bluuebunny/crossref_metadata_2025 huggingface dataset:
Sound diffraction by an underwater ridge with soft finite impedance
Authors: Zhou Ji-Xun , Zhang Xue-Zhen , Martin James S. , Berthelot Yves H.
Published: January 2006

Laboratory experiments have been conducted in a water tank to investigate sound propagation over an underwater ridge with soft, finite impedance, very low density (0.12 kg/m3) and sound speed (250 m/s), and very high attenuation (2–3 dB/cm in the frequency range of interest of 50–85 kHz). The diffracted acoustic pressure was measured along the ridge surface and along a vertical axis behind the ridge. Good agreement was found between predictions from the theory of matched asymptotic expansions (MAE) and the experimental data. The diffracted sound field is quite sensitive to the acoustic attenuation of diffraction material, thus showing potential as an inversion technique to characterize soft material attenuation.
Experimental validation of the use of Kramers–Kronig relations to eliminate the phase sheet ambiguity in broadband phase spectroscopy
Authors: Trousil Rebecca L. , Waters Kendall R. , Miller James G.
Published: January 2006

The technique of broadband phase spectroscopy proposed in 1978 by Sachse and Pao [J. Appl. Phys. 49, 4320–4327 (1978)] determines the phase velocity as a function of frequency from the Fourier transforms of a received reference and through-sample signal. Although quite successful, this approach can be influenced by an ambiguity in the phase velocity calculation which stems from the boundedness of the inverse tangent operation used to calculate phase. Several empirical approaches to resolve the phase ambiguity have been reported. An alternative approach that has not previously been considered appeals to the causal nature of the measurements. This article experimentally validates a method which uses the causally consistent Kramers–Kronig relations to eliminate the ambiguity in phase spectroscopy-derived phase velocity calculations. Broadband pulse and narrow-band tone burst measurements were performed on three gelatin-based phantoms containing different concentrations of graphite particles (0%, 10%, and 20% by volume). The phantoms were constructed to have attenuation coefficients which vary approximately linear-with-frequency, a dependence exhibited by many soft tissues. The narrow-band phase velocity measurements do not suffer from a phase ambiguity, and thus they serve as a “gold standard” against which the broadband phase velocity measurements are compared. The experimental results illustrate that using the Kramers–Kronig dispersion relations in conjunction with phase spectroscopy-derived phase velocity measurements is an effective means by which to resolve the phase sheet ambiguity in broadband phase spectroscopy.
The effect of electrode configuration and duration of deafness on threshold and selectivity of responses to intracochlear electrical stimulation
Authors: Rebscher Stephen J. , Snyder Russell L. , Leake Patricia A.
Published: January 2006

This report examines the effects of intracochlear electrode configuration and mode of stimulation (bipolar or monopolar) on neural threshold and spatial selectivity in the inferior colliculus (IC) of the cat. Single and multiunit IC recordings were made in three groups of animals; acutely deafened adults (controls), neonatally deafened animals studied at 6 to 18 months of age and neonatally deafened cats studied at 2.5 to 6.5 years. Response thresholds were plotted versus IC depth to measure the spatial distribution of responses. The response selectivity for each stimulating configuration was defined as the width of the resulting spatial tuning curve (STC) measured at 6 dB above threshold. Spiral ganglion cell (SG) survival was examined histologically in all neonatally deafened animals and correlated with physiological results. Animals studied at less than 1.5 years had SG densities of 23.5%–64.4% of normal (mean=42.7%) while animals studied at greater than 2.5 years had densities of 5.1%–18.3% of normal (mean=9.9%). Electrophysiological results include the following. (1) Monopolar thresholds were 7–8 dB lower than bipolar thresholds in the same animals. (2) Varying the configuration of bipolar contacts (measured as radial, offset radial and longitudinal pairs) did not systematically affect IC threshold in either controls or short-term neonatally deafened animals. In contrast, the long-term neonatally deafened animals showed a difference in threshold with each configuration. (3) The spatial distributions (Q6 dB) of responses to bipolar stimulation were approximately 40% more restricted than those for monopolar stimulation. (4) The spatial selectivity of neonatally deafened animals studied at ages up to 1.5 years was equal to that of control animals with normal auditory experience. However, selectivity was degraded in the older animals. (5) Selectivity was decreased in some animals with the longitudinal bipolar configuration and multiple response peaks were seen in several cases using this stimulus configuration.
Modeling of phased array transducers
Authors: Ahmad Rais , Kundu Tribikram , Placko Dominique
Published: January 2006

