bluuebunny/crossref_metadata_2025 huggingface dataset:
Momentum transfer in jet excitation of flute-like instruments
Authors: Coltman John W.
Published: October 2005

The excitation of flutes and organ pipes takes place partly by transfer of jet momentum, and partly by insertion of a pulsating volume of air into the pipe. An experimental determination of the relative importance of these two mechanisms was made by exciting a symmetrical resonant pipe with a pulsed jet source whose direction could be varied. The change in response with direction of the jet served to distinguish momentum transfer excitation from volume insertion excitation. The momentum effects were roughly of the magnitude expected, but the phase of the excitation, and the variation with steady airflow did not follow the simple theory. Momentum transfer was also demonstrated in a blown pipe.
A reply to Cohen et al.’s ’’Weighty voices and shaky evidence: A critique’’ [J. Acoust. Soc. Am. 68, 1884–1886 (1980)]
Authors: Lass Norman J.
Published: October 2005

Because of their omission of available data in published height and weight identification studies, as well as methodological differences between these studies and their weight-guessing experiment, Cohen et al. ’s [J. Acoust. Soc. Am. 68, 1884–1886 (1980)] conclusions appear to be unjustified.
A new procedure for venting a reflectionless tube
Authors: Hillman Robert E. , Weinberg Bernd
Published: October 2005

A reflectionless tube technique for estimating glottal waveforms has been described in the literature. Reflectionless tube construction has generally incorporated the insertion of a lateral vent to relieve air pressure which builds up within the tube during phonation. Data are provided which reveal that satisfactory relief of air pressure within the tube is not accomplished using lateral vent placement. A novel central venting procedure is described and is shown to provide satisfactory relief of air pressure build-up without disruption of the acoustic (anechoic) properties of the tube.
Detecting the presence of vocal disguise in the male voice
Authors: Reich Alan R.
Published: October 2005

This research examined the ability of naive and sophisticated listeners to detect extemporaneous disguise in the male voice. The experimental stimuli were sentences uttered in an undisguised and in a freely disguised fashion. The listeners were asked to decide whether a sentence was disguised or undisguised and to rate his/her degree of confidence in each decision. Both naive and sophisticated listeners were able to detect the presence of these particular disguises with a high degree of accuracy and reliability.
Spectral variance of aeroacoustic data
Authors: Rao Kodali V. , Preisser John S.
Published: October 2005

An asymptotic technique for estimating the variance of power spectra is applied to aircraft flyover noise data. The results are compared with directly estimated variances and they are in reasonable agreement. The basic time series need not be Gaussian for asymptotic theory to apply. The asymptotic variance formulae can be useful tools both in the design and analysis phase of experiments of this type.
Bleustein–Gulayev surface modes in elastic ferroelectrics
Authors: Pouget J. , Maugin G. A.
Published: October 2005

On the basis of a nonlinear theory of elastic ferroelectrics linearized about a fundamental ferroelectric state, it is shown that the symmetry breaking caused by the initial intense polarization orthogonal to the sagittal plane allows for the existence of Bleustein–Gulayev surface modes in ferroelectrics of the barium titanate type. The two cases of a free boundary and a grounded boundary are examined. In the first case it is shown that above a certain critical wavenumber (interaction of elastic and ferroelectric modes) the exponential decrease with depth of the amplitudes is sinusoidally modulated while there exists a minute dispersion of the mode. In the second case the Bleustein–Gulayev mode which is exhibited is strongly dispersive in the neighborhood of this critical wavenumber (which then corresponds to a unilateral repulsion of dispersion branches). All the features of this surface-wave propagation problem are examined both analytically and numerically (for BaTiO3) with a particular emphasis on second-order effects (corrective effects) and the appearance of boundary-layer effects connected with the influence of polarization gradients which account for the ordering proper to ferroelectrics.
Psychophysical tuning curves independent of signal level
Authors: Green David M. , Shelton Brian R. , Picardi Maria C. , Hafter Ervin R.
Published: October 2005

Psychophysical tuning curves were obtained for three subjects in a forward masking paradigm, with signal levels of 21, 30, and 50 dB SPL at 1000 Hz and 30, 40, and 50 dB SPL with a 3000-Hz signal. All tuning curves were measured in quiet and with a background noise adjusted to produce a constant signal-to-noise ratio of E/N0 = 15 dB. The results indicated that the tuning curves obtained in quiet change shape with increasing signal level, whereas the shapes of tuning curves measured in noise are the same at all signal levels. A control condition demonstrates that only signal energy in a narrow band near the signal frequency is useful in detecting the signal. This control along with the invariance of tuning curve shape with signal level support the interpretation that the broadening of tuning curves with increased signal level, observed when the signals are presented in quiet, is caused by the presence of off-frequency components.
Stationary response of a finite cable to a correlated moving turbulent force field
Authors: Alberti Frank P.
Published: October 2005

