bluuebunny/crossref_metadata_2025 huggingface dataset:
Brainstem auditory steady-state responses to multiple simultaneous stimuli
Authors: Lins Otavio G. , Picton Terence W. , Picton Peter E. , Champagne Sandra C. , Durieux-Smith Andrée
Published: October 2005

Brainstem auditory steady-state responses can be evoked by tones that are amplitude-modulated at rates of 70–110 Hz [Cohen etal., J. Acoust. Soc. Am. 90, 2467–2479 (1991)]. Steady-state responses to several stimuli presented simultaneously can be independently assessed by Fourier analysis if each stimulus is presented at a different rate [Regan, HumanBrainElectrophysiology (1989)]. Could auditory brainstem steady-state responses to tones of different frequencies be recorded simultaneously? The first experiment presented tones to the right ear using carrier frequencies of 500, 1000, 2000, and 4000 Hz and modulation rates of 81, 89, 97, and 105 Hz, respectively. The response amplitudes when the stimuli were presented simultaneously were not significantly different from when the stimuli were presented alone. The second experiment presented tones of 500 and 2000 Hz modulated at 81 and 97 Hz to the left ear and tones of 500 and 2000 Hz modulated at 89 and 105 Hz to the right ear. The amplitude of the response was slightly but significantly larger when the tones were presented to both ears simultaneously than when they were presented alone. The simultaneous stimulation technique should therefore facilitate the physiological evaluation of human auditory function.
Effects of competing noise on latency of P300 auditory event related potentials in adults with and without auditory processing disorders
Authors: Krishnamurti Sridhar , Stein Ramona , Gans Donald
Published: October 2005

P300 auditory event related potentials (P3AERP’s), discovered by Hallowell Davis in 1964, are endogenous potentials influenced by stimulus context (rather than stimulus features) and subjects’ attentional characteristics (rather than subject characteristics). The effects of competing noise no latency of P3AERP’s were investigated in the current study in adults with and without auditory processing disorders. P3AERP’s were recorded using an oddball paradigm in binaural and competing conditions. The binaural condition involved presentation of 3000- and 4000-Hz tone bursts to both ears while in the competing condition, 3000- and 4000-Hz tone bursts were presented to one ear and competing white noise to the contralateral ear. On average, both groups showed longer latencies for the competing condition, which supports the notion of the influence of stimulus context. Individuals in the auditory processing disorders group showed prolonged latencies in both conditions relative to those in the control group, reflecting the problems in speed of information processing on attentional tasks observed with this population.
Modulation rate transfer functions in three species of cetaceans
Authors: Dolphin William F.
Published: October 2005

A modulation rate transfer function (MRTF) is a quantitative description of the ability of a system to follow the envelope of a stimulating waveform. In this study MRTFs were obtained using auditory-evoked potentials in three species: false killer whale, Psuedorca; beluga, Delphinapterus; and bottlenose dolphin, Tursiops. MRTFs were obtained from nonsedated animals using two-tone stimuli consisting of frequencies at f1 and f2. Frequency f1 was held constant and f2 was varied such that difference frequencies ( f2−f1=f2,1) ranged from 18 Hz to 5.2 kHz; in all cases f2≳f1. In the study f1’s used were 0.5, 0.8, 1.0, 4.0, and 10.0 kHz. Evoked responses were recorded differentially from the scalp surface using suction cup electrodes. Responses to 350 stimulus presentations were averaged to yield the final response. Averaged responses were Fourier transformed. The magnitude and phase of the Fourier component corresponding to f2,1 was the dependent variable. The magnitude of the response at f2,1 as a function of modulation frequency was generally low-pass in shape with high-frequency corners of approximately 1.1, 1.5, and 2.2 kHz for Psuedorca, Tursiops, and Delphinapterus, respectively. Neither the amplitude nor corner frequency of the response exhibited a dependency on primary frequency over the range tested. The group delay, calculated from the response phase, indicated three distinct latencies: for 0<f2,1<50 Hz a delay of ∼18 ms; for 50<f2,1<300 Hz a delay of ∼4 ms; for f2,1≳300 Hz a delay of ∼0.5 ms. These latencies presumably indicate different neural generators for the responses to various modulation frequencies. [Work supported by ONR.]
Temporary threshold shift: Peripheral and central measures
Authors: Thodi Chryssoula , Gans Donald
Published: October 2005

Although the cochlea has been established as a primary site of auditory fatigue, contributions to temporary threshold shift (TTS) by the central auditory system have been debated by researchers. The present study investigated TTS in gerbils following a short-duration, moderate intensity exposure to pure tones. TTS was measured by tone burst-evoked VIIIth nerve action potentials, cochlear nucleus and inferior colliculus single unit responses, and inferior colliculus population-evoked responses. The TTS measured at the level of the cochlea was not significantly different from the TTS measured at the cochlear nucleus or the inferior colliculus levels. The stimuli used in this study allowed for a recording of VIIIth nerve action potential that was reflective of sensitivity changes in a specific frequency area. It was concluded that when frequency specific stimuli are used to evaluate thresholds, exposure to moderate intensity, short duration tones results in similar degrees of TTS measured in peripheral and central levels of the auditory pathway.
Click-evoked otoacoustic emissions in normal-hearing children
Authors: Smurzynski Jacek
Published: October 2005