Phased array transducers are multi-element transducers, where different elements are activated with different time delays. The advantage of these transducers is that no mechanical movement of the transducer is needed to scan an object. Focusing and beam steering is obtained simply by adjusting the time delay. In this paper the DPSM (distributed point source method) is used to model the ultrasonic field generated by a phased array transducer and to study the interaction effect when two phased array transducers are placed in a homogeneous fluid. Earlier investigations modeled the acoustic field for conventional transducers where all transducer points are excited simultaneously. In this research, combining the concepts of delayed firing and the DPSM, the phased array transducers are modeled semi-analytically. In addition to the single transducer modeling the ultrasonic fields from two phased array transducers placed face to face in a fluid medium is also modeled to study the interaction effect. The importance of considering the interaction effect in multiple transducer modeling is discussed, pointing out that neighboring transducers not only act as ultrasonic wave generators but also as scatterers.
Computation of scattering from clusters of spheres using the fast multipole method
Authors: Gumerov Nail A. , Duraiswami Ramani
Published: January 2006

A T-matrix based method of solution of the multiple scattering problem was presented by the authors [J. Acoust Soc. Am. 112, 2688–2701 (2002)]. This method can be applied to the computation of relatively small problems, since the number of operations required grows with the number of spheres N as O(N3), and with the sixth power of the wave number. The use of iterative techniques accelerated using the fast multipole method (FMM) can accelerate this solution, as presented by Koc and Chew [J. Acoust. Soc. Am. 103, 721–734 (1998)] originally. In this study we present a method that combines preconditioned Krylov subspace iterative techniques, FMM accelerated matrix vector products, a novel FMM-based preconditioner, and fast translation techniques that enable us to achieve an overall algorithm in which the cost of the matrix-vector multiplication grows with N as O(N log N) and with the third power of the wave number. We discuss the convergence of the iterative techniques, selection of the truncation number, errors in the solution, and other issues. The results of the solution of test problems obtained with the method for N∼102–104 for different wave numbers are presented.
Information theory analysis of patterns of modulation in the advertisement call of the male bullfrog, Rana catesbeiana
Authors: Suggs Dianne N. , Simmons Andrea Megela
Published: January 2006

Male bullfrogs often amplitude modulate the envelopes of the individual notes (croaks) in their multinote advertisement calls. These amplitude modulations change the envelope of the note from smooth and unmodulated to one with varying numbers of modulations. A Markov analysis shows the pattern of change in the envelope to be highly ordered, but not completely so (semi-Markovian). Three simple rules govern the presence or absence of modulations in individual notes. These rules are (1) all calls begin with an unmodulated note; (2) the first note to be modulated will contain only one modulation; and (3) when a change in modulation occurs from one note to the next, it does so with an increase or a decrease of one modulation only. The addition of modulations is correlated with an increase in note duration. Physiologically, the presence of modulations might increase the precision of temporal coding of note periodicities in the central auditory system.
Simplified nonlinear outer hair cell models
Authors: Deo Niranjan , Grosh Karl
Published: January 2006

We present a consistent second-order expansion of nonlinear constitutive theories for outer hair cells. For a particular theory, we will test the validity of such a model for small variations in voltage and strain about the resting state of outer hair cells. An analysis of the various terms in the simplified nonlinear model and their relevance to outer hair cell mechanics are presented. Results show that the second-order expansion is adequate for modeling outer hair cell mechanics in a global model of the cochlea. Model predictions agree with the notion that voltage nonlinearities are the dominant ones at low sound levels in vivo.
Regularization method for measurement of structural intensity using nearfield acoustical holography
Authors: Saijyou Kenji , Okawara Chiaki
Published: January 2006

The regularization method for measurement of structural intensity using nearfield acoustical holography is proposed. Spatial derivatives of normal displacement are necessary to obtain the structural intensity. The derivative operations amplify high-wave-number components of measurement noise. Therefore, the estimation of an appropriate wave-number filter is crucial for implementation of the measurement of structural intensity. In conventional methods, this wave-number filter is determined from the flexural wavelength. And the same wave-number filter is applied to obtain all spatial derivatives. As a result, structural intensity obtained from the pressure hologram, whose signal-to-noise ratio is low, is seriously contaminated by the noise. To overcome this difficulty, regularization theory is applied to determine the appropriate wave-number filter for each order of derivatives. The effectiveness of the proposed method is demonstrated by experiments.
A mean field transport theory for long-range ocean acoustics
Authors: Wolfson Michael , Henyey Frank
Published: January 2006

