bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of radiating flexural shell sonar transducers using the finite element method
Authors: Hamonic B. , Debus J. C. , Decarpigny J. N. , Boucher D. , Tocquet B.
Published: October 2005

New flexural shell transducers for low-frequency applications are currently developed which are characterized by a large volume velocity and a drastic reduction of their resonance frequencies as soon as they are flooded, due to added mass effect. To design these transducers, a finite element modeling is very useful, because it can accurately handle the assembling of three-dimensional and shell parts in the same structure, the piezoelectric driving force, the fluid-structure interaction as well as the radiation damping. This paper describes the analysis of a test axisymmetric transducer with the ATILA code [J. N. Decarpigny et al., J. Acoust. Soc. Am. 78, 1499 (1985)] using dipolar damping elements and a new extrapolation method to obtain the transducer farfield characteristics [R. Bossut et al., J. Acoust. Soc. Am. Suppl. 1 79, S51 (1986)]. In-air resonance modes, transmitting voltage response and directivity patterns are computed and compared to measurements, displaying a satisfactory agreement. Finally, the modeling of a transducer that is built with a glass-reinforced plastic shell is described, and the corresponding problems and results are discussed.
Performance of sinusoidally deformed line arrays
Authors: Caveny Deanna M. , Del Balzo Donald R. , Becklehimer Jeffrey L. , Ioup George E.
Published: October 2005

Previously it has been shown [M. J. Hinich and W. Rule, J. Acoust. Soc. Am. 58, 1023–1029 (1975); W. S. Hodgkiss, IEEE J. Ocean. Eng. OE-8, 120–130 (1983)] that deformations of towed arrays from a straight line shape can produce significant distortions in beam patterns and errors in bearing estimation if the beamforming assumes linearity. It has also been shown that a deformed array helps to remove left/right ambiguities in the beam patterns, provided the beamforming is done with the correct array configuration. In this work these two effects are studied for undamped and damped sinusoidally deformed arrays (as observed in practice) of one, two, and three half-cycles with relatively small array amplitudes. By use of fixed arc length separations along the array, the phone (x, y) coordinates are determined numerically for each sinusoidal shape. The complex pressure fields are modeled for sources at various locations. Then beamforming is carried out (1) with the known array configuration, and (2) assuming that the array is linear. Degradations resulting from assuming linearity and the ability to remove left/right ambiguities are discussed in terms of reduced gain, angular resolution, and bearing errors.
Automated in-service test and evaluation of sonar hydrophones
Authors: Self Richard E. , Johnson J. D. , Wilson O. B. , Garrett S. L.
Published: October 2005

Recent advances in microprocessor-based instrumentation permit rapid, precise, and detailed measurements on sonar transducers in the field. Reliable data combined with equivalent circuit models of the transducer provide information on acoustical sensor performance that can help to establish more realistic performance and maintenance criteria. This can substantially upgrade the quality of maintenance decisions made at the technician level in the field in light of the effects on well-understood parameters that relate directly to operational performance, such as sensitivity, array beam width, and bearing error, due to transducer degradation. Transducer complex admittance measurements made in-the-field using a commercially available computer controlled impedance meter will be described. Interpretation of the data and their relationship to the equivalent circuit model will be discussed and typical results will be presented. [Work supported by the Naval Sea Systems Command.]
Wind turbine technology—not as simple as it looks
Authors: Wehrey Michael C.
Published: October 2005

Wind is a clean and inexhaustible energy resource serving mankind for many centuries by driving windmills to grind grain and pump water. This presentation gives a brief historical review from the earliest drag-type windmills existing as early as 2000 BC through the early electricity-generating units in the early 1900s to the present-day wind turbine parks. The 1973 oil embargo and 1979–80 price increases brought new awareness of conservation and promoted new interest in renewable energy resources and wind turbine technology. Many lessons are being learned in the design of modern wind turbines. The quest for low installation and maintenance costs, energy conversion efficiency, and high reliability continues. Unforeseen environmental issues such as visual pollution, noise impacts, and TV reception interference are to be addressed. The technical features and operating characteristics of various designs are presented including problems encountered and their solutions.
Acoustic signatures of five wind turbine generators from 80–300 kW
Authors: DuBois T. James
Published: October 2005

As part of its research and development program for development of renewable energy sources, Southern California Edison has monitored the acoustic emission of several different horizontal and vertical axis wind turbine generators with power generation capacity ranging from 80–500 kW. Noise measurements included: frequency spectrum (infrasonic through audible range), directivity, nearfield and farfield, and short and long duration. This presentation will summarize the results of the tests and measurements of both vertical and horizontal axis wind turbines.
Evaluation of wind turbine noise levels and impact studies
Authors: Lane Samuel R.
Published: October 2005

