bluuebunny/crossref_metadata_2025 huggingface dataset:
A computer-controlled system for spectral analysis of violins
Authors: Pickering Norman C.
Published: October 2005

Over a five-year period, a system has been developed which gives repeatable frequency response curves of violins which agree well with subjective evaluation of the instruments. The method of holding the instrument without introducing spurious resonances is described. Excitation of the violin, which is in normal playing condition, is accomplished by tapping the edge of the bridge with a carefully controlled force produced by a spring-driven aluminum plunger. The plunger is magnetically retracted and released by an HP-85 computer which acts as system controller. With each tap a spectrum analyzer filter is advanced a predetermined amount and the peak sound intensity read into the computer. A single microphone is used in a fixed relationship to the violin and to the surrounding room. Repeatability is excellent, although it is recognized that only results obtained in this particular setup can be directly compared. A lateral disk reproducer is placed on the bridge for one series of measurements, the output of which provides information on the velocity of bridge motion for each constant-force tap at each frequency. Approximately 50 violins, good and bad, old and new, have been analyzed, some under different conditions of temperature and humidity. Results of physical modifications are clearly seen, and response characteristics of fine instruments are demonstrable. The object of this work is to establish procedures whereby violin makers can “tailor” selected portions of the spectrum in order to achieve a desired tonal result. Much has already been accomplished in this direction, and will be cited.
An electronic violin with a singing formant
Authors: Mathews M. V.
Published: October 2005

An electronic violin has been constructed with a resonance similar to the singing formant which Johan Sundberg discovered in the voices of good singers. The formant, as used in the electronic violin, is at 3000 Hz and has a relatively broad bandwidth of 2000 Hz. The formant strongly enhances the perceived liveness of the tone. The violin contains four ceramic microphones, one for each string, mounted in the bridge. Signals from the microphones are amplified by four separate amplifiers and are radiated from four separate loudspeakers in order to avoid intermodulation between strings. The radiated signal is the sum of the signal directly from the microphones and an adjustable amount of signal passed through a 3000-Hz resonance. With the most pleasing adjustment, about a 6-dB peak of 3000 Hz is produced by the resonance. There is some evidence that good acoustic violins have similar peaks.
Scattering behavior of a solid with a periodic rough surface
Authors: Johnson Richard K. , Chuang Shun-Lien
Published: October 2005

A theoretical approach based on the extended boundary condiiton for wave scattering from a liquid and solid periodic interface has been presented and compared with experimental data by Chuang and Johnson [J. Acoust. Soc. Am. Suppl. 1 70, S80 (1981)]. This theory is now applied to study scattering effects in water for several cases in order to demonstrate the physics of the problem. (1) The scattering from two different surface profiles: sinusoidal and triangular. (2) The diffraction efficiencies as functions of the frequency. (3) The effect of viscoelasticity on the diffraction efficiencies. The effects of frequency are also compared with experimental data measured for an acrylic block with a triangular surface profile. We observe peaks in the specular diffraction efficiency at two incidence angles both theoretically and experimentally. One peak occurs near the critical angle of the compressional wave of the solid. The second peak occurs at the angle of incidence such that the surface wave of the liquid and solid is excited. Changing the frequency will change the position of the second peak. The diffraction efficiencies of the peaks are also found to be sensitive to viscoelasticity in the solid.
Developmental, age, and sex effects on gap detection and temporal order
Authors: Ludlow Christy L. , Cudahy Edward A. , Bassich Celia J.
Published: October 2005

Developmental effects on gap detection and temporal order performance were examined cross sectionally in 18 males between 6 and 17 years, while age effects in adults were examined cross sectionally in 38 males and 23 females between 18 and 70 years of age. Thresholds for gap detection and temporal order were measured using a 21FC procedure. The gap was embedded in broadband noise while the signals for the temporal order task were 1000- and 2500-Hz tones. Percent correct detection and reaction time were assesed during a 15 min go-no-go vigilance task with a tonal signal at 10-dB sensation level in white noise. There was a statistically significant correlation between the young boys ages and temporal order threshold. Gap detection and temporal order thresholds were significantly correlated with age for the adult males but the relation was most marked after age 50. Significant correlations were found between age and all measures for the females. In addition to main effects for sex and age, there was a significant sex by age interaction for gap detection.
“Temporal masking” of tone glides in hearing-impaired ears
Authors: Collins M. Jane
Published: October 2005