Click-evoked otoacoustic emissions (CEOEs) were collected from 167 ears of 106 normal-hearing children using the ILO88 system with the stimuli presented at 80±2 dB pe SPL. Subjects were divided into five age groups: 13–24 months (24 ears), 25–36 months (49 ears), 37–48 months (31 ears), 49–60 months (34 ears), and 61–72 months (29 ears). All subjects had normal middle ear function and their audiological data were within normal limits. Mean overall CEOE level was calculated for each age group. None was statistically different from any other. However, the data of the 167 ears showed small but statistically significant decrease in CEOE level as age increased. Combined data of 61 subjects, who were tested in both ears, revealed statistically significant correlation between the CEOE levels from both ears of the same individual and also indicated that the right ears exhibited significantly higher CEOEs than the left ears. The CEOEs recorded from each individual ear were analyzed by calculating rms levels within five half-octave bands in the 0.8- to 4.8-kHz region. The values corresponding to the 10th percentiles were calculated for the five half-octave bands based on the rms CEOE data of the 167 ears. The 10th percentiles were used to define pass/fail criteria of the CEOE test for hearing-impaired children’s ears.
Periodicity in the spectrum of transiently evoked otoacoustic emissions
Authors: Uppenkamp S. , Neumann J.
Published: October 2005

Transiently evoked otoacoustic emission spectra typically show several maxima and minima with a frequency spacing, which might represent a periodic structure in the cochlea. A method studying the spectral properties of transiently evoked otoacoustic emissions is presented. A modified cepstral analysis is performed by calculating a backward FFT on samples of the power spectrum, which were taken equivally spaced on the bark scale, representing the frequency mapping on the basilar membrane. This results in a type of cepstrum, known from speech analysis, which can tell something about any periodicity in the spectrum. Analyzing EOAE results from 60 normally hearing subjects, half of the ears showed a periodicity with a spacing ranging from 0.4 to 0.8 bark. The synchronization of a strong spontaneous emissions by the transient stimulus results in an emission spectrum dominated by this single frequency and with no detectable periodicity. The finding of a periodic structure in case of broader emission spectra supports the model of ‘‘Bragg reflection’’ due to a periodic fluctuation of BM impedance [H. W. Strube, Hear. Res. 38, 35–45 (1989)] for the generation of TEOAE.
Suppression of transiently evoked otoacoustic emissions
Authors: Neumann J. , Uppenkamp S. , Kollmeier B.
Published: October 2005

The influence of additional continuous tones on transiently evoked otoacoustic emissions (TEOAE) is studied with normal hearing subjects. If a single continuous tone is present, nearby frequency components of the TEOAE are synchronized to this tone in a similar way as spontaneous OAE can be synchronized. This effect can be deducted from the reduction (‘‘suppression’’) of the corresponding OAE component since the additional continuous tone is designed to exhibit a phase shift of pi between successive averaging frames and thus cancels out. To suppress several spectral components of the TEOAE, a continuous tone complex was employed. The frequency difference between adjacent components of this tone complex yields an optimum value at about a critical bandwidth. An application of these findings is the stimulation and evaluation of TEOAE from a predefined region on the basilar membrane: While the frequency range of the evoking signal can be limited by using chirp stimuli (i.e., short frequency sweeps), the TEOAE components outside this frequency range can be suppressed by using an appropriate set of suppressor tones.
The effects of contralateral stimulation on synchronous evoked otoacoustic emissions
Authors: Long Glenis R. , Talmadge Carrick L. , Shaffer Lauren
Published: October 2005

Synchronous evoked otoacoustic emissions (SEOAEs) provide evidence that the impedance of the human auditory system varies systematically with frequency. Frequency-independent acoustic input to an intact human auditory system leads to regular patterns of maxima and minima in the acoustic stimulus measured in the ear canal. The pattern of SEOAEs is also seen in changes in the level of distortion product otoacoustic emissions (DPOAEs). Contralateral acoustic stimulation moves the entire pattern of SEOAEs up in frequency. Monitoring SEOAEs or DPOAEs at one frequency in the presence of contralateral stimulation would thus lead to a level increase at some frequencies and a reduction at others. This pattern was observed in a subject with elevated contralateral acoustic reflexes, making it probable that the effect is generated by efferent innervation. The implications for the use of oto- acoustic emissions to evaluate efferent function will be discussed together with the impact on cochlear models. [Work supported by NIDCD and DRF.]
Spontaneous otoacoustic emission prevalence patterns in humans
Authors: Dorn Patricia A. , Long Glenis R. , Talmadge Carrick L. , Shaffer Lauren
Published: October 2005

