulter D. C.
Published: October 2005

Sidetone delay (delayed auditory feedback) is known to cause speakers to talk more slowly, and at delays of about 200 ms also causes severe articulation disturbances. If shorter delays can slow speech without adverse effects on articulation, this effect could be used to make talkers speak more slowly in certain communications situations. Subjects read lists of 1, 2, 3, or 4 syllable words and of sentences under each of 6 delay conditions (0, 7.5, 15, 30, 60, and 100 ms). Delays of 15–30 ms caused a significant slowdown in speaking rate with no adverse effects on articulation. Delays of 60–100 ms caused a greater slowdown but also had a noticeable adverse effect on speech quality, especially for sentences and polysyllablic lists. In communications situations where the quality of transmitted speech is degraded (e.g., vocoded speech), sidetone delay may be useful in modifying the talk's behavior to improve overall speech quality.
Lower intensity limits of noise which produces measureable TTS following 24-h exposure
Authors: Melnick W.
Published: October 2005

If the assumption that noise which does not produce measureable TTS will not produce NIHL, and if asymptotic threshold shift (ATS) represents the limit of predictable hearing loss which might be expected from a given noise environment, then determination of the lowest intensity capable of producing measureable ATS should provide a reasonable estimate of the lower intensity bound of hazardous noise. To define this lower noise level, ten normal hearing males were exposed to pink noise at each of the LAM-76, 79, 82, and 85 dB for 24 h, a duration previously found to be sufficient for production of ATS. Thresholds were measured at 0.25, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 6.0, and 8.0 kHz before, during, and after the exposure. Significant threshold shifts were measureable for the frequencies from 1000 to 4000 Hz when the LA was 85 dB. Although there was a trend toward a systematic change in threshold with increased exposure duration at 82 dB, the variability of the measures precluded attaching any significance to these threshold shifts. [Work supported by Air Force.)
Interstimulus interval as it affects temporary threshold shift in serial presentations of loud tones
Authors: Tobias Jerry V.
Published: October 2005

Temporary threshold shifts were measured repeatedly during a session in order to determine effects of interstimulus interval (ISI) on the shift. The fatiguing sound was a 3-min, 110-dB-SPL, 4000-Hz pure tone. Immediately following the 3-min stimulation, Békésy-audiometric tracings were made for 3 min at 5656 Hz. Then the subject sat quietly for the ISI that was used during that session. The effect of the subject's rest time or time off was compared at two points on the recovery curve: at 30 s and at 2 min following the cessation of the fatiguing sound. For short-duration ISIs, each successive threshold showed a greater shift than the earlier ones, for at least four tests. As ISI was increased, improvement seemed not to follow the expected logarithmic form. At some critical value that varies from subject to subject, successive tests no longer differ from each other; each one is similar to a first trial in which no previous exposure to the high-level tone has occurred. For most subjects run under these conditions, the critical ISI value is at least 30 min.
Some nonauditory correlates of the hearing threshold levels of a noise-exposed aviation population
Authors: Thomas Gerald B. , Williams Carl E. , Hoger Norman G.
Published: October 2005

One of the distinguishing characteristics of noise-related research is individual differences in susceptibility to deleterious noise effects. In an effort to identify and verify possible contributing variables to the susceptibility question, an examination of the relationship between the hearing threshold levels and selected anatomical, physiological, and behavioral measures of a noise-exposed population was undertaken. Using data from NAMRL's “Thousand Aviator Study,” subjects categorized as “normal hearing” and “hearing-impaired” were compared along several nonauditory dimensions. Variables analyzed to date include systolic and diastolic blood pressure, serum cholesterol levels, measures of triglycerides and lipoproteins, smoking history, and eye color. Results indicate that the “normal hearing” and “hearing-impaired” groups differed significantly (p < 0.05) in regard to smoking behavior and eye color. Additional analyses to be presented will include such variables as finger pulse amplitude, alcohol consumption, and psychological temperament.
Measurement of the 2f1-f2 cubic difference tune with the binaural masking level difference
Authors: Lutfi Robert A. , Yost William A.
Published: October 2005

Investigators have demonstrated that the 2f1-f2 cubic difference tone (CDT) behaves in many respects as if a physical tone at the CDT frequency were actually present in the acoustic stimulus [J. L. Goldstein, G. Buchsbaum, and M. Furst, J. Acoust. Soc. Am. 63, 474–485 (1978)]. We further examined this property of the CDT by asking whether a binaural masking level difference (BMLD) can be obtained through the interaction of a 500-Hz physical tone to one ear and a CDT of the same frequency to the other ear. Thresholds for the physical tone were obtained as the phase of this tone varied through 360° relative to harmonically related primaries (f1 equals; 625 Hz,f2 = 750 Hz). A continuous low-pass (2000 Hz) diotic noise comprised the masking stimulus. The level of this noise varied to establish thresholds in a two-interval same-different adaptive procedure with the primaries occurring in both observation intervals. In keeping with other physical stimulus-like properties of the CDT, the results show BMLDs of 10–13 dB. CDT phase and level estimates derived from additional BMLDs are compared to estimates obtained with the traditional cancellation procedure. The implication of these results regarding the physiological origin of the CDT is discussed.
Fluctuations in the oscillation of the flue organ pipe—the unsteady steady state
Authors: Nolle A. W.
Published: October 2005