Following the method of Lyon [J. Acoust. Soc. Am. 28, 391–398 (1956)], the stationary response of a finite cable to a correlated moving turbulent force field is determined. The source correlation function assumed is not simply exponentially decaying (to reflect a loss of correlation) but harmonically varying, exponentially decaying [M. Yildiz, Univ. of New Hampshire (1974)]. The results obtained yield an expression for the mean-square response which, upon making proper limiting assumptions, reduces to results previously obtained by Lyon when the assumed harmonicity of the source correlation is omitted.
Frequency dependence of the acoustic radiation force function (Y
p) for spherical targets for a wide range of materials
Authors: Anson L. W. , Chivers R. C.
Published: October 2005

In a previous communication the authors reported a procedure for calculating Yp for spherical radiometer targets over wide ranges of ka, identifying the importance of fine steps in ka for accurate representations. The present paper summarizes the results of the calculation Yp, over the ka range 0–20, for over 50 different materials which are assumed to be immersed in water. A primary grouping according to material shear velocity and density is proposed. Material density has a substantial effect upon the form of the maxima and minima of the Yp curves, a low density producing higher maxima, deeper minima, and increasing the width of these features. The present calculations do not give a shear indication of the effect of the Poisson’s ratio of the material, nor explain the extremely high maxima at low wave velocities.
Nonlinear equations of acoustics, with application to parametric acoustic arrays
Authors: Tjo/tta Jacqueline Naze , Tjo/tta Sigve
Published: October 2005

The propagation and interaction of finite amplitude sound waves produced by a baffled piston source in a thermoviscous fluid are considered. Basic equations are derived and their ranges of validity established. This is used to relate some earlier works by others on nonlinear model equations in acoustics. Applications are made to the theory of parametric acoustic arrays, where the effects of nonlinear attenuation are discussed.
Investigation of chemical sound absorption in sea water: Part II
Authors: Mellen R. H. , Browning D. G. , Simmons V. P.
Published: October 2005

Resonator measurements of relaxational sound absorption by boric acid in artificial sea water exhibit pH anomalies similar to that observed in aqueous solution. Discrepencies between theory and experiment indicate that the simple two-step relaxation model is inadequate. However, the results are in good agreement with sea measurements in the sea water pH range.
Suppression of auditory nerve responses I: Temporal analysis, intensity effects and suppression contours
Authors: Javel Eric
Published: October 2005

Two-tone suppression was studied in response patterns of single auditory nerve fibers in anesthetized cats. Utilizing suppression of discharge synchronization in response to low- and moderate-frequency tones as an index, it was found that (a) suppression behaves in the same manner when the suppressor tone presented alone is strongly excitatory as when it is ineffective in altering discharge rate; (b) suppression exists throughout an auditory nerve fiber’s response area; (c) for fixed-intensity suppressors, suppression is maximal at a fiber’s characteristic frequency; and (d) suppression magnitude over a wide intensity range depends only upon the parameters of the suppressor tone and not of the tone being suppressed. The data are in general agreement with previously published reports of suppression behavior, and they support the concept that suppression is generated primarily as a result of interactions occurring within hair cells or in the subtectorial space.
Acoustic coupling between two finite-sized spheres; n = 2 mode
Authors: Reese J. Mark , Thompson William
Published: October 2005

The modification of the radiation impedance load on a spherical source vibrating in the third or n = 2 axisymmetric mode, caused by the nearby presence of another equal sized sphere which is either vibrating in that same mode (in-phase or 180° out-of-phase) or is a perfect scatterer (rigid or soft), has been calculated. Plots of the normalized resistive and reactive components of the modified radiation impedance are presented as a function of the wavelength separation distance between the two spheres.
Prototype laser auditorium reflection simulator
Authors: Terroux Peter
Published: October 2005

Development of a device for modeling of multiple reflections in two-dimensional representations of rooms. The self-contained unit developed employs a fixed laser, the beam of which is rotated using a motorized front-surface mirror, a steel plate to which plan or section drawings of rooms can be attached with magnets and a selection of mirror units, magnet attached, which can be rapidly re-oriented to change the room geometry. Multiple reflections from low-power lasers can be difficult to see; to overcome this problem, the beam is made visible by means of a smoke generator introducing smoke into a forced-draft, closed-loop, recirculation system, which includes the simulation chamber. The simulation chamber is accessed by a vertical sliding window, safety-interlocked to prevent exposing users to the laser beam, and the window itself protects observers from the beam since it strikes the glass at an angle which is less than the critical angle. The device makes fifth and higher order reflections visible and, due to the safety features incorporated, is suitable for classroom use, as well as for auditorium reflection pattern analysis.
Examination of the effect of source location on sound power measurement at low frequencies
Authors: Lang Mark A. , Rennie James
Published: October 2005