Measured A-weighted sound levels at 125-ft distance for individual wind turbines with 20- to 120-kW power ratings are typically in the range 65–75 dB at moderate to high power output conditions (20–30-mph wind speeds). Tonelike sounds in the 300- to 1000-Hz frequency range often are clearly audible. Cyclical fluctuations of 10 dB in low-frequency noise levels are propagated by some downwind-type turbines. The random aerodynamic rotor noise sounds like a roar, the gear box noise sounds like a whine, and the low-frequency noise fluctuations sound like “thump-thump” or “whoosh-whoosh.” All of these wind turbine noises are propagated from existing wind farms to residential areas and are judged intrusive and annoying. Measurements and predictions of wind turbine noise submitted with applications for wind farm development have often contained errors which understated the noise levels by 3–10 dB. These errors were due to noise measurements at minimal wind speeds and turbine power, and faulty modeling procedures. Simple analytical expressions have been developed which quickly and accurately predict the noise levels for large turbine arrays.
Forward masking studies on a multichannel cochlear implant patient
Authors: Lim H. H. , Tong Y. C. , Clark G. M. , Busby P. A.
Published: October 2005

The profile of neural excitation pattern along the cochlea produced by a longitudinally oriented bipolar electrode pair was estimated by forward masking. Two types of masking patterns were observed. The first was produced by electrode pairs with low (behavorial) threshold currents, and displayed two peaks approximately located above the two electrodes of the bipolar pair. The second was produced by pairs with higher threshold, and displayed a single peak approximately midway between the two electrodes. These masking patterns are similar to the two types of current distribution patterns observed in a tank model consisting of a 22-banded electrode array fixed into a normal saline filled tube of 5 mm diameter. It is possible that the bipolar pairs with lower threshold and double-peaked masking patterns are situated closer to the residual auditory fibers and neurons. In another study, the masking patterns for two bipolar electrode pairs interleavely stimulated were found to follow approximately the maximum of the two masking patterns for the two electrode pairs activated in isolation.
Segerstrom Hall—Evaluation of measurements and design details
Authors: Hyde Jerald R.
Published: October 2005

The design of a large multipurpose performing space contrasts the well-known criteria of theater against the acoustical requirements for symphony and other presentations. With a fan shape of extreme width the only solution for 3000 seats, unique yet workable design solutions are required. The criteria for all uses can push against each other in ways which derive opportunities out of what first might be seen as obstacles. Segerstrom Hall is presented as an example of this creative process. The objective measurement results including early decay time (EDT), sound strength versus position, lateral energy fractions, and early-to-late energy ratios will be discussed as they relate to model study results and finally to the subjective experience of the hall itself. Details will be given of test procedures, performance mode variations of the shell and reflector design, and the acoustical curtain system.
Modeling studies on current distributions produced by an Intracochlear electrode array
Authors: Lukies P. M. , Tong Y. C. , Clark G. M. , Busby P. A.
Published: October 2005

Modeling studies on current distributions along the cochlea produced by an intracochlear electrode array were conducted in a tank model. The tank consisted of a 22-banded electrode array fixed into a normal saline-filled tube of 5 mm diameter. Bipolar electrical stimulation was used, and the potentials within the saline were measured to enable the calculation of the current distribution. Current distribution depended on the ratio of the radial distance from the electrode array at which the distribution was measured to the distance between the two electrode bands used for bipolar stimulation. For small ratios, the distribution displayed two peaks directly above the two bands; while for large ratios, the distribution displayed only one peak midway between the two bands. Also investigated was the interaction that occurs when more than one bipolar pair were stimulated simultaneously. The results showed that the resulting distribution also depended on the above defined ratio. These results obtained from the tank model were verified by computer simulation.
Using multiple microphones and LMS adaptive beamforming to reduce interference in hearing aids from competing talkers in reverberant rooms
Authors: Peterson Patrick M.
Published: October 2005

To reduce interference in monoaural hearing aids from spatially separated sound sources, the information from multiple microphones might be useful in enhancing the signal from a desired source for monaural presentation. The technique of Griffiths and Jim [IEEE Trans. Antennas Propagat. AP-30, 27–34 (1982)] was used to filter and combine microphone signals ins way that preserves signals arriving from straight ahead of the microphone array while minimizing output power from off-axis signals. The filters adapt to the interference environment using a variation of the LMS (Widrow) algorithm. Although it adapts slowly (1 s), LMS approaches optimum performance in stationary, anechoic environments, providing a bound on performance in nonstationary, reverberant environments. In three simulated rooms, anechoic, living room, and conference room, with interferring babble 45° off-axis and on-axis target at − 12 dB/S/B, a two-microphone system with 100-point filters reduced the interference by 20, 12, and 4 dB, respectively. Informal listening indicated minimal degradation of the desired signal and substantial intelligibility improvement in anechoic and living room environments. [Work supported by NIH.]
Robust transformation of middle ear impedance parameters from an intra-aural measuring plane to the eardrum
Authors: del Rio J. A. , Kunov H. , Hong R. K. , Malone P.
Published: October 2005