Although the oscillation frequency of a flue organ pipe can usually be measured within 1% or less, observations of the signal with an oscilloscope may show small, apparently random fluctuations in the waveform. These fluctuations have been investigated with a model pipe having a specially designed flue to discharge turbulence below the jet opening. Nonperiodic fluctuations in the fundamental amplitude are found by digital signal processing. For example, the fluctuations are 1–2% for these conditions: Resonator section, 38 × 57 mm; length, 360 mm; lip height, 6.5 mm; jet opening, 0.6 mm; lip radius 0.2 mm; and supply pressure 45-mm water. The instability is attributed to interaction between the resonator feedback mechanism and the edge-tone feedback mechanism. (The tone has a “sizzle” which is commonly regarded as a vestigal edgetone effect.) The “partials” near the edgetone frequency (about four times the speaking frequency in this case) are shown to be effectively noise bands. Successive amplitude samples from this region have significant cross correlation with those from the fundamental.
Occupational and nonoccupational noise dosimetry measurements on Air Force personnel
Authors: Fairman Terry M.
Published: October 2005

Personal noise dosimetry monitoring devices have been used for some time by various Air Force bases to determine the occupational noise exposures of Air Force personnel. In May 1978, Aerospace Medical Research Laboratory began consolidating noise dosimetry data from these bases. The author has personally collected data during the past year on visits to four Air Force bases. Over 418 separate 8-h occupational noise exposure measurements were made on 120 different people. Some of the research involved 16 people wearing a dosimeter for 1 day or up to a week at a time. Seventy-three separate 24-h measurements were made. From these data a comparison was made between the off-duty noise exposures and the work-related noise exposures. The individual's work-related noise exposure (except in a few instances) contributed the highest noise levels to the person's 24-h noise dose. The 24-h noise levels ranged from 60 to 92 dBA with a median level of 77 dBA. Previous studies supported by AMRL have shown a median level of 75 dBA for the typical American. This paper will discuss the basis of the AMRL research, as well as the merits of noise dosimetry and some of the problems encountered during the study. [Work supported by EPA and USAF.]
Hydroacoustic low-frequency transducers
Authors: Bouyoucos John V. , Selsam Roger L.
Published: October 2005

Hydroacoustic transducers for generating acoustic signals underwater from hydraulic power are described. The acoustic transmission produced by such transducers is a high power replica of a low-level electric control signal input. The versatility of the power conversion process enables certain useful trade-offs to be obtained between bandwidth, source level, and power-conversion efficiency. These trade-offs are outlined. For low-frequency transmission (below 500 Hz) where pressure compensation is not desired, the acoustic properties of a radiating structure, designed to withstand the ambient pressure, can be modified by acoustic circuit elements internal to the transducer to shape the transmitted spectrum. The flexibility of the design approach permits cumbersome pressure compensation to be avoided while enabling optimization of the transduction process over a specified frequency band. An example of the design process will be given in some detail along with the performance characteristics of a practical device. [Work supported in part by the Office of Naval Research and the Naval Electronic Systems Command.]
Fluidic underwater sound source, 1–10 Hz range
Authors: Trott W. James
Published: October 2005

A one-watt sound source covering the frequency range from 1 to 10 Hz is under development. The source consists of a scoop towed 100 m beneath a ship feeding a modulated flow against a free piston backed by a compliant chamber. A constant sound-pressure output is obtained as the frequency is varied above the piston-compliant chamber resonant frequency. Fluidic circuit techniques are used to modulate the water jet that drives the free piston which produces the sound-source volume velocity. Low power electric signals are fed down the tow cable to control frequency and time modulation of the sound source. Ship speed determines the sound-pressure level.
Low ka scattering by air-filled shells
Authors: Dragonette L. R. , Flax L.
Published: October 2005

The very low ka (0 < ka ⩽ 0.2) scattering by air-filled spherical and cylindrical shells is calculated as a function of shell thickness. The reduction in amplitude and the shift in frequency of the well-known bubble resonances with even the thinnest shells is demonstrated.
Theory of shape oscillations of drops and bubbles driven by modulated radiation stresses
Authors: Marston Philip L.
Published: October 2005

