bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-reversal mirrors and rough surfaces: Experiment
Authors: Roux Philippe , De Rosny Julien , Fink Mathias , Rose James H.
Published: July 2002

A novel acoustic time-reversal technique has been tested for determining the surface-height autocorrelation function and rms height of rough surfaces. A time-reversal mirror (TRM) was used to insonify periodically and “randomly” rough surfaces of otherwise flat samples immersed in water. The standard use of the TRM is as follows: transmit an initial planar pulse, record the signals at each array element, digitally time reverse each signal, and then retransmit the time-reversed signal. As expected from time-reversal symmetry, one approximately recovers the incident planar pulse after the reflection of the retransmitted wave. The new technique is a simple modification of this procedure. Namely, as before, we record and time reverse the initial reflection. However, we next translate the transducer a fixed distance parallel to the surface before retransmitting. For very small displacements, little change is observed in the TRM’s signal. For larger and larger translations, the TRM’s signal decorrelates, i.e., it less and less resembles the incident pulse. The signal’s decorrelation as a function of displacement is directly related to the autocorrelation function of the rough surface—within the limits set by the system’s point response function. The TRM was used both in reflection mode and in transmission mode. Samples consisted of “randomly” rough surfaces of metal and plastic plates, as well as metal plates machined to have periodically rough surfaces. Evidence is provided that the time-reversal mirror is sensitive to the surface-height autocorrelation and, in favorable cases, determines the autocorrelation function and rms height.
Three-dimensional vibrations of hollow cones and cylinders with linear thickness variations
Authors: Kang Jae-Hoon , Leissa Arthur W.
Published: July 2002

A three-dimensional method of analysis is presented for determining the free vibration frequencies and mode shapes of hollow cones and cylinders with variable thickness. Displacement components us, uz, and uθ in the meridional, normal, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the s and z directions. Potential (strain) and kinetic energies of the cones and cylinders are formulated, and upper bound values of the frequencies are obtained by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Novel numerical results are presented for thick, linearly tapered, hollow cones and cylinders with completely free boundaries. Convergence to four-digit exactitude is demonstrated for the first five frequencies of the cones and cylinders. The method is applicable to thin cones and cylinders, as well as thick and very thick ones.
Ascertaining confidence within the ray-tracing method
Authors: Giner Javier , Militello Carmelo , Garcı́a Amando
Published: July 2002

The Monte Carlo method is applied to the ray-tracing method to obtain an error measure of the sound energy hitting a receptor during a time interval. Simple geometrical interpretations are introduced to guide the equation development. The variance measurement method introduced a few years ago as an error indicator for the ray-tracing technique is analyzed and compared with the new method. It is shown that the previous method cannot be considered either an error measure or an error estimator, and that the new one provides a consistent answer to many simulation problems. The effects of wall absorption, reverberation time, elapsed time, and integration interval in both formulas are evaluated.
Speech segment durations and quantity in Icelandic
Authors: Pind Jörgen
Published: July 2002

Icelandic has a phonologic contrast of quantity, distinguishing long and short vowels and consonants. Perceptual studies have shown that a major cue for quantity in perception is relational, involving the vowel-to-rhyme ratio. This cue is approximately invariant under transformations of rate, thus yielding a higher-order invariant for the perception of quantity in Icelandic. Recently it has, however, been shown that vowel spectra can also influence the perception of quantity. This holds for vowels which have different spectra in their long and short varieties. This finding raises the question of whether the durational contrast is less well articulated in those cases where vowel spectra provide another cue for quantity. To test this possibility, production measurements were carried out on vowels and consonants in words which were spoken by a number of speakers at different utterance rates in two experiments. A simple neural network was then trained on the production measurements. Using the network to classify the training stimuli shows that the durational distinctions between long and short phonemes are as clearly articulated whether or not there is a secondary, spectral, cue to quantity.
The fine structure of the recovering auditory detection threshold
Authors: Nizami Lance , Schneider Bruce A.
Published: July 2002

Detection thresholds were gathered for a 2 kHz Gaussian-shaped probe (standard deviation= 0.5 ms), centered at intervals of as little as half a millisecond over 0–30 ms following a 200 ms, 97 dB SPL, 2 kHz tone. Surprisingly, there were small, sudden rises and falls superimposed on each subject’s generally smooth recovery. Even more obvious were nonmonotonicities in the standard deviation of the cumulative normal fitted to each threshold’s psychometric function.
Implications of using colocated strain-based transducers for output active structural acoustic control
Authors: Vipperman Jeffrey S. , Clark Robert L.
Published: July 2002