In order to eliminate the risk inherent in the insertion of a measuring probe into the ear canal of a subject, a middle ear impedance transducer should be placed a safe distance away from the eardrum. A technique presented in this paper uses a function which represents the area function of the ear canal and transforms impedance parameters from the measurement plane to a plane at the eardrum. The effects of the geometry of the canal on impedance measurements, and the validity of the approximations over a wide frequency range are studied by means of a computer model. The area functions used to transform the impedance parameters are parabolic horns which are found to provide better results than the commonly used cylindrical approximation. The sensitivity of these approximations to errors in the estimation of the parameters defining the horn is also studied. The parabolic horns give a simple and very reliable correction to the interpretation of middle ear impedance data. [Work supported by the Natural Sciences and Engineering Research Council of Canada, CRD-8422.]
Noise trausmissibility of mechanical systems in a submerged elastic shell
Authors: Huang H. , Wang Y. F.
Published: October 2005

The effects of fluid-structure interaction on the force transmissibility of mechanical systems elastically mounted in a submerged elastic shell are investigated. An analytical solution for the ease of a harmonic-force-excited two-degrees-of-freedom undamped system attached inside a spherical elastic shell is obtained by the separation of variable technique. The transmissibility of the internal system is computed for a broad range of excitation frequencies and compared with that of the same system mounted on a fixed base. Due to the loss of energy through the radiation of the elastic shell, the transmissibility resonance peaks of the undamped system elastically mounted in the submerged shell are reduced to finite values and, for other nonresonance frequencies, the magnitude is in general also reduced. Moreover, the fluid-structure interaction effect shifts the peaks of the transmissibility towards lower frequencies. This information could be useful for the sound isolation of systems inside a submerged vessel.
Experimental investigation of fluid-coupled mechanical waves propagating on cylindrical shells at low ka
Authors: Garnier Bernard , Vernozy Bernard
Published: October 2005

A set of acoustical arrays has been constructed, the shapes of which are configurated in accordance with the cylindrical geometry of the nearfield of the shells (12–20 in.-diameter). Some are double layer arrays, and directly give the acoustic intensity of radiated noise through the array. Other give the dynamic pressure in the immediate vicinity of the shell, and reflect both propagating and nonpropagating fields, like those associated with subsonic flexural waves. The studied shells reflect a wide assortment of usual shell technologies in torpedoes or ship building: steel, aluminum alloys, glass, or carbon-fiber reinforced resins; ribbed shells, more or less disturbed by internal fittings, etc. They are mechanically excited by various arrangements of piezoelectric shakers driven by recurrent pulses. When the measurements are plotted as time/space recordings, they give a descriptive image of wave propagating in the shells: phase and group velocities, damping, and scattering on all discontinuities of the shell, which is generally the main phenomenon to explain the effective propagation of vibrations along realistic shiplike structures.
Waveform speech coding based on vector transform quantization
Authors: Cuperman Vladimir
Published: October 2005

This paper presents a waveform speech coding system based on vector transform quantization (VTQ). VTQ is a coding system where consecutive M samples of a waveform are transformed into a set of coefficients which are quantized by a set of m < M vector quantizers (VQs). A coding gain higher than for the known scalar transform coding systems is achieved by employing vector quantization rather than the usual scalar quantization. Moreover, a bit allocation closer to the optimal one may be achieved by vector quantizers as a result of improved round-off conditions. Assuming stationary input, the optimal bit allocation for the vector case is derived, and the coding gain achieved by such a system is evaluated. Techniques for adapting the bit assignment to the changing speech statistics are presented. These techniques are specific for the vector quantization approach and achieve adaptation along time and frequency axes. System simulation results are presented for typical speech waveforms at rates of 1–2 bits/sample.
A VQ-based speaker normalization method and its applications to speech recognition
Authors: Soong Frank K.
Published: October 2005

A speaker-specific vector quantization (VQ) codebook was proposed and applied successfully to both text-independent and text-dependent speaker recognition applications [e.g., F. K. Soong, A. E. Rosenberg, L. R. Rabiner, and B-H. Juang, ICASSP-85 (1985) and A. E. Rosenberg and F. K. Soong, ICASSP-86 (1986)]. In this talk the same VQ codebook is used for constructing a transformation, or more precisely, a mapping, between the feature space of a new speaker and that of a standard speaker. The mapping is constructed by using standard dynamic programming (DP) procedure to align training tokens spoken by a new speaker with tokens of the same text spoken by the standard speaker. Along the optimal alignment paths, a correspondence between the spectral feature vectors of the new speaker and the VQ codebook indices of the standard speaker is established and, for each VQ codebook index, a centroid is computed as the “average” of all the corresponding feature vectors of the new speaker. A new VQ codebook for the new speaker is therefore generated, and it is a one-to-one projected image of the VQ codebook of the standard speaker onto the feature space of the new speaker. This speaker normalization procedure has various applications in speech signal processing such as speech recognition, speech coding, and text-to-speech synthesis, etc. In this talk, isolated word recognition results are used as a demonstration of this new speaker normalization procedure. Results obtained from using speaker-adapted templates (the new method), speaker-independent clustered templates, and speaker-trained templates are compared.
Modifying normal mode models to permit special range dependence
Authors: Li Dong-Jye , Wood David H.
Published: October 2005

