bluuebunny/crossref_metadata_2025 huggingface dataset:
Random-bottom structural and topographical effects on sound transmission in a shallow channel
Authors: Ashley C. E. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

Effects of horizontal stochastic bottom structure on acoustic intensity in an isospeed ocean have been studied previously by the authors [J. Acoust. Soc. Am. 76, 1445–1455 (1984)]. The bottom density and sound speed were taken to be random and ray theory was used. In this study we add a rough water–bottom interface, consisting of large-scale, two-dimensional random facets upon which small-scale roughness may be superimposed. Each facet is assumed to possess small random depth deviation, slope, and curvature. Initially, we take acoustic rays to be specularly reflected from the facet bottom, and derive expressions for the mean and variance of incoherent intensity at a point receiver for a transmitted cw signal. The results are sufficiently general to permit their use with different bottom-acoustic models, but we employ Mackenzie theory here. Relative effects of structure and topography are compared. Subsequently, small-scale roughness is superimposed on the facets, and the added consequences of scattering are considered.
Optimum time domain signal transmission and source location in a waveguide
Authors: Clay C. S.
Published: October 2005

The research on transmission and filter operations has two purposes. The first purpose is to reduce channel distortion and the second is to locate a source. It uses impulse responses of transmissions between a source and a receiver in a waveguide. A time reversal of the impulse response gives the matched filter for the transmission. The matched filter is an optimum filter for the reduction of transmission distortion. A numerical example demonstrates distortion reduction. Since the impulse response between a source and receiver is a function of waveguide structure, source position, and receiver position, one can use the impulse response to determine source position by passing the received signal through a set of reference or theoretical impulse response functions for trial source positions. The ambiguity of source locations depends on waveguide structure and the complexity of the impulse response. Basically ambiguity decreases as complexity increases. A plane-layered waveguide requires at least three receivers that are not in a line. The signal processing consists of match filtering each receiver for a trial source location and then cross correlating the trial filter outputs. The pairwise cross correlations have a maximum when the trial location is the same as the source position. The cross correlation at match also gives an estimate of the autocorrelation of the source. The source can radiate impulsive transients or continuous random signals.
Effects of rate and bite block manipulations on kinematic characteristics of children’s speech
Authors: Smith Bruce L. , McLean-Muse Ann
Published: October 2005

The purpose of the present study was to investigate kinematic characteristics of the speech of children and adults under three speaking conditions. The effects of requiring subjects to produce speech stimuli were studied as they spoke: (a) in a normal manner; (b) at a faster than normal rate; and (c) while holding a bite block between their molars to restrict mandibular movement. Using a strain gauge monitoring system, superior–inferior lip and jaw movement data were collected from 24 subjects—six in each of three groups of normally developing children and an adult control group. For the normal condition, it was found that net peak velocity (i.e., the sum of the peak velocities of the individual articulators) was quite comparable among the three groups of children and the adults. Net peak velocity increased significantly for all four groups of subjects when they spoke at a fast rate, but it did not increase significantly in the bite block condition. For most measures, there were typically no differences in peak velocity across the various speaking conditions when comparing the three groups of children to one another. In general, articulatory displacement data showed patterns quite similar to those of the peak velocity data. In addition to the displacement and peak velocity data, pilot data are discussed concerning temporal properties of articulatory phases and also concerning maximum, nonspeech articulatory gestures.
Integral processing of phonemes: Evidence for a phonetic mode of perception
Authors: Tomiak Gail R. , Mullennix John W. , Sawusch James R.
Published: October 2005

To investigate the extent and locus of integral processing in speech perception, a speeded classification task was utilized with a set of noise-tone analogs of the fricative-vowel syllables /fæ/, /∫æ/, /fu/, and /∫u/. Unlike the stimuli used in previous studies of selective perception of syllables, these stimuli did not contain consonant–vowel transitions. Subjects were asked to classify on the basis of one of the two syllable components. Some subjects were told that the stimuli were computer generated noise-tone sequences. These subjects processed the noise and tone separably. Irrelevant variation of the noise did not affect reaction times (RTs) for the classification of the tone, and vice versa. Other subjects were instructed to treat the stimuli as speech. For these subjects, irrelevant variation of the fricative increased RTs for the classification of the vowel, and vice versa. A second experiment employed naturally spoken fricative-vowel syllables with the same task. Classification RTs showed a pattern of integrality in that irrelevant variation of either component increased RTs to the other. These results indicate that knowledge of coarticulation (or its acoustic consequences) is a basic element of speech perception. Furthermore, the use of this knowledge in phonetic coding is mandatory, even in situations where the stimuli do not contain coarticulatory information.
Transient response of plates with arbitrary shape in contact with a fluid subjected to general dynamic pressures on a fluid surface
Authors: Nagaya Kosuke , Nagai Katsumi
Published: October 2005