In humans the prevalence of spontaneous otoacoustic emissions (SOAEs) depends on gender, pigmentation (race), and auditory status. Potential sources for variations in SOAE prevalence may include outer/middle ear characteristics and trauma to the auditory system. To explore these variables, auditory system structure, status, and history was obtained for each subject from whom SOAE recordings were obtained. Outer ear characteristics were determined from resonance peaks in a spectrum of white noise measured in the ear canal. Middle ear characteristics were obtained with multifrequency tympanometry. Auditory system trauma was determined by assessing hearing thresholds and from reports of noise exposure, medication history, and otologic surgery/illnesses. The results will be discussed in terms of their implications for clinical applications and models of the auditory system. [Work supported by the Showalter Foundation.]
Measurements of distortion product phase in the cat ear canal
Authors: Fahey P. F. , Allen J. B.
Published: October 2005

Amplitudes of odd-order distortion products (DPs) that are detected in animal ear canals have been used to probe cochlear health, to search for cochlear amplification, and to measure aspects of cochlear mechanical frequency response. The DP phase is also a rich source of information about cochlear mechanical response and reported here are extensive measurements of DP phase in the ear canal of cat. Much of the phase data can be explained by constant time delays that are a function of f2. When a1 (the amplitude of the f1 primary) is greater than a2 (amplitude of the higher frequency, f2, primary), both third-order and fifth-order DPs’ time delays are the same. In our preparations values are 0.6 ms at f2≳10 kHz; 0.8 ms at f2=5 kHz; 1.3 ms at f2=1 kHz. For the 2f1−f2 DP, as a2 becomes greater than a1 the time delays increase, even doubling at f2<2 kHz. The DP phase as a function of the DP frequency is generally dependent upon primary level. An interesting exception to this is that, for a1≳3a2, the phase of three DPs (2f1−f2, 3f1−2f2, and 2f2−f1) is independent of the a2 level.
A suppressive ‘‘off-effect’’ in the f2−f1 DPOAE response to continuous, moderate-level primary stimulation
Authors: Kujawa Sharon G. , Fallon Maureen , Bobbin Richard P.
Published: October 2005

Following a short period of amplitude enhancement, the f2−f1 DPOAE can be suppressed during continuous ipsilateral stimulation with primary tones. Evidence for and against efferent control of such response alterations has been presented. Here, an exacerbation of f2−f1 suppression, apparent following a short rest from continuous stimulation, is described and the hypothesis that it is efferent-mediated is tested. The f2−f1 DPOAE to intermittent or continuous primaries ( f1=6.25 kHz; f2=7.5 kHz; L1=L2=60 dB SPL) was recorded in urethane-anesthetized guinea pigs with sectioned middle ear muscles before, during, and after perfusion of the cochlear perilymph compartment with antagonists of olivocochlear efferent activity (curare, 1 μM; bicuculline, 10 μM) or of action potentials in general (tetrodotoxin, TTX; 1 μM). Results confirmed an initial f2−f1 amplitude enhancement and gradual suppression during continued stimulation. Following a 1-min rest, however, the DPOAE was further suppressed from its pre-rest level. Thereafter, its amplitude increased rapidly, reaching a maximum within 1–2 min. These amplitude alterations were intensity dependent. Moreover, they were reduced, but not blocked by efferent antagonists and were largely unaffected by TTX, suggesting that additional (e.g., local) alterations in cochlear status impact the cochlear mechanical response to continuous sound stimulation. [Work supported by NIH DC00007; DAMD 17-93-V-3013.]
Changes in cochlear frequency selectivity caused by sound stimulation of the contralateral ear
Authors: Williams Deirdre M. , Brown Ann M.
Published: October 2005

Suppression of the 2f1−f2 distortion product by a third ipsilateral suppressor tone was measured in the presence and absence of contralateral broadband noise. The amount of ipsilateral suppression varied with suppressor frequency but was maximum close to the f2 primary frequency as previously demonstrated using similar stimulus parameters [A. M. Brown and D. T. Kemp, Hear. Res. 13, 29–37 (1984); F. P. Harris etal., Hear. Res. 64, 133–141 (1992)]. In general, the amount of ipsilateral suppression of the distortion product was reduced under contralateral stimulation. This interaction may indicate a common mechanism for ipsilateral and contralateral suppression. The decrease in ipsilateral suppression under contralateral stimulation was most pronounced at the peak of the distortion tuning curves and this produced some broadening of the tuning curves. In the majority of tuning curves, the peak ipsilateral suppression frequency was observed to shift upwards. These results suggest that contralateral stimulation alters the frequency-selective properties of the cochlear response. [Work supported by the Wellcome Trust.]
Scale model experiments on the diffraction and scattering of sound by a curved rough surface
Authors: Chambers James , Berthelot Yves
Published: October 2005

Scale model experiments have been conducted to study the propagation of sound over a curved rough surface with curvature much greater than the wavelength and roughness smaller than the wavelength. The MAE model [J. Acoust. Soc. Am. 92, 605–608 (1993)] is used to determine the sound field in the vicinity of the curved surface. The Tolstoy–Medwin roughness model [J. Acoust. Soc. Am. 79, 657–665 (1986)] is used to model the rough surface. The two models are combined to qualitatively describe the sound field. Experiments indicate that: (1) just above the surface, the roughness causes a boundary wave that is generated by the direct waves in the bright zone and by the creeping waves in the shadow zone; (2) there are two frequency regimes with the transition determined by the curvature and the roughness; (3) along the surface, more sound (compared with diffraction by the curved smooth surface) is tunneled into the shadow zone at low frequencies and less sound is tunneled at higher frequencies. Along the line of sight, the trend is similar but more complicated. [This work is supported by a Fannie and John Hertz Fellowship.]
Low-frequency ground impedance measurement using a folded duct and wave number transforms
Authors: Swanson David C. , Maniet Edward
Published: October 2005