An analysis of the relationship between source location and measured sound power output of discrete frequency sources in reverberation rooms is presented, based on data obtained during the qualification of the 94 m3 reverberation room at the Centre for Building Studies. Total measurement uncertainty is evaluated at several source positions for both a bare chamber and for the final configuration with a rotating diffuser and low-frequency absorption. A high total measurement uncertainty at low frequencies proved to be the major obstacle to qualification as has been observed in numerous other studies (see for example the Sept.–Oct. 1976 issue of Noise Control Engineering). The modifications to the room and averaging over some positions reduced the measurement uncertainty to acceptable limits. It was observed that source position averaging was ineffective for the bare chamber configuration as pressure/frequency responses were highly correlated for different source positions. The addition of diffusing elements and low-frequency absorption increase modal overlap and result in less correlated pressure/frequency responses between source positions and hence improve the averaging effectiveness. [Work supported by NSERC.]
Interactive role of formant transitions and steady-state spectral characteristics in the perceptual identification of nasal consonants
Authors: Recasens Daniel
Published: October 2005

Test sequences with VC stimuli for V = /a/ and C = unreleased /n, ɲ,ŋ/, were prepared using a software serial formant synthesizer. Transition ending point frequency values and nasal steady-state spectral patterns for /an/,/aɲ/, /aŋ/ were chosen as fixed and variable parameters and combined reciprocally. Several speakers of a language (Catalan) that allows the presence of unreleased /n, ɲ,ŋ/, in absolute final position took the perception test. Preliminary results indicate that while steep rising F2 and F3 transitions are the main perceptual cues for /ɲ/ identification, an optimal pattern of steady-state resonances and antiresonances is essential for /ŋ/ recognition. Appropriate transition and spectral characteristics are needed for a satisfactory /n/ identification. These findings are related to two important facts of acoustic theory of speech production: acoustic stability corresponding to substantial articulatory changes at place of palatal constriction and distinctive acoustic effects shown by the oronasal cavity system for /ŋ/. Further research on the phonemic identification of the palatal stimuli is to be done with speakers of American English.
Acoustical effects of shallow fronts in the deep ocean on short-range propagation
Authors: Rousseau T. H. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

The effects of sound-speed variations produced by shallow (less than about 300 m) deep-ocean fronts on short-range transmission between surfaced source and receiver are investigated using ray theory. A parametric model of such fronts, based on observational data, is constructed via sound-speed profiles which are trilinear with depth. The model is sufficiently general to permit determination of acoustical effects for fronts of varying strengths, vertical extents, and positions relative to the propagation range. Frontal influences on travel time and geometrical spreading loss are examined, and expressions for per-ray amplitude and phase are developed. Then, the dependence of total-field amplitude and phase for cw transmissions on frontal strength, vertical extent, and relative location are determined. All these frontal quantities are demonstrated to produce significant acoustical variations, such as total-field intensity changes of more than 6 dB depending on frontal location. Simple and accurate approximations to both per-ray and total-field variations are presented which could be useful in predicting changes in these quantities due to shallow fronts. [Work supported by ONR.]
The effect of compression limiting on the speech intelligibility of sensorineural hearing impaired listeners
Authors: Bustamante Diane K. , DeGennaro Steven , Braida Louis D. , Durlach Nathaniel I.
Published: October 2005

The purpose of this study was the evaluation of multiband compression limiting designed to protect hearing-impaired listeners from high-level speech and environmental sounds. The relative performance of two linear and four compression-limiting systems has been measured for two subjects with flat sensorineural losses. The test materials, consisting of nonsense CVC syllables spoken by male and female speakers, were presented over a 30-dB range of input levels. The subjects chose an overall listening level consistent with both maximum intelligibility over the range of input levels and long-term listening comfort. Preliminary results indicate that both higher average presentation levels and increased speech intelligibility scores are associated with compression limiting relative to linear amplification. [Work supported by NIH.]
Measurements of low-frequency wind-generated ambient noise in the deep ocean
Authors: Bannister R. W. , Denham R. N. , Guthrie K. M. , Browning D. G.
Published: October 2005

Southern Hemisphere oceans provide unique conditions for the measurement of low-frequency wind-generated ambient noise due to their relatively low shipping densities. Results (10–500 Hz) for a single location in the South Fiji Basin [R. W. Bannister, J. Acoust. Soc. Am. 60(S1), S20(A)(1976)] supported the two principal noise generation mechanisms that have been suggested: turbulence, bubbles and spray. For a given local wind speed, higher noise levels were observed than have been reported for the North Atlantic Ocean. This paper is an analysis of wind-generated noise data from additional sites throughout the Tasman Sea—Fiji Basin region. Variation in measured level is compared to wind speed, seastate, and propagation conditions. It appears that local wind-speed is not an absolute indicator of wind generated ambient noise level. [Work supported by NAVSEA.]
Acoustical properties of a porous plate
Authors: Lockwood J. C. , Benthien G. W.
Published: October 2005

