bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of pressure rise time on starting transients of flue pipes
Authors: Nolle A. W. , Finch T. L.
Published: October 2005

A special wind supply provides adjustable rise time Tr. Adjustable closed and open pipes having frequencies 198 to 256 Hz are studied. The steady-state supply pressure is 530 Pa. The precursor, at several times the fundamental frequency, and a subsequent burst dominated by the next mode above the fundamental are strongest for Tr between 1 and 10 fundamental periods, but may vanish for larger or smaller Tr. For nearly harmonic pipe resonances, the fundamental and higher components can grow simultaneously, and the burst may exceed the steady-state amplitude. For more inharmonic modes (e.g., a wider pipe) the fundamental quenches the burst when the overall amplitude is well below steady state. External sound at the fundamental frequency suppresses both the precursor and the subsequent burst. Important features of the experimental results occur in a computer model that involves time-delayed nonlinear feedback and uses simple oscillators to represent resonator modes [N.H. Fletcher, Acustica 34, 224–233 (1976)]. With numerical rather than analytical solutions it is possible to treat the realistic case of the fully switched jet.
Accentedness and givenness: Change in word, syllable, or segment duration?
Authors: Eefting Wieke , Nooteboom Sieb G.
Published: October 2005

In an earlier paper [W. Eefting, J. Acoust. Soc. Am. Suppl. 1 85, S97 (1989)] the results of a study concerning the relation between the features “givenness” and “accentedness” and the duration of Dutch words were presented. Production data from a highly trained, professional speaker indicated that the duration of one syllable and three syllable words is lengthened when accented. Information value had only an effect on one syllable words: One syllable words containing new information were lengthened as compared to the same words containing old information. It remained unclear whether the differences in word duration affected the temporal structure of the whole word; a local change within the word might be responsible for the differences. In the present study, the durations of the syllables and the segments within the target words are measured. Data will be presented showing that all segments in the one syllable words and all syllables in the three syllable words contribute to the differences in word duration as described above. These findings support our claim that in speech the control of word duration is an active skill and that words are the most important units of speech communication. [Work supported by the SPIN-ASSP Program.]
Sound field calculation for a circular array transducer
Authors: Lee Chankil , Kim Intaek , Benkeser Paul J.
Published: October 2005

Ultrasonic circular phased arrays have long been employed in sonar, NDT, and AGV applications. More recently, these arrays have been used in medical imaging applications. The ability of these arrays to image a 360° field makes them ideal for intravascular imaging applications. However, intravascular applications often require the diameter of the array to be on the order of 1 mm. The small size of the array dictates that trade-offs in its design, such as the number of elements versus resolution, be made. Field patterns produced by a circular phased array, required to evaluate such design trade-offs, have not been extensively examined. In this paper, a new field calculation method, which requires less computational time than existing methods for a given accuracy, is presented. The curved surface of the array, radiating either continuous-wave or pulsed signals, is subdivided into incremental areas which are small enough that the Fraunhofer approximation can be applied. The field pressure is computed by summing the contributions from all the incremental areas using the Rayleigh-Sommerfeld diffraction integral. Theoretical results obtained with this method are compared to those obtained using other methods as well as experimental data. The effects of some design parameters such as the geometry of the array, pulse bandwidth, and amplitude weighting of the excitation signal will also be presented.
How onset, offset, and ongoing interaural delays affect lateralization
Authors: Buell Thomas N. , Trahiotis Constantine
Published: October 2005

Several types of interaural delay can affect the lateral position of binaural signals. Delays can occur within the transient (onset and/off offset) or steady-state (ongoing cycle-by-cycle and/or envelope-based) portions of the signal, or both. The extent of laterality produced by these delays for simple and sinusoidally amplitude-modulated tones with an acoustic pointing task were measured. Relative potency of these delays was assessed by presenting them singly or in combinations (where the delays were consistent or in opposition). Also varied were rise/decay time, duration, rate of modulation, and center frequency. The major finding was that ongoing delays are much more potent than shown in previous tasks that required discriminations rather than judgments of location. [Research supported by NIH and AFOSR.]
Optimal stimulus placement in adaptive psychophysical procedures
Authors: Green David M.
Published: October 2005

A common misconception is that the stimulus should be presented near the threshold value in an adaptive psychophysical procedure to minimize the variance of threshold estimates. For maximum likelihood procedures, recent work by Laming, Watson, and Pelli shows that the stimulus should be presented at a relatively high level. For some psychometric functions, they found the optimal stimulus placement level produces 84% to 94% correct in a two-alternative forced-choice task. This result is particularly disquieting, because the popular two-down one-up rule tracks a relatively low percentage of correct responses, 70.7%. Our computer simulations, using a variety of psychometric functions, confirm the validity of their analysis. These simulations also demonstrate that the precise form of the psychometric function is not critical in achieving high efficiencies. Finally, data from human listeners indicate that the standard deviation of threshold estimates is approximately twice as large when the stimulus presented on each trial is at a stimulus level corresponding to 70.7%, rather than 94% correct. [This research was supported by NSF and AFOSR.]
Psychoacoustical masking of one pure tone by another and its relation to a model of the mechanics of the basilar membrane
Authors: Goldstein Julius L.
Published: October 2005