Piezoceramic transducers have become popular elements of smart structures that are used for active vibration control and active structural acoustic control. A spatial differentiation is performed by the piezoceramic transducers since they couple into the strain field of the piezostructure. This differentiation causes higher-frequency modes to be emphasized more heavily, causing the effective compliance of the structure as seen by the piezoceramic transducer to increase with frequency. This nonuniform compliance has significant impact on the performance that can be achieved through colocated direct rate feedback control. It is shown that the rectangular piezoceramic transducer is a low-pass wave number filter with a cutoff frequency inversely proportional to the aperture size. Thus DRFB performance can be greatly improved simply by making the size of the piezoceramic transducer large relative to the size of the structure. The resulting increase in coupling to the lower-frequency modes, which are generally targeted by the control system, results in a much reduced control effort. In the event that a large aperture is not practical, it is shown that dynamic compensation can be used to obtain good performance at the cost of much increased computational complexity. Analytical open and closed loop results for an acoustically radiating simply supported plate piezostructure are presented.
Detection and species identification of baleen whale calls
Authors: Helweg David A.
Published: July 2002

Baleen whales live over extensive home range and time scales. Study of how these animals use their vocalizations for communication requires massive data sampling over long periods. This paper describes a system for automating the sampling and analysis of baleen whale calls. Many species produce stable, homogeneous call structures which lend themselves to automated species identification. We have benchmarked a series of bioacoustical call identification algorithms against a set of blue and fin whale calls while systematically manipulating the signal-to-noise ratio. Blue (Balaenoptera musculus) and fin (B. physalus) whale calls are very stereotypical. Blue whale ‘‘A’’ and ‘‘B’’ calls have fundamental frequencies of approximately 17 Hz, narrow bandwidth, well-defined harmonic structure, and typical duration of 15–25 s. Fin whale ‘‘pulses’’ have fundamental frequencies of approximately 17 Hz, but are broadband in nature and short (approximately 1-s) duration. The results demonstrated a typical tradeoff of speed versus accuracy. The best algorithm was inserted into an underwater sound recording system and its signal-detection theoretic performance was quantified. Results will be discussed with respect to technological, ecological, and conservation aspects of baleen whale bioacoustics. [Project CS-1082 of the Strategic Environmental Research and Development Program.]
Excitation and response of surface waves on isotropic and nonisotropic viscoelastic half-spaces with application to medical diagnosis
Authors: Royston Thomas J. , Mansy Hussein A. , Sandler Richard H.
Published: July 2002

An analytical solution is proposed for the problem of surface wave generation on a viscoelastic half-space by a finite rigid circular disk located on the surface and oscillating normal to it. The solution is an incremental advancement of the work reported in two articles published in the 1950s in the Proceedings of the Royal Society. While the application focus of those articles was seismology, the application of interest here is medical diagnostics. Consequently, the solution is verified experimentally using a viscoelastic phantom with material properties that approximate biological soft tissue. Also, the effect of an inclusion on surface wave behavior within the otherwise isotropic medium is investigated. Measurement of wave motion on the skin surface caused by internal biological functions or external stimuli has been studied by a few researchers for rapid, nonintrusive diagnosis of a variety of medical conditions. Conditions considered include those associated with cardio-vascular dynamics, oedema and other skin ailments, hardened tissue regions, e.g., tumors, and extraluminal air in the abdomen, a.k.a. pneumoperitineum. It is hoped that the developments reported here will advance these techniques and also provide insight into related diagnostic techniques, such as sonoelastic imaging and other vibro-acoustic methodologies. [Work supported by the Whitaker Foundation.]
Dynamic response characteristics of upper respiratory system
Authors: Al-Jumaily Ahmed , Al-Saffar Ammar
Published: July 2002

A theoretical model is presented to study the general dynamic characteristics of the upper human respiratory system for a healthy as well as an unhealthy lung. The model is formulated by using perturbation technique on the fluid momentum and continuity equations taking into consideration the structural dynamic features of the air passage walls. A recursion formula is generated to compute the input impedance along the principal path. Also the distributed pressure response along a single pathway in the breathing system is investigated for different frequencies. The results indicate that for a healthy lung the magnitude of the impedance at the throat decreases to a minimum value at a frequency of 379 Hz, then increases again, and continues to fluctuate between maximum and minimum values. This prediction agrees very well with available experimental data and disputes earlier theoretical observations of double minimum values. However, it is indicated that a lung with some abnormality at a Horsfield order of 24 and above has its first minimum at a frequency of 238 Hz. A detailed explanation of the dynamic characteristics in terms of the impedance ration and the pressure distribution is presented in the paper.
Integrating acoustics into mechanical engineering education
Authors: Prasad M. G.
Published: July 2002

Acoustics is generally considered as an area of specialization. However, the significance of acoustics can be seen in several disciplines including science, engineering, and arts, etc. Thus acoustics as knowledge that deals with production, propagation, transmission, and reception of sound plays an important role in many different fields. Acoustics can be integrated into mechanical engineering education through core as well as elective courses. As core material, acoustics nicely fits into a course in dynamical systems. The topics such as room acoustics and Helmholtz resonator are effective examples of first- and second-order systems, respectively. Acoustics along with vibrations can be part of core course material in design and machine dynamics. Acoustics with mechanical engineering applications such as noise control using source-path-receiver concepts, active control, noise control materials, product design, acoustical measurements, etc. can be included as elective courses. It is important to integrate acoustics in engineering curriculum because it gives the students an experience of the system effects and their impact on design. The integration of acoustics through both core and elective courses into mechanical engineering will be presented.
‘‘Greenotation:’’ A system for representing African drum sounds and techniques
Authors: Green Doris
Published: July 2002