Deformations of drops and bubbles opposed by surface tension and driven by radiation stresses at the interface are calculated using spherical harmonic expansions for the radial and tangential stresses. Superposed acoustic waves produce stresses which oscillate at the difference frequency ω of the waves in addition to static stresses. When the effects of viscosity on the acoustic waves are omitted. the tangential radiation stress vanishes; a procedure is proposed for calculating the radial stresses from the theory for “Acoustic Radiation Pressure on a Compressible Sphere” [K. Yosioka and Y. Kawasima, Acustica 5, 167–173 (1955)]. The calculation of the response assumes incompressible second-order flow and omits the body forces which are normally associated with acoustic streaming. Resonance phase shifts and enhancements of the response should occur when ω is close to the natural oscillation frequency of a mode. Quadrupole resonance phase shifts and enhancements have been observed [P. L. Marston and R. E. Apfel, J. Acoust. Soc. Am. 63, S41(A) (1978): J. Colloid Interface Sci. 68, 280–286 (1979)]. [Work performed at Yale University and supported by ONR.]
The effect of glucose on the transport of kanamycin into perilymph
Authors: Juhn S. K. , Rybak L. P.
Published: October 2005

Understanding the mode of transport of aminoglycoside antibiotics into the inner ear fluids is important in elucidating mechanisms of ototoxicity and the processes that permit accumulation of toxic levels of these drugs in perilymph. Concentrations of kanamycin in serum and perilymph were studied in one group of chinchillas after 250 mg/kg IM (controls). A longer time was required for peak concentrations of kanamycin to be reached in perilymph compared to serum (four hours versus one hour). This suggests a selective blood-labyrinth barrier to kanamycin. A possibility of influencing the rate of transport of this drug by alteration of a blood component has been suggested (Guth et al., 1977). The effect of glucose loading (2.0 g/kg) on the rate of transport of kanamycin into perilymph was evaluated. Kanamycin concentration in perilymph after 250 mg/kg IM was significantly lower after glucose pretreatment compared to controls, suggesting that glucose may compete with kanamycin for transport through the blood-labyrinth barrier. A number of other factors may be responsible for these findings, however, a new method of affecting the transport of ototoxic drugs into the inner ear is introduced. The present study will help to characterize the alteration of the blood-labyrinth barrier to ototoxic drugs by administering a chemical substance which may compete with the passage of the drug into the labyrinth. [This work was supported by NIH Grant No. NS-12125.]
Development of aminoglycoside induced hearing loss in cats
Authors: Orr J. L.
Published: October 2005

Behaviorally trained cats [J. L. Orr, D. B. Moody. and W. C. Stebbins, J. Acoust. Soc. Am. 62, 1268–1272 (1977)] were tested with a threshold tracking procedure. Subcutaneous 60 mg/kg/day injections of kanamycin (Mcat. Fcat. and Ycat) or amikacin (Gcat) were given until a threshold shift of at least 20 dB occurred at 8 kHz. The hearing loss occurred first at 45 kHz and then progressed to 32, 16, and 8 kHz. Mcat, Fcat, and Gcat had similar cytocochleograms. No hair cells remained for several mm in the basal turn. For a few mm only inner hair cells were present, and then both inner and outer hair cells were present. These cats had normal low frequency hearing, threshold shifts (67 dB at 8 kHz for Mcat: 34 dB at 4 kHz for Fcat; 17 dB at 4 kHz and 59 dB at 8 kHz for Gcat), and no hearing at higher frequencies. Ycat had normal hearing to 8 kHz, no hearing at higher frequencies and cytocochleograms with a sharp transition from present to missing hair cells.
MITalk-79: The 1979 MIT text-to-speech system
Authors: Allen Jonathan , Hunnicutt Sharon , Carlson Rolf , Granstrom Bjorn
Published: October 2005

To mark the completion of a ten-year effort to develop a high performance text-to-speech algorithm, we have established a benchmark system called “MITalk.” Components of the computer-simulated bench mark include: (1) conversion of abbreviations and special text symbols, (2) a lexicon consisting of about 11 000 morphs with pronunciation and parts of speech, (3) morpheme analysis, (4) letter-to-sound rules, (5) syntactic analysis, (6) rules for stress assignment, boundary placement and phonological recoding, (7) fundamental frequency and segmental duration prediction, (8) phonetic-to-parametric conversion, and (9) digital formant synthesis. The MITalk-79 system is being extensively documented and its performance is being evaluated. The presentation will summarize aspects of system organization and performance. (A more complete description will be given in a one-week course to be offered June 25–29, 1979.) The oral presentation will include a five-minute demonstration of synthetic speech generated from English text with absolutely no human intervention. While currently simulated on a large digital computer, MITalk-79 is amenable to practical IC technology. Implementation issues will be briefly discussed. [We gratefully acknowledge the synthesis-by-rule programs and advice provided by Dennis Klatt.]
The effects of ADPCM coding and LPC vocoding on an automatic speaker verification system
Authors: McGonegal C. A. , Rabiner L. R. , Rosenberg A. E.
Published: October 2005