The acoustical properties of a porous metal plate are modeled and expressions are obtained for through-transmission impedance and fractions of power reflected, transmitted, and absorbed. The plate is modeled as a rigid boundary of thickness much smaller than the acoustic wavelength. A fraction of the surface is assumed to consist of holes of a given diameter. An expression applicable to incompressible, oscillating flow in a tube is used to predict the velocity distribution in the holes as a function of the acoustic pressure drop across the plate. The acoustic velocity immediately on either side of the plate is taken to be the average velocity on the surface taken over both the rigid area and the area occupied by holes. The acoustic properties are expressed in terms of the operational impedance defined as the ratio of the pressure drop to the average velocity. Calculated results for specimen impedance and fractions of power reflected, transmitted, and absorbed agree well with a set of in-water acoustical measurements reported by Fand, Gogos, and Jackson [J. Acoust. Soc. Am. 41, 530 (1967)].
On the depth dependence of the bubble pulse
Authors: Epstein D.
Published: October 2005

Many years ago [D. Epstein, J. Acoust. Soc. Am. 35, 800 (A) (1963)], the author analyzed a representative deep-fired long-range underwater explosion waveform. The most striking feature was the so-called double shock formation, e.g., a strong resemblance between the shock wave and bubble pulse in both amplitude and shape. Indeed, Fourier analysis showed that the influence of the bubble pulse was not confined to the low frequencies but that it interfered throughout the spectrum. Part of this may be attributed to a “propagation effect,” but according to the theory advanced here it is also partially due to an increase in bubble pulse amplitude vis-à-vis the shock wave with increase in firing depth. M. Blaik and E. A. Christian [J. Acoust. Soc. Am. 38, 50 (1965)] analyzed an extensive series of shots and fitted the bubble pulse data with the formula PbW1 3/r, where Pb = 4200 psi. My analysis shows that Pb is not constant but that it is a slowly varying function of the depth. Pb(z) is roughly proportional to zα where it is estimated that 1/9 > α > 1/7.
Age effect on speech perception in reverberation
Authors: Nábělek Anna K. , Jennings Evelyn
Published: October 2005

The Modified Rhyme Test (MRT) was processed through a room (volume 165 m3, reverberation time T= 0.4, 0.8, and 1.2 s). The tests were recorded for binaural and monaural earphone listening with a manekin Kemar and equalization amplifiers to compensate for the ear canal effect. Six groups of normally hearing subjects, 10 subjects each, had mean ages of 10, 27, 42, 54, 64, and 72 years and average Hearing Threshold Levels (HTLs) (for 0.5, 1, and 2 kHz) of 4, 6, 10, 14, 18, and 18 dB, respectively. The individual scores for MRT without reverberation were between 90% and 100%. The mean group scores for the 27-year-old group were the same for unreverberated speech and 0.4-s condition but declined for 0.8- and 1.2-s conditions. All other groups performed poorer than the young adults, e.g., the scores of the 72 year olds and the children were 16% and 8% lower, respectively. In all comparisons, the binaural scores were better than monaural ones by an average of 5%. There was a tendency for greater binaural advantages for older subjects. [Work supported by NIH.]
The effects of noise and reverberation on the intelligibility of speech processed through educational amplification systems
Authors: Sinclair J. Stephen , Sanders Jay W.
Published: October 2005

This study investigated the effects of noise and reverberation on the intelligibility of speech amplified through a hearing aid and two FM-wireless systems. Monosyllabic word lists were recorded through these instruments under anechoic and reverberant conditions with mean reverberation times of 0.0, 0.5, and 1.33 s. A multitalker babble was also recorded to provide a competing noise. The recordings were presented to 30 normal-hearing children through an earphone at 26-dB sensation level re: the subject's speech reception threshold. Presentations were made through the FM-wireless systems at a signal-to-noise ratio of +20 dB and through the hearing aid at +20, +12, +6, and 0 dB S/N ratios. The results revealed that increasing increments of noise and reverberation significantly reduced amplified speech intelligibility, that the inherent S/N ratio advantage provided by FM-wireless amplification produced superior intelligibility performance when compared to the hearing aid, and that the FM-wireless units did not perform equally well.
Signal processing for profound deafness
Authors: Villchur Edgar
Published: October 2005

An electronic model simulating the severely restricted dynamic range of hearing typical in profound deafness has been used to investigate the effect of this restriction on speech perception, and also to investigate the potential effect of signal processing designed to improve intelligibility under such conditions. The model is patterned on the average measured thresholds and discomfort levels of a group of profoundly deaf children. It rejects signal elements whose levels fall below electronic thresholds in each of ten adjacent 13-octave bands, and amplitude expanders in each band simulate the accelerated loudness growth of recruitment. Speech passed through the model is broken up by periods of silence that occur whenever signal levels drop below thesholds in all bands, and the speech becomes unintelligible. Three-channel amplitude compression restores the rhythmic pattern and some intelligibility to the speech. When compression is combined with synthetic fricatives (placed at 800-Hz center frequency), intelligibility is increased further. The performance of this model suggests that previous attempts to improve speech reception for the profoundly deaf by signal processing may have been compromised by a failure to deal with the problem of a very narrow dynamic range of hearing.
Review of sound propagation in the atmosphere
Authors: Piercy J. E. , Embleton T. F. W.
Published: October 2005