Within the past few decades technology has made it possible not only to write African music on paper like western notation, but also to retrieve and perform it from the printed page. In this paper I will present an overview of and demonstrate a system for writing African music I designed and tested over the past 20 years. Greenotation (after my name, Doris Green) was created for percussion instruments of Africa because Western musical notation could not notate the nuances and actions found in percussion music. Greenotation can notate the music of bells, rattles, drums, talking drums, sticks, stamping tubes, xylophones, hand clapping, and water drums; it is also able to represent dance movements that are integral to many sub-Saharan African drum and dance traditions.
Band-gap engineering in a two-dimensional periodic system of fluids
Authors: Kushwaha M. S. , Djafari-Rouhani B.
Published: July 2002

This work emphasizes that periodic binary systems can give rise to genuine acoustic band gaps (or stop bands) within which sound and vibrations remain forbidden. Extensive band structures for two-dimensional (2-D) periodic arrays of air cylinders in water background are computed. Complete, multiple, huge stop bands are found for both square and hexagonal lattices. The lowest stop bands are largest for a range of filling fraction 10%≤f≤55%, with a gap/midgap ratio of 1.8. The most interesting finding of the present investigation is that the low-frequency, flat passbands for a perfectly periodic system correspond to the discrete modes of a single airy cylinder. This almost exact correspondence is attributed to the low-filling fraction and the huge density contrast in air and water. It is stressed that such a simple inhomogeneous system as made up of air and water exhibits the largest stop bands ever reported for 2-D or 3-D elastic as well as dielectric (photonic crystals) composites. [Work partially supported by CONACyT Grant No. 28110E.]
A novel time-domain method to study the propagation of acoustic waves across composite media
Authors: Bosquetti D. , Sánchez-Dehesa J. , Caballero D.
Published: July 2002

It has been previously shown that the symmetric-split-operator technique is a useful method to study evolution problems in classical mechanics. In this work the technique is applied to obtain a finite-difference scheme which allows us to analyze the propagation of acoustic waves in time domain. This scheme is developed for a general three-dimensional composite system. Numerical results are presented here for some one-dimensional structures. [Work supported by UAM and CICyT of Spain.]
Variability in forward masking and intensity discrimination
Authors: Jesteadt Walt , Reimer Jason F. , Dai Huanping
Published: July 2002

Jesteadt and Bilger [W. Jesteadt and R. C. Bilger, J. Acoust. Soc. Am. 55, 1266–1276 (1974)] noted greater individual differences for frequency discrimination than for intensity discrimination and summarized this effect in terms of analyses of variance. In this paper, we report similar comparisons for forward masking and intensity discrimination. Four subjects were tested in a 2IFC adaptive procedure. The forward masker and the pedestal in the intensity-discrimination task were broadband stimuli consisting of 18 components with third-octave spacing from 200 to 10000 Hz. Thresholds were obtained for forward maskers from 20 to 80 dB SPL and for pedestals from 10 to 80 dB SPL in 10-dB steps, with eight 50-trial blocks per condition. When the results were analyzed in terms of signal power at threshold for forward masking and intensity discrimination, they showed smaller individual differences and less variability across repeated measurements in forward masking than in intensity discrimination. Psychometric functions reconstructed from the adaptive tracks were steeper for forward masking than for intensity discrimination. Thresholds obtained in forward-masking tasks are often considered to be highly variable, but may be more stable than those obtained in studies of intensity discrimination using comparable stimuli. [Work supported by NIDCD.]
Context effects with limited spectral information
Authors: Matthies Melanie L.
Published: July 2002

Speech recognition has been established and unified as a construct through the systematic study of its domain [Bilger, 1984]. To investigate the effect of limiting spectral information, items from the Revised Speech Perception in Noise (SPIN) test [Bilger et al., 1984] were impoverished to include two, three, or four channels of spectral information [cf. Shannon et al., 1995] and administered to 62 normal-hearing, young adults. Subjects also identified consonants that likewise had been spectrally limited via signal processing. When consonant confusion matrices were analyzed, transmission of place of articulation was strongly affected by spectral limitations followed closely by effects on manner perception, while voicing and resonance (oral/nasal) cues were relatively robust. High-context (HC) SPIN items were significantly easier for the subjects to identify than low-context (LC) items for the four-channel sentences. The context advantage decreased for the two-channel task because listeners were unable to utilize the sentence cues. Across channel conditions, a regression line fit to normalized HC by LC data had a slope of 0.9. Reduced semantic and syntactic information in LC items, therefore, contributed to a perceptual uncertainty network (PUN) when spectral information was limited and this SPIN PUN should be explored further. [Work supported by MURI Grant Z883402.]
Identification of multi-degree-of-freedom nonlinear vibratory systems consisting of unknown elastic forces
Authors: Richards Christopher M. , Singh Rajendra
Published: July 2002