Accelerated psychoacoustical masking effects with level for simple tone maskers of higher frequency tones [Wegel and Lane, Phys. Rev. 23, 226–285 (1924); Duifhuis, J. Acoust. Soc. Am, 67, 914–927 (1980)] have clear correlates with nonlinear suppression and excitation phenomena in auditory nerve and basilar membrane responses [Abbas and Sachs, J. Acoust. Soc. Am. 59, 112–122 (1976); Patuzzi, Sellick, and Johnstone, Hear. Res. 13, 19–27 (1984); Robles et al., J. Acoust. Soc. Am. 80, 1364–1384 (1986)]. A signal processing model of basilar membrane response is presented that quantifies basilar membrane mechanics as two nonlinearly interacting filter responses: (i) a sensitive, narrow-band compresslye response responsible for the tips of cochlear suppression and excitation tuning curves; and (ii) and insensitive, lowpass linearlike response responsible for the low-frequency tails of tuning curves. Dual filter processing along with mutual suppression between the filters, described by the model, allows conceptualization of known psychoacoustics in terms of competing cochlear mechanical responses. Detailed model accounts of data and methods for estimating model parameters will be presented.
Chairman's introduction: Mechanisms as bases for safety criteria
Authors: Nyborg Wesley L.
Published: October 2005

There is now considerable interest around the world in developing scientifically based safety limits for medical ultrasound, especially as applied in diagnosis. While there has been no evidence of harm caused by past exposures to diagnostic ultrasound, some of the newer applications employ higher intensities than were used formerly. Hence, there is need for quantitative information on acoustic conditions that pose different degrees of risk, to guide manufacturers, users, and regulators. It is fairly generally agreed that a promising way to generate such information is to consider the separate biophysical mechanisms by which ultrasound can cause biological damage. This special session is to deal with research findings that relate to these mechanisms, and their relevance to safety limits.
Ultrasonic heating of the skull
Authors: Carstensen Edwin L. , Child Sally Z. , Norton Stephanie , Nyborg Wesley
Published: October 2005

Comparatively simple analysis shows that diagnostic ultrasound devices, in some cases, may approach output levels that can produce significant heating of tissues, particularly if the propagation path includes bone. The model assumes that all of the ultrasonic energy transmitted into the bone is converted into heat at the surface. The heat source, therefore, is a disk with diameter equal to the sound beam. Experimental tests of these predictions using rodents show that temperature increments of the order of 3°C/W/cm2 are produced in skull bone with sharply focused fields under medically relevant conditions. [This work was supported in part by U.S.P.H.S. Grant No. CA 39241.]
Sonic boom measurements from very high altitude and Mach numbers on space shuttle-orbiter reentry
Authors: Stanley J. F. , Stansbery E. G. , Henderson H. R. , Maglieri D. J.
Published: October 2005

STS-orbiter reentry sonic boom measurements are presented with particular emphasis on those acquired at very high altitude and Mach numbers. Included, also, are the orbiter physical characteristics and reentry parameters along with a discussion of the nature of its sonic-boom characteristics as compared to previous experience with aircraft. The applicability of existing sonic-boom theory, used for aircraft, to the STS-orbiter is shown. Previous STS reentry boom measurements, along with recently acquired measurements from the STS-26 and STS-27 reentry are presented and discussed. The results indicate that there are no significant differences in sonic-boom signature characteristics from STS-orbiter and other aircraft. N-wave type signatures are observed on STS-orbiter up to Math 23 and altitude of 250 000 ft having an overpressure of about 0.1 psf and a period of about 3.0 s. It is also shown that orbiter reentry maneuvering conditions do not produce focus booms. Although STS-orbiter signatures are predictable up to Mach 6 and an altitude of 130 000 ft, sonic-boom theory improvements are required for Mach numbers greater than 6.0. [Work supported by NASA and USAF.]
Low-frequency noise for low flying aircraft
Authors: Sutherland Louis C. , Plotkin Kenneth , Speakman Jerry
Published: October 2005