Advances in our understanding of the mechanisms of outdoor sound propagation during the last five years which are relevant to community noise problems will be discussed, and an attempt made to fit them into a consistent overall picture. One aspect is studies of ground impedance and the relevance of modelling the ground plane by a semi-infinite porous medium. Another is the contribution of theoretical papers on propagation from a point source through a homogeneous atmosphere over a plane of finite impedance. A third is the effect of atmospheric inhomogeneity—most notably scattering by turbulence and refraction by the thin (∼10 cm) thermal boundary layer close to the ground. The attenuation of barriers will also be discussed including the application of modern theory to diffraction over the top, interference effects produced by reflection from the ground, and scattering down into the diffractive shadow zone by turbulence.
Exact treatment of leaky Rayleigh waves in the presence of a layer
Authors: Chimenti D. E. , Nayfeh Adnan H. , Butler D. L.
Published: October 2005

An exact theory, supported by experimental measurements, of bounded acoustic-beam reflection near the Rayleigh angle from a fluid-solid interface loaded by a solid layer is presented. We derive an analytical expression for the reflection coefficient by applying continuity conditions appropriate for the problem geometry to wave potentials in the three media. The reflected field, including leaky Rayleigh-wave effects, is calculated by evaluating numerically the Fourier integral containing the incident beam transform and the reflection coefficient. The dispersion of the Rayleigh wave speed is deduced from the behavior of the reflection coefficient in the complex plane. We find excellent agreement with measurements of the wave speed over a wide range of frequency and layer thickness in stainless steel samples loaded with copper layers. The beam displacement parameter, which is also deduced from characteristics of the reflection coefficient, displays an unexpected minimum as a function of frequency. Experimental results are compared to theory for the acoustic amplitude distribution in the reflected field, both near and at the Rayleigh angle.
Finite element modeling of borehole acoustics
Authors: Chang S. K.
Published: October 2005

The sonic wave propagation of a fluid-filled cylindrical borehole in a solid formation was modeled by the finite element method. The excitation was a point source located on the axis, hence the problem was assumed to be axially symmetric. The transient waveforms at the receivers in the borehole were generated by the finite element method using the explicit time integration with lumped mass simplification. The fine time step requirement of data processing ensured the numerical stability of the explicit scheme. For a homogeneous formation the finite element generated receiver waveforms compared very well with those obtained from the real axis integration method [L. Tsang and D. Rader, Geophys. 44, 1706–1720 (1979)]. Numerical dispersion and convergence in regard to grid sizes were investigated. Synthetic waveforms for the case having two solid formations with a horizontal interface, which were still not solvable by analytical means, were generated and studied.
Influence of ultrasound on heat and mass transfer
Authors: Fairbanks Harold V. , Fairbanks V.
Published: October 2005

This paper reports several studies made at West Virginia University in which ultrasound was introduced into some heat and mass transfer systems. The frequency of ultrasound used was 20 and 50 kc/s with sound intensities up to 170 dB. The heat transfer systems investigated included: (1) solar heating of water; (2) heat conduction in metals; and (3) heat convection. It was found that the introduction of ultrasound into a system increased the heat transfer coefficient from 2 to 4 times. The mass transfer systems investigated included: (1) the stimulation of crude oil flow through porous sandstone; (2) the filtration of solids from an oil slurry: and (3) drying of powdered coal with the aid of ultrasound. It was found that the introduction of ultrasound into these different systems substantially increased the liquid flow rate through the porous media used for the processes. Also, it was noted that the constant drying rate was increased when the intensity of the airborne ultrasound used was above 130 dB. [Work supported by Coal Research Bureau, West Virginia University.]
Multiple cues to syllable-final stop cognate opposition In English
Authors: Raphael Lawrence J.
Published: October 2005

Two representative tokens of peg, taken from different contexts, were edited so that many of the potential acoustic cues to syllable-final cognate opposition were individually altered. The durational and/or spectral values of the cues were set equal to those found in typical tokens of peck. In the first experiment listeners heard the stimuli in isolation and identified them as peg or as peck. It was found that several variables were individually sufficient to cue the perception of peck. Further, every variable tested produced some perceptual effect in either or both of the edited tokens of peg. In the second experiment the stimuli were heard in their original contexts and in contexts from which peck had been excised. Results indicated that the effects of the contexts frequently overrode the effects found for the edited variables in the isolated stimuli. The extra-syllabic cues to the /k/-/g/ opposition provide another instance in which acoustic cues for speech perception are broadly distributed in the temporal domain as the result of contextually induced constraints on articulation. [Work supported by NICHD.}
A real-time phonetic synthesizer
Authors: Olive J. P.
Published: October 2005