This paper is concerned with a method for solving dynamic response problems of arbitrarily shaped plates in contact with a fluid. By utilizing the Fourier expansion and the Laplace transform methods for disposing of general dynamic pressures, and by applying the Fourier expansion collocation method for satisfying the boundary conditions, expressions for the dynamic response of displacement and bending moment are obtained in a general form which is applicable to general dynamic pressures and arbitrarily shaped plates. Numerical calculations have been carried out for circular plates, rectangular plates, rectangular plates with round corners, and oval plates. The results obtained in certain plates are compared with the exact ones.
Auditory brain stem responses from human adults and infants: Wave V tuning curves
Authors: Folsom Richard C. , Wynne Michael K.
Published: October 2005

Decrement in ABR wave V amplitude was measured in the presence of simultaneous tonal maskers. Probe stimuli were 1.0, 4.0, and 8.0-kHz third-octave-filtered clicks. Adults and 3-month-old infants served as subjects. The resultant amplitude-decrement functions for each tonal masker were fit with regression lines. The sound pressure level (SPL) required to reduce wave V to 50% of the unmasked probe amplitude was plotted for each masker to develop tuning curves. The tuning curves were quantified by calculations of tip-to-tail difference, Q10, and SPL at maximum masker frequency (MMF). Tuning curves for adult and infant subjects were similar for the 1.0-kHz probe. For the high-frequency probes (4.0 and 8.0 kHz), smaller tip-to-tail differences and lower Q10 values were observed for the infant subjects. Ranges of MMF level were similar across adult and infant subjects. For the 8.0-kHz probe, tuning curves from infant subjects consistently showed maximum masker frequencies which were lower than the probe.
Individual differences in auditory capabilities. I.
Authors: Johnson David M. , Watson Charles S. , Jensen Janet K.
Published: October 2005

Twenty-eight audiometrically normal adult listeners were given a variety of auditory tests, ranging from quiet and masked thresholds through the discrimination of simple and moderately complex temporal patterns. Test–retest reliability was good. Individual differences persisted on a variety of psychoacoustic tasks following a period of training using adaptive threshold-tracking methods, and with trial-by-trial feedback. Large individual differences in performance on temporal-sequence-discrimination tasks suggest that this form of temporal processing may be of clinical significance. In addition, high correlations were obtained within given classes of tests (as, between all tests of frequency discrimination) and between certain classes of tests (as, between tests of frequency discrimination and those of sequence discrimination). Patterns of individual differences were found which support the conclusion that individual differences in auditory performance are, in part, a function of patterns of independent abilities.
Effects of signal envelope on the pitch of short complex tones
Authors: Houtsma Adrianus J. M. , Rossing Thomas D.
Published: October 2005

Envelope-induced pitch shifts were measured for exponentially decaying complex tones consisting of two sinusoidal components with frequencies  f 1=n f 0+50 Hz and  f 2=(n+1) f 0+50 Hz, where n equals 3, 4, or 5 and exponential decay rates were 0, 0.5, 1, and 2 dB/ms. Four subjects adjusted a sinusoidal comparison tone to match the virtual pitch of the (missing) fundamental and the pitches of the lower and upper partials  f 1 and  f 2. Pitch shifts for  f 1 are generally less, and pitch shifts for  f 2 always greater, than envelope-induced shifts observed in isolated sinusoidal tones of comparable frequency and envelope decay rate. Pitch-shift functions for virtual pitch are similar in magnitude and shape to average pitch-shift functions of the partials, which supports the idea that virtual pitch depends on spectral pitch.
Discrimination of spectral-peak amplitude by normal and hearing-impaired subjects
Authors: Turner Christopher W. , Holte Lenore A.
Published: October 2005

The present study compared the abilities of normal and hearing-impaired subjects to discriminate differences in the spectral shapes of speechlike sounds. The minimum detectable change in amplitude of a second-formant spectral peak was determined for steady-state stimuli across a range of presentation levels. In many cases, the hearing-impaired subjects required larger spectral peaks than did the normal-hearing subjects. The performance of all subjects showed a dependence upon presentation level. For some hearing-impaired subjects, high presentation levels resulted in discrimination values similar to that of normal-hearing subjects, while for other hearing-loss subjects, increases in presentation level did not yield normal values, even when the second-formant spectral region was presented at levels above the subject’s sensitivity thresholds. These results demonstrate that under certain conditions, some sensorineural hearing-impaired subjects require more prominent spectral peaks in certain speech sounds than normal subjects for equivalent performance. For the group of subjects who did not achieve normal discrimination results at any presentation level, application of high-frequency amplification to the stimuli was successful in returning those subjects’ performance to within normal values.
Influence of place synchrony on detection of a sinusoid
Authors: Cohen Marion F. , Schubert Earl D.
Published: October 2005