Measuring the impedance of the ground at frequencies below 200 Hz is a difficult job due to the large apparatus needed. The well-known method of measuring the standing wave ratio and nodal locations in the sound field inside a duct terminated with the impedance material becomes impractical. In order to scan the standing wave field, a large tube arrangement is needed. Therefore, a folded duct is fabricated that is over 8 m long but only 1.5 m high. A loudspeaker excites a standing wave in the duct, which has one end pressed into the soil approximately 10 cm, and an array of microphones measure the standing wave response. The Fourier transform for each microphone signal and the a spatial wave number transform (Bartlet beamforming) across the array to extract the reflection factor and impedance are then computed. The result is a nicely separated incident and reflected wave seen as two peaks in the wave number spectra. For very low frequencies (<50 Hz), a cardioid beam pattern is used to separate the incident and reflected waves. Simulation results showed accurate impedance measurements using this method down to below 20 Hz if microphones are spaced 0.1 m apart.
On the use of artificial neural networks to model sound quality
Authors: Laux P. , Davies P.
Published: October 2005

Loudness, percentile loudness, sharpness, and fluctuation strength have been shown in laboratory experiments to be correlated with annoyance. Zwicker proposed a model of unbiased annoyance (UBA) based on time of day (d), fluctuation strength (F), sharpness (S), and N10. In psychoacoustic tests on amplitude-modulated noise signals [P. Laux and P. Davies, NCEJ 40 (3) (May-June 1993)] UBA has been shown to have a higher correlation to annoyance than other commonly used noise measures, although, other correlation models were found to produce an even better model of the relationship between (S,N10,F) and the subjective ratings. The use of artificial neural networks (ANNs) to describe the relationship between (S,N10,F) and the subjective responses has been investigated. The smaller the network, the fewer the number of weights, and the fewer the number of signals that a subject has to rate. The objective of the research was to estimate a network that was the smallest possible model of the data. As a starting point UBA was modeled as a function of (S,N10,F); the resulting ANN model of UBA was then used as the initial conditions when subjective data were available.
New approaches for the urban noise modeling
Authors: Cammarata G. , Fichera A. , Graziani S. , Marletta L.
Published: October 2005

A lot of research work has been done for linking the noise emissions to the most relevant traffic parameters. So far, correlations are derived from multiple regression analysis under the hypothesis that modeling noise pollution in urban areas is a linear problem. Such an assumption can be overcome if more general approaches are used. This paper reports on the results obtained by the authors in modeling the traffic noise by means of neural network (NN) and fuzzy logic (FL). The models allow the prediction of the continuous equivalent level as a function of some typical parameters such as the traffic intensity (number of vehicles per hour), type of vehicles (cars, trucks, motorcycles), and geometrical features of the road (width of the lane, height of buildings). The database used for the NN and FL approaches refer to some typical towns of middle Europe, thus the resulting models should be valid for medium size cities. Comparison of the results with the measured data show better predictions than those based on more classical methods.
Noise problems of the supersonic civil airplane
Authors: Kouznetsov V. M.
Published: October 2005

Possibilities of complying with the community noise requirements for the supersonic civil airplane are discussed. Analysis of acoustic characteristics of the first supersonic civil airplanes Tu-144 and Concorde is given; comparison of the community noise level measurements and noise limits for subsonic passenger aircraft is carried out. Suggestions on the community noise reglamentation of SST’s are considered. Possibilities of using the following ways of jet noise reduction are discussed: gas thermal shield, multilobed or corrugated nozzle, surrounding air ejection, and application of sound absorbing linings. Results of the experimental investigations of model noise-suppressing nozzle efficiency with additional surrounding air ejection through the side surfaces, of corrugated nozzles with ejectors, the interior surfaces of which are treated with sound absorbing linings, are presented. The selection method of optimum parameters of sound absorbing linings is examined. Evaluation of the possible noise level reduction of the exhaust flow at the expense of ejector noise suppressor application is carried out. It is to be emphasized that only combined application of a series of jet noise reduction methods permits one to meet the community noise requirements.
Fine structure of transient waves in a random medium: The half N wave
Authors: Wenzel Alan R.
Published: October 2005

The propagation of a transient scalar wave in a one-dimensional random medium is considered. The initial disturbance is assumed to have a bilinear form characterized by a relatively short compression phase followed by a relatively long expansion phase. A wave having such a form is referred to here as a half N wave. Based on a general formula derived previously, an expression for the variance, which is a measure of the fine structure, of the half N wave is obtained. In a region encompassing the compression phase and the initial portion of the expansion phase of the wave, the behavior of the fine structure, as determined by this expression, is found to be consistent with observations of actual transient waves, such as sonic booms. Further into the expansion phase, however, discrepancies between theory and observations appear. These findings are described in detail. [Research supported by NASA.]
USAF single event sonic boom prediction model: PCBOOM
Authors: Plotkin Kenneth J. , Downing Micah , Page Juliet
Published: October 2005