It has been reported previously [M. J. Collins, J. Acoust. Soc. Am. Suppl. 1 69, S22 (1981)] that normal hearers' ability to discriminate the rate of frequency change of a gliding portion of a signal is affected by the duration of an adjacent fixed-frequency segment of the signal. This “temporal masking” is found to be greater when the glide precedes the fixed-frequency segment (backward masking) than when the glide follows the fixed-frequency segment (forward masking). The present paper reports some effects of sensorineural hearing loss on difference limens for glide rate as a function of the duration of an adjacent fixed-frequency segment. Using an adaptive procedure, data were collected on two ears of one, well-trained, hearing-impaired subject. The results show a trend for neither forward nor backward masking to occur when the discrimination is of some glide versus no glide. When the glide segment changes frequency at a rate of 17 Hz/ms, forward and backward masking is observed, with the magnitude of the effect appearing to be independent of degree of loss. The ear with the more severe loss shows the more normal result (greater backward than forward masking), while the ear with the less severe loss shows mixed effects. The results are discussed in relation in implications for speech perception. [Work supported by NINCDS.]
RAID—A new adaptive method for forced choice experiments
Authors: Pavel M.
Published: October 2005

Many problems in psychoacoustics are posed in terms of a psychometric function and the purpose of an experiment is to determine that value of stimulus for which the probability of a response is some predetermined number. In such situations it is desirable to choose stimuli on each trial so as to minimize the number of trials needed. This paper describes a new adaptive procedure RAID that has a number of advantages over currently available methods. RAID is a procedure used to both select stimuli for each trial during an experiment and to estimate points of a psychometric curve. The method makes use of all data available at any time from all previous trials. While the estimates are made with minimal assumptions regarding the psychometric function (one of which is monotonicity), the method is capable of utilizing as much prior knowledge as is available. In a few words, RAID first applies isotonic regression to relative frequencies of a given response resulting in maximum likelihood estimates of the probabilities. Then it combines these results with prior expectations and depending on the point on the psychometric function to be determined, it selects that stimulus which is likely to carry the most information. The stopping strategy is based on estimated confidence intervals. That is, the method stops when a given confidence has been achieved. This procedure was successfully applied in an intensity discrimination experiment designed to study the near-miss phenomenon. The method was particularly useful here because it permitted estimation of an entire portion of a psychometric curve.
Computer simulation of audiometric threshold procedures
Authors: Aldrich William M. , Arney Mary
Published: October 2005

Currently several clinical procedures are being advocated by various organizations for determination of an auditory threshold for pure tones. While little is known of how the procedures compare, they are being implemented on currently marketed microprocessor based equipment. We have examined the methods recommended by the American National Standards Institute (ANSI), the American Speech, Language and Hearing Association (ASHA), and the British Society of Audiology (BSA) by modeling the performance of a subject according to the psychometric function for detection of a pure tone. This approach has the advantage of allowing control or systematic variation of subject variables so that only the characteristics of the methods themselves become apparent. It also permits the generation of large sample sizes. Using a microcomputer, programmed in BASIC, the three procedures were simulated and compared with respect to number of presentations required to obtain a threshold, number of threshold crossings and threshold obtained for three slopes of the psychometric function. Results suggest that the ANSI recommendation has advantages over the ASHA and BSA methods.
Impulse response of the early reflections in an auditorium
Authors: Sakurai Yoshimasa
Published: October 2005

The practical calculation of the first reflections from elements comprising the boundaries of an auditorium (such as rigid plane panels, rigid curved panels, and panels having reflection coefficients other than unity) will be reviewed. Measured reflection coefficients of porous layers and auditorium seats at grazing incidence will be shown, concentrating on the time domain. Next, multiple reflections between two plane panels, two rigid convex panels, two plane panels with reflection coefficients different from unity, and those inside a rigid concave panel are calculated, based on the calculation of the first reflections mentioned above. These results are in good agreement with those measured. Finally, the calculated pulse response of the early reflections in a scale model auditorium, which is the convolution of the calculated impulse response and a direct sound generated by a point source, will be compared with the measured one. Comparison will also be made of their frequency characteristics.
Characterizing heat transfer coefficients for heat exchangers in standing wave thermoacoustic coolers
Authors: Paek Insu , Braun James E. , Mongeau Luc
Published: October 2005

The thermal performance of heat exchangers within a thermoacoustic cooler was investigated. Experimental procedures and calculation methods to evaluate the oscillating flow heat transfer coefficients were developed. Dimensionless heat transfer coefficients, or Colburn-j factors, were estimated based on the oscillating-flow variables and compared with results from steady-flow measurements. The results were also compared with heat transfer coefficients predicted from a boundary-layer conduction model, and methods that utilize steady-flow correlations with Reynolds numbers that characterize oscillating flow conditions. Although the boundary layer model is commonly employed for thermoacoustic calculations, it did not accurately predict heat transfer coefficients and the influence of Reynolds number on heat transfer performance. However, accurate predictions were obtained using a steady-flow correlation and a modified Reynolds number that accounts for the oscillating flow field, assuming a half-cycle Reynolds number correction value of 0.109.
Improvements in measuring the attenuation of personal earprotectors with artificial heads
Authors: Schroeter J.
Published: October 2005