In an earlier report [C. A. McGonegal et al., J. Acoust. Soc. Am. 62, S4(A) (Fall 1977).] the effects of several transmission systems on speaker verification by human listeners were investigated. There it was shown that the transmission system played a significant role in the speaker verification process. In this talk we show the effects of the transmission system on an existing automatic speaker verification system [A. E. Rosenberg, Bell Systems Technical Journal 55, 723–744 (1976)] in which the measured features are pitch and gain as a function of time for a specified utterance. There were ten male and ten female customers and 40 male and 40 female imposters in this experiment. All utterances were recorded using a conventional telephone connection. Post processing included ADPCM coding and LPC vocoding. Preliminary results indicate that, on the average, the transmission system affects the verification accuracy, especially when the reference and test utterances are subjected to different transmission conditions.
Fricative discrimination based on human audition
Authors: Kimberley B. P. , Searle C. L.
Published: October 2005

As a continuation of our study of phoneme recognition based on human audition, we report on an attempt to recognize fricatives. Our system uses a bank of 13-octave bandpass filters to model to a first approximation the tuning curve data of Kiang, as well as the critical band data, over the speech frequency range. Five hundred and ten isolated fricative-vowel pairs, spoken by 19 different speakers: both male and female, were spectrally analyzed with the 13-octave system. Following spectral analysis 54 spectral features were quantified for each utterance. These features included voice onset time, time averaged spectra, and gross spectral energy distributions. The features from half the data set were used to train a decision algorithm, discriminant analysis. The system achieved 89% correct overall classification of the training set data. This classification system was then applied to an “unknown” set of utterances of ten different voices. This prediction experiment yielded 77% overall accuracy. In order to put the performance of the system into better perspective a psychophysical test was performed to determine the accuracy with which humans discriminate isolated fricatives. The results were 86% correct overall, not substantially better than the system performance.[Work supported by Medical Research Council and National Research Council.]
Automatic prototype selection for continuous speech recognition
Authors: Baker J. M.
Published: October 2005

Automatic prototype selection of phones, and other entities allows large amounts of data to be processed very efficiently. The HEAR acoustic processor, wholly developed and tested for continuous speech recognition at the IBM Thomas J. Watson Research Laboratory in Yorktown Heights, NY, applies Baum's algorithm for prototype selection. Peformance on two tasks with extensive training on a single speaker, in a quiet, high quality recording environment are reported for HEAR, used in conjunction with the standard training and decoding programs developed by the IBM Research Continuous Speech Recognition Group. Sentence recognition on a set of 125 test sentences (1010 words) of the artificial language 250 word “New Raleigh Language” is 100%. The word recognition rate on a set of ten test sentences (282 words) of the natural language, 1000 word “Laser-1000 Task” is 80% and reflects the performance of all the system components; e.g., search strategy, language model, pruning procedures, acoustic processor, etc. For only 3.2% of the words is the correct word hypothesized, fully matched, and rejected in favor of an incorrect word. These errors are comprised exclusively of substitutions and deletions of short function words (e.g., “of,” “the,” etc.), 2.2%, and deleted commas (realized acoustically only by optional interword pauses), 1.0%.
The human factor in isolated word data entry
Authors: Phelps R. W. , Wiesen R. A.
Published: October 2005

At present, most of the applications at Dialog Systems involve numeric input of one kind or another. Applications accomodate telephone speech from a large population and range from telephone toll management and switching to telephone bill paying which involves rather lengthy data entry. All entry is by isolated word. This paper will concentrate on users of these systems. Training and user format design along with human and system performance will be discussed in the context of a system that has been in operation for about nine months with some 4000 users. Since the user is affected by constraints of voice recognition protocol and parameters of the voice recognition system, these topics will also be addressed. Particular emphasis will be given to two styles of digit input. In the first, each digit is verified on input. In the second, short strings of digits are input and then verified by the user. Data from about 60 subjects will be presented and trade-offs between the two systems will be discussed. Dependent upon recognition rate, a mixture of the two styles gives an optimum solution.
Small sample statistics for likelihood-ratio tests
Authors: Bahler L. , Moshier S. , Rey T.
Published: October 2005

Classification by likelihood ratio of a one-dimensional random variate drawn randomly and with equal probability from one of two independent Gaussian populations is known to be optimal if misclassification costs are equal and statistics (true means and variances) are available; the expected classification error is then a known function of the statistics. In practice, likelihood functions are computed with sample statistics estimated from training sets of n samples. The effect of sample statistics in lieu of true statistics on the expected classification error is calculated to order n−1. The error is found to increase by a term proportional to n−1 over a wide range of statistics, unless the random variate is from the training set; in the latter case, the error decreases by that term. Monte Carlo experiments were performed with results supporting the theory.
Psychometric functions for frequency discrimination in spectral regions of normal and impaired sensitivity
Authors: Turner C. W. , Nelson D. A.
Published: October 2005