The United States Air Force is required to analyze the environmental impact from sonic booms produced by supersonic maneuvering aircraft. To meet this need, a single event prediction model PCBOOM3 has been developed. This model uses full ray tracing propagation theory and includes the effects of aircraft maneuvers, non-standard atmospheric profiles, and winds. Calculations include focused superbooms when they occur. Input parameters are flexible to allow general supersonic maneuvers. The program accepts user-defined F functions, and has F functions built in for current USAF aircraft. The model predicts the location and waveforms of sonic booms on the ground. Predicted sonic boom footprints are in the form of contours (psf, CSEL, etc.) and isopemps, or as tabular values at specific points. Signature output is provided in either graphical or tabular format for arbitrary points within the footprint. This program will enhance the ability to predict sonic booms for operational planning or for incident investigation. It will also be used as a research tool to investigate sonic boom generation and propagation. [Work supported by USAF AL/OEBN.]
Sonic booms near and beyond the edges of primary carpets
Authors: Pierce Allan D.
Published: October 2005

Sonic booms received on the ground tend to be restricted to a region of finite lateral extent below the flight track. This occurs because of refraction and because the effective speed of sound, even with winds taken into account, decreases with altitude in the lower atmosphere. Not all rays proceeding initially downwards from the flight track within an allowable range of initial directions will reach the ground. The restricted region, which can be reached by rays impacting the ground, is known as the primary carpet. However, weak rubles are heard in the nominal shadow zone beyond the edge of this carpet. A full wave theory is necessary for explaining waveforms in that region, and the present paper gives a matched asymptotic expansion technique for a suitable approximate full wave theory that involves a relatively small number of parameters. The outer solution is derived from the structure of the system of rays, the impact near the corridor edge, the inner solution involves a solution of the parabolic equation and results in the special functions encountered in the diffraction of sound over the tops of hills. [Work supported by USAF, Armstrong Laboratory, WPAFB.]
The dynamic response of a window embedded in a 3-D structure to sonic boom overpressures
Authors: Martini Kyle , Garrelick Joel
Published: October 2005

Ground level sonic boom overpressures are often in the linear acoustic regime, allowing structural damage assessments to be performed using structural acoustic techniques. In this talk the boom-induced dynamic response and stress of a glass window is computed. The window, modeled as an elastic thin plate, is embedded in an enclosure that may also be elastic. Solutions are obtained numerically using nashua, a general purpose finite element/boundary element computer code. Peak response/stress is calculated as a function of the relative orientation of the incident wave in azimuth and elevation, the former determined by the flight path and the latter by the Mach number. For a given boom spectrum level, the peak response probability density function (PDF) is calculated assuming a uniform probability of flight direction. By invoking structural acoustic reciprocity, this is related to the directivity of the pressure radiated by a force applied to the window at the peak response location. Finally, the effects of enclosure baffling on the surface pressure itself is presented and compared with free field and infinite baffle approximations. [Work sponsored by Armstrong Laboratory, WPAFB, U.S. Air Force.]
A nonlinear traveling-wave amplifier model of the cochlea
Authors: Hubbard Allyn E. , Gonzales Denise A. , Mountain David C.
Published: October 2005

A traveling-wave model of the cochlea [A. E. Hubbard, Science 259, 68–71 (1993)] is comprised of two transmission lines coupled tightly by feedback. The model works because the variable speed of the traveling wave on one transmission line, a classical long-wave model, slows over a region to match approximately the natural propagation velocity of the second line. When this happens, amplification occurs. A fundamental difference between this model and many other active models is that power is generated principally in the tip region of the response, not in the region basal to the tip. The traveling-wave amplifier model replicates several experimental results: stapes/basilar-membrane-velocity ratios versus frequency and the effects of cochlear damage. The original model has been changed so that inter-line coupling function is nonlinear. Basilar-membrane velocity responses having good correspondence with experimental data have been obtained using click pressure stimuli at varying levels. The distortion product emission (DPOE) 2f1−f2 produced by the model shows qualitative correspondence with experimental data. [Work supported by ONR and NIH.]
Local wave dispersion in the cochlea
Authors: Dimitriadis Emilios K. , Chadwick Richard S.
Published: October 2005

Fine tuning in the cochlea is attributed to interactions in the gap between the tectorial membrane (TM) and the reticular lamina (RL). Acoustically driven traveling waves are controlled by outer-hair-cell (OHC) activity triggered in response to TM–RL relative motions. Variable geometry makes the dispersion of these waves location-specific. Here, such local dispersion diagrams (complex wave number, k, frequency, ω, axial position, z) for the cochlea with emphasis on the manifestation of dispersion within the TM–RL gap are constructed. The model employs a two-mode cochlea cross section that includes fluid loading both within and outside the gap. The two degrees of freedom represent basilar and tectorial membrane motion. Insights are sought into the allowed wave types, their localization along the cochlea, and the nature of the vibration modes. Future, more sophisticated models follow from these insights. Here, it is found that the gap presents a complex impedance to the traveling waves. The dissipative component of the gap impedance is strongly dependent on location z, for a given k and ω. This greatly affects the TM–RL relative phase, and hence, for a given frequency, a place principle.
Stability analysis on the time-domain finite-difference solution of a basilar-membrane vibration model: Application to acoustic signal processing
Authors: Deng L. , Kheirallah I.
Published: October 2005