An artificial head was developed, suitable for the measurement of earmuffs as well as earplugs. Three major factors determine it's performance: (a) The mechanical characteristics of the artificial flesh at the area of contact between the protector and the head. The mechanical impedances of 100 subjects at four points around the pinna and the shear impedances of the ear canal walls were measured. Layers of polyurethane rubber were finally designed which fit the average of the impedances. (b) Bone conduction: We suppose that a set of standard curves of bone/air conduction level differences will prove feasible to give a conservative value of attenuation by simply “adding” it to a measured insertion loss of a protector. (c) Influence of the pinna, ear canal and eardrum: It can be shown that any error in insertion loss caused by a wrong eardrum impedance can be corrected afterwards. However, it seems to be more practical using an appropriate “ear simulator.” A method to determine the needed accuracy of the coupler is given. Finally construction details and sample results compared to subjectively measured data are shown. [Work supported by Bundesanstalt fuer Arbeitsschutz und Unfallforschung, Dortmund, FRG.]
Measuring sound attenuation capabilities of helmets using a KEMAR manikin
Authors: Ivey E. S. , Nerbonoc G. P. , Tolhurst G. C.
Published: October 2005

Sound attenuation measurements were made on three Army helmets and one headset. A Knowles Electronic Manikin for Acoustic Research (KEMAR) was instrumented to read the sound pressure level of one-third octave band filtered white noise. Sound pressure levels were measured using two different procedures. The first procedure employed a Zwislocki coupler microphone responding as a human eardrum and the second procedure used a probe tube located at the ear canal entrance of the manikin. All measurements were taken with the manikin in a diffuse sound field in a sound isolation room. Attenuation values were calculated by subtracting the sound pressure level measured with the helmet on the manikin's head from those sound pressure levels recorded without the helmet in place. These attenuation values compare favorably at most frequency bands with similar measurements made using human subjects in the same sound field wearing the same helmets. [Work supported by U.S. Army, Natick Laboratories, Contract No. DAAK 60-80-C-100.]
Hearing protector effects on identification of sound source azimuth
Authors: Howse W. R. , Elfner L. F.
Published: October 2005

Six normal hearing listeners who were presented with 750-ms bursts of wideband noise at 60 dB SPL from randomly selected positions on the horizontal plane indicated the apparent locus by adjusting a dial. Five conditions including active and passive protective modes with monaural and binaural devices and an unprotected control were run. Results provide a description of normal auditory localization ability and estimates of resolution of angle in the horizontal plane. Results also indicate severe distortion of localization functions when active hearing protectors were worn. Effects appear to be more strongly influenced by loss of information due to characteristics of amplifier circuits than by physical configuration of hearing protectors.
Audio-motor reflex responses in orbicularis oris single motor units having different recruitment thresholds
Authors: McClean Michael D. , Sapir Shimon
Published: October 2005

There is some evidence that the magnitude of reflexes in single motor units is well correlated with their mechanical and electrophysiological properties. This design feature of somatic reflex systems may have significance for speech production if it is present in speech activated muscles. The objective of the present investigation was to determine whether the reflex responsiveness of motor units within the orbicularis oris inferior muscle (OOI) is dependent on recruitment threshold. Recruitment threshold was quantified as a percentage of maximum surface EMG at which a motor unit was recruited during a 6-s ramp contraction of OOI. The reflex responsiveness of each motor unit to auditory stimulation was tested with clicks presented binaurally at 75 dB SL during voluntary activation of the motor unit at a steady firing rate of approximately 20 ips. The magnitudes of reflex suppression and excitation were quantified by means of computer analysis of poststimulus time histograms obtained on each unit. Data obtained on 61 motor units to date indicate a positive correlation between recruitment threshold and the magnitude of both reflex suppression and excitation in two subjects, and a negative correlation in a third subject. [Work supported by NINCDS.]
Physiologic stages of vocal reaction time
Authors: Shipp Thomas
Published: October 2005

Although simple reaction time (RT) studies have been conducted on normal and some pathologic subjects, these data have not been divided into the substages of neural and mechanical time. To establish after presentation of a 1-kHz stimulation tone after electrodes were placed in laryngeal muscles and a catheter inserted intratracheally. Results showed that subjects used one of two prephonatory postures—either with vocal folds tightly adducted and subglottal airpressure somewhat elevated or with vocal folds slightly abducted and the respiratory system in a “pause” state. Regardless of prephonatory strategy, temporal values for muscle, aerodynamic, and acoustic activity were similar. Mean onset values (N = 10) derived from each subject's fastest trial were: RT, 185 ms; Interarytenoid muscle, 88 ms; Thyroarytenoid muscle, 96 ms; posterior cricoarytenoid muscle, 121 ms; and subglottal airpressure rise, 125 ms. Neural and mechanical stages of RT were equally divided: neural time, 91 ms and mechanical time, 94 ms. [Work supported by NIH.]
Observations on timing of tongue gestures and stress in medial /t/ and /d/ production
Authors: Laferriere Martha
Published: October 2005

