bluuebunny/crossref_metadata_2025 huggingface dataset:
Geometrical theory of diffraction for high-frequency coherence functions in a weakly random medium with inhomogeneous background profile
Authors: Mazar R. , Felsen L. B.
Published: October 2005

The localization of high-frequency wave propagation around ray trajectories and the reflection, refraction, and/or diffraction of these local plane wave fields by boundaries, inhomogeneities, and/or scattering centers have been combined via the geometrical theory of diffraction (GTD) into one of the most effective means for analyzing high-frequency wave phenomena in complex deterministic environments. These constructs are here incorporated into a stochastic propagation and diffraction theory for statistical moments of the high-frequency field in a weakly fluctuating medium with inhomogeneous background profile, provided that the correlation length ln of the fluctuations is small, compared with the scale of variation, but large, compared with the local wavelength λ = 2π/k = 2πc/ω in the fluctuation-free background, with k being the local wavenumber, c the local wave speed, and to the radian frequency. The major analytical building blocks for coherence functions and paired random functions (PRF) include propagators described in local coordinates centered on the curved GTD ray trajectories in the deterministic inhomogeneous background environment; multiscale expansions in these coordinates to solve for statistical measures of the parabolically formulated ray fields; Kirchhoff or physical optics (PO) approximations for fields reflected from extended smooth surfaces; and “point scatterer” solutions for small scatterers and edges. The PRFs are useful for correlating incident and backward fields traversing the same propagation volume. The theory is illustrated for forward propagation in a fluctuating medium with inhomogeneous and caustic forming background, for reflections and refraction due to a plane or smoothly curved interface in such a medium, and for diffraction due to a wedge and a small scatterer. [Work supported by RADC and ONR.]
The influence of channel boundaries on remotely sensed target resonances
Authors: Gaunaurd G. C. , McCarthy M.
Published: October 2005

Target resonances are unique characteristics of scatterers and serve to identify them unambiguously. In the vicinity of environmental boundaries, the way resonances are perceived by sensors is different than in the absence of boundaries. Thus, even though the resonances themselves do not change. the way in which they manifest themselves in the scattering cross section of scatterers as sensed at the receiver, changes near an environmental boundary. A formalism is developed to study this change and to assess the effect of boundaries upon the way elastic scatterers are excited into resonant vibration by incident sound waves. This formalism reduces to an earlier one developed [J. Acoust. Soc. Am. 73, 1–12 (1983)] for an infinite medium lacking boundaries. In general, the effect of boundaries on the resonance features present in the sonar cross section depends on the azimuthal wavenumber m, even for spherical scatterers. It also depends on the depths H and h of the elastic scatterer and the receiver, beneath the free surface z = 0 of the half-space. The boundary's influence is greatest for m = 0, or H ≫ 1, or both. The method relies on addition and translation theorems for various wavefunctions.
Results from applying various audiometric data base analysis procedures to data provided to the ANSI S12.12 Working Group
Authors: Royster Julia Doswell , Royster Larry H.
Published: October 2005

The ANSI S12.12 Working Group has received over 20 audiometric data bases contributed by U.S. and Canadian industries from their hearing conservation programs (HCPs). The data include at least four approximately annual audiograms for about 12 000 male employees and at least eight audiograms for about 3000 male employees. The authors applied various analyses to the data to identify statistics which differentiate the level of protectiveness of the HCPs represented. Some statistics are based on variability in the audiometric thresholds (percentages of employees showing defined hearing changes either for better or for worse). Other statistics are based on the rates of change in group mean audiometric thresholds over time, compared to expected age-effect changes for nonindustrial reference populations. Desirable ranges for the statistics are suggested based on determining the results for non-noise-exposed and low-noise-exposed populations.
Diffraction and nonlinear distortion in sound beams as interacting wave phenomena
Authors: Ginsberg J. H. , Miao H. C. , Foda M. A.
Published: October 2005

Discrepancies between the nonlinear King integral [J. H. Ginsberg, J. Acoust. Soc. Am. 76, 1201–1214 (1984)] for a sound beam and experiment are encountered in the nearfield in high-frequency, high-intensity situations. It is shown that the nonlinear, as well as linear, signal at all locations may be represented as groups of quasiconical waves converging and diverging on the axis, as they propagate away from the transducer. Nonlinear distortion to the nearfield arises from interaction of different transverse wavenumber modes in each group, and also from interaction between the groups. The latter effect ceases to be significant in the farfield, whereas the self-distortion arising in either group grows. The nonlinear King integral is shown to be the limiting form for long ranges. The results for nearfield locations are extremely challenging to evaluate, and an approximation that can be used to evaluate waveforms in some situations is discussed. [Work supported by the ONR, Code 1125-UA.]
Finite amplitude acoustic waves generated by a baffled, multiharmonic transducer
Authors: Edgerton James B. , Ginsberg Jerry H.
Published: October 2005