Benchmarks for testing range-dependent computer models are very scarce. We suggest that well validated normal mode models having no range dependence can be modified to permit their modeling a range dependence of a special form having parallel boundaries. This would permit modeling a three-dimensional index of refraction of the special form n2 = a(z) + c + b /(x2 + y2), where a(z) is any depth-dependent function that an existing normal model will accept. Existing normal mode models are found to need only minor coding changes to permit generating special three-dimensional solutions of the Helmholtz equation or solutions of the standard parabolic equation.
An exact solution to the ideal, 3-D wedge as a proposed benchmark
Authors: Buckingham M. , Tolstoy A. , Doolittle R.
Published: October 2005

An exact solution for the field from a cw point source in an ideal wedge exists in the form of normal modes where the mode coefficients contain the entire range and cross-range dependence. This model is proposed as a benchmark 3-D solution. For the case when the wedge angle is a submultiple of π the solution has been implemented on a VAX 11/750, and results are available for the following: (a) the complete complex field throughout the wedge including the vicinity of the source; (b) individual mode coefficients (amplitude and phase); (c) transmission loss as a function of position; and (d) the spatial coherence of the field. The model is suitable for a general sensitivity analysis.
Measurement of tactile spatio-temporal sensitivity
Authors: Van Doren Clayton L.
Published: October 2005

The perception and discrimination of texture is an important part of cutaneous tactile function, and requires the use of both spatial and temporal information. Earlier studies that have used a variety of stimulators to measure tactile responses to temporal and spatial variations will be reviewed. A stimulus that has been successfully employed in the study of visual pattern perception, but has not been available for tactile research, is the spatio-temporal sinusoid, where the amplitude of the stimulus varies sinusoidally along one spatial dimension and in time. A new, 88-element linear stimulator array, constructed to produce tangible spatio-temporal sinusoids, is described. Each element in the array is a plate of a piezoelectric ceramic. The elements are assembled on 0.38-mm centers for a total array length of 33.4 mm. Therefore, the spatial wavelengths that can be produced by the array range from 0.76–33.4 mm. The temporal bandwidth of the array is 0.8–1000 Hz, and the maximum stimulus amplitude is 8 μ zero to peak. The array was used to measure detection thresholds at live temporal frequencies (1, 4, 16, 64, and 256 Hz) and five spatial wavelengths (1.81, 3.62, 7.23, 14.5, and infinite mm). The detection thresholds reveal two receptor populations, presumably the NP I and P systems described by Verrillo and colleagues. The NP I system is more sensitive than the P system at short wavelengths and at low temporal frequencies, and less sensitive than the P system at high frequencies and long wavelengths. These results are consistent with earlier psychophysical and physiological experiments.
Dual-channel FFT analyzers
Authors: Kienholz David A.
Published: October 2005

Adding a second channel to a Fourier analyzer greatly increases its capability by allowing investigation of the relationship between two signals which occur simultaneously. A number of important two-channel frequency functions can be measured, all derived from the cross-power spectral function. These include frequency response, ordinary coherence, and sound intensity. This presentation reviews the definitions, physical significance, and some practical applications of these data types. Practical considerations for two-channel measurements with typical dual- or multiple-channel analyzers are discussed.
Practical solutions of engineering problems through the application of FFT analysis
Authors: Trethewey Martin W.
Published: October 2005

The analysis of many actual engineering problems can be greatly enhanced through the application of fast Fourier transform (FFT) signal processing. The purpose of this paper is to demonstrate some typical problem solving approaches and subsequent solutions obtainable through FFT analysis. The problems and solution techniques are chosen to illustrate the use of the various available spectral quantities. The topics discussed include: (1) source identification and preventative maintenance monitoring through comparison of power spectra; (2) the estimation of radiated acoustic intensity using the cross spectrum between two closely spaced microphones; (3) machinery noise source identification via the ordinary coherence function; and (4) the measurement and estimation of dynamic structural characteristics from frequency response functions. Techniques to assess the spectral quality for each application are discussed to ensure that accurate results are obtained. Each topic area is presented in a pragmatic fashion to illustrate the use and interpretation of the spectra required for each application.
Using FFT analyzers in undergraduate physics courses
Authors: Rossing Thomas D.
Published: October 2005

FFT analyzers are very useful, not only in acoustics demonstration and laboratory expeximents, but in courses in electronics, electricity and magnetism, mechanics, optics, etc. A few of the pedagogical applications of these useful instruments will be described.
Recent experience with the new ANSI S12.10-198S procedure for identifying prominent discrete tones
Authors: Wittig Larry E. , Hellweg Robert D.
Published: October 2005