Voronovich has found from an ocean model that the mean acoustic wavefield at low frequency persists after multi-megameter propagation in the deep ocean. The common belief has been that only the incoherent field survives long propagation distances. His results, if true in the real ocean, have important consequences to extracting signals from long-range propagation. The results of an alternative ocean model, for which the mean field is evaluated using transport theory, are presented, and compared to his results. Our model consists of a single background sound speed field superposed with sound speed fluctuations due to internal waves. We present results for sources used in recent experiments such as LOAPEX (75 Hz with about 30 Hz bandwidth).
An automated admittance measuring system for electroacoustic transducers
Authors: Ruggiero Clementina M. , Henriquez T. A.
Published: January 2006

A fully automated method of obtaining admittance loops of piezoelectric transducers has been designed to be utilized in conjunction with the H-P 4192A impedance analyzer. The algorithm determines the frequencies at maximum and minimum admittances; the series and parallel resonance frequencies; the resonance and antiresonance frequencies as well as the mechanical quality factor of the element under test. The collected data are plotted in the form of admittance loops with evenly spaced points. This program has been implemented successfully at the Underwater Sound Reference Detachment as a means to rapidly obtain the admittance information of various loaded and unloaded underwater transducers and transducer elements. [Work sponsored by NAVSEA.]
Relationship between reflection and transmission coefficients of a linear passive junction
Authors: Maga L. J. , Maidanik G.
Published: January 2006

The impulse response function of coupled, one-dimensional dynamic systems can be described in terms of the wavenumbers of the constituent dynamic systems together with the reflection and transmission coefficients at junctions which couple the dynamic systems. The junctions also define the terminal positions of the dynamic systems. Constructions of some simple but useful junctions are considered and the corresponding reflection and transmission coefficients that can be assigned to the junctions are derived. The characteristics of these coefficients and their relationship with each other are discussed.
The interaction of age and response condition in the use of acoustic cues to voicing in final stops
Authors: Wardrip-Fruin C. , Peach Sharon
Published: January 2006

The developmental use of vowel duration, final transition, and voicing during closure as cues to voicing in final stop consonants was investigated, using subjects ages 3 to 6 years and adult The stimuli were alterations of eight stop-vowel-stop words. The presentation of each stimulus item was response contingent. There was evidence that the adults responded more to duration cues than did the children. The response to spectral cues was more similar for the three age groups. A comparison of the response of these adults with response of adults in a previous study suggested that condition of response had a very significant effect on the direction and/or magnitude of response to specific treatments. In the earlier study the stimuli were presented at 750 ms. The response contingent presentation of the stimuli in this study seemed to result in a very different decision strategy on the part of the listeners. For example, adult subjects judged the same stimulus item voiced (67%) at 750 ms ISI but voiceless (62%) under the open interval condition. Listeners gave much more definite judgments under the fixed interval condition,judging many stimuli ambiguous in the open interval condition. Implications of these findings for the design and the interpretation of speech perception studies will be discussed.
Vowel normalization by 3-year-old children
Authors: Kubaska Cathy A. , Aslin Richard N.
Published: January 2006

A two-alternative forced-choice procedure was used to assess vowel normalization in 3-year-olds. The stimuli were edited natural tokens of [æ] and [ʌ] produced by male and female adults and male and female children. Subjects were visually reinforced for making an appropriate pointing response to one of two televisions. Initial training of the pointing response consisted of pairing an adult male [æ] with one television and an adult male [ʌ] with the other. After reaching an 90% correct criterion on the training stimuli, subjects were presented with blocks of eight stimuli (four [æ]s and four [ʌ]s). The tokens of [ʌ] by the female adult and the children had formant values which were closer in frequency to the male adult's [æ]. For subjects in the constant vowel group, all the [æ]s were assigned to one pointing response, and all the [ʌ]s to the other. For subjects in the mixed vowel group, two [æ]s and two [ʌ]s were assigned to each pointing response. The constant vowel group was able to categorize the vowels appropriately, despite the differences in absolute frequency; the mixed vowel group performed near chance. These results provide empirical evidence for vowel normalization in young children.
Chidren's identification of synthesized /r-w/ continua for adult and child speakers
Authors: Ohde Ralph N. , Sharf Donald J.
Published: January 2006