Both normal-hearing listeners and listeners with abrupt high-frequency sensorineural sensitivity losses were trained to asymptotic performance in a 2AFC pure-tone frequency discrimination task. Stimulus presentation levels were 80 dB SPL and base frequencies for Δf measurements were 300, 1200, and 3000 Hz. A method of constant stimuli was used to obtain psychometric functions and Δf was specified as the 75% correct performance level. Results from the normal-hearing listeners were consistent with other results recently reported [Wier, et al., J. Acoust. Soc. Am. 61, 178–184 (1977)]. Sensorineural hearing-loss listeners exhibited frequency discrimination deficits, relative to the normal-hearing listeners, in frequency regions of sensitivity loss and also in frequency regions of normal sensitivity, even after asymptotic performance levels had been attained. The psychometric functions from the impaired listeners exhibited slope values that were less than those obtained from normal-hearing listeners. Practice effects were observed to be considerable in all listeners. [Work supported by NIH Grant No. NS12125.]
Temporal-order judgments of speech and noise stimuli by normal and brain-injured subjects
Authors: Hughes L. F. , Holtzapple P.
Published: October 2005

Two classes of subjects (normals and brain-injured patients) were dichotically presented with either the six stop-consonants coupled with the vowel /a/ or two uncorrelated noise stimuli. A method-of-limits with stimulus-onset asynchronies (SOAs) varying from −60 to +60 ms was used in a two-alternative, forced-choice paradigm. The results indicate that an asymmetry exists in the perceptually generated data as a function of the ear receiving the leading signal. There was a greater probability of the right ear being identified as the ear receiving the leading stimulus for all SOAs less than 60 ms when the stimuli were CVs. This same finding holds for uncorrelated noise stimuli with SOAs less than 30 ms. The magnitude of the ear bias is greater and appears at longer SOAs for the brain-injured group. A major finding was that smaller SOAs were needed for noise stimuli than for the CVs to obtain the same accuracy for perceived order. [Work supported in part by NIH.]
Analysis of speechreading cues using an interleaving technique
Authors: Scheinberg Judy S.
Published: October 2005

A method of locating visible differences between “homophenous” phonemes has been developed. Alternating frames from two video recorded VCV utterances which differ only in the consonant are interleaved. The output contains odd frames of one utterance and even frames of the other. Presentation of these frames at 30 frames per second result in a video recording that contains areas of jitter in those regions of the face that are not identical positions at the same time during the production of the two utterances. The areas of jitter indicate the points of interest for detailed measurement. For homophenous VCV pairs involving /p/, /b/, and /m/, interleaving resulted in strong jitter in the lower lip and cheeks. There was no jitter when two utterances of the same phoneme were interleaved. A concurrent perceptual study showed that good speechreaders were able to discriminate between members of a homophenous pair in a forced-choice experiment.
Evaluation of a paired comparison elimination paradigm as a method of selecting hearing aids
Authors: Studebaker Gerald A. , White Richard E. C. , Hoffnung Steven
Published: October 2005

Continuous discourse material with a background of interfering (“Cafeteria”) noise was processed by eight different hearing aids fitted to KEMAR. Tape recordings of the processed signals were then presented in pairs to individual listeners, whose judgements of relative intelligibility were used to eliminate competing aids and select an eventual winner. Discrimination scores were also obtained from each listener, using speech discrimination tests processed under identical conditions. In general, for each individual, there was a high correlation between the aid selected by paired comparisons and that selected by the highest discrimination score. Thus paired comparisons appeared to be a reliable means of identifying hearing aids yielding maximal speech discrimination scores. However, some aspects of the results raised questions about the nature of intelligibility judgments and whether different types of test material or different characteristics of the background noise might lead to different hearing aid selections. The problem of selecting valid testing procedures will be discussed. [Work supported by NIH.]
Sound transmission in acoustic tubes: Exact and approximate solutions
Authors: Mook Douglas
Published: October 2005

This study is concerned with sound transmission in the ear canal and associated acoustic tubing used with hearing aids. The results obtained, however, are quite general. Use was made of Rayleigh's equations for sound transmission in acoustic tubes to derive the propagation constant [γ] for the transmission-line model. Calculations in cylindrical coordinates gave values of inductance [L] and resistance [R] which sufficed to determine all the parameters of the system. The equations have been solved numerically for a range of frequencies and tube radii. The solutions were compared to those obtained from Flanagan's approximate transmission-line model [J. L. Flanagan, Speech Analysis, Synthesis, and Perception, (Springer-Verlag, New York, 1972)]. Computed values of γ, R. and L for the two solutions were within 10% for radii in excess of 0.1 cm and within 3% for radii in excess of 0.25 cm over the frequency range of interest (200–4000 Hz). [Work supported by NINCDS.]
Lined ducts in parallel for low-frequency noise reduction
Authors: Patrick William P. , Ingard K. Uno
Published: October 2005