Nonlinear system identification techniques often require a priori knowledge of the nature and mathematical form of the nonlinearities. Unfortunately, for practical systems, this is not always possible. As a result, nonlinearities are often approximated and questions remain as to whether an accurate model can be determined. In addition, under experimental conditions, the amount of measurement noise present in the identification process must also be quantified. To address these issues, identification of discrete systems consisting of nonlinear elastic forces is examined in the presence of uncorrelated noise. It is assumed that the mathematical form of the nonlinearities is unknown but can be approximated by polynomials. Coherence functions are introduced which are based on a ‘‘reverse path’’ spectral approach developed by the authors for multi-degree-of-freedom systems. These coherence functions, as calculated from conditioned spectra, indicate the extent of uncorrelated noise present and the accuracy of the assumed mathematical models. Using several example simulation systems, including a system with a continuous nonlinearity described by a noninteger exponent, both temporal and spectral identification techniques are employed to study the issues described above.
Acoustical forced oscillation nondestructive testing method for meshing gears
Authors: Gelman Leonid M. , Iievlev Alexandr S.
Published: July 2002

Nondestructive testing and evaluation method of gears is considered. Differential equations of meshing gears forced oscillations are considered with time-variant piece-constant gear mesh stiffness and exciting force. New expressions of spectral density of mentioned oscillations are received for two cases: with defect and without one. For the first case modulation of gear mesh stiffness and exciting force is considered.
Telephone speech enhancement for elderly hearing-impaired listeners
Authors: Sheffield Amy E. , Krishnamurthy Ashok , Feth Lawrence , Davidson Stephanie , Hoglund Evelyn , Roth Lynette
Published: July 2002

Many elderly persons with high-frequency hearing loss find telephone use frustrating due to lower intensity levels and reductions in acoustical information that can be useful in deciphering speech. The purpose of this project is to pre-process the speech signal before it is sent over the phone line and provide speech enhancement without the use of amplifying handsets or hearing aids at the receiving end. The enhancement technique takes into account the limited bandwidth of the phone line as well as the hearing characteristics of the user. Two pre-processing schemes, a single channel and a double channel approach, used to increase the intelligibility of speech in these situations are discussed. The single channel method performs amplitude compression of the entire signal. The two-channel method filters the incoming signal into high-frequency and low-frequency channels and performs independent compression on each before recombination. Results comparing the two speech enhancement schemes against no processing for a group of elderly hearing-impaired subjects are presented. [Work supported by a grant from the Franklin County Office on Aging.]
Vocal-tract length normalization for acoustic-to-articulatory mapping using neural networks
Authors: Dusan Sorin , Deng Li
Published: July 2002

A new method of estimating the overall vocal-tract (VT) length and the normalization of acoustic parameters of different speakers is reported in this paper for acoustic-to-articulatory mapping. The main goal of this work was a high accuracy of VT length estimation from a short speech utterance. An articulatory model, originally developed by Maeda, was used as a reference female VT. Linear scaling was used to synthesize training data for VT lengths between 100% and 125% of the reference VT length (14.96 cm). These data had 250 utterances, resulted from different VT lengths, each containing six vowels. A neural network with two hidden layers was trained using vectors of 10 mel-frequency cepstrum coefficients and the corresponding VT lengths of these utterances. For the same VT length range, similar test data were synthesized using the training vowels but in different contexts. With the trained network, evaluation of this method on test data has shown an average error of less than 1% and a maximum error of 3.2% in estimating VT length from single test utterances. Frequency warping was used to normalize the cepstrum parameters according to estimated length factors ranging between 1.0 and 1.25. [This work was supported by NSERC.]
DSP circuit to improve speech intelligibility
Authors: Metz Michael J. , Shaw Neil A.
Published: July 2002

Two studies, one equipment based and one clinically based, were attempted to verify the contention that a DSP circuit is capable of changing the intelligibility of speech in noise. The first used two intelligibility metrics (RASTI and %ALcons) to measure the change in metric score under the conditions of test signal with (1) no DSP speech signal processing of the test signal, and (2) with DSP speech processing of the test signal in the presence of pink noise in the background. The second study measured the articulation functions of normal ears using phonetically balanced word lists under conditions of (1) no speech signal processing, and (2) ‘‘maximum’’ DSP processing when each condition was varied in the presence of a set of level of pink noise. The algorithm used in this study is the ‘‘Voice Intelligibility Processor,’’ or VIP signal processor. The studies indicate an increase in the intelligibility metric scores and the measured articulation functions. For the articulation studies, when the processor is ‘‘normalized’’ to account for the perceived increase in loudness level produced by the processor algorithm, the mean shift in ‘‘50% point’’ of the articulation function was approximately 6 dB. For the RASTI study, similar improvement was also found.
A vowel synthesizer based on F0-modulated formant sinusoids
Authors: Hertrich Ingo , Ackermann Hermann
Published: July 2002