In the past several years, models for nonlinear wave motions in the basilar membrane based on the hydrodynamic principle and on the biophysical mechanisms of the cochlear function have been developed. The significance of such models can be projected to be their potential applications in designing front-end components of advanced speech processing systems, as well as in serving a powerful tool for studying information processing in central parts of the auditory system. Unfortunately, computer simulations of the models in the past had been exceedingly slow and sometimes unstable, which had prevented use of the models in many possible speech-processing applications. In this paper numerical properties of a finite-difference scheme for the time-domain solution of a one-dimensional nonlinear transmission line basilar membrane model are studied. In particular, the von Neumann method is applied to obtain a sufficient condition under which the finite-difference solution to the model is guaranteed to be stable. The utility of this condition is that it determines the optimal time and spatial mesh sizes, thereby guaranteeing a minimal amount of computation in obtaining stable and accurate model outputs. Also presented are preliminary results on applying the basilar-membrane model, based on the most efficient computation schemes derived from the stability analysis, to process speech signals.
Global and local parameter and response attributes in a box-cochlea model
Authors: Wilson Timothy A. , Siebert William M.
Published: October 2005

The similarities and distinctions among linear, passive, cochlear models of one-, two-, and three-dimensional fluid motion—models popularized by (among others) Zwislocki, Ranke, and Steele, respectively—are confounded by fuzzy terminology (e.g., ‘‘long-wave’’ and ‘‘short-wave’’). Such models are frequently evaluated by comparing their place responses with measured frequency responses; their global impedance parameters are sometimes chosen solely to secure fit to local observations. Steele’s WKB (phase-integral) approach is often treated as a technique for solving cochlear dynamical equations rather than as a conceptual framework yielding insight into cochlear phenomena. In this presentation, cochlear dynamical equations are developed for one-, two, and three-dimensional fluid motion in a box-cochlea model. The phase-integral approximate solution to these equations is described; the utility of this framework for explaining cochlear phenomena is discussed. Generalized representations for both cochlear-partition impedance and cochlear-gain response are developed highlighting the similarities and distinctions between the place response at a single frequency and the frequency response at a single place. The generalized representations clarify which aspects of partition impedance determine global features such as cochlear maps and which aspects determine local features such as magnitude-response peakiness and phase-response steepness.
The use of focused ultrasound for stimulation of receptor’s nervous structures
Authors: Gavrilov Leonid R.
Published: October 2005

It has been shown that short and relatively intense pulses of focused ultrasound (FUS) are able to stimulate selectively a variety of nervous structures [L. R. Gavrilov, Ultrasonics 22, 132–138 (1984)]. Different tactile, temperature (warmth and cold), and various pain sensations can be produced in the skin at the surface of the body. Pain sensations can also be produced in deep-seated structures, e.g., joints and muscles. Pulsed FUS acting on electroreceptors of skates induced spikes of neuronal activity. Stimulation of the ear labyrinth in humans with normal hearing by amplitude-modulated FUS induced hearing sensations that corresponded to the envelope of the amplitude-modulated ultrasonic signal. In similar circumstances deaf people, with clinically diagnosed destruction of the hair cells in the labyrinth, perceived the FUS signals. The mechanism of all these physiological phenomena has been attributed primarily to a mechanical effect of the FUS stimulation of the nerve structures. FUS stimulation has been applied successfully to the clinical diagnosis of a number of neurological and dermatological diseases and hearing disorders involving changes in the perception of various sensations.
Vibrotactile sensory characteristics
Authors: Verrillo Ronald T.
Published: October 2005

Human responses to mechanical vibrations delivered to the surface of the skin are given for frequencies between 0.4 and 500 Hz. Vibrotactile response characteristics are given for the threshold of detectability, suprathreshold measurements and for a number of subject variables, including gender and age. Also presented will be the linkage between psychophysical results and underlying neural mechanisms that mediate mechanoreception in cutaneous tissue. [Work supported by grants from NIH, NIDCD.]
Tactile response of ultrasound exposure in humans
Authors: Dalecki Diane , Child Sally Z. , Raeman Carol H. , Cartensen Edwin L.
Published: October 2005