In a recent study [D. J. Sharf and P. J. Benson, J. Acoust. Soc. Am. 71, 1008–1015 (1982)], adults were found to reliably identify synthesized /r-w/ continua modeled after adult and child vocal tracts after one testing session. In order to determine the stability of children's perception of these continua, we tested ten 6–7-year-old subjects with normal articulation and hearing. After passing a criterion test of at least 90% correct identifications of the end-point stimuli, each child listened to randomizations of the stimuli from the adult and child continua on two separate days. The results showed no significant difference in category boundaries between the two testing sessions for both adult and child continua. The children correctly identified the three stimuli at each end of the adult and child continua at least at the 95% level and the category boundary occurred within the three middle stimuli. These findings suggest that children are at least as reliable as adults in their responses to variations in the F2 and F3 separation of glide onset frequencies even when the absolute frequency spectrum of stimuli differ by a factor of 1.5. [Work supported in part by NINCDS.]
Acoustic characteristics of stop consonants in the speech of children
Authors: Ohde Ralph N.
Published: January 2006

Although there are theoretical and practical reasons for studying the acoustic correlates of speech sounds in children, few studies have attempted to examine characteristics of their production which may directly vary as a function of place of articulation. Research on the spectral characteristics of stops in adults have shown that frequency and amplitude parameters vary systematically and somewhat invariantly with place of articulation. The purpose of this study was to determine the acoustic correlates of stop consonants in the speech of children. Six children between 8 and 9 years recorded five repetitions each of voiceless aspirated /ph, th, kh/ and voiced /b,d,g/ stops in combination with the vowels /i,e,u,o,ɑ/. Spectral characteristics of burst onsets were determined according to LPC analyses. The findings showed that place of articulation systematically influenced the spectral characteristics of stop consonants. Average resonant peaks for labials were generally below 2 kHz, and for alveolars they were generally above 2500 Hz. Spectral characteristics of velars, on the other hand, were highly influenced by vowel context; the resonant peaks were high preceding high front vowels and low preceding back vowels. The findings will be discussed in terms of these acoustic correlates of place of articulation and their variability in children's speech production. [Work supported in part by NINCDS.]
Vowel formant characteristics in Huntington's disease
Authors: Murry Thomas , Caligiuri Michael
Published: January 2006

The speech of Huntington's disease (HD) has been described with a variety of terms including slow, hesitant, and staccatolike, yet virtually no data have been presented to quantify these characteristics. Acoustic analysis of the vowels in HD speech may provide information about the nature of the speech output. In this study, two questions were posed. (1) Are the vowels of HD subjects different from normal speakers as determined by the formant cluster patterns? (2) Are HD speakers capable of reaching vowel formant targets when more complex speech utterances are utilized? Ten subjects with HD ranging in age from 26 to 58 years old were studied. Each subject was asked to produce four vowels in isolation and in CVC syllables in which the initial consonant was either /d/ or /g/ and the final consonant was always /d/. Measurements of F1 and F2 were made for all vowels from wideband spectrograms. The results indicate that the isovowel targets, especially for F2, for HD speakers, were different from normal F2 values. When compared to the isovowels, the formants in the CVC context reflected centralization. The results suggest that formant trajectories for the vowels in HD speech fail to reach normal isovowel formant targets and that as the stimulus complexity increases, approximation to normal vowel formant frequencies decreases. [Work supported by the Veterans Administration.]
Scattering of elastic surface waves by a semi-infinite fluid-filled crack
Authors: Möhring W.
Published: January 2006

Wave momentum considerations lead to the conclusion that scattering problems involving a fluid-filled crack (normal stress and displacement continuous, vanishing tangential stress) should be in many respects simpler to solve than similar problems with a zero-stress crack. To illustrate this, an elastic half-space with a semi-infinite fluid-filled crack parallel to the free surface and extending to the left is considered. Incident surface waves, both from the left and from the right are assumed. The Wiener-Hopf technique is used to determine the reflected and transmitted surface waves for different frequencies and different values of Poisson's ratio. It is found that, in terms of the normal free-surface displacement, scattering is larger for waves incident from the left. The method can be extended to a semi-infinite fluid-filled crack in an elastic layer. The solution can also serve as a starting point in well-known efficient methods to calculate the scattering of elastic waves by a finite crack or by a finite sized connection between two elastic layers. Similar results for zero-stress cracks have apparently been obtained only in symmetrical configurations.
Auditory time constants unified
Authors: Divenyi Pierre , Shannon Robert V.
Published: January 2006