A series of experiments was performed to study the ability of the ear to code the temporal envelope of a waveform as demonstrated by comodulation masking release (CMR). The stimulus for all experiments was composed of a tone-burst signal, a 100-Hz-wide masker band centered at the signal frequency, and a second 100-Hz-wide noise band of variable frequency, the cue band. The cue band had a temporal envelope which was either correlated with or independent of that of the masker. The signal was a 100-Hz tone burst for most experiments. For the monotic stimulus, the correlated cue band results in lowered signal detection thresholds over a range extending from around 2/3 oct below the signal frequency to 1/3 oct above that frequency. When measured dichotically, with the signal and masker band in one ear and the cue band in the opposite ear, that effective range is expanded but the detection threshold shifts are a bit smaller. The greatest CMR is observed when the stimulus is presented diotically. With regard to effects of level and frequency, our data show CMR increasing with increasing stimulus level for a cue band lower in frequency than the signal, but show little effect of level for a cue band higher in frequency. Similarly, CMR increases with increasing stimulus frequency when the cue band is lower in frequency, but shows little effect of frequency for a cue band higher in frequency.
Masker-bandwidth dependence in homophasic and antiphasic tone detection
Authors: Zurek P. M. , Durlach N. I.
Published: October 2005

Thresholds for the detection of 500-ms tones in noise at either 0.25 or 4 kHz and either interaurally in-phase (NoSo) or out-of-phase (NoSπ) were measured as a function of the bandwidth of a diotic masking noise (with total noise power held constant). NoSo thresholds followed the classic trend indicative of an effective critical band in noise masking. NoSπ thresholds also indicated critical-band filtering, but with a wider effective critical bandwidth. At subcritical masker bandwidths, for both 0.25 and 4 kHz, NoSπ thresholds increased with an increase in noise bandwidth, despite the fact that total noise power was constant. This latter finding is attributed to binaural insensitivity to rapid fluctuations in the interaural cues that subserve detection in the NoSπ condition. These results suggest a new interpretation for the small difference between NoSo and NoSπ thresholds measured with high-frequency tones in a broadband noise masker. This interpretation is based partly on the inability to utilize rapidly varying interaural cues, partly on out-of-band interference effects, and partly on loss of information related to stimulus fine structure.
Acoustic analyses of infant fricative and trill vocalizations
Authors: Bauer Harold R. , Kent Ray D.
Published: October 2005

Closants, or consonantlike sounds in infant vocalizations, were described acoustically using 16-kHz spectrograms and LPC or FFT analyses based on waveforms sampled at 20 or 40 kHz. The two major closant types studied were fricatives and trills. Compared to similar fricative sounds in adult speech, the fricative sounds of the 3-, 6-, 9-, and 12-month-old infants had primary spectral components at higher frequencies, i.e., to and above 14 kHz. Trill rate varied from 16–180 Hz with a mean of about 100, approximately four times the mean trill rate reported for adult talkers. Acoustic features are described for various places of articulation for fricatives and trills. The discussion of the data emphasizes (1) dimensions of acoustic contrast that appear in infant vocalizations during the first year of life, and (2) implications of the spectral data for auditory and motor self-stimulation by normal-hearing and hearing-impaired infants.
Acoustic analyses and perceptual data on anticipatory labial coarticulation in adults and children
Authors: Sereno Joan A. , Baum Shari R. , Marean G. Cameron , Lieberman Philip
Published: October 2005

The present study investigated anticipatory labial coarticulation in the speech of adults and children. CV syllables, composed of [s], [t], and [d] before [i] and [u], were produced by four adult speakers and eight child speakers aged 3–7 years. Each stimulus was computer edited to include only the aperiodic portion of fricative-vowel and stop-vowel syllables. LPC spectra were then computed for each excised segment. Analyses of the effect of the following vowel on the spectral peak associated with the second formant frequency and on the characteristic spectral prominence for each consonant were performed. Perceptual data were obtained by presenting the aperiodic consonantal segments to subjects who were instructed to identify the following vowel as [i] or [u]. Both the acoustic and the perceptual data show strong coarticulatory effects for the adults and comparable, although less consistent, coarticulation in the speech stimuli of the children. The results are discussed in terms of the articulatory and perceptual aspects of coarticulation in language learning.
A model for the nearfield acoustics of the fish swimbladder and its relevance for directional hearing
Authors: de Munck Jan C. , Schellart Nico A. M.
Published: October 2005

It is a well-known fact that fish can determine the direction of an underwater sound source. For bony fish without Weberian ossicles the mechanism proposed here is the analysis of the elliptical movement of the otolith macula relative to the otolith in case a pure tone is emitted. This movement results from the superposition of the direct displacement wave and the displacement wave scattered by the swimbladder acting as a damped harmonic oscillator. A derivation of a closed analytical expression of the scattered wave is given for a prolate spheroidal air bubble (representing the swimbladder) in water. The elliptical displacement orbits of the surrounding medium were calculated. A general numerical approach is given for irregular gas bodies.
Comments on ‘‘A method for solving free vibration problems of three-layered plates with arbitrary shape’’ [J. Acoust. Soc. Am. 7
8, 2042–2048 (1985)]
Authors: Laura P. A. A. , Gutierrez R. H. , Alvarez S. I.
Published: October 2005