A consideration in the evaluation of aircraft noise impact on structures near airports and under low-level military training routes is the significance of the low-frequency content below 50 Hz. Based on analysis of measurements obtained under military training operations, a preliminary prediction model has been developed for application to environmental assessment of possible effects on structure. The model is based on the hypothesis that the major source to this low-frequency noise is radiation from the aircraft wake and vortices shed by the airflow over the wings or fuselage. The resulting empirical model predicts that the average maximum one-third octave band noise level, L, in decibels, in the frequency range of 5 to 40 Hz is given by: L = 48 log [V/100] + 10 log[A/R2] + 91, where V is the aircraft speed in kn, A is the wing area, and R is the slant range. Fortuitously, the same expression also provides reasonable estimates of this low-frequency noise level in the same frequency range for helicopters where V is now the helical tip speed and A is the rotor disk area. The resulting empirical model is similar to that developed for higher frequency airframe noise (J. C. Hardin, NASA SP-416, 1976). Further study is required to assess the validity of this model in comparison to more sophisticated models of low-frequency airframe noise. Comparisons between the prediction model and measured data will be illustrated. [Work supported in part by U. S. Air Force Harry G. Armstrong Aerospace Medical Research Laboratory.]
Fluctuating pressure and thermal environments of runway joint seals exposed to jet engine exhaust
Authors: Lancey Timothy W. , Cooper Eugene E.
Published: October 2005

Jet engine exhaust flow impinging on runway joint seals creates an aerothermoacoustic environment consisting of fluctuating pressure (acoustical and hydrodynamic) and incident gas temperature rapidly increasing with time. Fluctuating pressure at the surface of a joint seal on a runway was measured with microphones and low-pressure transducers positioned along the runway centerline. Temperatures were measured with thermocouples imbedded within the seal and on the surface, along the runway centerline and at several sideline distances. Pressure and temperature data were recorded during aircraft takeoff and landing operations. Measurements indicated incident noise pressure levels of approximately 164 dB re: 20 μPa, surface temperatures over 155 °C, and seal internal temperatures of 100 °C. Fluctuating velocity of the seal was calculated, treating the seal as a fluid flowing between parallel walls. Energy absorption rate was found to equal 850 W/m2, 4.7% of the power available from the incident fluctuating pressure field. Thermal energy through convective heat transfer was absorbed at 34 000 W/m2, 97.5% of total energy absorption.
A general analysis of the active control of sound radiation from a baffled panel
Authors: Snyder Scott D. , Jie Pan , Hansen Colin H.
Published: October 2005

Previous theoretical investigations of active means to control sound radiation from a vibrating panel have considered only the use of either acoustic control sources or vibration (point force) control sources. As such, a general understanding of the physical mechanism employed in this noise control technique has been lost. This paper presents a general analysis of the active control of sound radiation from a simply supported, baffled panel. It considers the use of both acoustic and vibration control sources. The minimization of the total sound power output is used as a criterion for actuator placement, and minimization of the sound pressure at a point is used for error microphone placement. Analytical results for minimization of the sound pressure at a point are verified experimentally. It is shown analytically that acoustic control sources operate by altering the radiation impedance seen by the vibrating panel. Vibration control sources operate by changing the panel velocity distribution, either decreasing the amplitude of the offending panel mode, and/or altering the temporal phasing of the panel modes, thereby decreasing the effective power radiation from the panel.
Plane-wave analysis of acoustic signals in a sandy sediment
Authors: Altenburg Robert A. , Faulkner Carl , Chotiros Nick
Published: October 2005

Acoustic pusles entering a sandy sediment through the water-sediment interface were observed. An acoustic projector located in the water column was used to insonify an array of sensors embedded in the sediment. Carrier frequencies of from 5 to 80 kHz were projected toward the sediment interface at grazing angles below, near, and above the critical value. Sound-pressure levels and time of arrival differences associated with the passage of the acoustic pulse were determined from the sensor data. A weighted least-squares algorithm was used to fit a plane to the arrival time differences yielding wave-front direction and speed estimates. Estimates of acoustic attenuation and wave-front coherence were also obtained. [Work supported by ONT under NORDA management.]
Is diffusion in concert halls a property of the volume or of the surface?
Authors: Lee James B.
Published: October 2005

For nearly a century, the principal concept of the theory of concert halls has been that of a nearly uniform field of energy, generated by many reflections, that varies but slowly with time. This supposed uniformity and isotropy gave rise to the term “good diffusion,” a property of the volume; it is difficult to quantify. An alternate approach is to apply the photometric concept of diffuse reflection at the surfaces: This is readily quantified, permits calculation of intensity at the audience, and posits nothing about the properties of the volume. Microcomputer programs to implement the concept are at hand and have been applied to a study of Boston Symphony Hall, renowned for its highly diffuse ceiling and walls. Modeling techniques, also borrowed from photometry, are available too: 1/50th scale architectural models are eminently suitable; note that models employing mirrors—specular reflectors—are not accurate representations of good concert halls.
Individual differences in voice quality perception
Authors: Kreiman Jody , Gerratt Bruce R. , Precoda Kristin
Published: October 2005

Sixteen listeners judged the similarity of all possible pairs of 18 pathological voices and, in a separate session, 18 normal voices. Individual differences, multidimensional scaling was used to derive a separate perceptual space for each listener/voice set combination. These scaling solutions accounted for an average of 83% of the variance in similarity ratings for pathological voices, and 77% for normal voices. Listeners varied substantially in the acoustic characteristics they attended to when judging vocal similarity: Although all perceptual spaces included an F0 dimension, no other parameter was used by more than half the listeners, for either voice set. Listeners who shared common perceptual dimensions often differed in the way they used the same acoustic information. For example, F0 was used as a continuous dimension by some listeners, and to sort voices into groups (high- and low-pitched groups, pathological and normal groups, etc.) by others; combinations of these strategies also occurred. Implications of these results for models of voice quality perception will be discussed.
The perception of the low-high (LH) tonal sequence
Authors: Hata Kazue , Hasegawa Yoko
Published: October 2005