Arbitrary periodic excitation of a baffled piston transducer leads to harmonic and intermodulation distortion when finite amplitude effects are considered. An analysis of the radiation signal in such a situation is initiated by representing the linearized signal as a sum of King integrals associated with each harmonic in the excitation. A nonuniformly accurate expression for the velocity potential is derived using a singular perturbation procedure that identifies the dominant tendency of nonlinearity to generate second-order interactions. This form is obtained from an asymptotic integration, which leads to spectral decomposition of the signal into groups of quasi-one-dimensional waves. The renormalization version of the method of strained coordinates is used to obtain a uniformly accurate expression for the acoustic pressure at all locations preceding the formation of a shock. [Work supported by the ONR, Code 1125-UA.]
Temperature dependence of the ultrasonic nonlinearity parameters of NaCl
Authors: Jiang Wenhwa , Breazeale M. A. , Kashkooli Ali
Published: October 2005

The ultrasonic harmonic generation technique using a capacitive detector has been used to measure the ultrasonic nonlinearity parameters of sodium chloride single crystals between 300 and 77 K. Since NaCl is a typical ionic crystal, its ordinary elastic constants have been of interest to many physicists. Likewise, its nonlinear properties, its third-order elastic constants, and their temperature dependence have been of interest to solid-state theory. However, to date the large thermal expansion coefficient and the fragility of NaCl have thwarted measurement of the temperature dependence of its nonlinearity parameters. Differential expansion between NaCl and a bonded quartz transducer often has resulted in sample cleavage. A special technique for bonding the quartz transducer to the NaCl sample has been developed. With the aid of this technique, ultrasonic nonlinearity parameters of three different oriented samples of NaCl have been measured for the first time in the temperature ranges of 300 to 77 K for the (100) sample, 300 to 100 K for the (110) sample, and 300 to 110 K for the (111) sample. The TOE constant C111 and two combinations of the other TOE constants and their temperature dependence have been obtained. The results are compared with theory describing interatomic forces in alkali halide crystals. (Research supported in part by the ONR and the UT-ORNL Science Alliance.]
Dissipative structure of shock waves in fluids having large specific heat
Authors: Cramer M. S.
Published: October 2005

Recent studies indicate that the nonlinearity parameter 1 + B/2A may become negative in fluids whose specific heats are sufficiently large. The present study examines the dissipative structure of weak shocks in such fluids and contrasts the results obtained with those of the classical Taylor structure. Estimates for the thickness will also be presented. Conditions under which the thickness increases, rather than decreases, with increasing shock strength will be given.
Anomalies in the scattering-induced attenuation of backscattered ultrasonic waves
Authors: Nagy Peter B. , Adler Laszlo
Published: October 2005

Scattering-induced ultrasonic attenuation offers a simple way to characterize quantitatively material inhomogeneities. This method has a wide range of applications from tissue characterization to ultrasonic NDE such as grain size measurement in polycrystalline materials and porosity assessment in cast metals. The scattering-induced attenuation of a through-transmitted well-collimated ultrasonic wave can be readily related to certain characteristics of the inhomogeneity via its total scattering cross section. In many cases, ultrasonic attenuation measurement is not feasible except from the backscattered signal. For want of better approximation, the scattering-induced attenuation is presumed to have the same relation to the inhomogeneity as if it were measured by the simpler transmission technique. Experimental results are presented to show that the backscattered signal is much less attenuated than is predicted by the planewave approximation, and that this effect is not simply due to multiple scattering. Furthermore, it is shown that the scattering-induced attenuation of the incoherent backscattered signal is mainly due to backward scattering, while strongly forward scattering inhomogeneities, such as surface roughness, will cause negligible attenuation. [Work sponsored by the Air Force Wright Aeronautical Laboratories/Materials Laboratory under Contract No. W-7405-ENG-82 with Iowa State University.]
Effect of ambient pressure on the pressure Wave from the rapidly expanding bubble
Authors: Kwak Ho-Young
Published: October 2005

Calculation on the intensity of evaporation and the rapidly expanding bubble formed from the droplet at the superheat limit is calculated. An analysis is presented for the amplitude of the pressure wave generated by the rapidly expanding bubble. For estimating the amplitude, linear acoustics theory for the evaporating droplet and the Rayleigh equation for the expanding bubble are employed. The result shows that the amplitude and the frequency of the pressure wave depend crucially on the difference in pressure between vapor within the bubble and the surrounding liquid. This result is in qualitative agreement with previous experiment.
Forced radial oscillations of single cavitation bubbles: Period-doubling, chaos, and hysteresis
Authors: Holt R. G. , Crum L. A.
Published: October 2005