A new method to enhance the low-frequency sound attenuation characteristics of a lined duct is presented. A rigid, longitudinal splitter plate is used to separate the lined duct section into two parallel branch ducts. The phase speed of the fundamental sound mode in each parallel branch is a function of the liner configuration and can differ substantially from the free space phase speed. By lining the parallel branches dissimilarly, destructive interference of the fundamental mode of the transmitted wave occurs downstream of the parallel absorbers at a selected set of frequencies. Strong reflections also occur at the silencer inlet for a larger set of frequencies due to an acoustical impedance mismatch at the junction of the main duct and the parallel branches. These interference effects, which result from placing the rigid splitter plate into the lined duct can increase the low-frequency transmission loss of the duct by more than two fold over a broad low-frequency band and by as much as 5-dB/unit duct width at selected frequencies.
Assessment at full scale of nozzle/wing geometry effects on OTW aeroacoustic characteristics
Authors: Groesbeck D. , von Glahn U.
Published: October 2005

The effects on acoustic characteristics of nozzle type and location on a wing for STOL engine over-the-wing configurations are assessed at full scale and equal aerodynamic performance. Three types of nozzle configurations are evaluated: a circular nozzle with external deflector mounted above the wing, a slot nozzle with external deflector mounted on the wing and a slot nozzle mounted on the wing. Nozzle locations with respect to the wing leading edge were varied from 10% to 46% (flaps retracted) with flap angles of 20° (takeoff mode) and 60° (approach mode). Data of PNL as a function of flyover distance at 500 ft are presented for all cases. From these plots, relative values of EPNL were calculated and plotted as a function of lift and thrust ratios. From such plots the acoustic benefits attributable to variations in nozzle/deflector/wing geometry at full scale are assessed for equal aerodynamic performance.
The effect of endolymphatic potential on basilar membrane linearity
Authors: Mountain D. C.
Published: October 2005

The cochlear microphonic (CM) difference tone (F1−F2) was used as a measure of nonlinearity in order to examine the effects of small changes in endolymphatic potential (EP). KC1 filled pipettes were placed in scala media of the first and third turns of the guinea pig cochlea. Acoustic stimulation consisted of a pair of high frequency tones (>10 kHz) separated by 700 Hz. The 700 Hz CM difference tone was measured in the third turn while the EP was changed by passing polarizing current through the first turn. Positive current increased the difference tone and negative current decreased it. The polarization effect was greater for lower SPLs. The same current levels had no effect on the CM generated by a single tone at 700 Hz. EP changes caused by polarization, which are on the same order of magnitude as the EP changes caused by acoustic and efferent stimulation, significantly altered the CM difference tone. [Work supported by NIH.]
An improved method for predicting the effects of flight on jet mixing noise
Authors: Stone James R.
Published: October 2005

An improvement to the NASA method (1976) for predicting the effects of flight on jet mixing noise has been developed. The earlier method has been shown to agree reasonably well with experimental flight data for jet velocities up to about 520 m/s (∼1700 ft/s). The poorer agreement at high jet velocities appeared to be due primarily to the manner in which supersonic convection effects were formulated. The purely empirical supersonic convection formulation of the earlier method has now been replaced by one based on theoretical considerations. Other improvements of an empirical nature have been included based on model-jet/free-jet simulated flight tests. This report presents the new prediction method and comparisons with experimental data obtained from the Bertin Aerotrain with a J85 engine, the DC-10 airplane with JT9D engines, and the DC-9 airplane with refanned JT8D engines. It is shown that the new method agrees better with the data base than either the earlier NASA method or a recently proposed SAE method.
Sound transmission path investigations using correlation, coherence, and acoustic intensity methods
Authors: Mielnicka Anna , Crocker Malcolm J.
Published: October 2005

Sound transmission paths through a barrier were investigated using a fan as a broadband noise source. The barrier was described theoretically by a single-input, two-output, linear, constant parameter system. For the system, the relation between the energy of the penetrating and diffracted wave was estimated at a chosen observer point located behind the barrier. The correlation method was used for the barrier investigations. Also idealized experimental investigations have been carried out to compare the applicability and limits in the use of correlation, coherence and acoustic intensity methods for identifying sound transmission paths. Using the methods mentioned above, sound transmission paths between known sources (broadband loudspeaker signals) and an observer point inside a plexiglass box were investigated. [Work supported by the U.S. Department of Transportation. Dr. Mielnicka is presently on leave from the Institute of Mechanics and Vibracoustics, University of Mining and Metallurgy, 30-059 Krakow, Poland.]
Sampled-continuous wave technique for ultrasonic frequency analysis
Authors: Cantrell John H. , Heyman Joseph S.
Published: October 2005

A new method of ultrasonic frequency analysis is introduced which employs frequency tracked gated rf drive pulses rather than shock-excited broadband spikes for the ultrasonic waveform. The new technique, a variation of the sampled-continuous wave technique, eliminates problems associated with finite pulse widths and transducer ring-down of conventional methods. It is shown to yield correct ultrasonic wave velocity measurements of the sample irrespective of receiver gate width or position provided any portions of two successive echoes are gated simultaneous into the spectrum analyzer. The experimental observations are substantiated by a theoretical model based on the time-frequency domain formulation of ultrasonic frequency analysis.
Rigorous evanescent wave theory of ducted propagation
Authors: Arnold J. M. , Felsen L. B.
Published: October 2005