It has been reported that the primary cue for the HL tonal perception in Japanese is not the actual F0 peak location but rather a falling F0 contour. The F0 fall may be significantly delayed, resulting in the F0 peak within the L-toned syllable. Furthermore, it was found earlier that (1) the later the F0 fall in the L-toned syllable, the steeper the fall rate required and (2) the fall must begin within the first two-thirds of the duration of the vowel in the L-toned syllable. The present experiment investigates whether a lack of synchronization between F0 change and syllable boundary can be found in the perception of the LH as well. Synthesized nonsense words/mamama/were prepared in such a way that both the onset of F0 rise and the F0 peak occur at various locations, while maintaining the overall F0 contour (level-rise-peak-slight fall). The stimuli were presented to native speakers of Japanese to determine the boundary between the categorical perception of LHH and LLH. The results show that the LH sequence is more constrained than the HL in terms of temporal alignment of F0 change and the syllable boundary.
The frequency scale of intonation
Authors: Hermes Dik J. , van Gestel Joost C.
Published: October 2005

Results will be presented showing that accent-lending pitch movements are perceived on a critical-band scale. A sentence was resynthesized in two versions differing in pitch and in formant frequencies. The lower-pitched version sounded like a male voice, the higher one like a female voice. One syllable was rendered prominent by means of a pitch movement. The pitch contours of the two versions ran parallel on any of three frequency scales: a logarithmic frequency scale (semitones), a critical-band scale, or a linear frequency scale (Hz). In 2AFC experiments, subjects indicated in which version the accented syllable was more prominent. Only when the excursions of the pitch movements were equal on a critical-band scale, the choice was random. In case of equality in semitones, subjects perceived the accent in the higher version as more prominent. In case of equality in Hz, the accent in the lower version was perceived as more prominent. These results allow a perceptually more realistic measuring of the prominence of accented syllables. [Work supported by Instituut voor Doven, St-Michielsgestel, The Netherlands.]
Continuative intonation in Mandarin
Authors: Mirza J. S.
Published: October 2005

The linguistic phenomenon of continuation in speech that manifests itself by modification of pitch contour in a preconjunction period was investigated for Mandarin. Mandarin is a tonal language; it has four tones. Its continuative intonation was investigated by examining selected parts of intonation contours prior to conjunctions for nine sentences each spoken by five speakers. Slopes of intonation contours across the words immediately before the conjunction were measured. It is reported here that the effect of continuation on Mandarin tones is highly dependent upon the type of conjunctions used. The continuation mostly drives up the slope values of Mandarin tones 2, 3, and 4, while the slope value of tone 1 is pushed down. The depression in slope value of tone 1, however, cannot be taken seriously because its isolation mode value slope is close to zero and the percent changes can be erroneous. The continuation affects on the average tone 2 most of all (+ 26%), then tone 3 (+ 21%), and then tone 4 (4%). The conjunction “and” has the greatest effect on the tones on the average (+ 25%) followed by conjunction “but” (23%) and “and then” (18%).
Using noise dosimeters in an industrial noise control program
Authors: Erdreich John
Published: October 2005

Traditional use of the noise dosimeter to assess employee exposure is to satisfy a regulatory mandate. Issues of effects of microphone placement and statistical reliability of the measurements have limited the usefulness of exposure measures so obtained and furthermore, have deflected attention from the real utility of the device to provide critical information for noise reduction. Experience with measurements on maintenance workers shows that time histories that are provided by certain dosimeters allow the engineer to identify noise generating processes that produce the major components of the exposure. As a practical matter, the high-level processes that contribute several decibels to the time-weighted-average exposure are of greater concern than statistical variability induced by other factors. For this reason, acquisition of time histories in employee exposure assessment is encouraged.
Measurement of hearing protector attenuation using the physical ear attenuation test (PEAT)
Authors: Michael Kevin
Published: October 2005

The attenuation provided by a sample of circumaural hearing protectors (ear muffs) was measured using the physical ear attenuation test (PEAT). The PEAT utilized a small electret microphone mounted in a silicon ear plug in the outer ear of a human subject. The subjects were exposed to a high level (about 100 dBA) of pink noise with and without the hearing protector fitted. The attenuation provided by the protector was calculated by subtracting the spectrum measured under the protector from the spectrum measured without the protector. The results of the PEAT evaluation were compared to the results obtained using the test method described in ANSI Standard S12.6-1984, the Method for the Measurement of the Real-Ear Attenuation of Hearing Protectors. Agreement was found between the methods for the test frequencies from 250 to 8000 Hz. The PEAT results at 125 Hz were lower than the results obtained with the ANSI S12.6-1984 method.
Low-frequency sound intensity measurement and free-field sound-pressure propagation
Authors: Gallagher William D. , Heitkamp Lawrence F.
Published: October 2005