Utilizing an optical scattering technique previously reported [J. Acoust. Soc. Am. Suppl. 1 80, S24 (1986)], the radial response of a single bubble to an acoustic field has been observed and analyzed. A scattered light intensity versus radius transfer function has been obtained for the system, enabling a quantitative description of the radius versus time. Some universal features of driven nonlinear systems have been observed, among them period-doubling, chaotic solutions (with corresponding fractal attracting sets in the phase plane), and bistability due to hysteresis in the resonance structure. [Work supported by ONR.]
Predictions for binaural masked detection with frozen-noise maskers
Authors: Kline Gary C. , Colburn H. Steven
Published: October 2005

Biomedical Engineering Department, 110 Cummington Street, Boston University, Boston, MA 02215 A model of binaural heating based on combinations of interaural time and intensity differences [Gabriel et al., J. Acoust. Soc. Am. Suppl. 1 74, S85 (1983)] was used to predict results obtained previously [R. H. Gilkey, D. E. Robinson, and T. E. Hanna, J. Acoust. Soc. Am. 78, 1207–1219 (1985)] in a binaural masked detection experiment with repeatable samples of masking noise. The narrow-band model generates its decision variables through a linear combination of interaural time and intensity differences followed by a sluggishness filter (averager). A computer simulation of the model was used to predict the hit and false-alarm rates for each of ten independent, frozen-noise masker samples, and for target phase angles of 0 deg and 90 deg. Model predictions disagree with the experimental results in two respects. First, the false-alarm rates predicted by the model show almost no variation across masker samples, while the experimental results show changes from 5% to 80%. This disagreement illustrates the inadequacy of the additive internal noise assumption of the model. Second, the model predicts changes in the hit rate as large as 80% when the tone phase changes from 0 to 90 deg for a given masker sample, while the experimental results show changes less than 20% for a given masker sample (although hit rates vary over a range of 75% across masker samples). This significant correlation in hit rates for these two phase angles is not easily explained within a model based on interaural differences since the interaural differences in the stimulus are uncorrelated for these phase angles. [Work supported by NIH.]
Extending the position-variable model: Dependence of lateralization on frequency and bandwidth
Authors: Shear Glenn D. , Stern Richard M.
Published: October 2005

The position-variable model [R. M. Stern, Jr. and H. S. Colburn, J. Acoust. Soc. Am. 64, 127–140 (1978)] is extended to describe the subjective lateral position of tones as a function of frequency and ITD, and the lateralization of bandpass noise as a function of bandwidth, ITD, and interaural phase shift. The two major modifications made to the model are (1) the use of a frequency-dependent form of the function that expresses the relative number of binaural coincidence detectors as a function of their characteristic delay and (2) additional processing of the display of interaural cross correlation to emphasize those regions of the function which exhibit peaks at the same internal delay across a range of frequencies. For most naturally occurring broadband stimuli, these regions indicate the set of primary modes of the corresponding cross-correlation functions, thereby enabling the central processor to determine without ambiguity the value of ITD present in the stimulus. The extended model describes lateralization data for a much wider range of stimulus frequencies than the original model, which could only describe responses elicited by 500-Hz tones. [Work supported by NIH.]
Nonlinear spectral interferometry (NLSI): A new approach to modeling binaural hearing and aural communication channeling
Authors: Cohen Nathan , Cummins Dean
Published: October 2005

A biointerferometric model for spatial hearing is described in which binaural information is processed as an interferometric response via a nonlinear spectral transform of the cross-correlation function. Relevant observables include phase delay, phase delay rate, visibility amplitude, and visibility phase. Our model accounts for a broad range of hearing phenomena including: (1) localization below diffraction limited frequencies by overtone generation at the cochlea; (2) localization acuity by superresolution of the synthesized beam; (3) beam synthesis by visibility plane sampling through overtone content in speech and cochlear response; (4) the binaural advantage in intelligibility through interferometric rejection and neuronally driven beam steering; and (5) transformation from phase to amplitude localization cues through loss of visibility phase above the phase-locked frequency range. This model obviates the need for multiple cue and/or component models and has distinct advantages over other cross-correlation models. Additional psychoacoustic tests to corroborate this NLSI model are described.
The effect of head-induced interaural time and level differences on speech intelligibility in noise
Authors: Bronkhorst A. W. , Plomp R.
Published: October 2005

The effect of interaural time delay (ITD) and acoustic headshadow on binaural speech intelligibility in noise was studied. A free-field condition was simulated by presenting recordings, made with a KEMAR manikin in an anechoic room, through headphones. Recordings were made of speech, reproduced in front of the manikin, and of noise, emanating from seven angles in the azimuthal plane, ranging from 0° (frontal) to 180° in steps of 30°. From this noise, two signals were derived, one containing only ITD, the other containing only headshadow. Speech-reception thresholds for sentences in noise for a group of normal-hearing subjects showed that for noise azimuths between 30° and 150°, the gain due to ITD lies between 3.9 and 5.1 dB, while the gain due to headshadow ranges from 3.5 to 7.8 dB. A second experiment with similar stimuli, presented monaurally or with a 20-dB interaural level difference, indicated that for noise with only headshadow, the gain relies on the ear presented with the most favorable signal-to-noise ratio, but decreases when the noise presented to the other ear becomes relatively loud.
Motion aftereffects with horizontally moving sound sources
Authors: Grantham D. Wesley , Luethke Lynn E.
Published: October 2005