The American National Standard for measuring noise emitted by business equipment, ANSI S12.10-1985, includes a new procedure for identifying prominent discrete tones. The procedure is based upon comparing the sound pressure level in the tone to the sound pressure level in the Zwicker bandwidth centered around the tone. In general this new procedure is a substantial improvement over the previous procedure described in ANSI S1.29-1979, and based on Appendix B of ANSI S.13, which uses sound pressure levels outside the Zwicker handwidth to determine the strength of the masking noise. However, after several months of use with a FFT analyzer it is dear that the S12.10 procedure raises questions that should be addressed. This paper presents examples of tones that sound prominent but do not calculate to be prominent by the new procedure, and examples that do not sound prominent but calculate to be prominent. This paper also presents limitations on use of one-twelfth-octave-band filters to make the measurements required by the S12.10 procedure.
On shrinking the world's oceans into a physics laboratory
Authors: Medwin Herman
Published: October 2005

Traditional operations of a physical acoustics laboratory involve the use of sound as a probe to determine the physical constants and characteristics of fluids and solids. The same techniques can be used, and the same physical insight can be achieved, when one scales down complex extended oceanic phenomena to manageable laboratory dimensions. A scale model solution to underwater acoustics propagation problems has the advantage that the intimately intertwined character of the real world can be tested, one parameter at a time, in the laboratory micro-ocean. The unraveling of ocean acoustical mysteries has been performed to advantage in several problems: In the case of shadowing by a seamount, the specific contributions of diffraction at the seamount crest, multiple reflections between seamount and ocean surface, scatter at the rough bottom, and scatter from wind waves at the ocean surface have been clarified. Current research in our laboratory involves the evaluation of components of scatter from a model of the arctic ice canopy where reflection, specular scatter from steep-sloped roughness elements, boundary waves, diffraction at the edges, and flexural waves within the ice plate exist simultaneously. All these contributors play their parts in producing what has been innocently described as the “reflection coefficient” and the “backscattering strength” of the arctic ice cover. [Work supported by ONR.]
The long and short of random media: Acoustic Anderson localization
Authors: Maynard Julian D.
Published: October 2005

Wave propagation in random media relates to a large number of important current problems in physics and acoustics. For long wavelengths the wave equation is locally approximated by the Laplace equation, and this together with the complex boundary conditions provided by the random medium describes many interesting phenomena involving percolation, fractional dimensionality, etc. An important puzzle in the long wavelength regime was solved just recently; a homework problem once assigned by I. Rudnick provided the key to the solution. In the short wavelength regime, where wavelengths are on the order of the variations in the random medium, one may observe effects of Anderson localization, which is currently receiving much attention in the study of quantum phenomena in disordered solids. Recent experiments on acoustic Anderson localization, including nonlinear effects, will be reported. [Work supported by ONR.]
Correlation between frequency and position of soliton creation
Authors: Barber Brad , Wu Junru , Rudnick Isadore
Published: October 2005

A water trough which has the property that there is a correlation between the frequency of drive and the position at which the soliton is created has been designed and constructed. It has a linearly increasing width and a quadratically increasing depth. This results in a trough which has a cutoff frequency for solitons which varies with position when driven parametrically. Self-trapping localizes the soliton to the same degree as in a conventional trough with constant rectangular cross section [J. Wu, R. Keolian, and I. Rudnick, J. Acoust. Soc. Am. Suppl. 1 74, S11 (1983)]. The observed correlation between frequency and position agrees unexpectedly well with an ad hoc approximate theory. [Work supported by ONR.]
Nonlinear flexural modes in thin shells: Observation of envelope solitons
Authors: Wu Junru , Wheatley John , Rudnick Isadore
Published: October 2005

Olson [AIAAJ. 3, 177S (1965)] measured the flexural eigenmodes of a thin metallic shell and found that the dispersion curve for the (p,q) mode, where p refers to azimuthal and q to height waves, has an unusual shape. When q is kept constant, the shape is that of a distorted U. We have reexamined this system and found it to be very rich in nonlinear properties. These phenomena include nonlinear mode interaction, multiple hysteresis, and quasiperiodicity. Of particular interest is the observation of envelope solitons propagating with a group velocity which is equal to the slope of the abovementioned dispersion curve. Since the sign of the slope is different in the two branches of the U, the solitons associated with each of them propagate in opposite directions. Observations of this behavior will be described. To our knowledge this is the first direct observation of solitons in macroscopic elastic waves in solids. [Work supported by ONR and DOE.]
Effects of relative starting phase and frequency separation on two-tone auditory brainstem responses
Authors: Sammeth Carol , Burkard Robert , Hecox Kurt
Published: October 2005