In this investigation, acoustic radiation force was used as a stimulus to determine the threshold for tactile perception in the human finger and upper forearm as a function of frequency and pulse length. Initially, a small (1.8 cm2) acoustically reflecting disk was affixed to the anatomical exposure site to maximize the delivered radiation force. Exposures were performed using a 2.2-MHz unfocused source modulated to produce square waves at 50, 100, 200, 500, and 1000 Hz. For the finger, maximum tactile sensitivity occurred at 200 Hz with a threshold radiation force of ∼0.4 mN. For single pulses of 1 to 100 ms at 2.2 MHz, threshold radiation forces were an order of magnitude greater than for continuous exposure at 200 Hz. Subsequently, thresholds of tactile perception were determined for direct exposure of the upper forearm (avoiding bone) to single pulses of 2.2-MHz ultrasound. Comparison of perception thresholds with and without the reflecting material over the forearm were consistent with the hypothesis that the tactile sensation experienced when tissue is exposed to ultrasound is its response to the radiation force associated with the transfer of momentum from the sound field to the tissue medium.
Measurement of the vibrational response of porcine lungs to low-frequency underwater sound
Authors: Lewis Thomas N. , Martin James S. , Rogers Peter H.
Published: October 2005

Because of their high compliance, the lungs are probably more susceptible to injury from low-frequency underwater sound than any other part of the anatomy. Therefore, it is desirable to have a complete understanding of the vibrational response of the lungs to underwater sound. The NIVAMS (noninvasive vibration amplitude measurement system) was used to measure the response of the lungs of an animal model (domestic pigs) to low-frequency underwater sound. NIVAMS uses continuous wave ultrasound to measure lung vibrational displacement amplitudes invivo. Advantages of the NIVAMS are that it is noninvasive (no surgery is required to make the measurements) and that it is nonintrusive (the motion is unaltered by the measurement process). Displacements were measured in two locations, between the ribs and upward through the diaphragm. A PUBA (porcine underwater breathing apparatus) was developed to allow measurements to be made below the water surface. Displacements measurements were found to be significantly larger than the particle motions associated with the acoustic pressure driving the air filled lungs. Multiple resonances were found in the response curves. The necessity for the use of live, intact subjects was demonstrated by differences in the response curves for other conditions. [Research supported by ONR.]
Selective anti-cancer drug enhancements with therapeutic ultrasound
Authors: Tata Darayash , Tritton Tom R. , Wu Junru , Dunn Floyd
Published: October 2005

Continuous wave 1-MHz ultrasound at the therapeutic intensity of 1 W/cm2 was found to enhance significantly the hydroxyl radical production from two clinically employed redox cycling drugs, viz., Adriamycin (Doxorubicin) and Mitomycin C, with respect to the control drug-free insonicated phosphate buffer suspension. Benzoic acid (Bz) was employed as a sensitive chemical probe to detect hydroxyl radicals (OH⋅). Bz is initially nonfluorescent and upon aromatic hydroxylation becomes permanently fluorescent. A series of time course studies up to one-half hour were performed on drug suspensions to characterize the OH⋅ generation in the presence and absence of ultrasound at 37 °C. Identical ultrasound treatments on non-redox cycling clinical drugs 5-Fluorouracil and Methotrexate did not yield any significant enhancement in the production of OH⋅ in comparison to the drug-free insonicated phosphate buffer suspension. One-half hour ultrasound exposures did not yield measurable changes in the chemical constitution of the four drugs as assessed through high-pressure liquid chromatography. Identical ultrasound treatments at 3 MHz did not produce at OH⋅ in the presence or in the absence of these four anti-cancer drugs. Free radical scavengers such as mannitol, superoxide dismutase, catalase, and a transition metal chelating agent were employed independently to discern the chemical species and pathways involved in the production of the OH⋅. The findings strongly implicate an active role of acoustically induced cavitation in potentiating redox cycling drugs via chemical reduction and, thereafter, production of the OH⋅ via Fenton’s pathway.
The effects of aging on temporal summation in the Pacinian (P) channel
Authors: Checkosky Christine M. , Gescheider George A. , Beiles E. J. , Bolanowski Stanley J. , Verrillo Ronald T.
Published: October 2005

Threshold for detecting vibratory stimuli of variable duration were measured in 16 subjects ranging in age from 19 to 81 years. The 250-Hz vibratory stimuli were applied to the thenar eminence of the hand through a large (2.9 cm2) contactor, selectively activating the P channel in glabrous skin. Detection thresholds were higher in older than in younger subjects. Correlation coefficients for the relation between threshold and age ranged from 0.94 to 0.96 depending on signal duration. In addition, the amount of temporal summation was negatively correlated with age. Both the elevated detection thresholds and the reduced amount of temporal summation in elderly subjects may be partially due to the decrease in the number of Pacinian corpuscles in the hand that occurs with aging. Another factor that could be responsible for the reduced temporal summation in older as compared to younger subjects is impairment of the temporal integrator. [Work supported by NIH, NIDCD.]
Tactile forward masking in Pacinian and non-Pacinian channels
Authors: Makous James C. , Gescheider George A. , Bolanowski Stanley J.
Published: October 2005