Continuous sounds were presented in an anechoic chamber through two horizontally rotating loudspeakers that traversed a full 360° around the observer at ear level (distance: 1.5 m). At 10-s intervals this “adaptation stimulus” was interrupted and a 750-ms “probe stimulus” was presented from a pair of stationary loudspeakers (separated by 7.5°) 1.6 m in front of the observer. The probe could itself be stationary or could “move” (employing a stereophonic balancing algorithm) in either direction. During a run the adaptation stimulus was held at a constant velocity (− 200° to + 200°/s), while probes with velocities varying from − 10° to + 10°/s were presented in a random order. Observers judged the direction of motion (“left” or “right”) of each probe tone. When the frequency content of the adaptation stimulus was the same as that of the probe stimulus (either 500-Hz low-pass or 6300-Hz high-pass noise), stationary probes were consistently judged to move in the direction opposite to that of the adaptation stimulus. This effect increased with the velocity of the adaptor. Possible sensory and nonsensory mechanisms underlying this aftereffect will be discussed. [Work supported by NIH.]
The duplex nature of the brain-stem binaural interaction component: Frequency, rate, and intensity effects
Authors: Parthasarathy T. K. , Moushegian G.
Published: October 2005

As in a previous study [J. Acoust. Soc. Am. Suppl. 1 79, S6 (1986)], stimuli were varied to evaluate the binaural interaction component (BIC) of the auditory brain-stem response (ABR) in normal hearing adults. In addition to a clicklike sound, tone bursts (0.5, 1.0, and 2.0 kHz), having two cycles of rise-fall time and one of duration, were presented at two intensities (85 and 100 dB SPL). Binaural wave III and V amplitudes were smaller with shorter latencies than summed monaural amplitudes and latencies at both intensity levels of the click and 2.0-kHz tone burst. Increasing stimulus rate produced longer latencies and smaller peak amplitudes of the binaural interaction components and concomitantly longer latencies and smaller wave III and V amplitudes of ABR. Wave V latency shift was greater at 85 than at 100 dB SPL, whereas the BIC exhibited greater latency shifts at 100 than at 85 dB SPL. The derived frequency following response (FFR) to 0.5 and 1.0 kHz [J. Acoust. Soc. Am. Suppl. 1 79, S6 (1986)] had shorter latencies and larger amplitudes at 100 than at 85 dB SPL. All of the findings suggest that the BIC, in conformity with the findings from medullary neuronal physiology, is differentially sensitive to rate, frequency, and intensity.
Performance of adult subjects on a dichotic speech test under both directed and free recall listening conditions
Authors: Baran Jane A. , Musiek Frank E.
Published: October 2005

Twenty-five young adult subjects with negative otologic histories were administered a dichotic rhyme test under three different listening conditions: (1) free recall, (2) directed listening to the right ear, and (3) directed listening to the left ear. The dichotic rhyme test used is composed of 30 well-aligned synthetic CVC words that were presented at 50 dB SL (re: speech reception thresholds). The nature of the test is such that under normal conditions (i.e., free recall), listeners tend to repeat either the word presented to the left ear or to the right ear. Normal performance is approximately 50% correct identification in each ear, with a slight right ear advantage evident. In an earlier investigation using a dichotic CV test, Keith et al. [Ear Hear. 6, 270–273 (1985)] demonstrated a clear left ear advantage on a directed left ear task and an obvious right ear advantage on a directed right ear task. In the present investigation, no significant differences in the test scores were observed when the right and left ear scores were compared with the same ear scores across the three test conditions. In all three test conditions, a slight right ear advantage was noted. The implications of these findings as they relate to our understanding of how dichotic stimuli are processed will be discussed.
Monaural perception of the rapidly alternating speech perception test (RASP)
Authors: Harris Richard W. , Kaspar Ruth , Brey Robert H.
Published: October 2005

One test that claims to measure binaural fusion, and is routinely utilized as a measure of central auditory function, is the rapidly alternating speech perception (RASP) test. There has been some controversy over the clinical validity of this test. The purpose of this study was to investigate information contained in a single channel of the RASP. Twenty-four normal hearing subjects listened to one channel of the RASP: twelve to channel 1, twelve to channel 2. Sentence scores for a single channel of the RASP ranged from 0% to 70%, with mean sentence scores for subjects listening to channels 1 and 2 of 37.72% and 20.8%, respectively. An ideal binaural fusion test would contain no, or very little, information when listening to only one channel. It is possible that a single channel of the RASP contains too much information. Many of the sentences were repeated correctly, in their entirety, by at least a few of the subjects listening to either channel in isolation, a task previously assumed to be possible only in the binaural condition.
The lexical status effect on place of articulation and voice onset time contrasts
Authors: Reed Marjorie A.
Published: October 2005