A vowel synthesis algorithm was developed resembling parallel formant synthesizers. However, formants are computed as amplitude- and phase-modulated sinusoids instead of being represented by recursive filters or resonators. The fundamental frequency is imposed on the signal in the following way: Each pitch period starts with a short initial rise of a duration of pi/2 of the first formant frequency; at the end of this ramp phase all formants start as sinusoids at pre-defined phase angles and amplitudes, and successively undergo linear attenuation toward zero amplitude at the end of each pitch period. Adjacent pitch periods, thus, do not influence each other. In principle, the signals produced by this algorithm resemble the output of parallel formant synthesizers [e.g., D. H. Klatt, J. Acoust. Soc. Am. 67, 971–995 (1980)]. However, by incremental sample-by-sample computation of the formants’ phase angles, formant frequencies are allowed to continuously change within single pitch periods. This algorithm produces vowels as well as formant transitions signaling stop consonant–vowel syllables such as /ba/, exhibiting a homogeneous, stereotypic voice quality. Because of its additive procedure, this method might allow for the implementation of a variety of further acoustic aspects of the human speaking voice in a well-controlled manner.
Comparison of high-frame rate and delay-and-sum imaging methods
Authors: Lu Jian-yu , Liu Anjun
Published: July 2002

Recently, a high-frame rate imaging method has been developed with limited diffraction beams to construct either two-dimensional (2-D) or three-dimensional (3-D) images (up to 3750 frames or volumes/s for biological soft tissues at a depth of about 200 mm). In this talk, the new method is compared with the conventional delay-and-sum (dynamic focusing) method. Both computer simulation and experiment results show that the quality of images constructed with the two methods are virtually identical when the maximum Axicon angle of X waves in the high-frame rate method is approaching to 90 degrees. Theoretical analysis is carried out to confirm the results. This is significant because the high-frame rate method requires thousands of times less computations while achieving the same high-imaging quality as the conventional delay-and-sum method. [This work was supported in part by grant HL 60301 from the National Institutes of Health.]
High-frequency dependence of the backscatter coefficient on selected bovine tissues from 10–30 MHz
Authors: Maruvada Subha , Shung Kirk K. , Wang Shyh-Hau
Published: July 2002

Very high-frequency diagnostic ultrasonic imaging operates at frequencies of 20 MHz and higher. Thus it is critical to obtain data on ultrasonic attenuation and scattering in this frequency range. At high frequencies, it is not feasible to make scattering measurements with unfocused transducers due to their decreased sensitivity, therefore focused transducers are needed. Using the standard substitution method to calculate the backscatter coefficient, as is used with unfocused transducers, yields erroneous results for focused transducers. The assumption that the reflected echo from a perfect reflector in the far field can be calculated as though the transducer acted like a point source is not valid for focused transducers. A method is presented for focused transducers where the flat reflector is substituted by a particulate reference medium whose backscatter coefficient is well known and documented, in this case, a red cell suspension. Results between focused and unfocused transducers match closely between 10 and 20 MHz. The backscatter coefficient for bovine tissues has been well documented between 1 and 10 MHz. These measurements have been extended to 30 MHz. The frequency dependence of backscatter on bovine tissues will be presented in the range 10–30 MHz and compared to previous results.
Real-ear measurement of hearing-aid interference from digital wireless telephones
Authors: Levitt Harry , Harkins Judy , Kozma-Spytek Linda , Yeung Eddy
Published: July 2002

Two studies were performed. The first measured hearing-aid interference under field conditions. Signal levels in the ear canal were measured using an in-the-canal probe system, the output of which was stored digitally in a laptop computer. Both bystander and user interference were measured as well as the user’s ratings of intelligibility, annoyance, and usability (of the digital wireless telephone). The levels of user-interference were found to be unacceptably high for the large majority of hearing-aid wearers. In contrast, bystander interference was at a relatively low level under conditions typical of telephone use. The second experiment controlled the level of interference by means of the test mode in the digital wireless telephone. Speech-to-interference ratios were measured in the ear canal for various levels of intelligibility and usability, as rated by the subjects. Data were obtained for 37 subjects on each of three digital wireless technologies (PC1900, TDMA, CDMA). [Research supported by NIDRR.]
Validation of the C63.19 standard: Acoustic measurements and subjective evaluations
Authors: Schlegel Robert E. , Grant Hank , Fry Tamy L.
Published: July 2002