Classical acoustical equations relate the sound power of a source to sound-pressure level at a given distance from that source. Sound intensity of a source can be measured, sound power determined by integration over the radiation area, and the sound-pressure levels at a distance from the source can be calculated. An assumption is made when the sound power to sound-pressure calculation is made, that at low frequencies (20–100 Hz) the waves have propagated and the resultant sound-pressure level is from the source. This work tests the reliability of that assumption. A speaker was suspended inside three different size boxes, and powered by a noise generator bandpassed at discrete frequencies. Sound intensity measurements were recorded near field at the same discrete frequency. Free-field sound pressure measurements were then recorded at distances from the boxes. This paper reports the results of the measurements.
Radial oscillations of gas bubbles in viscoelastic materials
Authors: Church Charles C. , Roy Ronald A.
Published: October 2005

Most previous studies of acoustic cavitation in biological tissue have treated the material surrounding the bubble as a Newtonian fluid with sometimes increased viscosity. The present work describes the derivation of a generalized Rayleigh-Plesset equation for a gas bubble in a continuous viscoelastic material. Viscoelasticity is modeled to include either stress relaxation (Maxwell fluid) or aftereffect (Voigt fluid). Several cases are considered: (1) a bubble with a (a) viscous shell suspended in a Newtonian fluid, (b) viscoelastic shell suspended in a Newtonian fluid, (c) viscoelastic shell suspended in a viscoelastic fluid; and (2) a “clean” bubble suspended in a (a) viscous or (b) viscoelastic fluid. In general, the effect of viscoelasticity is to decrease the resonance frequency and increase the threshold for transient cavitation. Preliminary measurements of cavitation thresholds in a liquid seeded with Albunex® stabilized microbubbles are presented and interpreted in light of the theory. [Work supported by NIH.]
Biophysical mechanisms in the formulation of Canadian guidelines for diagnostic ultrasound devices
Authors: Bly Stephen H. P. , Morison D. A.
Published: October 2005

A mechanistic assessment of ultrasound safety is presented as a method to formulate guidelines for diagnostic ultrasound devices. This approach was adopted since surveys had indicated that ultrasound output levels from some existing devices were higher than the no-effect levels found in epidemiological studies and studies of mammalian bioeffects. Existing studies on two mechanisms, heating and cavitation, were examined. It was found that knowledge of the cavitation mechanisms in vitro and in nonmammalian model systems could not be extrapolated to predict cavitation thresholds in humans. For the thermal mechanism, sufficient data were available [AIUM Bioeffects Committee, J. Ultrasound Med. 7, S1–S38 (1988)] to formulate a guideline. The guideline recommends that, for diagnostic ultrasound devices used for fetal examinations and yielding free-field spatial peak temporal average intensities greater than 500 mW/cm2, estimates should be provided of maximum local temperature elevations in fetal tissues.
Adults and infants show a “prototype effect” for speech sounds
Authors: Kuhl Patricia K.
Published: October 2005

Dennis Klatt provided valuable assistance to many speech perception researchers. His advice on the synthesis of speech signals was particularly helpful, and investigators relied on his expertise when problems arose in the development of stimuli designed to approach a problem in a new way. This was the case in the preparation of stimuli to test whether there are “prototypes” for vowel sounds. The experimental question was whether or not adults and infants responded differently in a within-category vowel discrimination task when the “standard” stimulus was an exceptionally good instance of the vowel /i/—a prototype of the category—as opposed to a nonprototypic /i/ vowel. The results showed that when the prototype of the category served as the standard stimulus, it was more difficult to hear differences between it and novel /i/ vowels than it was to hear differences between the nonprototypic stimulus and novel /i/ vowels. In other words, the prototype was perceived to be more similar to new members of the category than was the nonprototypic stimulus. The effect was observed both in adults and in 6-month-old infants. Described first will be the hypothesis underlying the prototype test, the method used to construct the stimuli (the test stimuli for the prototype and the nonprototype were scaled psychophysically using the “mel” scale), and the results on English adults and infants. Described next will be the second phase of the research program, which entails cross-language tests on Swedish adults and infants. The cross-language tests are designed to assess two different explanations for the prototype effect: (1) that particular vowel stimuli (/a,i,u/) are inherently more resistent to the effects of articulatory/acoustic change (Stevens' quantal theory) and (2) that the effects observed in American adults and infants are attributable to experience in listening to English, even in the first 6 months of life. Careful preparation of the English and Swedish stimuli was critical in designing these experiments. Dennis Klatt was always ready to provide advice on such matters; his assistance is gratefully acknowledged and sorely missed. [Work supported by NIH.]
Acoustic properties of /h/
Authors: Manuel Sharon Y. , Stevens Kenneth N.
Published: October 2005