Ganong [J. Exp. Psychol.: Hum. Percept. Perform. 6, 110–125 (1980)] first reported that the presence of a word at one end of a voice onset time series influenced the classification of stimuli near the boundary. Fox [Percept. Psychophys. 34, 526–540 (1983)] reported a similar effect using place of articulation stimuli. In the present experiment, the lexical status effect on two voice onset time continuua (/bot/ to /pot/ and /bok/ to /pok/) was compared to that on two place of articulation continuua (/bon/ to /don/ and /bop/ to /dop/). Results showed effects of lexical status for both types of stimuli. Ambiguous tokens near the category boundary were perceived in favor of the word, while the classification of endpoint stimuli was not influenced. The lexical status effect was significantly larger for voice onset time stimuli than for place of articulation stimuli. This difference may result from the time required for the lexical status effect to develop, suggesting alternate interpretation of Fox's data on the time course of the effect. Implications for interactive and separate stage models are discussed.
Context effects in spoken language
Authors: Pedlow Robert
Published: October 2005

The effects of different types of linguistic context on the intelligibility of spoken language were examined. A set of words was produced by the same speakers in three different types of linguistic context: ordinary sentences, anomalous sentences, and a word list context. The anomalous sentences were constructed by changing one nonadjacent-to-target word to an anomalous alternative. The word list context was set up as short, sentencelike strings, seven words in length, including the target word. In the production phase of the experiment, speakers were instructed to speak with the same intonation over all the materials. To encourage this, the different context types were randomly interleaved in the materials which speakers read. No significant differences were found in the intelligibility of the words produced in the different context conditions. It is argued that these results demonstrate that, contrary to the findings of (Lieberman, 1963), it is the overall speech “mode,” rather than the immediate linguistic context, which acts to determine the intelligibility with which individual words are produced.
Perceptual differentiation of spontaneous and read utterances after resynthesis with monotone fundamental frequency
Authors: Remez R. E. , Bressel R. S. , Rubin P. E. , Ren N.
Published: October 2005

Our prior research revealed that naive listeners can differentiate spontaneous speech and read speech even when lexical, syntactic, and semantic components are equated in the two modes of production. On a typical trial in our tests, a listener hears a pair of excerpts identical in these three levels of description, taken from a spontaneous and a read monologue produced by the same talker. The perceptual task is to identify the spontaneously produced member of the pair. In the present case, LPC resynthesis was employed to create constant F0 versions of highly differentiable pairs of sentences, to test our working hypothesis that the variation of F0 serves as the most reliable index of perceptual performance. Three conditions were tested: whole sentence comparisons, initial-half-sentence comparisons, and final-half-sentence comparisons. Subjects performed above chance when listening to whole sentences only, indicating the existence of residual information for production mode in the absence of F0 variation. Implications and extensions of this finding will be discussed, [Work supported by NINCDS and NICHHD.]
Computers in architectural acoustics
Authors: Schroeder Manfred R.
Published: October 2005

Already in the 1950s difficult problems in acoustics were being successfully attacked by computer simulation. One of the first digital simulations of a signal processor was that of an artificial reverberator to produce natural-sounding reverberation. Other early applications of computers used Monte-Carlo simulations to study random wave interference in enclosures. Later, computers were used extensively in the measurements in Philharmonic Hall (now Avery Fisher Hall) in New York City. This work also led to the development of new methods for measuring reverberation time. In the 1970s, with the support of the German Science Foundation, a large number of concert halls were investigated with the help of sound field reproduction and multidimensional scaling methods using digital computers. The most important new parameter emerging from these studies was “interaural dissimilarity.” The diffusely reflecting surfaces called for by these results are based on number-theoretic principles [M. R. Schroeder, Number Theory in Science and Communication (Springer, New York, 1986) 2nd enlarged ed.]. Computers have also been used to crack complicated integral equations to yield accurate relationships between reverberation time and sound absorption that are sensitive to absorber location and sound diffusion.
Evaluation of room speech transmission index and modulation transfer function by the use of time delay spectrometry
Authors: Keele D. B. , Eger Donald
Published: October 2005

The literature shows that the modulation transfer function (MTF) and speech transmission index (STI) can be computed from the squared impulse response of a linear passive system. This paper describes an extension of this method to measurements of systems using time delay spectrometry (TDS). The new method makes use of both the real and imaginary parts of the complex analytic impulse response of the system (the energy-time response). This allows more accurate determinations of STI and MTF because the calculations are based on a measurement that more closely follows the true energy decay in the room. The method requires fewer samples of the room's sound field and less spatial averaging to yield a given accuracy.
A presentation of acoustical impulse responses with an analog-to-digital converter
Authors: Clautice Edward G.
Published: October 2005