In a previous paper [M. Laferriere and O. Fujimura, J. Acoust. Soc. Am. Suppl. 1 70, S13 (1981)], movements of the tongue in the production of medial /t/ and /d/ were discussed using x-ray microbeam data. It was found that stops generally involve tongue-body fronting and blade/tip raising, whereas flaps involve only blade/tip raising; and that, for stops, stress of surrounding vowels determines the extent of dynamic tongue-body gesture. The present study examined stop and flap production in terms of tongue blade displacement, duration and velocity of transition into the consonant, and stress status of surrounding vowels. It was found that (1) peak velocity of tongue blade displacement increased as the amount of displacement increased, and (2) the tenseness of the stressed vowel following the alveolar consonant affected the degree of tongue blade displacement when the preceding vowel was unstressed.
Sign language perception and linguistic experience
Authors: Mayberry Rachel , Fischer Susan D.
Published: October 2005

Most deaf children have parents who hear normally. Consequently most deaf adults who use American Sign Language (ASL) did not learn it from infancy from their parents. Rather, most deaf signers first learned to sign after infancy outside their homes. The experiment reported here examined the relationship between the length of time that signers have used sign language and their ability to repeat ASL utterances. Forty-five, congenitally deaf, young adults both shadowed and recalled ASL sentences and scrambled-ASL sentences (simultaneous reception and reproduction versus successive reception and reproduction). The signers were grouped according to the age at which they first learned to sign: 0, 5, 13–15, and after 18 years of age. The quantitative results show that the greater number of years a person has signed, the more accurately she or he can shadow and recall ASL utterances. More important, the qualitative results show that the groups make errors that are linguistically distinct: The first two groups perform like native users of spoken language, whereas the last two groups perform like non-natives. The results demonstrate that fluency is a crucial factor in sign language perception. [Work supported by NTID and NINCDS.]
Evaluating a tactile aid on four-year-old profoundly deaf children
Authors: Bond Sandi L. , Scott Brian L.
Published: October 2005

Our purpose has been to develop a set of procedures for evaluating a speech reception aid on young, profoundly deaf children with limited linguistic skills. The subjects were two males and two female children ranging in age from 3 years and 7 months to 4 years and 3 months. Pure tone averages range from 93 dB HL to no response. The tasks reported are a subset of a broader range of tasks being investigated as tools for analyzing the effects of speech reception aids on the growth of linguistic skills. The current tasks have stressed focal training and reflect fundamental speech reception skills. At the most rudimentary level is the detection task, measuring the child's awareness of sound. The second task tests the child's ability to perceive and reproduce the syllable structure of brief utterances. The final task uses animal sounds to determine reception and production skills at a segmental level. The study ran for 6 weeks during which half the children began the study with the aid on and then switched to aid off after three weeks. The other two children began with the aid off, then switched to aid on. Results show a statistically significant difference in the rate of learning with the aid relative to the rate of learning without the aid. Data on each child will also be shown to illustrate the individual differences across subjects with differing linguistic skills. We believe this study illustrates a technique for fairly evaluating the efficacy of a sensory aid on young, prelingually deaf children. [Work supported by NINCDS.]
What are we waiting for? The development of Godot, II
Authors: Walsh John P. , Dadoun Norman
Published: October 2005

The design of Godot, a computer system for computer-aided room acoustics modeling and simulation, was described in an earlier paper [J. Acoust. Soc. Am. Suppl. 1 69, S36 (1981)]. In this paper, issues affecting its use in the production environment are discussed and current research issues are examined briefly. The system has been moved from a mainframe computer to a minicomputer having graphics facilities suitable for interactive design; we will review the way room acoustics modeling and simulation are treated in the larger context of computer-aided architectural design. Taped examples of simple simulations will be presented, and compared with examples recorded in the actual rooms. Godot currently traces sound beams incrementally; in this way it avoids exhaustive intersection testing with all faces in the room representation. Current work aims at generalizing the orientation-dependent “bounding boxes” used in coarse “hit” detection to yield an intrinsic bounding volume for each wall element. As a side benefit this method will allow us to model moving portions of a room. [Work supported by the Science Council of British Columbia, grant ♯41 (RC-4).]
The acoustical design of Wellington Town Hall
Authors: Marshall A. Harold , Hyde Jerald R.
Published: October 2005

This paper is a review of the evolution of research and acoustical design objectives which have been the basis for the design of the Wellington Town Hall, New Zealand. A discussion of research and developments over the past 20 years traces the development of the importance of early lateral reflections and the architectural means by which they are achieved in a directed reflection sequence (DRS) hall. The use of Quadratic Residue Diffusors [A. H. Marshall and J. R. Hyde, Proc. 10th ICA, Sydney (1980)] and the results of 1:10 scale model objective and subjective tests performed by the authors with M. F. E. Barron at the Acoustics Institute are presented.
Modes of vibration and decay times in cymbals
Authors: Shepherd Robert B. , Ressing Thomas D.
Published: October 2005