In a recently proposed high-frequency theory of propagation in transversely inhomogeneous ducts, based on evanescent waves [S. Choudhary and L. B. Felsen, J. Acoust. Soc. Am. 63, 661–666 (1978)], the expansion coefficients of the modal field amplitudes and eigenvalues were determined by invoking analyticity of the field on the duct axis although the asymptotic expansion is nonuniform there. Nevertheless, the asymptotic solutions so derived agreed with rigorous results for special index profiles. It is shown here that the modal expansion coefficients must be single-values in a strip of the complex coordinate plane. This property leads to the same results as the previous procedure, thereby avoiding the analyticity condition. Choudhary and Felsen sought to correct the non-uniformity near the axis by extracting the canonical solution for a parabolic profile. This local parabolic approximation is examined here within the framework of a uniform asymptotic theory. [Work supported by NSF.]
The shear wave velocity in near-surface basalt
Authors: Diachok Orest
Published: October 2005

The shear wave velocity in near-surface basalt was inferred from low frequency reflectivity versus grazing angle measurements from the basalt-water interface at the East Pacific Rise. This data, together with previously reported low frequency measurements by Spudich and by Helmberger and Morris, are correlated with Christensen's high frequency determinations of shear wave velocity vs geologic age in small solid-basalt samples, through an analytical model of the velocity of sound in a randomly disordered two phase medium, in which neither phase acts as the host or matrix material (Budiansky, 1965). This theory, which appears to be qualitatively consistent with Hyndman's heuristic description of the ratio of solid rock to sediments/water in near-surface basalt, offers a plausible quantitative account of the observed relationship between the high and low frequency measurements, and a working hypothesis for the development of a geoacoustic model of the upper crust.
Reflection of low-frequency sound from a randomly layered ocean bottom
Authors: Gilbert Kenneth E.
Published: October 2005

This paper presents results from a statistical study of random layering effects in finely layered sediments. A Monte Carlo algorithm was used to generate a large ensemble of random layer sequences typical of those found in turbidites. The algorithm fixed the statistics of the sediment model but allowed the detailed structure to vary randomly on each trial. In all cases the thickness of each individual layer was considerably less than an acoustic wavelength. For example, the maximum thickness of fine-grained layers was 2 m and the maximum thickness of coarse-grained layers was 0.5 m. The complex plane-wave reflection coefficient, R, was computed for each random layer sequence so that a distribution of R values was produced at each grazing angle. The scatter in R and the associated bottom loss, −20 log10|R|, is significant and varies with both grazing angle and frequency. Some simple models are presented for estimating the ensemble average of the bottom loss distribution. [Work supported by Naval Electronic Systems Command.]
Observations of bottom refracted and subbottom reflected signals in the deep ocean
Authors: Frisk G. V. , Doutt J. A. , Hays E. E.
Published: October 2005

Results of a deep ocean bottom reflection experiment are presented. Data were obtained in the Hatteras Abyssal Plain using a deep 220 Hz pulsed CW source and two receivers anchored near the bottom. For ranges less than 10 km, corresponding to bottom grazing angles less than 10° the amplitude and phase of the received signal were recorded digitally. The observed pressure field shows a strong spatial interference pattern which is composed of the direct and bottom interacting arrivals. For small source-receiver separations, the bottom return appears to be dominated by a subbottom reflection. With increasing separation this arrival evolves into a refracted arrival due to the presence of a positive linear sound speed gradient in the overlying sediment. The gradient causes the formation of a caustic, and a corresponding high intensity region is observed in the data at the expected range. [Work supported by ONR.]
Slope enhancement due to changes in surface decoupling loss
Authors: Bannister R. W.
Published: October 2005

Many experimental observations of downslope enhancement have been made recently. Two mechanisms are commonly advanced to explain the effect. Firstly, a conversion of energy from bottom bounce paths into less lossy refracted paths. Also the geometrical effect of concentrating energy into a smaller channel over a shoaling bottom. In addition to these, a new factor is identified and described. It is shown that the dependence of surface decoupling loss on vertical angle can dominate propagation loss changes in the vicinity of a sloping bottom. As the local angle steepens, surface interference losses diminish and an “enhancement” occurs. The implication of the three mechanisms are discussed in terms of the expected frequency, source depth and receiver depth dependence of slope enhancement. [Appreciation is given to Mr. C. D. Smith (NAVSEA 06H1) and DSE (NZ) for support of the scientist exchange program.]
Acoustic variability due to intrusive Arctic finestructure
Authors: Schulkin M. , Garrison G. R. , Wen T.
Published: October 2005