Four subjects were tested with a forward masking paradigm to determine the time course of masking in the Pacinian (P) and a non-Pacinian (NPI) channel. Stimuli presented to the thenar eminence were either centered below 27 Hz or at 500 Hz to preferentially activate the NPI or P channels, respectively. Two-interval forced-choice tracking was used to measure thresholds. A masking stimulus was presented 100 ms after each interval onset and a test occurred in one of the two intervals at some specified delay (delay t) relative to the masking stimulus. Delta t was varied from 10 to 1000 ms and the masking stimulus level varied from 5 to 25 dB above thresholds in 5-dB steps. The results showed that the masking functions varied significantly with delta t. At longer delta t’s there was less masking that followed an exponential decay. The results from the individual channels differed from each other with respect to the slope of the masking functions and the exponential decay of masking with delta t. The time constants for the PC channel ranged from 20 to 40 ms, whereas the time constants for NPI ranged from 50 to 120 ms. [Work supported by NIH, NIDCD.]
The Fessenden oscillator: History, electroacoustic model, and performance estimate
Authors: Rolt Kenneth D.
Published: October 2005

The first practical man-made sonar oscillator, conceived and designed by the Canadian Reginald A. Fessenden, was a 540-Hz air-backed electrodynamically driven clamped-edge circular plate. Work on the oscillator started in 1912 while Fessenden was working for the Submarine Signal Company, Boston, MA. In January 1914, in Boston Harbor, underwater communication was first shown by using a Morse code carrier to modulate the oscillator, thus demonstrating a means of ship–submarine acoustic communication. In March 1914, the oscillator was later tested aboard the U. S. Coast Guard cutter Miami on the Grand Banks, off Newfoundland Canada, where echo ranging from a 3200-m distant iceberg and depth sounding were demonstrated. In 1915, the oscillator was even tested at 100 kHz. The Fessenden oscillator models (ca. 500, 1000, and 3000 Hz) were so successful that they were even used until, and during, World War II for sonar and mine detection purposes. Despite these landmark achievements, at present no oscillators are known to exist, and no modern acoustic measurements have ever been made to establish the acoustical performance. To partially fill in this gap, the Fessenden oscillator, will be described and an electroacoustic model will be used to predict the acoustic performance.
Application of the T-matrix method to the numerical modeling of an array of active acoustic transducers
Authors: Baker Steven R. , Scandrett Clyde L. , Ruiz Arthur
Published: October 2005

The conventional T-matrix method is a procedure for the computation of the far-field scattering of a plane wave by a compact but otherwise arbitrary collection of scatterers [cf. V. V. Varadan and V. K. Varadan, J. Acoust. Soc. Am. 70, 213–217 (1981)]. Its strength is that the effects of multiple scattering to all orders are rigorously and self-consistently obtained from the single-scattering properties of each scatterer in a free-field environment. For acoustic waves, the T-matrix method has been extended to the case where the source of the scattered radiation is the scatterers themselves, i.e., to the case of an array of active transducers. As an example, the method has been applied to an array of piezoelectric spherical shell sonar transducers. A description of the T-matrix method applied to active acoustic arrays will be given. The use of the finite-element code ATILA [J. N. Decarpigny etal., J. Acoust. Soc. Am. 78, 1499–1507 (1985)] to compute the single-transducer radiation and scattering properties will be described. Results will be compared to Pritchard’s approximation. [Work sponsored in part by the Naval Postgraduate School and the Naval Undersea Warfare Center.]
Comparison of the coupling between two flexural underwater transducers computed using the finite-element method and the Pritchard approximation
Authors: Cortambert Jean-Marc , Baker Steven R.
Published: October 2005

Understanding the coupling between transducers in the array becomes fundamental to proper beam forming in the active sonar array. The paper presents the study of two-dimensional, axisymmetrical closely spaced, class V flexural disks. The analysis was performed by using a finite-element program, ATILA, developed to compute easily the near-field radiated pressure between the two double trilaminar disks. Their self and mutual impedance are computed and compared to those obtained by the Pritchard formula. The distance between the two transducers is optimized to point out multiple scattering when it occurs. The goal of the study is to correlate the limit of the validity of the Pritchard formula with the distortion of the near-field pressure between the transducers. The results are compared with the impedance measurement of the flexural disk and the pressure field near the transducers. [Work supported by the French Delegation Generale pour l’Armement and the Naval Postgraduate School.] a)Permanent address: DCN Toulon, CERDSM, BP77 Toulon 83 000, France.
Transducer array interaction modeling using variational principles
Authors: Robinson Harold C.
Published: October 2005

The radiation impedance acting on a pair of fluid-loaded sonar transducers is calculated using a variational principle for radiated power developed by Pierce [IEEE Trans. Ocean Eng. OE-12, 404 (1987)]. The structural motion of each transducer is approximated as a series of in-vacuo resonance modes linked via the fluid loading. These in-vacuo modes can then be utilized to determine the surface pressure on each of the transducers variationally. The normal velocities and surface pressures determined variationally are substituted into the expression for the radiated power. By separating the contributions of each structural mode to the radiated power, the mutual radiation impedances between each transducer mode can be calculated [C. H. Sherman, ‘‘General Transducer Array Analysis,’’ Cont. N00014-67-C-0424, Parke Math. Labs., Carlisle, MA (February 1970)]. Judicious summations of these contributions lead to the self and mutual radiation impedances of the transducer as a whole. Radiation impedance calculations as a function of dimensionless separation distance kd for a pair of baffled unimodal pistons and a pair of flexural disks will be presented and compared with existing theoretical predictions. [This work was sponsored by the Office of Naval Research.]