The ANSI C63.19 measurement and performance standard addresses the electromagnetic compatibility of hearing aids with wireless communication devices. Validation of the measurement procedures and performance criteria comprised a pilot study, objective validation, and subjective validation. Objective validation involved acoustic measurements of 80 combinations of hearing aids and wireless phones. The E-field and H-field immunity levels of each hearing aid and the E-field and H-field emissions of each wireless phone were measured according to the standard. These data were used to theoretically predict the overall input referenced interference level. Across a broad range of hearing aid immunity levels, the measured acoustic interference was accurately predicted from the individual C63.19 measurements. Subjective validation involved the testing of twenty hearing aid wearers with six phone technologies. Hearing aids offering a variety of immunity levels were custom manufactured for the participants and tested according to the C63.19 measurement procedures. While using each wireless phone, participants provided ratings of the speech intelligibility, usability, and annoyance caused by any rf interference. In addition to confirming the existence of compatible hearing aids and phones, the results of this study contributed to the setting of the immunity and emissions criteria for a usable hearing aid wireless phone system.
A senior engineering design elective with industry and community-sponsored noise control projects
Authors: Celmer Robert
Published: July 2002

One of the transitions that engineering students must make as they enter the work force is the progression from theoretical concepts, or book learning to applied or real world applications. At the University of Hartford, engineering design courses serve as culminating experiences devised to bridge this passage. One such course, Noise Control Design, challenges the student to apply the past three years’ conceptual base to a problem solving opportunity replete with actual scenarios encountered in industry or the community. Each year local firms and organizations approach the laboratory for assistance with a variety of sound or vibration problems. After an initial training period, students make use of the laboratory’s dual channel FFT and real time analyzers, anechoic chamber, sound intensity and modal analysis software, acoustic modeling software, vibration tables and transducers, portable sound level meters and digital tape recorders. Using a consultant-client model, students work collaboratively in teams of two defining the problem, developing a method of approach, making appropriate measurements, devising alternate solutions, and ultimately delivering a written and oral presentation at the end of the semester. The paper discusses specific projects and some experiences students had with their first industrial assignment.
Vortex-driven whistling tube undergraduate experiment
Authors: Lancey Timothy W. , Haeggstrom Tracy J.
Published: July 2002

An experiment to investigate the tones produced by the generation and shedding of periodic vortices in a tube was designed, constructed, and implemented as a student project in a senior laboratory course. A 0.102-m-diam by 0.762-m-long lucite tube was installed in a subsonic wind tunnel; the longitudinal axis of the tube was located streamwise with the mean flow, laterally centered in the test section, 0.178 m above the floor. Two lucite rings, with minimal clearance at the tube inside diameter and each having inside diameters of 0.0762 m, were connected inside the tube. One of the rings was at the tube inlet plane, while the other was slightly downstream, at a location which could be varied. A microphone was attached to the tube near the exit plane and connected to a PC which incorporated a data acquisition system. Airflow through the wind tunnel was varied until tones were heard, and the air velocities and frequencies of the tones were recorded. Results of the data analysis indicated that the frequency of vortex shedding, at the measured air velocity and ring separation, was in agreement with the natural frequency of the tube, for each of the audible tones.
Asymmetrical properties of a vibrating wire and their effects
Authors: Hanson Roger J. , Macomber H. Kent , Morrison Andrew
Published: July 2002

Some effects of the asymmetries causing a splitting of the fundamental natural vibrating frequency of a wire have previously been reported [Hanson et al., J. Acoust Soc. Am. 103, 2873 (1998)]. It has been demonstrated in this work on brass harpsichord wire that the splitting of the frequency is due to intrinsic properties of the wire itself and not of asymmetries in the end clamps. The two frequencies are associated with two definite orientations with respect to the wire. These two vibrational directions have been determined to be orthogonal within one degree experimental uncertainty. This orthogonality is in agreement with predictions of a simple model which assumes that, for small-amplitude free vibrations, the observed portion of the wire moves under the action of a linear anisotropic conservative restoring force. Measured splittings for several samples of harpsichord wire have ranged from 0.12 to 0.30 Hz for a frequency of about 70 Hz. The nonlinear effects of generation of motion perpendicular to the driving direction [Hanson et al., J. Acoust. Soc. Am. 96, 1549–1556 (1994)] and generation of higher harmonics are profoundly influenced by the orientation of the driving direction with respect to these vibrational orientations for low-driving forces. Related effects for plucked strings will be discussed.
Resonance inversion for elastic moduli of anisotropic rocks
Authors: Nakagawa Seiji , Nihei Kurt T. , Myer Larry R.
Published: July 2002