A previous paper [J. Acoust. Soc. Am. 64, S22 (1978)] discussed the results of acoustic transmission measurements in the frequency range of 10 to 60 kHz, in the presence of layered, thermal finestructure under an arctic ice island. “Layered finestructure” refers to relatively stable, slowly, changing thermal layers in the ocean that have a vertical scale of about a meter to tens of meters. Their horizontal extent may be 10 to 100 times larger. Acoustic transmission was found to be strongly affected by the presence, near the transmitter, of a layer or layers with a sound speed maximum or minimum. In the present paper, additional spectral and statistical properties of the acoustical field are presented, including dependence on ray angle, range, and frequency. Some attempt is made to relate these acoustic properties to oceanographic properties of the medium. [Work supported by Arctic Submarine Laboratory of the Naval Ocean Systems Center, San Diego, CA.]
Acoustical behavior of an elastomer-coated submerged steel plate with one unconstrained surface
Authors: Rudgers Anthony J. , Ring Martin D.
Published: October 2005

The results of a computer evaluation of the theoretical equations that describe the acoustic field either radiated or reflected by a 5-cm-thick steel plate, to which is bonded an elastomer coating, are reported. The equations that describe the acoustical behavior of the coated plate were derived by applying Timoshenko-Mindlin thick-plate theory to both the plate and the coating layer. The coated plate has water on one side and is unconstrained on the other. The computations treat elastomeric coating layers of various thicknesses. Two different elastomeric coating materials are also considered, a relatively soft, low-loss nitrile rubber and a stiffer high-loss neoprene. The computations demonstrate that the presence of an elastomeric coating, whatever the elastic properties of the coating material might be, does not significantly affect the acoustical characteristics of the steel plate, even when the coating thickness becomes equal to the thickness of the plate. The reason why elastomer-coated plates exhibit this behavior is discussed.
The extent of a vowel's influence: Evidence from a study of velar function
Authors: Bell-Berti F.
Published: October 2005

Velar position for a phonetic segment is determined by both the nature of the segment and the phonetic environment in which it occurs. Thus, velar position for consonants is higher in a close-vowel than an open-vowel environment. This observation led to an experiment designed to provide data for quantifying the temporal extent of carryover and anticipatory influences of vowels on consonants. Velar position was determined from frame-by-frame analysis of motion pictures of the velum of a native speaker of English. The 27 experimental utterances, repeated from 4 to 7 times each. were disyllables having either /aCni/ or /iCna/ patterns, with Cn containing various combinations of /t/ and /s/. Consonant-string durations were measured from digitized waveforms of the speech signal. Preliminary analysis of the data reveals that the velum is higher at the temporal mid-point of a consonant string for utterances whose second vowel is /i/, suggesting that anticipatory influences predominate at that time. [Work supported by NINCDS and BRSG.]
Aspiration: What is it and how is it produced?
Authors: Prakash Dixit R.
Published: October 2005

Physiologic and acoustic data from Hindi will be presented to show that aspiration associated with voiced or voiceless stop consonants cannot be produced unless the following conditions are met: (1) the glottis is open, (2) the supraglottal vocal tract is unobstructed, and (3) the rate of air flow through the glottis relative to the size of glottal aperture is adequate. In accordance with the above, aspiration can be defined as glottal friction produced with or without glottal pulsing while the glottis is narrowly or widely open and the supraglottal vocal tract is unobstructed. There may be some cavity friction during the aspiratory period of a stop consonant, however, this friction will be minor as compared to glottal friction. Above definition will be discussed in relation to other current definitions of aspiration. which seem to be unsatisfactory in one or more ways.
Laryngeal articulation in Swedish obstruent clusters
Authors: Löfqvist A. , Yoskioka H.
Published: October 2005

Laryngeal articulation in the production of Swedish voiceless obstruent clusters was investigated using the combined techniques of electromyography, fiberoptic filming and transillumination of the larynx. In single voiceless obstruents the laryngeal articulation seems to be a continuous movement in the form of an opening and closing gesture and in clusters one, two or three separate gestures were found. According to movement data, two gestures occurred in clusters of fricative + aspirated stop or fricative + unaspirated stop + fricative, three gestures were found in clusters of fricative + unaspirated stop + fricative + aspirated stop, whereas only one glottal gesture was seen in clusters of fricative + unaspirated stop or stop + fricative. The results suggest that the laryngeal articulatory gesture is an inherent feature in certain articulatory units and that its occurrence can be explained with reference to the aerodynamic requirements for the production of the respective segment(s) in the unit, i.e., the need of an egressive air flow during fricatives and periods of aspiration in stops. [Work supported by NINCDS and BRSG.]
Rare earth octagonal transducer
Authors: Butler J. L. , Ciosek S. J.
Published: October 2005

A low frequency transducer in the form of an “octagonal ring,” 10 in. in diameter and 6 in. high, driven by 16 rare earth Terfenol D (Tb0.3Dy0.7Fe2) rods, has been developed. In the design, eight curved magnesium pistons couple the small magnetostrictive rods to the water medium. The transducer resonates in a circumferential expansion mode at 750 Hz with a mechanical Q of 2.4 and an effective electromechanical coupling coefficient of 0,4. Measurements were made using both continuous and pulsed bias methods. Results are also presented for a smaller “square ring” rare earth transducer. [Work supported by NOSC.]