A research program in architectural acoustics at the University of Florida has been using analog electrical equipment to process signals. An analog-to-digital converter was acquired to allow faster and better signal analysis. Several computer programs were written that control the analog-to-digital converter and subsequent processing of the digital data. The ability of the analog-to-digital converter to analyze some properties of known signals was evaluated. The analog-to-digital converter was then used to evaluate signals from magnetic tapes which had the recorded acoustical impulse response from several positions in a 1500 seat auditorium. The processing programs were used to produce echograms. Those digital echograms were able to duplicate the echograms produced by the laboratory's existing instrumentation in terms of the relative location of events in time and the decay process through time. The process and results of this research will be surveyed.
The use of an IBM personal computer (PC) for performing room acoustics measurements
Authors: Talaske Richard H.
Published: October 2005

The general acceptance of the PC microcomputer and the subsequent availability of additional hardware and software have offered researchers and practitioners some formidable tools for acoustical investigations. Using an IBM portable PC, ILS signal-processing software, and additional signal gathering and signal conditioning equipment, an inexpensive and portable room acoustics and data collection system was developed for the purpose of investigating the acoustics of theaters, concert halls, and other assembly spaces. This system will be described, and the results of data will be presented and discussed.
Acoustical scale modeling in the classroom at MIT
Authors: Cann Richard G.
Published: October 2005

This is an actual demonstration of the acoustical scale modeling methods that have been used by the author for several years to help teach some basic acoustics to students in two classes at the Department of Architecture. One class in the curriculum of Building Technology, instructed by Cad Rosenberg of BBN, uses scale modeling to show how the reverberant sound within an interior space forms from numerous wall reflections. Echograms from various model room configurations illustrate simple defects that may occur in the quality of the interior sound. Also, students see demonstrated clearly the difference between the reduction of noise by surface absorption and by transmission loss. Another course attended by equal numbers of undergraduate and graduate students is instructed by Tim Johnson and John Furlong. It explores various aspects of the microclimate. One part, acoustics, is presented in the form of one lecture and a brief acoustical scale modeling demonstration immediately followed by a laboratory activity in which students investigate the control of sound from a highway into a nearby community. Students use the scale modeling instrumentation to help select the appropriate noise barrier that will give an acceptable community noise level, or/and noise reduction, at the lowest cost. There is no one solution to the problem, but students must show their understanding of acoustics by justifying their selection quantitatively.
A method to evaluate the acoustical effects of design decisions in the architectural studio class
Authors: Siebein Gary W.
Published: October 2005

The results of a research project in acoustical modeling conducted by the author were used to facilitate the investigation of acoustical issues in the conceptual stage of the design process of students in a fourth-year architectural studio. The students worked on a semester-long project to design a multipurpose performing arts center. The intent of the studio was to look at the potential of acoustics as a formgiver in architecture. The acoustical modeling technology was used as a mechanism to evaluate the proposed solutions. The technique allowed students to receive immediate feedback on the acoustical quality of a proposed scheme. The results of tests in models of the students' designs were compared to the results of similar tests made in many different auditoria gathered as a part of the research project. Students were able to test many alternative design schemes and understand the resulting changes in acoustical quality (as evaluated by new objective design criteria such as early to late temporal energy ratios and reflectograms) in small-size study models. Once a basic solution was reached, more detailed architectural and acoustical refinement of the scheme followed. The high energy level and enthusiasm of the students and the most satisfactory design projects at the end of the semester attested to the success of this new design tool. [Work supported by NSF.]
A microcomputer-based demonstration system for musical acoustics education
Authors: Maher Robert , Beauchamp James
Published: October 2005

While an ideal musical acoustics education laboratory would include an extensive collection of electronic measurement, recording, and display equipment together with appropriate space, staff, and maintenance staff to support student use, this situation is seldom possible because of limited funds. Our solution has been to configure and program a microcomputer (IBM PC AT) to serve as a mobile multifunction demonstration station. The station is capable of high-resolution color display, stereo audio/digital input/output, hardware FFT analysis, and MIDI input/output. Thus far, the following demonstrations have been completed: (1) animated display simulation of wave propagation on strings and within pipes; (2) waveform/spectrum display and sound synthesis from given Fourier amplitudes and phases; (3) single frame spectrum analysis of audio signals; (4) display simulation of modes on square and circular vibrating membranes; and (5) sound synthesis comparison of just, Pythagorean, and equal-tempered scales. One advantage of this microcomputer-based system is that new demonstrations can be incorporated easily by writing new programs for the existing hardware. [Work supported by an IBM grant to UIUC.]
Detection of time-varying sequential constraints in finite-state auditory pulse trains
Authors: Pollack Irwin
Published: October 2005