The principal modes of vibration of a cymbal, which dominate at low frequency, have m radial nodes extending outward from the cup to the rim. Their modal frequencies can be fitted to an equation of the form f = cmk, where parameters c and k take on one set of values for small m and another for large m [R. W. Peterson and T. D. Rossing, J. Acoust. Soc. Am. Suppl. 1 66, S18 (1979)]. We have studied modes of vibration in over 60 cymbals having diameters from 8 to 24 in. and thicknesses from 0.02 to 0.09 in. Although c varies with diameter and thickness, as expected, values of k are surprisingly similar in large and small cymbals. Average values are k1 = 1.73 and k2 = 1.60. Decay times have been measured when the individual modes are excited at small amplitude in the steady state, and also when the cymbal is struck in various ways. Modal decay times decrease with increasing frequency, whereas decay of the percussive sound depends upon the manner of striking. [Work supported in part by the Avedis Ziidjian Company.]
Gradient driven coupling between shear and compressional waves
Authors: Vidmar Paul J.
Published: October 2005

Exact generalized potentials are developed to describe the motion of isotropic, continuously stratified media. The approach due to Richards [Bull. Seis. Soc. Am. 64, 1575 (1974)] is generalized by using tensor rather than scalar scale factors in defining the generalized shear (S) and compressional (P) potentials in terms of the displacement. This generalization leads to: (1) exact coupled second-order differential equations for the P and S wave potentials, (2) P and S decoupling at high frequencies and for special media, and (3) an explicit form for the gradient driven P-S coupling. The coupling has a frequency-dependent resonance structure as a function of depth into the sediment. For a typical deep sea sediment, clay, this P-S coupling is negligible above about 5 Hz. For sand sediment types, typical of shallow water environments, this P-S coupling can be important up to about 60 Hz and represents a potentially important low-frequency loss process. [Work supported by Naval Ocean Research and Development Activity.]
Sound scattering from elastic objects and their complex eigenfrequencies
Authors: Gaunaurd G. C. , Überall H. , Subrahmanyam J. V.
Published: October 2005

A variety of surface waves is created at a smooth elastic target during acoustic scattering, including internal Rayleigh-and whispering-gallery type elastic waves, and external Franz-type creeping waves. Previously, we studied these using a Watson transformation, searching for poles of the scattering amplitude in the complex mode-number plane. The Singularity Expansion Method (SEM) of radar scattering instead characterizes the amplitude by its poles in the complex frequency plane. It is shown that each surface wave contributes a well-defined set of complex-frequency poles, and that the phase and group velocity dispersion curves of both elastic-type and Franz-type waves may be obtained from this set of poles. This approach is here carried through for the case of spherical and infinite-cylindrical elastic targets, and the ensuing dispersion curves are shown to characterize the surface waves as to Rayleigh or whispering gallery type. [H. Überall is also at Catholic University, Washington, DC, sponsored by the Office of Naval Research.]
A hybrid system approach to recognition of acoustically similar items
Authors: Bradshaw Gary L. , Cole Ron , Reddy Raj
Published: October 2005

Speech recognition systems based on spectral template-matching have proven successful in restricted speech understanding tasks: especially, speaker-dependent recognition of isolated words with acoustically distinct vocabularies. Such systems, however, have only been of limited utility where vocabulary items are acoustically similar, as in the set B, C, D, E, G, P, T, V, and Z. We will describe a hybrid system which supplements the spectral template with a set of feature measurements extracted from the signal. A learning mechanism automatically extracts a weighting vector, which emphasizes informative features as well as informative frames in the template. Recognition performance of the hybrid system is superior to the performance of the system using either the spectral information alone or the featural information alone. Hybrid recognition architectures are therefore useful in overcoming present limitations of speech recognition systems. [Work supported by NSF.]
Optimal vector quantization of speech spectral principal components
Authors: Zahorian Stephen A.
Published: October 2005

The vector quantization method described by Linde et al. [IEEE Trans. Commun. 28, 84–95 (1980)] was used to optimally quantize speech spectral principal components. The spectral principal components, obtained from linear combinations of spectral band energies, are an optimal uncorrelated parameter set containing a very large amount of spectral variance with a relatively small number of dimensions. For a given percentage of quantization distortion, the vector quantizer required fewer bits per frame than individual quantization of principal components, thus indicating a clustering of the speech data in the uncorrelated parameter space. Using the principal components parameters to measure both gain and spectral shape and using eight bits per frame, the mean square vector quantization error was about 2.5% in a four-dimensional space, and about 5% in a seven-dimensional space. Speech synthesized from the vector quantized principal components using nine bits per frame was somewhat inferior in quality to speech synthesized with full precision principal components, but quite intelligible. [Work supported by NSF.]
On pitch-synchronous abridgement of the linear prediction residual
Authors: Smith Nancy David
Published: October 2005