The authors propose an alternative approach which is quite simple and convenient when determining the fundamental frequency of transverse vibration of sandwich plates if the mapping function which transforms a unit circle onto the given, complicated domain is known in advance.
Torsional dispersion relations in a radially dual elastic medium
Authors: Kleczewski D. , Parnes R.
Published: October 2005

Exact dispersion relations for torsional waves are derived for a system consisting of an elastic cylindrical core embedded in an elastic medium having different material properties. Dispersion curves are presented as a function of an aspect ratio and ratios of material properties. Cutoff wavelengths dependent on material properties are established. The results are compared with a previous solution obtained using a simplified approximate model. While the approximate model is seen to yield the correct range of phase velocities, the resulting dispersion relations are shown to be inaccurate for relatively short wavelengths in systems for which the surrounding material is markedly stiffer or denser than the core. The approximate model is also shown to be overly restrictive in predicting cutoff wavelengths.
Impedance of grass-covered ground at low frequencies measured using a phase difference technique
Authors: Daigle G. A. , Stinson Michael R.
Published: October 2005

Although the impedance of natural outdoor ground surfaces has been measured extensively at frequencies above about 200 Hz, measurements at lower frequencies are scarce and have been inaccurate. To overcome some of the difficulties at low frequencies, a two-microphone, phase difference technique to obtain the ground impedance has been adapted. A point source is suspended above the ground and the sound field is measured with two microphones along the vertical line below the source. The magnitude and phase of the reflection coefficient, and hence the impedance, is inferred from the variation of the phase difference between microphones as a function of height above the ground surface. Measurements were made in the range 25–300 Hz on flat, grass-covered ground, free of reflecting objects. The results obtained are consistent with recent seismic/acoustic coupling experiments and theoretical calculations based on layered poroelastic frame models for the ground. In particular, the measured results show evidence for fine structure expected from the layered nature of the ground.
Estimating horizontal coherence in the ocean
Authors: Beran Mark J. , McCoy John J.
Published: October 2005

The horizontal and vertical coherence that results from scattering of acoustic waves in the ocean cannot, in general, be treated separately. The governing equation couples the two effects. If, however, changes in horizontal and vertical coherence occur on widely different range scales, approximate decoupling is possible. Here we shall show what conditions are necessary for this decoupling and, using a two-scale embedding procedure, derive an equation governing the horizontal coherence in terms of effective horizontal scattering functions. Several special cases will be considered.
Propagation of sound in vibrationally excited N2/H2 mixtures
Authors: Shields F. Douglas
Published: October 2005

Measurements of the resonant reverberation of sound in a closed tube have shown an amplification of the sound following the rapid excitation of the gas by an electrical discharge. The measurements have been corrected for tube losses due to viscosity and thermal conductivity and the corrected amplification studied as a function of energy in the electrical discharge, sound frequency, gas pressure, and percentage of H2 in the mixture. The translational temperature during the relaxation process is monitored by measuring the sound speed in the tube. Amplification is attributed to the relaxation of the vibrational temperature which is left elevated to several thousand degrees following the electrical discharge. Experimentally measured gains have been compared to values previously predicted.
Experimental study of forward scattering for a periodic arrangement of slotted waveguides
Authors: Amram Maurice , Simard Louis Philippe , Chvojka Vick J. , Ostiguy Germain
Published: October 2005

Phase reversal sound barriers, composed of periodic slotted waveguides, have shown promising results in low-frequency noise control for plane waves normal to the obstacle, when compared with solid barriers. The phase reversal effect results in destructive interferences in the shadow zone of the barrier. In order to introduce this new phase-controlling device in real conditions (obliquely incident ground reflections, variable source position, etc.), it was necessary to investigate its performance at any angle of incidence. This complementary experimental study, performed in an anechoic chamber, is a verification of the previous theoretical [Mongeau et al., J. Acoust. Soc. Am. 80, 665–671 (1986)] and experimental [Chvojka et al., J. Acoust. Can. 13 (1985)] studies. The results show that, in a measuring plane normal to the slots (waveguide entrances), the performance of this new type of barrier remains quite unchanged at any oblique angle of incidence within −60 ° to +60 °. On the other hand, the studies have clearly shown that this performance is much more angle dependent in a measuring plane parallel to the slots.
Uniform asymptotic solution for the Green’s function for the two-dimensional acoustic equation
Authors: Yedlin Mathew J.
Published: October 2005

A uniform asymptotic expansion in the frequency domain is derived for the Green’s function of the two-dimensional acoustic equation. The expansion is uniform in that it is valid near the source region. It is not valid for caustics, which can arise due to rapid changes in the gradients of the material parameters, the density, or the bulk modulus. The Green’s function which is obtained describes only the body wave acoustic arrivals in a smoothly varying whole space. Other wave types, such as surface waves or critically refracted (head) waves, are not included in this expansion.
Measurement of sound propagation downslope to a bottom-limited sound channel
Authors: Carey William M. , Gereben Istvan B. , Brunson Burlie A.
Published: October 2005