Listeners discriminated between auditory pulse trains generated by (a) unconstrained finite-state random sequences and (b) statistically constrained finite-state sequences. The nature of the statistical constraint was to make one half of the possible set of successive n-tuples more likely than the remaining half. The statistical constraint was changed periodically and aperiodically about an average zero constraint level. Discrimination performance deteriorates as the statistical constraint is changed more frequently, as might be anticipated with a fixed informational integration period or “auditory moment.”
Evidence for sensitivity to rates of change of frequency and intensity
Authors: Dooley Gary J. , Moore Brian C. J.
Published: October 2005

Thresholds for the detection of differences in duration were measured in a two-alternative forced-choice task for four types of signals, all centered at 2 kHz with a mean level of 65 dB SPL: (1) sinusoids fixed in frequency and level; (2) sinusoids of fixed frequency whose level was swept up or down by 5 or 10 dB; (3) sinusiods of fixed level whose frequency was swept up or down by 100 Hz; and (4) sinusoids whose level was swept up or down by 10 dB and whose frequency was swept up or down by 100 Hz. The duration of the standard was either fixed at 500 ms, or was varied randomly from trial to trial by up to ±7% about 500 ms. The pattern of results was similar for all four subjects tested. Thresholds for the signals which were swept in level and/or frequency were lower than those for the fixed signals, typically by 10 to 20 ms. This indicates that subjects were sensitive to the rate of change of frequency and/or intensity, and could use this as a cue for duration discrimination. [Work supported by the MRC, United Kingdom.]
When theory and practice collide: The use and abuse of statistics in bioacoustics
Authors: Wheeler Leslie A. , Busnel René-Guy
Published: October 2005

All of us have been guilty of favoring statistical procedures that support our hypotheses. This is fine if our hypotheses are correct. But what if they are false? No matter. By use of appropriate statistical procedures, applied in just the right way, even the saggiest of hypotheses can be propped up. This paper explains how. As an example, the usefulness of 14 useless acoustic features in the differentiation and recognition of lovebird calls will be shown statistically in two different ways.
Articulatory parameters used to generate vocal tract shapes and bark-difference dimensions
Authors: Wold Donald C.
Published: October 2005

In this study, the correlation between two articulatory parameters used to generate vocal tract shapes from formant frequencies and three bark-difference dimensions were examined. Ladefoged et al. [J. Acoust. Soc. Am. 64, 1027–1035 (1978)] identified the articulatory parameters w1 and w2 as the front-raising and back-raising proportions of tongue shape and showed how they may be calculated from formant frequencies. The ten American English vowels of Peterson and Barney were used for men and women. The three bark-difference dimensions were described by Syrdal and Gopal [J. Acoust. Soc. Am. 79, 1086–1100 (1986)]. The F1−F0 dimension represents vowel height and the F3−F2 dimension corresponds to vowel place of articulation. The linear correlation between F1−F0 and w2 was −0.86 (p < 0.001) and that between F3−F2 and w1 was −0.96 (p < 0.001).
The F1 structure influences final-consonant voicing decisions
Authors: Summers Walter V.
Published: October 2005

Previous acoustic analyses [W. V. Summers, J. Acoust. Soc. Am. Suppl. I 79, S36 (1986)] showed higher F1 steady-state frequencies and higher F1 offset frequencies for consonant-vowel-consonant (CVC) utterances ending in voiceless consonants than voiced consonants. These analyses examined the vowels /a/ and /æ/ and the final consonants /b/, /p/, /v/, and /f/. The present experiments examined whether these differences in F1 structure provide perceptual information to the listener concerning final-consonant voicing. The CVC stimuli were synthesized with format steady-state frequencies appropriate to /a/ or /æ/ and with final formant transitions appropriate to the bilabial stops, /b/ and /p/. Several series of synthetic stimuli were created differing in F1 steady-state frequency, F1 final transition slope, and F1 offset frequency. Stimuli within a series varied in steady-state vowel duration. At each steady-state duration, stimuli containing higher F1 steady-state frequencies were heard as containing voiceless final consonants more often than stimuli containing lower F1 steady states. The F1 offset frequency also influenced voicing judgments with higher offset frequencies producing more voiceless responses: The F1 final transition slope did not have a consistent influence on voicing judgments. [Work supported by NIH.]
An investigation of some acoustic characteristics of prenasalized stops
Authors: Burton Martha W. , Blumstein Sheila E.
Published: October 2005

Prenasalized stops occur in a number of languages, often contrasting phonemically with prevoiced stops, voiceless stops, and nasal consonants. The present study compares and contrasts these sounds in Morn, a Central Sudanic language. A single speaker of Morn produced real word tokens with word-initial prenasalized stops, voiced stops, voiceless stops, and nasal consonants in various vowel environments. Acoustic analyses of these tokens included duration measurements and critical band analyses. The results indicated that prenasalized stops may be characterized by a nasal murmur followed by a 10-dB drop in amplitude, lasting approximately 25–30 ms prior to the release. Critical band analyses of the murmur and prevoiced portions of the prenasalized stops and prevoiced stops, respectively, suggested that the spectral properties differ. In contrast, the spectral properties at the release appear to be similar. These findings will be considered in relation to both phonetic and phonological theories of speech. [Work supported by NIH.]
“Post-stopped nasals”: An acoustic investigation
Authors: Chan Marjorie K. M. , Ren Hongmo
Published: October 2005