In this research, acoustic resonance spectroscopy was applied to determine the dynamic elastic constants of isotropic glass and transversely isotropic rock cubes. This technique consists of resonating the specimen over a broad range of frequencies, measuring the resonance frequencies, and computing the elastic constants by nonlinear inversion of the measured resonance frequencies. Specimens were tested under unconfined, traction free conditions. Resulting surface vibrations were measured using a miniature accelerometer and their spectral characteristics were analyzed. The inversion was performed using a numerical algorithm based on the Rayleigh–Ritz method that minimized the difference between measured and computed resonance frequencies iteratively. Mode shapes of the anisotropic specimens were also measured using a laser Doppler vibrometer and compared with the prediction of the numerical model. Comparison between the elastic moduli of rock specimens determined by static loading tests, resonance inversion, and ultrasonic transmission tests showed good agreement between the ultrasonic and resonance results but the moduli determined from ultrasonic measurements were consistently higher than the resonance inversion. Such results may be due to the frequency-dependence of the wave velocity in microscopically heterogeneous rock and nonelastic (frictional) deformation of the rock specimen during the static loading tests.
Temporal factors in auditory peak detection of modulation of tones
Authors: Goldstein Julius L. , Hall Joseph L.
Published: July 2002

Auditory detection of tone modulation has been modeled as envelope-peak detection of the cochlear filterbank responses [J. L. Goldstein, J. Acoust. Soc. Am. 41, 458–479 (1967)]. To study the ability of this model to quantify temporal smoothing in detection, new psychophysical experiments using a 4IFC paradigm were conducted, with the authors as subjects. AM or quasi-FM sinusoidally modulated tones were discriminated from the carrier tone. Only one should was modulated among the four pushed sounds in the paradigm. The first series of exploratory experiments (1994) focused on low modulation frequencies (4–16 Hz). A second series of systematic experiments (1996) with a wide range of modulation frequencies allowed estimation of detector smoothing at carrier frequencies of 0.25, 1, and 4 kHz. Despite differences between subjects in estimated spectral filtering, modulation thresholds for both subjects gave similar estimates of smoothing at each carrier frequency. At modulation frequencies above 20 Hz, the smoothing function showed similar dependence on carrier frequencies as found from the early experiments (1967). Below 20 Hz, the early experiments, which used a method of adjustment paradigm, reveal a hyperacuity. This suggests a second slower detection mechanism that exploits repeated presentations of test sounds. [Work supported by NSF Grant IBN-9728383.]
Advances in ultrasonic nondestructive evaluation
Authors: Green Robert E.
Published: July 2002

The fundamental principles of linear elastic-wave propagation in isotropic and anisotropic materials emphasizing the modifications to ultrasonic wave propagation caused by anisotropy will be reviewed. Among the topics covered will be wave-propagation modes, energy-flux vector, diffraction-beam spreading, attenuation, and nonlinear effects. Verification of these principles by optical probing of ultrasonic-wave fields in transparent solids will be presented. Recent advances and practical applications of noncontact ultrasound, including pulsed lasers, optical interferometers, electromagnetic acoustic transducers (EMATs), and air-coupled systems will be described. Application of x-ray diffraction topography to verify the mechanical vibration modes of quartz crystals will be illustrated. Finally, suggestions will be made about possible future advances in ultrasonic nondestructive evaluation of materials and structures.
The effect of vocalic F0 on the identification of Korean stops
Authors: Kim Mi-Ryoung
Published: July 2002

This study investigates the contribution of vocalic F0 following the release of an initial stop to the identification of the three-way stop contrast (aspirated, lenis, and fortis) in Korean. Previous acoustic studies have shown an effect of initial stops on F0 of the following vowel. Using synthetic stimuli, perceptual studies [Han (1996); Cho (1996)] have shown that listeners use F0 in contrasting stops. However, the relative contribution of the consonantal and vocalic information remains unclear. To address this issue, a perceptual study was conducted using cross-spliced stimuli from three naturally produced syllables across all three places articulation in the /a/ context and for alveolars in the /i/ context. Stimuli were created by cross-splicing each consonantal portion (prior to voicing onset) with each vocalic portion (after voicing onset) to create all possible combinations. Twelve Korean listeners each responded to a total of 1444 tokens. The results showed that vocalic F0 is more important than the consonantal onset to stop identification, suggesting that Korean uses tonal variation to differentiate consonant types.
Cross-language speech intelligibility in noise: The comparison on the aspect of language dominance
Authors: Uchida Yasue , Lilly David J. , Meikle Mary B.
Published: July 2002

The purpose of this study is to obtain information about the influence of language characteristics on the results of speech intelligibility in two different languages: English and Japanese. This study investigates the speech intelligibility of both English and Japanese under quiet and noisy situation on 14 bilingual subjects aged 23 to 42 years with normal hearing. As test materials, the CID W-22 word lists which are meaningful monosyllables are used for English and the 57-S word lists which are nonsense monosyllables are used for Japanese. The subjects whose dominant language is English are 6. Results show that percentage-correct of speech intelligibility is higher in Japanese than in English at lower intensity and noisy situation. This advantage in Japanese is seen regardless of the language dominance. It is considered that the phonetic characteristics and the simple structure of Japanese can make it relatively resistant to the hard listening condition. [Work supported in part by Japan Foundation for Aging and Health.]
An acoustic analysis of Cantonese rising tones
Authors: So Connie
Published: July 2002