We developed an approach to abridging the short-term LPC residual and using the abridged information to generate speech at 16.0 kilobits per second (kb/s). The abridgement logic requires an average of less than one multiply per speech input sample. It offers a simple way to add a high-rate, improved quality capability to existing 2.4 kb/s LPC voice communication systems. Our simulated 16.0 kb/s residual-excited linear prediction (RELP) transmission system using abridgement generates very good quality speech output. Our abridgement approach is independent of voiced/unvoiced decisions, restricts the influence of errors to a single frame, and strongly resists brief input anomalies. We designed this medium-rate system as an alternative to the baseband residual-excited coder currently used in the NRL Multirate Processor (MRP). Our (computationally) simpler approach scores lower overall on the Diagnostic Rhyme Test than the MRP baseband system at 16.0 kb/s: 87.4 vs 93.9. Listening suggests that the speech quality from our approach is closer to the MRP quality for continuous speech than for the DRT words. For some applications, the computational efficiency and stability of our approach could out-weigh the quality advantage of the MRP.
Frequency effects in backward masking
Authors: Dolan Thomas G. , Small Arnold M.
Published: October 2005

Frequency effects in auditory backward masking were examined by psychophysically determining the thresholds of 0.5, 1, 3, 5, and 7 kHz tone burst probes followed at different delay times by a noise burst masker. It was found that for each probe frequency condition, the amount of backward masking (defined as the shift in probe threshold due to the presence of the masker) as a function of the time interval between the probe and masker (Δt) could be approximated reasonably well by a simple decaying exponential function. The rate of decay of the masking effect as a function of Δt was found to increase with increasing probe frequency. This latter result qualitatively supports Duifhuis's [J. Acoust. Soc. Am. 54, 1471–1488 (1973)] theory which attributes short term backward masking to the temporal overlap of cochlear responses to the probe and masker.
Auditory perception experiments with sine-wave analogs to the voice-onset time dimension
Authors: Hillenbrand James
Published: October 2005

Previous research has shown that the voice-onset time dimension can be modeled using nonspeech stimuli. Labeling data from these experiments are in close agreement with the VOT crossover point for labial stops. The VOT boundary, however, varies with place of articulation; this effect appears to be attributable to differences in the duration of the first-format transition. Results from the present study demonstrate that this effect can also be found with stimuli consisting of a midfrequency sine wave (analogous to F2) and a low-frequency sine wave (analogous to F1). The two frequency components were separated in relative onset time by 0 to 50 ms in 10-ms steps and were synthesized with frequency sweeps similar to formant transitions found in speech. Labeling results showed that, like synthetic speech, the boundary location for relative onset time is influenced by the duration of the lower frequency tone sweep. These findings, and the results of discrimination tests with these stimuli, suggest an auditory rather than phonetic explanation for the shift in VOT crossover with place of articulation.
Perceptual and acoustic evidence for tradeoffs in anticipatory coarticulation effects
Authors: Martin James G. , Bunnell H. Timothy
Published: October 2005

The stimuli were /stri, stru/ pairs produced by four talkers. A part of /s/, /t/, or /r/ was exchanged between the pairs so that any coarticulatory information within the exchanged interval incorrectly predicted the remainder of the sequence. Recognition time (RT) was observed to final vowel targets /i/ or /u/. Results showed generally slower RT (interference) in exchanged compared to intact (as spoken) sequences. Within a given pair, however, when there was large interference from exchange of /t/ there was little interference from exchange of /r/, and vice versa. The tradeoff in perceptual effects between /t/ and /r/ was mirrored in acoustic differences, e.g., rate of F2 rise in /r/ toward /i/. Apparently the effects of anticipatory coarticulation are not necessarily always manifested to the greatest degree in the nearest segment. Articulation appears to be a more or less closed system of mutual constraints among segments in a sequence such that the various tokens of a given sequence may be seen as members of a set or class of utterances. Discussion concerns some theoretical implications of this notion for production and perception. [Work supported by NIH.]
Perceptual assessment of coarticulation in sequences of two stop consonants
Authors: Repp Bruno H.
Published: October 2005