This paper describes a small real-time speech synthesizer. The synthesizer requires as its input a string of phonemes and the associated duration, pitch, and amplitude parameters. The synthesis scheme uses a large table of stored transitions (dyads) between phonemes. These transitions are stored in terms of LPC-derived area parameters. To obtain the area parameters for a particular string of phonemes, the appropriate transitions are retrieved and their durations adjusted to reflect the desired durations of phonemes in the string. The speech synthesizer consists of an LS111/23 microcomputer, a digital signal processor chip, and a digital-to-analog converter. The microcomputer processes the input, retrieves the stored transitions, adjusts the durations, and smooths the area, pitch, and amplitude parameters across the dyadic boundaries. The smoothed parameters are used to synthesize the speech signal on the digital signal processor.
Central auditory focus in neonatal hyperbilirubinemia using evoked potentials
Authors: Lenhardt M. L.
Published: October 2005

Increase in bilirubin levels in neonates has been considered a risk factor for sensorineural hearing loss. Recent brainstem evoked potential (BEP) and electrocochleographic studies have suggested that the focus of the lesion is in the brainstem and not in the cochlea for those who have hearing loss. It was consequently postulated that every infant whose bilirubin levels are elevated have at least some temporary auditory brainstem involvement that would be reflected in the BEP waveform. All infants born in the hospital during June, July, and August, 1980 were given BEP testing using clicks at 70 and 30 dB EQSPL. Normal full term babies served as controls. For those infants, at 70 dB, wave I averaged 1.7 ms, wave III averaged 4.7 ms. and V averaged 7.0 ms. Infants with increasing bilirubin levels were recorded at 1/2-day intervals. For all jaundice infants waves III and V increased in latency as the bilirubin level increased. Wave I did not change. Conduction time, between waves III and V was within the normal range, while conduction time betwen wave I and III was abnormal. Since wave I was always normal, hyperbilirubinemia was found to specifically affect wave III which is thought to reflect activity at the second and third synapes in the brainstem. Normal neural function beyond wave III was suggested.
The effects of broadband noise on brainstem evoked potentials
Authors: Burkard Bob , Malischke Mary , Hecox Kurt
Published: October 2005

Wide-spectrum acoustic transients were presented simultaneous with continuous white noise. In study one, click intensities ranged from 20 to 60 dB nHL, in 10-dB increments, with noise intensities ranging from a no-noise condition to a perceptually based 0-dB signal-to-noise ratio. In study two, click intensity was held constant at 50 dB nHL, with noise intensities similar to those cited above, and stimulus repetition rates of 15, 40, 65, and 90 Hz. The primary dependent variable in both studies was wave V latency. These studies indicate that the effect of continuous masking noise on wave V latency is a function of absolute noise intensity, rather than signal-to-noise ratio. Further, the effect of noise intensity on wave V latency appears to be additive with click intensity and repetition rate. Preliminary data on the interaction of signal frequency and noise masker will also be presented. [Work supported by NIH.]
Auditory brainstem responses in patients with tinnitus
Authors: Mitchell Curt , Vernon Jack
Published: October 2005

Masking tones may produce a temporary cessation of tinnitus after a masker is terminated. This after-effect of masking is called residual inhibition (RI). Twelve patients with tinnitus who displayed considerable RI were used in this study. Auditory brainstem responses to tone-pips were obtained before, during, and after RI was induced. The latency, amplitude, and interpeak interval of waves I, III, and IV–V were analyzed for changes related to the presence of tinnitus. Although changes were found in some cases no consistent feature was found to be correlated with tinnitus.
MM2. The use of dynamic modeling in engine design
Authors: DeJong R. G.
Published: October 2005

Dynamic models of the rotating parts of engine structures are frequently used in engine design to meet the requirements of rotational balance and fatigue endurance. These models are usually developed for the frequency range of the engine rotation rate and the first few harmonics. There has been an interest in increasing the frequency range of these dynamic models in order to study the noise and vibra- tion characteristics of engines at audible frequencies. A major complication in doing this involves the inclusion of the modes of vibration of the engine block and their interaction with the rotating parts of the engine. The succes of these models often depends on their ability to model the distinctive characteristics of the lower order modes of the engine structure and the random characteristics of the higher order modes. Examples are given of the use of these dynamic models to design engines for low noise and vibration in certain frequency ranges. [Work supported in part by EPA/ONAC.]
Fluid loading of plates—Acoustic consequences and coincidences
Authors: Roebuck Ian
Published: October 2005