Signal transmission loss and spatial coherence data for source–receiver separations between 100 and 250 km were acquired in the Gulf of Mexico with a calibrated seismic-streamer measurement system at 400-m depth, a towed projector at 100-m depth which emitted 67- and 173-Hz tones, and a moored Webb sound source at 988-m depth driven at 175 Hz. Range-dependent bathymetry and sound velocity profiles and other environmental data were measured. The 67-Hz data showed a persistent sound transmission with a mean of measured range-averaged loss values (corrected for cylindrical spreading) of 41 dB ranging between 37 and 45 dB; the 173-Hz data showed several pronounced transmission loss minima with a mean measured range-averaged loss value of 51 dB ranging between 41 and 60 dB as well as a rapid increase in loss over the slope at ranges greater than 225 km and water depths less than 1.2 km. Slope enhancements were found to be on the order 2–4 dB at 67 Hz and 6 dB at 173 Hz when compared to flat bottom calculations. Pair wise coherence data showed the effect of signal-to-noise ratio variations due to multipath interference. Estimates of signal coherence length from the coherent summation of streamer hydrophones yielded coherence lengths ranging between 70 m (8λ) and 300 m (35λ) with an average of 181 m (20λ) at a frequency of 173 Hz (λ=8.67 m). Fast asymptotic coherent and normal mode transmission loss calculations produced results in qualitative agreement with measured data for the deep flat portion of the measurement track when measured geoacoustic profiles or the derived bottom loss curves were used. The results of implicit finite difference parabolic equation calculations were consistent with range-averaged data for the flat portion of the track as well as on the slope. These results show that if proper descriptions of the subbottom velocity profiles are used, then computations employing either parabolic equation or normal mode techniques provide qualitative agreement with experimental results.
Downslope propagation of normal modes in a shallow water wedge
Authors: Tindle C. T. , Hobaek H. , Muir T. G.
Published: October 2005

Experimental results are presented for the downslope propagation of acoustic normal modes in a shallow water wedge with a penetrable bottom and a slope of up to 9°. A 7-element line source was used to generate individual low-order normal modes. To obtain single modes in a wedge it was necessary to align the line source to form an arc of a circle centered on the wedge apex. The resulting normal modes propagate with wave fronts which are also curved into arcs of circles centered on the wedge apex. These ‘‘wedge modes’’ propagate without coupling. The amplitudes, mode functions, and group velocities of the wedge modes are described by simple adiabatic normal mode theory, but the wave front curvature is not.
Normal mode filtering for downslope propagation in a shallow water wedge
Authors: Tindle C. T. , Hobaek H. , Muir T. G.
Published: October 2005

Experiments to measure downslope sound propagation in a shallow water wedge with a penetrable bottom have been conducted in an indoor tank. Mode filtering has been applied to the signals received on a vertical array to extract the waveforms of individual normal modes. Results show that the normal modes of the wedge propagate with wave fronts which are curved into arcs of circles centered on the wedge apex. These wedge modes propagate downslope without coupling and are therefore the true normal modes of the wedge. Conventional normal modes with vertical wave fronts show coupling effects for slopes of 2° and higher. The group velocities of the wedge modes are strongly dependent on the slope and water depth and are in agreement with adiabatic normal mode theory. Modes which are not trapped in the water depth at the source can become trapped when the water depth is sufficient to support them.
Decorrelation of acoustic energy propagated over disjoint paths in a turbulent ocean
Authors: Yang C. C. , McDaniel Suzanne T.
Published: October 2005

The path integral technique is applied to investigate the effects of internal waves and temperature fine structure on multipath propagation in the ocean. The novel feature of this study is the use of ray tracing to evaluate the stationary paths between source and receiver. An expression for the correlation of the acoustic pressure propagated along disjoint paths is derived which describes both deterministic and random effects. Numerical results are obtained for the interference of two rays in the presence of a bilinear sound-speed profile. These results clearly demonstrate that internal waves rather than oceanic fine structure govern the decorrelation of acoustic energy propagated along the two paths.
Resonance spectra of elongated elastic objects
Authors: Überall H. , Stoyanov Y. J. , Nagl A. , Werby M. F. , Brown S. H. , Dickey J. W. , Numrich S. K. , D’Archangelo J. M.
Published: October 2005

The eigenfrequencies at which smooth convex objects resonate under the incidence of an acoustic wave correspond to the real parts of those complex frequency values at which circumferential waves generated by the incident signal phase-match after repeated circumnavigations around the object [H. Überall, L. R. Dragonette, and L. Flax, J. Acoust. Soc. Am. 61, 711 (1977)]. A resonance condition based on this principle is formulated, and applied to the case of elastic prolate spheroids and cylinders with hemispherical endcaps. Using then the known phase velocities of surface waves on elastic spheres, with a radius equal to the local radius of curvature along the surface path, the elastic resonance frequencies of these objects can be predicted. This was done for the Rayleigh wave on a prolate spheroid, where comparison with resonances in the scattering amplitude as obtained by a T-matrix calculation led to good agreement.
Intensity fields of continuous-wave axisymmetric transducers
Authors: Mair H. D. , Hutchins D. A. , Puhach P. A.
Published: October 2005