Two-tone complexes have been used as stimuli in auditory brainstem response (ABR) studies examining two-tone suppression and the critical band (Stanny and Elfner, 1983; Zerlin, 1986). The relative starting phase of the tones in a two-tone complex can have dramatic effects on the stimulus envelope. In light of the onset nature of the brainstem response and its integration of energy over only the first few cycles of a tone-burst stimulus (Suzuki and Horiuchi, 1983), phase effects on the stimulus envelope may be a confounding factor in two-tone studies. We recorded ABRs to single-tone stimuli, and to two-tone complexes with homophasic and antiphasic relative starting phase. Frequency separations were arithmetically centered around 4000 Hz, and ranged from 200 to 3200 Hz. Relative starting phase had a significant effect on wave V amplitude for narrow frequency separations where stimulus envelope effects are most pronounced, but had no significant effect on wave V latency. ABRs to single-tone stimuli were summed and compared to the responses obtained with the two-tone complexes. The amplitude of the summed single-tone responses exceeded the amplitude of wave V of the two-tone complexes at all frequency separations. We conclude that relative starting phase of the tones in two-tone complexes can significantly influence wave V amplitude, especially for small frequency separations.
Central masking paradigms and alterations in the auditory brainstem response
Authors: Simhadri-Sumithra Radha , Gerken George M.
Published: October 2005

Contralateral masking is often recommended in auditory brainstem response (ABR) testing in order to reduce or eliminate the participation of the nontest ear. The present study evaluates the effects of contralateral sound on the ABR. Vertex-mastoid recordings were made on a total of 30 young-adult subjects with normal heating. Stimulus paradigms employed a 4-kHz probe and a contralateral continuous tone or a contralateral forward masker. Both the continuous-tone and forward-masking experiments resulted in statistically significant amplitude changes in the probe-evoked ABR. Waves III and VI, averaged across experiments, conditions, and subjects, showed a 28.7% increase in amplitude in the presence of a contralateral stimulus. In contrast, the amplitude of wave V, averaged across experiments, conditions, and subjects, was reduced by 11.2%. Latency measures for all waves often showed a slight, but statistically significant, increase. In regard to the enhancement of wave III by contralateral sound, we speculate that the descending auditory system is involved. The amplitude changes obtained for waves III, V, and VI contrast strongly with earlier results on ipsilateral masking.
Effects of attention on auditorily evoked potentials
Authors: Kuk Francis K. , Abbas Paul J.
Published: October 2005

Auditorily evoked responses to tone bursts (4-ms duration with 1-ms rise/fall) were recorded from the promontory as well as the ipsilateral mastoid of five human listeners while they were performing a visual duration (standard light flash of 50 ms) and an auditory frequency (center frequency at 2, 4, and 8 kHz; 250-ms duration) discrimination task. Response evoking tone bursts were presented prior to and between the discrimination tone bursts. Visual and auditory stimuli were presented simultaneously. ABR and AP measurements were made during separate sessions. The method of constant stimuli was used for the discrimination tasks and the separation between stimuli was set for the value of the difference limen determined during a training session. Recordings obtained with acceptable discrimination performance were analyzed. No difference in amplitude, latency, or shape of the recordings was observed between the two discrimination tasks. The results suggest that the attention demand of the present task is not a central factor in the control of the auditory efferents.
The use of paired clicks to examine forward masking in auditory brainstem responses
Authors: Shotland Lawrence , Hecox Kurt
Published: October 2005

Forward masking was assessed in ten normal and ten sensorineural hearing-impaired subjects using a paired-click paradigm. Auditory brainstem responses (ABR) were obtained using single and paired clicks. The single or click pairs were repeated at 4.9/s while the separator between clicks for click pairs was 5 ms. First or single clicks were presented at 60 dB nHL for the normal listeners and at levels sufficient to produce a 6.0-ms wave V in the hearing-impaired group. The second click was presented at the same intensity, 10 dB, less intense, and 20 dB less intense than the first click. A digital subtraction technique was utilized to visualize the response to the second click in the pair. Differences in response threshold and in the rate of latency of amplitude growth were observed between the hearing-impaired and normal population. Control conditions suggested that these findings cannot be attributed solely to differences in the level of presentation between the two groups. The contribution of adaptation/forward masking to the results found in the hearing-impaired data will be discussed.
Auditory sensitivity via BAEP and electrocochleography: Method for improved low-frequency region response
Authors: Shepard Neil , Brady Laura , Potesta Eugene
Published: October 2005

Difficulty in realizing a repeatable low-frequency region response near threshold for click (low-frequency) or tone-burst stimuli is partially due to the reduction in synchronous discharge of auditory nerve fibers innervating areas of the cochlea most sensitive to low-frequency input. This problem is exacerbated by the use of random or alternating phase onset to reduce electrical and physiological interference. A method shown to eliminate the time smearing effect of random or alternating phase onset for click stimuli using a fixed phase onset with broadband masking and a subtraction technique was applied to tone-burst stimuli for BAEP and EcochG recordings. Preliminary results show the technique to be as applicable to BAEP recordings and tone-burst stimuli as with EcochG and clicks, provided a sufficient level of broadband noise is presented. The success regarding low-frequency response in both normal-hearing and hearing-impaired subjects will be presented.
Clinical validation of special hearing-impaired norms for BAEP interpretation
Authors: Shepard Neil T. , Burtka Mary-Jo , Turner Robert G.
Published: October 2005