Psychophysical measures of auditory temporal integration typically yield several different time constants depending on the task. An integration time constant of 100 to 300 ms is proposed to explain the relationship between threshold and burst duration [R. Plomp and M. A. Bouman, J. Acoust. Soc. Am. 31, 749–758 (1959)]. When click thresholds are measured in amplitude-modulated noise the results are consistent with a much shorter integration time of 10 ms or less [N. F. Viemeister, in Psychophysics and Physiology of Hearing, edited by Evans and Wilson (Academic, New York, 1977, pp. 419–427)]. The difference between these time constants is thought to be due simply to the different tasks involved. The longer time constant is calculated assuming a linear integrator operating on the input intensity. Any physiological integration mechanism, however, integrates neural activity, which is a compressive nonlinear function of the input intensity. An integrator with a 10-ms time constant preceeded by a compressive nonlinearity will produce apparent threshold integration times of 100–300 ms, depending on the magnitude of the compression. Thus a single integration mechanism can account for the apparently long time constants for threshold and the shorter time constants for temporal discrimination.
Calculation of the external-ear directional filter function of the KEMAR manikin
Authors: Davis R. E. , Koshigoe S. , Tubis A.
Published: January 2006

In order to assess the quantitative reliability of the calculation of sound diffraction by the external ear using the boundary-integral-equation method [S. Koshigoe and A. Tubis, J. Acoust. Sac. Am. Suppl. 1 73, S76 (1982)], we calculate the directional filter function for the KEMAR manikin external ear. The calculations are based on the assumptions of blocked meatus conditions and the embedding of the external ear in a plane rigid baffle. [Work supported by NSF.]
Gap detection in sensori-neural and simulated hearing impairments
Authors: Florentine Mary , Buus Søren
Published: January 2006

The minimum detectable gap MDG in a low-pass (fc = 7 kHz) noise was measured monaurally as a function of level in listeners with normal hearing, hearing impairments of primarily cochlear origin, and impairments simulated by masking. The listener judged which of two intervals, marked by lights, contained the gap and a modified BUDTIF procedure was used to measure the MDG. The results for normal listeners agree with previous data. Results for seven impaired listeners indicate that in most cases their MDGs depend on their high-frequency thresholds. For example, at high levels, one listener with a low-frequency impairment had nearly normal MDGs, whereas listeners with high-frequency impairments showed enlarged MDGs. Most of the reduction in temporal acuity could be produced by presenting a normal listener with a masking noise spectrally shaped to simulate the audiogram. However, for two impaired listeners with almost identical audiograms, one listener's performance could be simulated well by masking a normal ear, but the other's MDGs were worse than the simulation by a factor 1.5 at the high levels. These results indicate that temporal acuity, per se, may be reduced in some, but not all, impaired listeners. [Work supported by NIH Grant RR07143 and the RSDF of Northeastern University.]
Diffraction limitations on sound-imaging experiments for hearing-aided listeners
Authors: Kuhn George F.
Published: January 2006

It had been proposed by Bauer [J. Acoust. Soc. Am. 33, 1536–1539 (1961)] that two loudspeakers of different source strengths in the horizontal plane could be used to produce a virtual sound image, located at other than the actual source location. It is shown here that, due to the diffraction of sound by the head, this particular method produces simultaneous and interdependent interaural time (ITD) and level differences (ILD). The particular ITDs and ILDs produced by Bauer's method do not generally correspond to a unique spatial location and therefore produce potentially conflicting localization cues. This difficulty is aggravated by unbalancing the hearing aid gains or their phase response. It appears from the study by A. Nabelek, T. Letowski, and D. Mason [J. Speech Hear. Res. 23, 670–687 (1980)] that aided listeners position the sound image on the basis of interaural time differences. The role of interaural pressure level differences on the positioning of sound images could not be established unambiguously from these data.
A note on the acoustics of a duct with a wall treatment of axially partitioned porous material
Authors: Rienstra S. W.
Published: January 2006

Considered is the problem of sound propagation through a cylindrical duct with a wall treatment consisting of a layer of porous material, usually fixed by a segmented structure. The mathematical problem is one of sound fields in the duet and in the layer coupled by conditions of continuity across the interface. So, in general, the layer is not locally reacting and cannot be represented by an impedance of the wall. As a result calculations tend to be quite complex. However, in the present paper it is shown that if the porous layer is segmented by an axial array of annular partitions with a small enough pitch, the coupling of the fields simplifies in such a way that the condition of continuity reduces to a boundary condition, per circumferential mode similar to that of a point reacting liner. So then the porous material is characterized by a circumferential mode number-dependent impedance of the duct wall. Consequently, all the well-established theory for sound propagation in ducts with uniform wall impedance is applicable from here on.
The effect of grazing flow on the impedance of Helmholtz resonator
Authors: Nguyen-Vo Nghiem-Minh , Monkewitz Peter A.
Published: January 2006