The intensity fields of disk, bowl, and conical transducers have been evaluated theoretically throughout their nearfield regions at a single frequency. The results have been compared to the fields resulting from the square of the pressure (P2). It is shown that the two types of fields differ most markedly on axis and close to the transducer face. The direction of energy flow has also been analyzed, and it is demonstrated that parallel flow lines occur in regions where P2 is the closest to intensity.
The relative loudness of third-octave bands of speech
Authors: Holte Lenore , Margolis Robert H.
Published: October 2005

The purpose of this experiment was to determine the relative loudness of various spectral portions of speech. The loudness of each of seven third-octave bands of speech was determined for ten normal-hearing listeners who matched the loudness of an unfiltered speech sample to that of each of the filtered speech bands. The results suggested that the loudness of third-octave bands of speech is approximately constant from 500 through 3150 Hz, and perhaps through 4000 Hz.
Threshold characteristics of the human auditory brain stem response
Authors: Elberling C. , Don M.
Published: October 2005

Auditory brain stem responses (ABRs) were recorded from ten normal-hearing subjects in response to 100-μs clicks from a TDH 49 earphone at a rate of 48 pps and at levels randomly varied in 2-dB steps between 34 and 52 dB p.e. SPL. At each level, 10 000 epochs were averaged with use of a weighted concept and a running estimate was made of the signal-to-noise ratio (SNR). This quantity was used to detect the presence of the ABR and the median threshold was found at 38 dB p.e. SPL. The mean averaged background noise level was 11.3 nVrms, and the ‘‘true’’ ABRrms amplitude function crossed this value at 35.5 dB p.e. SPL, which indicates the level where the SNR=1. By extrapolation, it was found that the ABR amplitude became zero at 32 dB p.e. SPL. The perceptual thresholds of the click were estimated by means of a modified block up–down procedure, and the median value was found at 33 dB p.e. SPL. The slope of the amplitude function and the magnitude of the averaged background noise are the two factors responsible for the ABR threshold sensitivity, which thus depends on both physiological and technical parameters. Therefore, these have to be considered together with the method of detection when the ABR is used to indicate the hearing sensitivity.
Binaural versus monaural loudness: Supersummation of tone partially masked by noise
Authors: Marks Lawrence E.
Published: October 2005

A series of three experiments used the method of magnitude estimation to examine binaural summation of the loudness of a 1000-Hz tone heard in the quiet and against various backgrounds of masking noise. In the quiet, binaural loudness as measured in sones, is twice monaural loudness. Two conditions of noise masking acted to increase the ratio of binaural/monaural loudness in sones above 2:1—that is, to produce supersummation. (1) When tone was presented to both ears, but masking noise to just one ear (dichotic stimulation), the loudness of the binaural tone was 30%–35% greater than the sum of the loudnesses of the monaural components. This increase in summation provides a suprathreshold analog to increases in threshold sensitivity observed with dichotic stimulation (masking-level differences). (2) Supersummation was also evident when tone and noise alike were presented to both ears (diotic stimulation); here, the binaural tone’s loudness was 10%–25% greater than the sum of the monaural components. The increase in summation with diotic stimulation may be related to the characteristics of binaural summation of the noise masker itself.
The NBS conical transducer: Analysis
Authors: Greenspan Martin
Published: October 2005

The NBS conical transducer is a sensitive, broadband device for the measurement of surface displacement as a function of time. Its uses include acoustic-emission testing. Here, the operation of this transducer is subjected to a straightforward analysis. Although several approximations, some more dubious than others, are made, the model predicts the main features rather well. The important parameters are the size and shape of the active element, the source impedance (looking into the area whose deflection is being measured), and the terminating impedance (back load).
Further measurements of low-frequency attenuation in the Southwest Pacific Ocean
Authors: Denham R. N. , Guthrie K. M. , Browning D. G.
Published: October 2005

Previously unpublished results from a 1978 acoustic propagation experiment in the Southwest Pacific Ocean to the east of New Zealand are combined with earlier data to produce measured values of the water column attenuation over the frequency range 32–1000 Hz. The attenuation values so obtained compare well with a modified Thorp formula having a boron relaxation term and a scattering term generally consistent with earlier estimates for the region.
Inversion of data for near-grazing propagation over graveled surfaces
Authors: Lucas R. J. , Twersky V.
Published: October 2005

Data obtained by Medwin and D’Spain [J. Acoust. Soc. Am. 79, 657 (1986)] for low-frequency propagation over gravel-covered rigid planes are inverted by applying the procedure [J. Acoust. Soc. Am. Suppl. 1 79, S68 (1986)] developed for regularly shaped protuberances. The development is based on analytical results for a point source irradiating an embossed plane, and on the uniform asymptotic form of the coherent field as a Sommerfeld type wave system in terms of the complex error function complement (Q). Initial estimates of unknown parameters are obtained by working with elementary approximations of the Q integral, and then used in the complete integral for refinements and final computations. The procedure delineates the roles of interference and damping on the elementary wave components of the Q system, and the resulting graphs display the primary data trends.
Time and frequency representation of acoustic signals by means of the Wigner distribution function: Implementation and interpretation
Authors: Yen N.
Published: October 2005