This study investigated whether any perceptually useful coarticulatory information is carried by the release bursts and formant transitions of two successive, nonhomorganic stop consonants. The VC or CV portions of natural VCCV utterances were replaced with matched synthetic stimuli from a VC or CV continuum spanning the three places of stop articulation. When the VC and CV portions in the resulting hybrid VCCV stimuli were separated by a fixed silent interval, the context in which the natural portion has been produced had no influence on listeners' identification of the synthetic portion, suggesting that VC and CV formant transitions and CV release bursts contained no perceptually salient coarticulatory cues. However, when a natural VC portion was separated from a synthetic CV portion by the original closure interval, which included a brief release burst of the first stop, there was a sizeable effect of the original CV context on the perception of the second stop consonant. Thus the release burst of a syllable-final stop contains significant coarticulatory information about a following, nonhomorganic stop. The data also revealed contrast effects and other perceptual interactions between two successive stop consonants. This report will include results of an acoustic analysis of the stimuli. [Research supported by NICHD and BRS.]
Discrimination and identification of voicing and place contrasts in aphasic patients
Authors: Yeni-Komshian Grace H. , Lafontaine Linda
Published: October 2005

Aphasic patients and controls were given discrimination and identification tasks using synthesized stop-initial CV syllables. Three different seven-step continua were used as stimuli: voicing (bee-pea); place (bee-dee); and vowel (bee-bow). All subjects were given both tasks for each continuum. The aphasic patients were devided into a good and a moderate comprehension group on the basis of their scores on an auditory language comprehension test. In comparison to the controls, aphasics with moderate comprehension had difficulty perceiving voicing and place contrasts, while aphasics with good comprehension generally had difficulty with place contrasts only. There were no group differences on the vowel tasks. The majority of the subjects either discriminated and identified the stimuli, did not discriminate or identify the stimuli, or discriminated but did not identify the stimuli. A small number of subjects could not discriminate but could identify the stimuli, mainly on the voicing continuum.
Modeling of partitioned and straight-through resonators
Authors: Thawani Prakash T. , Jayaraman K.
Published: October 2005

Straight-through concentric resonators have been modeled by coupling the acoustic wave propagation through the inner perforated pipe and the outer cavity by means of the radial particle velocity through the perforate holes. The decoupled equations of wave propagation are solved [K. Jaysraman and K. Yam, J. Acoust. Soc. Am. 69, 390–396 (1981)] using the boundary conditions in the cavity resulting in a two by two transfer matrix. In this paper the transfer matrix for a partially perforated straight-through resonator has been derived including the mean flow and temperature effects. This transfer matrix can be used for predicting any of the muffler performance criteria for resonator configurations using a fully/partially perforated length or a series of such resonators. The theoretical details of the analysis with experimental and analytical results of several resonator configurations are presented showing good agreement. Additional analytical results have also been presented to illustrate the effect of various physical parameters involved in the performance of straight-through resonators.
Physical geometry and adaptive attenuators
Authors: Warnaka Glenn E. , Tichy Jiri
Published: October 2005

In a previous paper G. E. Warnaka and J. Tichy [Proc. Inter-Noise 80, 683–688], the authors described the importance of the geometry of an active noise attenuation system for duct-borne noise. Only geometries which are highly favorable to good mixing of both the noise and cancellation fields can produce large attenuations since large values (20 dB) of cancellation require precise matching of both amplitude and phase. This paper discusses additional geometries in which the canceling signal is mixed with the noise by means of a waveguide. The effects of the angle of introduction and relative diameter of the waveguide are discussed. In addition, the use of wave guides is compared with introducing the canceling sound directly by loudspeakers placed in. the noise field. The use of two waveguides for introducing the canceling sound is also discussed since previous work had shown that a carefully phased symmetrical arrangement could double the effective frequency range of the system. Experiments with conventional loudspeakers and a flat diaphragm loudspeaker demonstrated the superiority of this latter in achieving good cancellation.
Sound transmission in elliptical ducts
Authors: Hadden W. James , Anderson Craig A.
Published: October 2005

Transverse pressure distributions and cut-on frequencies for higher order duct modes were computed using series expansions of the relevant Mathieu functions. Of particular interest is the shift of the cut-on frequencies relative to those of a circular duct. Propagation of the first few higher order modes were observed by transmission loss measurements of expansion chambers of elliptical cross section with inlet and outlet tubes preferentially located to excite these modes. Propagation of these modes can be observed by a decrease in transmission loss after the cut-on frequency for a particular mode. Observed cut-on frequencies are compared to computed cut-on frequencies. [This work was begun under NSF Grant No. SPI-8160217 and continued with support from Nelson Industries, Inc.]
Imaging of flaws with tomographic processing of time domain ramp responses
Authors: Cook Bill D. , McKinney R. L. , Opsal Jon
Published: October 2005

When a flaw (void or inclusion) is radiated with an ultrasonic pulse with the shape of a ramp, the backscattered echo contains information that is easily interpretable. In fact, the amplitude of the echo (appropriately scaled for range and impedence changes) as a function of time maps the cross-sectional area of the flaw as a function of distance. This distance is along the line-of-sight between transducer and flaw. By combining data obtained from several directions all of which lie in a plane, it is possible to construct three-dimensional images of the flaws using tomographic processing. The consequence of sparse sampling is demonstrated using T-matrix calculations for scattering from spheroids.
The musical saw-operational features and simple dynamical theory
Authors: Tubis Arnold , Davis Robert E.
Published: October 2005