The aim of this paper is twofold: (1) to investigate the physical mechanisms of sound generation for the consonant /h/ and (2) to examine the timing of supraglottal and glottal movements of /h/. Utterances in which /h/ was present or absent (e.g., “new heart” versus “new art”) were analyzed acoustically and contrasted. The corpus consisted of about 20 such utterances repeated several times by three speakers. The acoustic data showed evidence of breathy voicing at the /h/-vowel boundary in all cases, and that generation of turbulence noise during the consonant occurred both in the vicinity of the glottis (aspiration noise) and the vicinity of the supraglottal constriction (frication noise). The relative contribution of the two noise sources depended on the vowel, with greater frication noise occurring for high vowels. When an /h/ was in position between two vowels or glides, it generally added little or no duration to the utterance, relative to the contrasting utterance with no /h/. Implications for the phonological status of /h/ as discussed. [Work supported by NIH grants to MIT.]
Cochlear mechanical model stability
Authors: Matthews John W. , Molnar Charles E.
Published: October 2005

The introduction of nonlinear damping into computational simulations of stable active cochlear mechanical models has introduced instability in computational simulations of models used here. Nonlinear dynamical systems theory provides tools that give insight into the possible sources of such instability. Analysis of differential equations for a simplified cochlear mechanical model with a computer program (“AUTO” by Eusebius Doedel) suggests that the unstable behavior of earlier simulations is an artifact of the computations rather than an inherent feature of the differential equation model. [Work supported by NIH grants NS21592 and RR01379.]
Impulse response for propagation in the ocean sound channel
Authors: Flatté Stanley M. , Colosi John , Duda Timothy F. , Rovner Galina , Martin Jan
Published: October 2005

Using the SDSC/CRAY and the parabolic equation, pulse propagation was simulated in the ocean sound channel. Pulses with 200 frequencies between 10 and 50 Hz were synthesized, giving a pulse width of approximately 25 ms, and a pulse repetition time of 5 s. The wave fronts created by this technique have a simple and intuitive character, unlike the fields for single frequencies. Pictures of wave fronts out to 1000 km, and possibly a movie, will be shown. Wave front reconstruction by means of a much faster calculation in terms of ray theory will be demonstrated. The effects of internal waves on the wave fronts will be described in terms of wave front corrugations, and the use of impulse measurements over vertical arrays to measure the properties of the internal-wave field will be discussed. [Work supported by ONR, Code 1125OA.]
Combined oceanographic and acoustic modeling
Authors: Porter Michael , Piacsek Steve , Henderson Laurel , Jensen Finn
Published: October 2005

An important class of oceanographic models is the mixed layer models that, simply stated, provided predictions of mixed layer depth and temperature. These predictions take into account the surface winds that drive the mixing and the solar radiation that heats the mixed layer. As interest has increased in using such models as a step in the process for making acoustic forecasts or nowcasts, a recurring question has been that of what information is needed for accurate acoustic predictions. For instance, how precisely do mixed layer depths need to be calculated? Is mixed layer temperature important? These and other questions are addressed through a parameter study using synthetic sound-speed profiles as input to an acoustic model. The implications are demonstrated in a somewhat more concrete form in a two-step process: The SSP is predicted using particular mixed layer models (Niiler, Mellor-Yamada, Garwood, etc.) and passed to an acoustic model to provide transmission loss calculations. The results are also compared to predictions based on both measured and historical SSP measurements.
An objective correlation to subjective ratings of vehicle passenger compartment noise
Authors: Hodgdon Kathleen K.
Published: October 2005

The intent of this research was to identify a more desirable sounding noise for the passenger compartment of the Pontiac 6000 LE and to establish an objective correlation to the subjective ratings of the automobile passenger compartment noise. The noise spectrum within the passenger compartment was acquired utilizing an artificial head during an acceleration run from a complete stop to maximum acceleration. The noise was then analyzed and the original noise sample and seven synthesized variations were paired in all possible combinations and randomly recorded for subjective presentation. Subjects were given a two-alternative forced-choice task in which they were instructed to choose either the first or second member of each pair as more desirable. Two independent objective procedures, the articulation index (AI) and Steven's Mark VII, were calculated based on the physical parameters of each noise spectrum. The eight noise samples were then rank ordered for desirability based on the subjective responses. The objective calculations for the spectra were rank ordered and compared to the subjective rankings. Statistical comparisons between the rankings, as well as the ability of the objective calculations to predict the subjective responses, were discussed.
Application of laser velocimetry to the measurement of basilar membrane vibrations
Authors: Ruggero Mario A. , Rich Nola C.
Published: October 2005