The Wigner distribution function, originally introduced in quantum mechanics, is shown to have a similar formulation as the Fourier transform of the time-dependent correlation function for a time-varying signal. Review of its mathematical properties indicates that such an expression is suitable for representing the signal simultaneously in the time and frequency domains. Furthermore, reformating the Wigner distribution function with a certain window function leads to a proof that this modified version, the pseudo-Wigner distribution function, always has a positive value and hence can be interpreted as a proper description of the dynamics for the signal’s power density spectrum change with time. The implementation of the Wigner distribution function for digital processing can be carried out simply by adapting the fast Fourier transform algorithm. Examples of its application to several types of acoustic signals are used to illustrate their dynamic features jointly in time and frequency representation.
Vowel intelligibility in the absence of the acoustic reflex: Performance-intensity characteristics
Authors: Dorman Michael F. , Lindholm Julie Mapes , Hannley Maureen T. , Leek Marjorie R.
Published: October 2005

Performance-intensity functions were defined for ten synthetic vowels whose durations (50 ms) were shorter than the time necessary for the acoustic reflex to alter the transmission characteristics of the middle ear. Recognition accuracy for ten listeners with normal auditory function was asymptotic from 72 to 90 dB and then fell linearly to 108 dB. Thus, at SPLs greater than approximately 90 dB, the auditory encoding of vowels is altered by the absence of the acoustic reflex.
Dynamic response of a two-dimensional elastic solid of arbitrary shape having a circular cavity subjected to a transient pressure along the cavity
Authors: Nagaya Kosuke , Niiyama Humihiko
Published: October 2005

This paper is concerned with a method for solving response problems of an elastic solid of arbitrary shape with a circular cylindrical cavity subjected to a transient pressure along the cavity. In the analysis, the exact solutions which satisfy the boundary conditions along the cavity are obtained by applying the Laplace transformation to the equations of motion of elastic solids based on the two-dimensional theory of elasticity. The boundary conditions along the outer surface of arbitrary shape are satisfied by means of the Fourier expansion collocation method. The Laplace transform inversion integral is obtained from the residue theorem. Reasonably accurate results are obtained when the integration for finding the coefficients of the Fourier series and the numerical differentiation are carried out appropriately. To discuss the accuracy of the present analysis, results are compared with those from an exact method for circular rings. Numerical calculations are carried out for sample cases.
Stem-Cell Homeostasis and Growth Dynamics Can Be Uncoupled in the
Arabidopsis
Shoot Apex
Authors: Reddy G. Venugopala , Meyerowitz Elliot M.
Published: October 2005

The shoot apical meristem (SAM) is a collection of stem cells that resides at the tip of each shoot and provides the cells of the shoot. It is divided into functional regions. The central zone (CZ) at the tip of the meristem is the domain of expression of the
CLAVATA3
(
CLV3
) gene, encoding a putative ligand for a transmembrane receptor kinase, CLAVATA1, active in cells of the rib meristem (RM), located just below the CZ. We show here that CLV3 restricts its own domain of expression (the CZ) by preventing differentiation of peripheral zone cells (PZ), which surround the CZ, into CZ cells and restricts overall SAM size by a separate, long-range effect on cell division rate.
Mg-Protoporphyrin IX and Heme ControlHEMA, the Gene Encoding the First Specific Step of Tetrapyrrole Biosynthesis, inChlamydomonas reinhardtii
Authors: Vasileuskaya Zinaida , Oster Ulrike , Beck Christoph F.
Published: October 2005

HEMAencodes glutamyl-tRNA reductase (GluTR), which catalyzes the first step specific for tetrapyrrole biosynthesis in plants, archaea, and most eubacteria. In higher plants, GluTR is feedback inhibited by heme and intermediates of chlorophyll biosynthesis. It plays a key role in controlling flux through the tetrapyrrole biosynthetic pathway. This enzyme, which inChlamydomonas reinhardtiiis encoded by a single gene (HEMA), exhibits homology to GluTRs of higher plants and cyanobacteria.HEMAmRNA accumulation was inducible not only by light but also by treatment of dark-adapted cells with Mg-protoporphyrin IX (MgProto) or hemin. The specificity of these tetrapyrroles as inducers was demonstrated by the absence of induction observed upon the feeding of protoporphyrin IX, the precursor of both heme and MgProto, or chlorophyllide. TheHEMAmRNA accumulation following treatment of cells with light and hemin was accompanied by increased amounts of GluTR. However, the feeding of MgProto did not suggest a role for Mg-tetrapyrroles in posttranscriptional regulation. The induction by light but not that by the tetrapyrroles was prevented by inhibition of cytoplasmic protein synthesis. Since MgProto is synthesized exclusively in plastids and heme is synthesized in plastids and mitochondria, the data suggest a role of these compounds as organellar signals that control expression of the nuclearHEMAgene.
Candida albicans
-Conditioned Medium Protects Yeast Cells from Oxidative Stress: a Possible Link between Quorum Sensing and Oxidative Stress Resistance
Authors: Westwater Caroline , Balish Edward , Schofield David A.
Published: October 2005