The two Cantonese rising tones (the High Rising and the Low Rising) are traditionally described as Tone 35 and Tone 23. Recent studies, however, show that the High Rising tone has changed from Tone 35 to Tone 25. It starts at a pitch level similar to that of the Low Rising tone. The High Rising tone is also claimed to have a long and sharp rise from the midway of its fundamental frequency pattern. The present study attempts to look for these phenomena and to describe their characteristics in the two rising tones. Native Hong Kong Cantonese speakers were asked to read two sets of Cantonese rising-tone words formed of root-words /si/ and /fu/. Fundamental frequency patterns and duration of both rising tones in these two root-words are compared and discussed.
The effect of the Lombard reflex on speech produced by Cantonese speakers of English
Authors: Li Herman Chi Nin
Published: July 2002

The Lombard reflex is a phenomenon according to which, in the presence of noise, people unconsciously raise their vocal levels in order to compensate for the level of the ambient noise. It is well documented that speech produced in noisy environments exhibits increases in duration, fundamental frequency, and amplitude. Most studies associated with the Lombard reflex have been carried out with native speakers, but research with second language speakers is much less common. The present study describes a pilot project that aims at studying the effect of cafeteria noise on the production of native English and Cantonese-accented speech. Participants read aloud to the experimenter a set of simple true/false English statements under both no-noise and noise conditions. In the latter, masking noise of 70 dB SPL was fed through headphones to the speaker to elicit the Lombard speech. The characteristics of the sentence-length utterances produced under quiet and noise conditions by the two speaker groups, and by male and female speakers are discussed. [Work supported in part by the SSHRC.]
Acquiring dynamic coarticulatory information
Authors: Oh Eunjin
Published: July 2002

This paper investigates the acquisition of dynamic coarticulation information in French [du] by native English speakers. English [du] characteristically shows a concave-downward trajectory, while French [du] shows a concave-upward transition. As an index of coarticulation degree, an absolute understoot measurement [i.e., difference between the undershoot F2v (the F2 frequency at the steady state of the vowel) and the estimated target value] is potentially problematic since F2 transitions with the same F2v values would be treated as equivalent even when their dynamic natures are quite different [C. S. Crowther, UCLA Working Papers in Phonetics 88, 127–148 (1994)]. The learning effects of the dynamic coarticulatory information were quantified by calculating the value of the second derivative of the F2 transition curve and comparing the values of their English and French transition curve. The preliminary results showed (i) the dynamic coarticulatory information can be acquired by L2 learners; (ii) the advanced learners showed closer approximation to the native speakers in the value of the second derivative for F2 transition curve than the beginning learners. The results suggest that the L2 learners are sensitive to the detailed acoustic parameters and could progressively acquire the L2-specific dynamic patterns of coarticulation.
Acoustic band gaps and localization in water with air-cylinders
Authors: Hoskinson Emile , Ye Zhen
Published: July 2002

Multiple scattering of waves may lead to many peculiar phenomena such as complete band gaps in periodic structures and wave localization in disordered media. Within the gaps excitations are evanescent, when localized waves remain confined in space until dissipated. Here we show that waves are not always localized in 2-D, but when localized there is a coincidence between the gaps in periodic structures and the ranges of localized states in the case of acoustic propagation through water containing an array of air-cylinders. We report that inside the gap or localization regime, an interesting collective behavior of the cylinders appears. Exact numerical calculations reveal the unexpected result that localization is relatively independent of the precise location or organization of the scatterers.
Nonlinear scattering of crossed ultrasonic beams in the presence of turbulence: Multiple scattering effects
Authors: Manry Rebecca A. , Korman Murray S.
Published: July 2002

The nonlinear scattering of two finite-amplitude mutually perpendicular crossed ultrasonic beams—interacting in the presence of turbulence—generates a scattered sum frequency component that radiates outside the interaction region. In the absence of turbulence, virtually no scattering, at the sum frequency, is observed [M. S. Korman and R. T. Beyer, J. Acoust. Soc. Am. 84, 339–349 (1988); 85, 611–620 (1989)]. Here, two primary cw (f1=2.05 MHz and f2=1.95 MHz) beams are generated by 2.54-cm-diam circular plane array piston transducer units (T1 and T2). A 4-MHz receiving unit (R) is of similar construction. All beam axes form a common plane and overlap region with the axis of a submerged circular water jet, which generates the turbulence. With R fixed, T1 and T2 rotate on radius arms—always keeping the beams perpendicular. Symmetry suggests an angle θ*, where θ*=0° defines forward scattering. This geometry allows a nonlinear forward scattering intensity component to exist without concern for a coherent component. Here, multiple scattering effects are needed to predict their results. Supplemental scattering experiments will be presented in an attempt to identify a transition from single (Born approximation) to multiple scattering. [Work supported by Naval Academy Research Council.]