A commercially available laser Doppler-shift velocimeter has been coupled to a compound microscope equipped with ultra-long-working-distance objectives for the purpose of measuring basilar membrane vibrations in the chinchilla. The animal preparation is nearly identical to that used in our laboratory for similar measurements using the Mössbauer technique. The vibrometer head is mounted on the third tube of the microscope's trinocular head and its laser beam is focused on high-refractive-index glass microbeads (20–50 μm) previously dropped, through the perilymph, on the basilar membrane. Sensitivity of the laser velocimetry system is at least one order of magnitude greater than usually attained using the Mössbauer technique. However, the most important advantage of laser velocimetry vis-à-vis the Mössbauer technique is its linearity, which permits undistorted recording of signals over a wide velocity range. Thus, for example, basilar membrane responses to clicks have been measured for stimulus intensities ranging over 80 dB. At low stimulus levels, these responses are as sharply tuned as frequency-threshold curves of cochlear afferents with comparable characteristic frequency; at higher levels, sharpness of tuning diminishes. [Work supported by NIH.]
Simulation of learning and transfer in profile analysis by artificial neural networks
Authors: Harpster Jeffrey L. , Howard James H. , Miller Maxwell H.
Published: October 2005

Two aspects of profile analysis previously investigated in human listeners by Green and his associates were simulated by artificial neural networks (ANNs). First, the time course of learning was compared in the neural networks and the human listeners. Both had learning curves that showed a rapid initial improvement followed by gradual leveling to asymptote. Several values of the learning rate parameter were used for the ANNs, and network learning at the different rates was compared to the human data. Second, the transfer of learning between profile analysis and intensity discrimination tasks was compared for the ANNs and humans. Again the pattern of performance was similar for the ANNs and human listeners. Given comparable stimuli, sensitivity was better for profile analysis than for intensity discrimination, and negative transfer occurred when switching from profile analysis to intensity discrimination or vice versa. These studies extend previous work [Howard et al., J. Acoust. Soc. Am. Suppl. 1 85, S37 (1989)] using feed-forward artificial neural networks trained with the back propagation learning rule to model human auditory phenomena. [Work supported by ONR.]
Changes in auditory sensitivity during and following exposure to intense sound in the young chick
Authors: Saunders James C.
Published: October 2005

Tone-burst-evoked potentials recorded from electrodes placed in the cochlear nuclei were used to measure auditory function in groups of chicks, at different time intervals during and after exposure to an intense pure tone. Threshold sensitivity, defined as the stimulus SPL that produced a just-detectable response in a quiet environment, was measured at test frequencies between 0.1 and 4.5 kHz. A simultaneous masking paradigm obtained masked evoked response thresholds, and from these masked tuning curves were constructed at five different probe-tone frequencies. Lastly, the relation between evoked response magnitude and stimulus SPL was measured to explore the presence of evoked-response recruitment. The growth of threshold shift and tuning curve selectivity loss exhibited a dual process. The recovery of threshold sensitivity, following exposure, was more rapid than the recovery of tuning curve sharpness. Evoked-response recruitment was severe immediately after exposure, but completely recovered within 3 days. These results are considered with respect to cochlear pathology and the regeneration of receptor cells on the chick basilar papilla. [Work supported by the Deafness Research Foundation, Pennsylvania Lions Hearing Research Foundation, and the NIDCD.]
Temporary threshold shift produced by low- and high-frequency tones
Authors: Young I. M. , Lowry L. D.
Published: October 2005

A subject with normal hearing was exposed to pure tones of 125 and 10 000 Hz at 105 dB SPL for 15 min. Temporary threshold shift (TTS) was measured at frequencies of 100–10 000 Hz by automatic audiometry. The maximal TTS was produced in the frequency regions of 500–1000 Hz by an exposure to a 125-Hz tone and in the frequency areas of approximately 12 oct below the exposure tone, i.e., 5500–6000 Hz, by 10 000-Hz tone. An exposure to a low-frequency tone, 125 Hz, did not demonstrate the 12-oct shift as shown by exposures to other frequency tones. The TTS phenomenon by an exposure to a high-frequency tone, 10 000 Hz, was not consistent with the idea of a basalward migration of the traveling wave envelope. These findings were compared and discussed with the TTS results of exposure to other frequencies.
Articulatory synthesis: The Kelly-Lochbaum model as a finite-difference approximation
Authors: McGowan Richard S.
Published: October 2005

The computation of acoustic pressure fluctuations in a variable area tube is often done using the Kelly-Lochbaum reflection model. The numerical scheme provided by this model can be seen to be a finite-difference approximation to a differential equation describing acoustic wave propagation, the Webster horn equation. An alternative scheme that has less truncation error is examined. Quantitative criteria for goodness of finite-difference approximations (truncation error, stability, and dispersion) are discussed without considering the effects of boundary conditions. The quantitative criteria applied to approximate computational schemes used in synthesis can help assess physical models of wave propagation.
Text-independent talker identification using recurrent neural networks
Authors: Rudasi Laszlo , Zahorian Stephen A.
Published: October 2005