In view of recent controversy over the “leaky pole” contribution in the pressure field of vibrating fluid-loaded thin plates, this paper considers the variation with frequency of the modal behavior of a thick elastic layer immersed in fluid. The “thin plate” equation is recovered as a low-frequency, low-wavenumber approximation, but is demonstrated that this equation is significantly modified as the frequency increases to the extent that appreciable energy is stored in the fluid nearfield. The consequence is that the flexural mode which these equations describe is slower than the corresponding mode in vacuo by an increasing amount; “coincidence frequency” in the sense of phase speed equal to that of acoustic waves in the fluid is never reached—the flexural mode is subsonic at all frequencies. Ultimately it transforms continuously into the free plate wave described by Crighton [J. Sound Vib. (1979)]; his conclusions on the absence of other physically identifiable “free coupled modes” are confirmed. The role of group velocity in controlling energy transfer is specifically invoked in deriving these conclusions.
Impact response of a rope
Authors: Yen N.
Published: October 2005

The dynamic response of a rope with finite length is analyzed when one of its terminals is suddenly given an impact disturbance. Based on the strain wave formulation, it indicates that stress developed on the rope during transient stage may be many times larger than that of steady state. The magnitude of the resultant internal force depends on the Mark number of initial disturbance velocity, its wave form, and the physical property of rope. The parting of a synthetic rope even stressed below its rated break strength, according to present study, is attributed to the shock loading and the high elasticity and low loss factor property of rope's fiber.
Acoustic evaluation system from off-the-shelf instrumentation
Authors: Ledoux Claude
Published: October 2005

Electro-acoustic testing in a bounded medium has traditionally been done with the use of specialized test systems. Due to recent developments in the field of digital instrumentation, it is now possible to configure a complete test system from commercially available instruments. Off-the-shelf equipment allows the user considerable dollar savings, quick and easy test system assembly, and assures first time operation with minimal troubleshooting. This paper describes an integrated, automated, and computerized system which can be used to perform electroacoustic measurements as well as any other transfer function evaluation, such as vibration, amplifiers, filters, etc. Operating system programming can be done in most of the hi-level languages, such as FORTRAN and BASIC, or in assembly or machine languages. A brief description of user programming is furnished. Research and development facilities should find the described test system useful in performing acoustic as well as other transfer function measurements. Off-the-shelf hardware, including a positioner, software, and assembly, can all be done for about $200 000 or less. Limited production facilities should find this system adequate and large production can be accommodated by effecting minor changes in the system. [Work supported by NUSC Independent Research Program.]
A measurement of the harmonic content of a bounded ultrasonic beam
Authors: McLennan Douglas D. , Ngoc Tran D. K.
Published: October 2005

The nonlinearity of acoustic waves manifests itself via the generation of harmonics as an acoustic wave travels through a medium. This phenomenon evolving under the influence of competing mechanisms such as absorption, diffraction, and dispersion can be described for a finite source by examining changes in wave shape and beam profile. Measurements of the acoustic amplitude of the fundamental and several harmonic components across the sound beam produced by a finite source in water are presented. The sound field was produced by a plane circular transducer 2 cm in diameter and driven at a frequency of 3 MHz. Beam profiles were mapped separately for the fundamental and the first two harmonics at various distances ranging from 15 to 25 cm by use of a miniature hydrophone. The frequency response of the hydrophone was calibrated for each involved frequency by comparing the probe output to the acoustic amplitude measured simultaneously by the light diffraction technique. The significant features of the resulting profiles are found to be consistent with available theoretical results.
Parametric acoustic array formation in relaxing fluids
Authors: Fenlon F. H. , Hamilton M. F.
Published: October 2005

The effect of physical relaxation mechanisms on the formation of acoustic arrays is deduced via Gaussian beam theory for the case of weakly interacting finite-amplitude carrier waves. This theory, which permits the sum and difference-frequency fields of the nonlinear interaction to the determined throughout the near and far-field regions of the carrier wave interaction zone, clearly exhibits the effect of relaxation-induced absorption and dispersivity on the parametric array for both monorelaxing and multirelaxing fluids. In the paper the axial sum and difference-frequency pressure fields, and farfield directivity patterns are presented as functions of basic relaxation parameters in terms of suitably chosen dimensionless variables. Anticipated results in several liquid polymers are then deduced from these characteristics. [Work supported by ONR.]
Analysis of a nonlinear equation describing Helmholtz resonator response to acoustic forcing
Authors: Crighton D. G. , Innes D.
Published: October 2005

The mass flux G(t) out of a Helmholtz resonator, with resonance frequency ɷ, under the influence of grazing mean flow and external acoustic forcing with unit frequency, has been modeled by A. S. Hersh and B. Walker [NASA CR—3177 (1979)] by the forced non-linear equation |G(t)|Ġ(t) + ε[G̈(t) + ɷ2G(t)] = −sin t. (1) Numerical results were given for the first sine and cosine Fourier coefficients. Conventional analytic methods fail on (1), where the essential balance is between forcing and nonlinear radiation damping. Here we use asymptotic methods for small ε to predict the entire waveform G(t). The numerical results are recovered, but the functional forms previously assumed for them are shown to be in error and are convected. Both off-resonance and near-resonance ɷ close to 1) cases are treated; the methods are widely applicable to problems of forced nonlinear oscillations.
Segmental durations in connected speech signals
Authors: Crystal T. H. , House A. S.
Published: October 2005