A model predicting the effects of high-frequency hearing loss of cochlear origin on the BAEP [N. T. Shepard and J. C. Webster, J. Acoust. Soc. Am. Suppl. 1 74, S40 (1993)] was used to develop criteria based on degree and configuration of loss of sensitivity for interpreting clinical BAEP testing. Two and one-half years of experience with these criteria were reviewed by a retrospective study of 389 patients tested during that period. Validation of the model was indicated by an 8% increase in specificity of the test with no change in sensitivity when use of the special criteria were compared to criteria based solely on normal-hearing subjects in the same clinical population. Also discussed will be overall BAEP performance, an explanation of high false positive rate based on population mix, and improved criteria for test enhancement.
Frequency selectivity of the active cochlear filters inferred from otoacoustic emissions evoked by steady-state tones
Authors: Divenyi Pierre L.
Published: October 2005

Spontaneous otoacoustic emissions have been shown to represent an oscillatory process rather than amplification of a narrow-band noise centered at the emission frequency: Instantaneous amplitudes of the emission have the bimodal distribution characteristic to oscillations (W. Bialek and H. P. Wit, Phys. Lett. 104A, 173–178). The present paper attempts to demonstrate that similar bimodal distributions may be observed when the response to a low-level (<30 dB SPL) steady-state tone is recorded near the tympanic membrane and the energy at the tone frequency is eliminated from the recording. At either side of the stimulus frequency, points at which the narrow-band instantaneous amplitudes shift from a unimodal to a bimodal distribution may be mapped into bandwidths that are comparable to those deriving from physiological measurements of the tip of the tuning curve. [Work supported by the Veterans Administration.]
Otoacoustic emissions and cochlear pathology
Authors: Grizzle J. L. , Divenyi P. L. , Simon H. J.
Published: October 2005

Otoacoustic emissions, evoked by clicks and brief tone bursts, were measured in normal-hearing subjects and patients with sensorineural hearing loss. The emissions were recorded using an electret microphone assembly inserted in the meatus. The stimulus was delivered through a transducer attached to a 1.3-mm plastic tube terminating at approximately 1 cm from the eardrum. Spectral analysis of the click-emitted emissions showed discontinuities similar to those observed in spontaneous emission recordings. In addition, the comparison of emission and audiometric data in the impaired ears will be reported. [Supported by the Veterans Administration.]
The biological significance of ultrasonically induced cavitation
Authors: Dyson Mary , Crum Lawrence A. , Mortimer Alan
Published: October 2005

There is now considerable evidence that levels of ultrasound employed clinically can produce cavitation in vitro and, in certain circumstances, in vivo. Transient and prolonged cavitation is potentially damaging, destroying cells locally and inducing chemical changes through free radical production. Although not necessarily lethal, the effects of free radical activity may modify cell activity, particularly if chemical changes are produced in the components of the cell membranes. In contrast, acoustic cavitation of the stable type can have effects which may be of advantage when ultrasound is used as a therapeutic agent, although their production should be avoided in embryonic and fetal tissue; these effects include the enhancement of protein synthesis and cell motility, and could result in the stimulation of repair phenomena by ultrasound. The conditions under which cavitation occurs must be determined so that it can be avoided where advisable and employed where appropriate. [Work supported in part by the Medical Research Council and, through grants to Lawrence A. Crum, by the National Institutes of Health, National Science Foundation and the Office of Naval Research.]
Ultrasonically induced cavitation in mammals
Authors: Frizzell Leon A. , Lee Chong S.
Published: October 2005

The role of cavitation in the production of biological effects in mammals is reviewed with emphasis on recent studies in the mouse neonate. The levels for hind limb paralysis from 1 MHz, continuous wave unfocused ultrasound in the neonatal mouse, within 24 h of birth, have been investigated at 1 and 16 bars ambient pressure and temperature between 10° and 37°C. Above certain intensity levels the exposure duration for paralysis of 50% of specimens exposed increases with increased ambient pressure. Since an increased ambient pressure tends to suppress cavitation, such changes suggest cavitational involvement. Results show that cavitation may be involved in the resultant paralysis above approximately 150 W/cm2 at 10°C, and above approximately 60 W/cm2 at 37°C. This temperature dependence is consistent with a cavitation mechanism. [Work supported by National Institutes of Health.]
Doppler ultrasound pulses can induce SCE In human lymphocytes in vitro
Authors: Barnett Stanley B. , Barnstable Sandra M.
Published: October 2005