A theoretical model for the acoustic impedance of a Helmholtz resonator with grazing flow is presented for the case of low-excitation frequency and amplitude and moderate grazing flow mach number. The analysis is based on the two-dimensional linearized invicid equation of motion. The method of matched asymptotic expansions is combined with the Green's function technique to solve the boundary value problem. It is shown that the vorticity generated by sound incident on a rigid body is “carried away” by the grazing flow. This results in a transfer of acoustic energy to the one associated with vortical distribution. The acoustic impedance obtained agrees well with experimental results available in the literature. [Research supported by NASA.]
Vibroacoustic habitability of space stations
Authors: Stephens David G.
Published: January 2006

The prediction and control of noise and vibration is essential in the design and operation of future space stations to ensure maximum crew efficiency and utilization. On a number of previous space vehicles, noise and vibration levels have exceeded design specifications and have evoked crew complaints, particularly in the areas of sleep and communication, thus suggesting the need for better vibroacoustic prediction and control techniques. In other cases, adverse reactions have resulted despite design specifications being met which suggests that earth based design criteria may be inadequate for space applications. A technology program is being formulated to develop prediction methods and control techniques for use in the design and operation of space stations to ensure acceptable vibroacoustic levels for bearing, communication, performance, comfort, and sleep. The goals include: accurate vibroacoustic prediction and assessment models for space station design; criteria for assessing the effects of different space station crew exposure levels; and new techniques for controlling the vibroacoustic environment within a space station.
Turbulent boundary layer beneath blankets: Measurements and interpretations
Authors: Geib F. E. , Maidanik G.
Published: January 2006

An analytical formulation of the performance of a blanket as a spatial-temporal filter for turbulent boundary layer pressure fluctuations is presented. The formulation is developed as an aid for the design of experiments and experimental procedures for measuring the performance of blankets. The interpretation of data acquired in such experiments is treated in some detail. A simplified analytical model, which has the gross features of the pressure field beneath a convecting turbulent boundary layer, is utilized. This serves to illustrate the trends that can be anticipated in data and to illustrate the effects of undesireable stray pressure fields. Some limited data were acquired in a quiet turbulent pipe facility and are treated with the developed formalism. Significant features in the data are briefly discussed.
Measured and predicted features of the quasisteady wall pressure field beneath turbulent spots in a laminar boundary layer
Authors: De Metz Fred C.
Published: January 2006

The measured features of the quasisteady components of the wall pressure field beneath naturally and artificially generated turbulent spots in a laminar boundary layer are compared with those calculated from structural models based on the large-scale motions within the spots. Contrasts reported in the literature concerning whether the wall pressure disturbance during spot passage is initially negative or positive and the spatial distribution of the spot's wall pressure field are discussed [Cantwell, Coles, and Dimotakis, J. Fluid Mech. 87, 641–672 (1978); Mautner and Van Atta, J. Fluid Mech. 118, 59–77 (1982)].
Electroacoustic assistance of parish church organ music
Authors: Prater R. L. , Christie F. W. , Stockbridge C.
Published: January 2006

When the new organist at St. George's-by-the-River church in Rumson, New Jersey complained that his greatest efforts at filling the church with music seemed futile because the reverberation time was too low, we attempted to quantify this feeling and explore low-cost remedies. The church is of modest size, a 8.1×9.6-m chancel area and a 19.7×17.8-m nave. We measured an average reverberation time near 1.5 s (measured in third octave bands up to 8 kHz), observed inefficient coupling of sound energy from the pipe organ chamber via the chancel to the congregation, due to location of the sole acoustic feed high in the side wall of the chancel. To augment the acoustic coupling a microphone was positioned in front of the organ chamber, and the signal was digitally delayed by 82 ms, amplified, and fed into a pair of powerful loudspeakers positioned high and against the rear corners of the nave. This produced a substantial increase in sound level (>6 dB over 3 octaves). Both we and the organist found the natural character of the pipe organ with this mild electroacoustic assist quite gratifying.
Vibratory patterns of the vocal folds during pulse register phonation
Authors: Whitehead Robert L. , Metz Dale E. , Whitehead Brenda H.
Published: January 2006