From the readings, by many talkers, of two scripts of approximately 300 syllables, two groups of seven talkers were selected on the basis of overall reading time to form a group of fast talkers and a group of slow ones. The phonetic makeup of each script and of the first two sentences of each script were analyzed to determine if they represented American text. The entire readings were segmented, using computer graphics and digital playback, into breath groups and pauses; and the first two sentences of each into phones. Average numbers and durations of breath groups and pauses were computed as a basis for categorizing talkers according to their natural tempo. (These data can be compared to those based on “unnatural” tempos obtained by having individuals speed or slow their reading.) Differences between the groups were also noted in the average durations of various categories both in and out of context. Finally, probability distributions were obtained for the durations of various categories.
Synthesis by rule of a female voice
Authors: Klatt Dennis H.
Published: October 2005

Most speech synthesis-by-rule systems mimic the speech of a male talker. The reason is simple—the speech analysis tools that are available measure formant frequencies with greater accuracy when fundamental frequency is low, as in a male voice, and formant frequency data is essential when driving a formant synthesizer by rules. The research to be described attempts to convert an existing rule system (KlaTTalK) to a female voice quality through a judicious combination of theory and measurements on a particular female voice. The following steps were taken to this end: Fundamental frequency was scaled by a simple multiplicative factor of 1.8. Formant frequencies for vowels were scaled initially by “k factors” published by Fant to take into account differences in average formant sensitivity to changes in the length of the oral and pharyngeal vocal tract between males and females. The scaled formant values were then modified in some cases to better match observed data from the selected speaker. K factors were also extrapolated to apply to consonant articulations. Then formant bandwidth targets and parallel-branch amplitude targets were adjusted so as to match relative formant peak heights in selected consonant—vowel syllables. A demonstration tape will be played of the resulting synthetic voice.
TTS and the time pattern of noise exposure
Authors: Hétu Raymond
Published: October 2005

TTS is related to the time pattern of noise exposure in a relatively complex fashion. This relationship essentially involves the on-fraction, the intermittency period, and the sound level during noise bursts and quiet intervals. Data from recent studies on the influence of these exposure parameters and more specifically of their mutual interactions is reviewed. Unpublished data is presented on the effect of the interaction between the on-fraction and the intermittency period on the growth of TTS and also on the effect of the ambient sound level on the recovery from TTS. The predictability of TTS is examined in the context of both laboratory and real life conditions. The implications for the time-intensity trade-off in occupational noise exposure limits and for administrative control of exposure is discussed.
Neurophysiological basis of TTS
Authors: Henderson D. , Salvi R. , Hamernik R. P.
Published: October 2005

Traditionally, our understanding of TTS has been limited to relatively gross measures of cochlear function such as cochlear microphonics, whole nerve action potential, and evoked potentials from the central nervous system. In the last few years, advances in our understanding of the psychophysics of TTS, improvements in physiological recordings of 8th nerve fibers and the development of animal models with multiple measures of voluntary performance allow us to converge on a more molecular understanding of TTS. In the few studies that have been completed, it is clear that a number of characteristics of TTS are mirrored in the pattern of 8th nerve and cochlear nucleus responses. The threshold shift of the audiogram is paralleled by the distribution of sensitivities of individual 8th nerve and cochlear nucleus neurons, even to the extent of showing the “half-octave shift.” Another aspect of TTS is the breakdown in frequency selectivity which is seen both psychophysically and physiologically. However, other aspects of auditory perception influenced by TTS may or may not have a simple counterpart in the neural afferent flow. For example, there are few physiological cues to explain the reliable psychophysical changes such as tinnitus, recruitment, and reduced temporal integration. We should not have to wait another one hundred years for the next step in our understanding of TTS because we are beginning to appreciate the contribution of changes in the stereocilia, the micro-mechanics of the cochlear partition, and membrane physiology.
Variable acoustics: A review of several auditoria
Authors: Wetherill Ewart A.
Published: October 2005

Variation in the acoustical response of an auditorium requires the use of devices by which the factors affecting articulation and reverberance can be adjusted quickly and conveniently. The primary methods of adjustment are (1) changing early reflections by reorientation or relocation of reflecting surfaces, (2) changing the volume of the space, and (3) changing reverberant sound energy by the addition or removal of sound-absorbing materials. The former is very sensitive to fine adjustments. The latter two are relatively insensitive, requiring significant changes in volume or absorption. Combinations of these devices have been used successfully to attain optimum conditions for uses ranging from symphonic music to speech. Several auditoria, covering a period of roughly 12 years, are reviewed. The degree of variability of each hall, its effect on usability for a varied repertoire, and the success in integrating acoustical devices with other performance requirements are discussed.