Recurrent neural networks (RNNs), i.e., artificial neural networks with internal feedback, have the potential to perform pattern classification using both static and dynamic spectral information. Experiments were conducted to determine if these networks can be trained to identify talkers in a text-independent mode using short samples of speech for training the network. The database for experimentation consisted of the first 200 ms of 60 CVC syllables for each of 30 speakers. Ten of these speakers were adult males, ten were adult females, and ten were children. Thirty syllable segments (6 s of speech) were used for training and 30 different syllable segments (6 s) were used for testing. To speed up the training times for the RNN, four independent RNNs were used. One RNN was used to differentiate the speaker type (man/woman/child) and each of the other networks was trained to differentiate among the ten speakers in each group. For each RNN, ten input nodes (corresponding to ten modified cepstral coefficients) and 30 hidden nodes were used. With test words for evaluation, the RNNs were able to identify the speaker group for all speakers (i.e., 100% accuracy). The RNNs also identified the individual speakers with 100% accuracy. These results indicate that recurrent neural networks can be successfully trained in a text-independent talker identification task, even with a relatively small amount of data.
Learning the association between speech acoustics and articulatory trajectories with a neural network
Authors: Thomas Timothy R. , Papcun George J. , Shelton Kennan
Published: October 2005

Because the relationship between the motion of the speech articulators and the acoustic signal produced is nonlinear and of great complexity, it has previously proved impossible to accurately infer the articulatory motions that produced natural continuous speech. However, a carefully tuned back-propagation neural network has the capability of learning such complex relationships. The present results show that such a network can learn the map between a female speaker's continuous speech and the x-ray microbeam record of the associated articulator movements. The discovered map can then be used to successfully infer the movements of a male speaker saying the same thing (r=0.82 between inferred and actual tongue tip vertical position). The Bark scaled spectrum of counting at a normal rate from 1 to 10 was used as input, and separate nets learned the position of the tongue tip, body, dorsum, and lower lip. Alternative input normalization schemes, network configurations, and training procedures were evaluated. [Work supported by DOE Contract W-7405-ENG-36.]
Speech recognition based on inferred articulatory movements
Authors: Papcun George , Thomas Timothy R.
Published: October 2005

A neural network was trained to learn the associations between speech acoustics, suitably transformed and normalized, and associated articulatory movements, which were recorded at the University of Wisconsin x-ray microbeam facility. Training was done on the numbers “one” through “ten” spoken by a female speaker; articulatory templates were selected from her speech. Speech from a male speaker was transformed and normalized and passed through the trained neural network. Articulatory movements inferred from his speech by the neural network were compared, by Euclidian distance, with the templates from the speech of the female speaker. To assign a single point of match for each template, an extremum finding algorithm was passed over the function that relates temporal position to degree of match. A threshold, defined as a distance of more than two standard deviations from the mean of the distance measure taken at each step in the speech sample, was used to successfully recognize the words spoken. Enhanced discrimination was obtained by weighting the articulatory parameters. [Work supported by DOE Contract W-740S-ENG-36.]
Vowel-vowel transitions, analysis, and modeling
Authors: Carré René , Mrayati Mohammed
Published: October 2005

Male and female vowel-vowel formant transitions are analyzed using cepstral techniques. The first three formants are detected and represented as trajectories in the F1−F2, F1−F3, and F2−F3 planes. Distinctive formant trajectories are clearly revealed, exhibiting specific trajectory angles at the onset during the initial vowel and at the offset during the target vowel. Formant stabilities are also studied. Generally, depending on the vowel identity and the vowel context, either F1 or F2 is kept almost stable. These trajectories are interpreted using a region concept [Mrayati et al., Speech Commun. 7, 257–286 (1988)]. Trajectories predicted by the region model combined with an extremely simple dynamic strategy correspond well with those observed on natural speech. Explanations on the articulatory timing control can be deduced and compared with published cineradiographic and labiofilm data.
Templates as states in a hidden Markov model
Authors: Ghitza Oded , Sondhi M. M.
Published: October 2005

In most implementations of hidden Markov models (HMM) a state is assumed to be a stationary random sequence of observation vectors whose mean and covariance are estimated. Successive observations in a state are assumed to be independent and identically distributed. These assumptions are reasonable when each state represents a short segment of the speech signal. When states represent longer portions of the signal (e.g., phonemes, diphones, etc.) both assumptions are inaccurate. Recently some attempts have been made to incorporate correlation between successive observations in a state. But to our knowledge, nonstationarity has not been dealt with. An alternative representation is proposed in which a state of an HMM is defined as a template, i.e., a “typical” sequence of observations. The template for a state is derived from an ensemble of segments corresponding to that state. In the present implementation, the observations are 13th-order cepstrum vectors plus energy; states represent diphones; and ensembles of the diphones are obtained from a hand-labeled speaker-dependent database of 2000 sentences spoken fluently. The probability of a test sequence being generated in a given state is obtained by time warping the test utterance to the template and assuming the differences between the corresponding observations to have a joint distribution. Preliminary tests on 26 sentences (outside the training set) indicate a correct recognition rate for diphones of about 73%.