In a previous paper [R. L. Whitehead et al., J. Acoust. Soc. Am. Suppl. 1 73, S47 (1983)] we reported that during a single vowel sample of pulse register phonation, each vibratory cycle of the vocal folds consisted of either a double or triple pulsing motion prior to achieving complete glottal closure. The current paper presents data on two additional vowel samples obtained on the same female subject phonating in pulse register. Glottal area-time functions were calculated, using high speed laryngeal films, for 35 consecutive cycles from one film and for 33 consecutive cycles from the other. The results from the first film indicated that each vibratory cycle of the vocal folds consisted of a single opening/closing gesture followed by a lengthy closed period. The results from the second film indicated that each vibratory cycle consisted of a double opening/closing vocal fold pattern followed by the lengthly period of closure. From our data, it appears that one of the physiological descriptors of pulse phonation is that of multiple, as well as single, vibratory patterns of the vocal folds. [Work supported by U. S. Department of Education.]
Acoustic characteristics of flap productions by American English-speaking children and adults
Authors: Rimac Robert , Smith Bruce L.
Published: January 2006

Acoustic characteristics of underlying, intervocalic /d/ and /t/ flaps produced by a number of children and adults were studied to determine whether children's flaps showed similar properties to their other speech segments when compared with adults' productions. Closure durations of flaps and other consonents and a number of vowel durations were measured using a laboratory mini-computer system. Contrasts such as “pudding/putting” and “writer/rider” produced in a carrier phrase were elicited using pictures so that no auditory model would be available for the children. Preliminary results showed that flaps from underlying /d/ were about 10% longer in duration than flaps from underlying /t/ for both the children and adults. Although stressed vowels preceding underlying /d/ flaps were longer in duration than those preceding underlying /t/ flaps for both groups, this contrast was substantially greater for the adults. It was also observed that flap durations were approximately 40% longer for the children than for the adults, while the durations of the children's vowels and nonflap consonant productions were more comparable to the adult's durations for those segments.
Computation of mapping from muscular contraction patterns to formant patterns in vowel space
Authors: Kakita Y. , Fujimura O.
Published: January 2006

In previous papers [J. Acoust. Soc. Am. Suppl. 1 62, S15(1977); in Frontiers of Speech Communication Research, edited by B. Lindblom and S. Ohman (Academic, London, 1979)], pp. 17–24, we demonstrated that a three-dimensional static model of the tongue can be used to explain some basic characteristics, in particular an insensitivity of the formant pattern of the vowel [i] to changes in the magnitude of muscle contraction force over a wide range when an appropriate set of muscles is used. We have implemented a computer program to compute systematically the mapping relation between various combinations of muscle contractions and the resultant formant frequencies in the vowel space. Muscular modeling for different vowels are being experimented based on available anatomical and physiological data, in particular those reported by K. Honda et al. [J. Acoust. Soc. Am. Suppl. 1 72, S103 (1982)]. Eventually, after the work by M. V. Mathews et al. [J. Acoust. Soc. Am. 63, 1535 (1978)] on mapping between area functions and formant patterns, this would illustrate inherent characteristics of the inverse relations from F patterns to muscular patterns for vowels. Uniqueness problems will be discussed with quantitative examples.
The word-position similarity constraint on segmental speech errors: Further experimental results
Authors: Shattuck-Hufnagel Stefanie
Published: January 2006

In earlier experiments it was shown that speech errors involving the interaction of two target segments are governed by a word-position similarity constraint: two segments are more likely to interact in an error if they are word initial then if they are stressed-syllable initial or simply syllable initial. Further experiments have shown that this effect (1) is more pronounced for nonwords than for words, suggesting that the phenomenon arises during the computation of a short-term representation of the units of the utterance rather than during lexical access, and (2) is found in sentence generation tasks as well as in the original tongue-twister repetition tasks, making an explanation in terms of memory constraints less likely and an account in terms of production planning more likely. [Work supported by NIH-NINCDS Grant ♯2 RO 1 NSO4332 19.]
Array gain improvements at low SNR and low frequency via maximum entropy beamforming
Authors: Del Balzo Donald R.
Published: January 2006

It is fairly well accepted that nonlinear beamformers will significantly improve array performance for the case of moderate to high input SNR and near the design frequency. Most applications of high-resolution beamformers have been target resolution and localization, assuming an initial detection has been made. This work addresses array gain at low SNR for blade rate frequencies well below design using a maximum entropy beamformer (MEB) on a horizontal, bottomed array. Simulation results show array gain improvements for the MEB, when compared to a conventional approach, that depend on the input SNR and averaging time.
Variability of acoustic reflectivity over a manganese nodule field
Authors: Spiess F. N. , Weydert Marco M. P.
Published: January 2006