In some dialects of Chinese and Miao, the nasals in syllable-initial position have been described as being accompanied by a homorganic stop, which are often transcribed with superscripts: [mb], [nd], and [ŋg], as a deliberate attempt to characterize these segments as phonetically distinct from prenasalized stops, [mb], [nd], [ŋg]. In our study, the acoustic nature of these “post-stopped” nasals will be explored, since no instrumental study has been conducted on them. A preliminary investigation of data from two Zhongshan Chinese speakers confirm that these nasals are different both perceptually and acoustically from the prenasalized stops in other languages. It is found that the so-called “stop” component in Zhongshan syllable-initial nasals is not a stop, but a burst that occurs simultaneous with the oral release following the nasal. Such bursts occur sporadically in English, but are consistently produced in the Zhongshan nasals, and are perceived as homorganic stops accompanying the nasals. The waveforms also show a characteristic shape, with a sharp rise in amplitude at vowel onset. The results suggest the precise synchronization of velic closure with oral release.
Pronunciation variation within and across speakers
Authors: Cohen Michael H. , Bernstein Jared , Murveit Hy
Published: October 2005

An understanding of the structure of pronunciation variation over a population of speakers and over time in the utterances of one speaker should be useful in designing speaker-independent speech recognizers. This paper reports a series of experiments designed to show different kinds of patterns observed in alternative forms of words in constant contexts (e.g., the presence or absence of frication in the “y” in “had your”). An analysis is presented of transcribed data from 630 speakers reading two sample sentences as well as data from four speakers reading the same two sentences 24 times each, separated by filler material, in three separate sessions. The analysis quantifies the relative usefulness of competing models of variation in information theoretic terms. The results indicate that (1) speakers can be clustered into low variation groups such that the variation within a group is significantly less than the population variation, and (2) individual speakers show greater consistency than comparable clustered subsets of the population. Finally, it is suggested how this structure may be used to guide rapid, automatic adaptation in speech recognition. [Work supported by NSE.]
Articulator movement in anticipatory coarticulation
Authors: Lee Gina M.
Published: October 2005

The results of previous studies examining EMG activity (and, to a smaller extent, articulator movement) in anticipatory gestures have not been consistent. In some studies, the onset of activity for a given feature was time locked, in that it began at a fixed interval prior to the acoustic onset of the corresponding segment. This suggests that timing plays an intrinsic role in the organization of speech production, and that segmental targets are dynamic. Other studies have shown evidence for feature spreading, where the onset of activity begins within the earliest preceding segment which makes no contradictory demands on the articulators, regardless of the length between the onset of activity and the acoustic onset of the relevant segment. This suggests that time is extrinsic to segmental specification, and that targets are represented as static. However, Gelfer, Bell-Berti, and Harris (1985) and Perkeli (1986) argue that the different findings may be due to experimental design: /s/ and /t/, the consonants used in such studies, may not be unspecified with regard to lip protrusion, as previously assumed. In the current study, the issue of feature specification for presumed neutral segments is considered. Pellet traces from selected bases of x-ray microbeam data were examined. The point of onset of lip protrusion with respect to the acoustic onset of the rounded vowel in VCnu utterances was measured. Velocity patterns of articulator movement were also considered.
Interarticulatory timing and single articulator velocity-displacement relationships in English stress pairs
Authors: deJong Kenneth
Published: October 2005

Evidence has been brought forward that there exists a direct timing relationship between the articulator movements associated with vowel production and those associated with consonant production. Tuller and others have interpreted such results as evidence for a model of speech production that posits a metrical relationship between vowels and their coproduced consonantal neighbors [cf. Harris et al., in Invariance and Invariability in Speech Production, edited by J. Perkell and D. Klatt (Erlbaum, Hilldale, NJ, 1986); and Tuller et al., J. Exp. Psychol. 9, 829–833 (1983)]. A more strictly segmental ordering of speech events could be posited to handle such data. The difference between these models can be brought to light by making reference to statistical correlations between the timing latencies of various articulatory events [cf. K. Munhall, J. Acoust. Soc. Am. 78, 1548–1553 (1985)]. This study investigates the effects of stress pattern and syllable structure on articulator timing, using x-ray microbeam traces of jaw, tongue blade, and lip movement. Unlike in earlier studies, real English words were used. Each token was placed in two contexts, natural sentences and short, frame sentences. The effects of these two environments are also to be noted. The traces will also be used to replicate the velocity-displacement relationship in the movement of the jaw, found in earlier studies of reiterant speech [Kelso et al., J. Acoust. Soc. Am. 77, 266–280 (1985)].