Candida albicans
, the most frequent fungal pathogen of humans, encounters high levels of oxidants following ingestion by professional phagocytes and through contact with hydrogen peroxide-producing bacteria. In this study, we provide evidence that
C. albicans
is able to coordinately regulate the oxidative stress response at the global cell population level by releasing protective molecules into the surrounding medium. We demonstrate that conditioned medium, which is defined as a filter-sterilized supernatant from a
C. albicans
stationary-phase culture, is able to protect yeast cells from both hydrogen peroxide and superoxide anion-generating agents. Exponential-phase yeast cells preexposed to conditioned medium were able to survive levels of oxidative stress that would normally kill actively growing yeast cells. Heat treatment, digestion with proteinase K, pH adjustment, or the addition of the oxidant scavenger alpha-tocopherol did not alter the ability of conditioned medium to induce a protective response. Farnesol, a heat-stable quorum-sensing molecule (QSM) that is insensitive to proteolytic enzymes and is unaffected by pH extremes, is partly responsible for this protective response. In contrast, the QSM tyrosol did not alter the sensitivity of
C. albicans
cells to oxidants. Relative reverse transcription-PCR analysis indicates that
Candida-
conditioned growth medium induces the expression of
CAT1
,
SOD1
,
SOD2
, and
SOD4
, suggesting that protection may be mediated through the transcriptional regulation of antioxidant-encoding genes. Together, these data suggest a link between the quorum-sensing molecule farnesol and the oxidative stress response in
C. albicans
.
The
Candida albicans
Vacuole Is Required for Differentiation and Efficient Macrophage Killing
Authors: Palmer G. E. , Kelly M. N. , Sturtevant J. E.
Published: October 2005

Yeast-hypha differentiation is believed to be necessary for the normal progression of
Candida albicans
infections. The emergence and extension of a germ tube from a parental yeast cell are accompanied by dynamic changes in vacuole size and morphology. Although vacuolar function is required during this process, it is unclear if it is vacuolar expansion or some other vacuolar function that is important. We previously described a
C. albicans vps11
Δ mutant which lacked a recognizable vacuole compartment and with defects in multiple vacuolar functions. These include sensitivities to stress, reduced proteolytic activities, and severe defects in filamentation. Herein we utilize a partially functional
VPS11
allele (
vps11hr
) to help define which vacuolar functions are required for differentiation and which influence interaction with macrophages. Mutant strains harboring this allele are not osmotically or temperature sensitive and have normal levels of secreted aspartyl protease and carboxypeptidase Y activity but have a fragmented vacuole morphology. Moreover, this mutant is defective in filamentation, suggesting that the major role the vacuole plays in yeast-hypha differentiation may relate directly to its morphology. The results of this study support the hypothesis that vacuole expansion is required during germ tube emergence. Both
vps11
mutants were severely attenuated in their ability to kill a macrophage cell line. The viability of the
vps11
Δ mutant was significantly reduced during macrophage interaction compared to that in the control strains, while the
vps11hr
mutant was unaffected. This implies some vacuolar functions are required for
Candida
survival within the macrophage, while additional vacuolar functions are required to inflict injury on the macrophage.
Ras1-Induced Hyphal Development in
Candida albicans
Requires the Formin Bni1
Authors: Martin Ronny , Walther Andrea , Wendland Jürgen
Published: October 2005

Formins are downstream effector proteins of Rho-type GTPases and are involved in the organization of the actin cytoskeleton and actin cable assembly at sites of polarized cell growth. Here we show using in vivo time-lapse microscopy that deletion of the
Candida albicans
formin homolog
BNI1
results in polarity defects during yeast growth and hyphal stages. Deletion of the second
C. albicans
formin,
BNR1
, resulted in elongated yeast cells with cell separation defects but did not interfere with the ability of
bnr1
cells to initiate and maintain polarized hyphal growth. Yeast
bni1
cells were swollen, showed an increased random budding pattern, and had a severe defect in cytokinesis, with enlarged bud necks. Induction of hyphal development in
bni1
cells resulted in germ tube formation but was halted at the step of polarity maintenance. Bni1-green fluorescent protein is found persistently at the hyphal tip and colocalizes with a structure resembling the Spitzenkörper of true filamentous fungi. Introduction of constitutively active
ras1

G13V

in the
bni1
strain or addition of cyclic AMP to the growth medium did not bypass
bni1
hyphal growth defects. Similarly, these agents were not able to suppress hyphal growth defects in the
wal1
mutant which is lacking the Wiskott-Aldrich syndrome protein (WASP) homolog. These results suggest that the maintenance of polarized hyphal growth in
C. albicans
requires coordinated regulation of two actin cytoskeletal pathways, including formin-mediated secretion and WASP-dependent endocytosis.