The bowing of a flexed handsaw blade produces very nearly pure musical tones. The musical saw has been a staple of 19th and 20th century American folk music. It reached its peak of popularity in vaudeville acts of the 1920's especially in central U.S.A. Several composers including Katchaturian and Crumb have included saw solos in their orchestral compositions. The higher the musical note to be produced on the saw, the larger is the required blade flexure, and the farther from the handle end is the bowing point. These operational features of saw playing may be semiquantitatively accounted for by modeling the saw blade as a plate with two free edges and two clamped edges. The fourth-order nonlinear dynamical blade equation is solved exactly in the time-independent case to yield static shapes of the flexed blade. The static shape functions are then used in a linearized dynamical equation to obtain the modal frequencies and shape functions for small transverse oscillations about the static shapes. The required bowing points correspond to the antinodal positions of the dominant plane modes.
Intensity calculations in a random medium with channel velocity profile using coherence theory
Authors: Mazar R. , Beran M. J.
Published: October 2005

We use a three scale expansion to calculate the intensity distribution of acoustic radiation propagating in a sound channel in the presence of random inhomogeneities. We develop equations which show how the coherence function varies along the characteristic rays (identical to the rays of geometrical acoustics in the parabolic approximation). Solving these equations we obtain an expression for the vertical intensity distribution resulting from an acoustic beam propagating in a random medium with a sound velocity profile. When the fluctuations of the medium are statistically homogeneous and isotropic, this expression is simplified for two limiting cases: weak scattering and strong scattering. We present an example of high-frequency scattering in a random medium with a mean cubic profile. We calculate the intensity corrections in the vicinity of a caustic under typical ocean conditions. The results of the corrected intensity distribution are compared with the uncorrected intensity results obtained previously.
Mechanisms and modeling of wind-generated ambient noise in the ocean
Authors: Liu A. K. , Larry T. L.
Published: October 2005

The wind-generated acoustic noise in the ocean has been studied in the frequency range between 1 and 3000 Hz in terms of wind speed and environmental parameters. Several possible mechanisms that can couple energy from the wind to the oceanic acoustic field were examined. It is concluded that the wind-generated noise is produced by at least three mechanisms: surface wave interactions significant in the 1-to 5-Hz range; turbulent pressure fluctuations, dominant in the 5-to 50-Hz range; and the impact of ocean spray, dominant above 50 Hz when wind speeds are greater than 10 knots. [Work supported by APL/JHU.]
The phase distribution of the pressure alongside a manikin's head and on the surface of a sphere of equivalent perimeter
Authors: Kuhn George F.
Published: October 2005

The pressure-phase distribution for a frontally incident wave was measured at typcial hearing aid locations, alongside the head of KEMAR and behind its pinna at 0.5, 1.0, 2.0, 4.0, 5.0, 6.3, and 8.0 kHz. The measured phase data and the predictions of the phase on the surface of a rigid sphere of equivalent perimeter as the head are in reasonable agreement throughout, except at 6.3 and 8.0 kHz directly behind the pinna. Here, the measured results at the immediate rear of the pinna's helix have phase jumps of nearly 180°. These phase jumps result from the first higher order transverse acoustic mode, excited in the pinna. However, this mode decays rapidly, causing the phase jumps to disappear at a nominal distance of 5 mm behind the pinna. Also, the measured phase data reaffirms the earlier theoretical predictions [G. F. Kuhn and T. Munro, J. Acoust. Soc. Am. 65, S138 (1979)] of phase-derived interaural time differences for normally hearing listeners and for aided listeners calculated on the basis of a spherical model of the head. [The help of Ed Burnett with the phase measurements is gratefully acknowledged. Work supported by NSF].
Fundamentals of guitar tone
Authors: Jansson Erik V.
Published: October 2005

The guitar is a complex physical system containing many resonances. Fundamental tonal properties such as initial levels and initial level decays are set by properties of the guitar. The decays of partials are approximately proportional to the inverse of the initial level. Furthermore, the initial partial levels, and thus the inverse level decays, are approximately proportional to the frequency response of the guitar body (recorded as radiated sound for a constant driving force). At resonance frequencies, however, the peak level of the frequency response overestimates the initial tone level and underestimates the decay. In spite of a more rapid decay, a high initial level may give a tone of longer duration, i.e., longer duration above a masked threshold. The guitar gives a decaying tone spectrum with the higher partials decaying more rapidly than the lower ones. Initially the decaying vibrations of the eigenmodes play a noticeable role. High sound pressure levels, including high levels at 500–800 Hz and at 1500–4000 Hz, seem to be favorable. Frequency components above 5000 Hz are perceptible only at the attack of tones. [Work partly in cooperation with G. W. Caldersmith.]