Human lymphocytes were exposed to an ultrasound pulsing regimen similar to that typically employed in clinical Doppler measurements of fetal blood flow, to determine whether such pulses were able to alter the frequency of sister chromatid exchanges (SCE). A 3.1-MHz, 1.5-cm-diam transducer emitted 5- to 50-cycle pulses in a beam that was directed vertically along the axis of a stationary tube containing the blood suspension. Hydrophone measurements within the tube showed that the beam intensity profile was maintained beyond the free field focal region, thereby ensuring maximum exposure of the contents of the tube. A significant increase in SCE frequency was observed in blood from two random donors exposed to “diagnostic” levels of ultrasound, where the SPTA intensity ranged from 1 to 4 W/cm2. However, a number of further studies on blood from a single (different) donor have failed to show any effect from ultrasound even after an exposure dwell time of 24 h. This extraordinary finding may have some relevance towards explaining some of the controversial reports of SCE induction in human lymphocytes. Research continues to try to identify the mechanisms responsible for this effect.
Vowel quality and word stress in native and non-native English
Authors: Fokes Joann , Bond Z. S.
Published: October 2005

In a recent study [Fokes and Bond, J. Acoust. Soc. Am. Suppl. 1, 79, S27 (1986)], we reported that non-native speakers of English lengthened unstressed syllables and shortened stressed syllables of three and four syllable words, such as confession and combination, in comparison to native English speakers' patterns. While all speakers were not consistent in their use of either fundamental frequency or amplitude in differentiating stressed from unstressed syllables, the non-native speakers were much more variable. In an attempt to clarify differences in speech patterns between these two groups of speakers, we measured the first two formants of the first and second syllable of the same set of words as produced in isolation and in sentence context. The F1 and F2 values of the native English speakers were as expected and differed little from isolation to sentence context. The non-native English speakers varied F1 and F2 from isolation to sentence context but with no discernible pattern. The formant measurements will be discussed both in terms of intended and perceived vowels.
Co-occurrence of allophonic forms
Authors: Bernstein Jared , Baldwin Gay , Murveit Hy
Published: October 2005

Recent analyses of the allophonic variants of phonemes in particular environments often seem to assume one or more of the following: (1) The proportions of variants encountered in a multispeaker sample represent an “irreducible” statistical component of phonology; (2) these proportions predict the likelihood of encountering these same allophones in new material; (3) the probability of encountering a particular allophone of some phoneme is independent of the observed allophones of other phonemes nearby. These related assumptions are questioned on theoretical and practical grounds, using transcribed data from 630 speakers reading two sample sentences. The frequencies of occurrence of all the allophones of certain phoneme tokens in the sample sentences were measured across all speakers; then the conditional co-occurrence of all the allophones of certain phoneme pairs in the sample sentences were analyzed. For example, first the occurrence of a flap in the words “suit in” was counted across all speakers; then the occurrence of a flap in “suit in” was counted for only those speakers who deleted /t/ in “don't ask,” and so on. Comparing these two kinds of analysis has implications for theories of variation. The application co-occurance analysis in speech recognition will be illustrated. [Work supported by DARPA.]
Discrete acoustic analysis of intonation patterns in controlled contextual settings
Authors: Pratarelli Marc E.
Published: October 2005

Acoustical and temporal correlates of intonation patterns in eight semantically distinct sentences made up of the same three words, “Bob bit Todd,” were quantified, verified perceptually, and analyzed statistically for degrees of variability. The phrases consisted of four declaratives and four interrogatives. Three of each group of four systematically varied the stress component on each of the three words. The fourth phrase type was a neutral version with no particular emphasis on any member. A single speaker produced ten replications over three successive days in response to experimenter queries; listener judgments were used to verify the contextual appropriateness in all 80 utterances. Duration, fundamental frequency, and intensity were measured systematically to study both the variation of each and the interrelations between them. Several graphs are presented that depict the movement of the means and standard deviations of the acoustic and temporal correlates, and pitch contours are presented which depict the degree of stability of instability of the correlates. Canonical correlations and regression analysis predictably isolated the magnitude of fundamental frequency stability in the interrogatives but not the concomitant high degree of variability in the same utterances. An index of what “normal variation” may be, and its impact on recognition, is discussed. [Work supported by the House Ear Institute.]
Effect on F of the linguistic use of tense and lax phonation
Authors: Maddieson Ian , Hess Susan
Published: October 2005

Laver [Phonetic Description of Voice Quality (Cambridge U.P., London, 1980)] remarks that “there is a strong possibility that in tense voice the pitch range will be higher than in lax voice,” but notes that adjustments can be made to compensate for this tendency. Three languages with phonological contrasts between syllables with tense (somewhat creaky) and lax (somewhat breathy) phonation were examined to see how greatly F0 differed between such syllables. It was expected that compensatory adjustments would be made in tone languages in order to preserve contrasts between tones, but not in nontonal ones. In Wa and in Northern Yi, after most types of consonants were examined, there was no significant F0 difference between tense and lax syllables. In Jingpho, F0 at vowel onset was reliably higher in tense syllables, but there was no difference at vowel offset. Since Wa is nontonal, while Yi and Jingpho have similar tonal systems, our expectations were not met. However, a potential role for a lax/tense phonation contrast in tonogenesis and tone splitting was revealed. [Work supported by NIH.]