The backscattering from a manganese nodule field is studied. The theory predicts a dependence of reflectivity on acoustic wavelength, nodule shape, nodule size and number of nodules per unit area. First results from a recent deep tow expedition (ECHO Leg 01, June 1983) are presented. The variability of reflectivity with nodule coverage and size is discussed for each of several frequencies (4.5, 9, 28, 60, 110, 163 kHz). The acoustic data, obtained some 70 m above the deep sea floor, are compared with bottom photographs and box cores taken along the same path.
Spectra and limits of boundary waves at grazing incidence over rough surfaces
Authors: D'Spain Gerald L. , Childs Emily H. , Medwin Herman
Published: January 2006

Previously we have presented measurements of the large, coherently scattered, boundary wave amplitude and dispersion for low-frequency grazing propagation over rigid planes with rigid hemispherical or hemicylindrical bosses. Recent laboratory studies with wedge corrugations and with spherical roughness elements, and for ranges up to kR = 3000, show that: (a) the growth of the boundary wave amplitude is self-limited; and (b) the spectrum of the boundary wave amplitude is a function of the slope and size of the wedge corrugations. [Research supported by the Office of Naval Research.]
Model of high-frequency ambient noise in coastal waters
Authors: Dunlap David
Published: January 2006

A computer simulation of the directional dependence and level of intensity of high-frequency ambient noise in coastal waters has been developed. Many investigators have shown the directional dependence of surface generated noise. This paper extends that work to higher frequencies to simulate the background in which some active sonar systems must operate. Contributions from thermal noise and biologically produced noise are also considered in the total levels. The surface wind noise component is modelled as a variable geometric pattern of point sources whose density may also be varied. Initial levels and bottom reflection coefficients are taken from the literature, and results are compared with measured data. The noise intensity is presented as a function of frequency, depth and vertical direction.
Observations of scattering at 300 kHz
Authors: Huff Lloyd C. , Williams Robert G.
Published: January 2006

Observations made with a modified Ametek-Straza model DCP4400/300 Doppler current profiler during an experiment to characterize the current measurement performance of the DCP4400/300 in a bottom-mounted, upward-looking configuration afforded the opportunity to observe narrow-beam backscattering over an interesting range of environmental conditions. CTD casts, water samples for particulate distributions, and wind velocity measurements were made concurrently with the acoustic observations. The functional forms of surface backscatter at normal and 30° angles of incidence versus windspeed are presented. Profiles of volume scattering are shown in relation to the water column characteristics. The bottom scattering, as observed via a surface-bottom-surface path is controlled by surface roughness. Statistical distributions of the backscattering observations are compared with the Rayleighian probability density function. These observations clearly indicate the potential of utilizing the DCP4400/300 to gain useful information about sea surface conditions and about high-frequency backscattering in general.
Array processing to eliminate standing wave effects in shell radiation measurements
Authors: Thomas E. V.
Published: January 2006

The spectral measurement of a cylindrical shell's radiation characteristics in a tidal basin were desired to compare with deep ocean farfield radiation characteristics. Standing wave effects from the surface and bottom of the basin spectrally distorted the radiation measurements. The techniques evaluated to provide relief from standing wave effects were: large, highly directive arrays; line arrays in the nearfield with detection before averaging; and line arrays in the semifarfield with and without beamforming. Detection methods were linear, square law, and logarithmic. An analytical evaluation of the detection methods indicated linear or logarithmic detection had a lower standard deviation than square-law detection. Also, a large, highly directive array wrapped around the shell (i.e., the very nearfield) was evaluated. The best smoothing of the standing wave effects of the medium were achieved using a ten-element line array (normal to cylinder axis) in the semifarfield using logarithmic detection before averaging. Further experimental work simplified this array to a three-element sloped line with logarithmic detection. This system allowed measurement of the shell's radiation characteristics over 212 decades without perturbation by standing waves.
The NBS conical transducer
Authors: Proctor T. M.
Published: January 2006

The NBS conical transducer was first reported on in 1980 [T. M. Proctor, Jr., J. Acoust. Soc. Am. Suppl. I 68, S68 (1980)]. A number of changes have been made in this transducer that improve its usefulness and its frequency response for acoustic emission work. A design for use as a secondary standard in the calibration of other acoustic emission transducers is discussed. A smaller version has been constructed with virtually the same frequency response as the original version. Electrode problems are discussed and solutions indicated.
An acoustic analysis of coarticulatory phenomena in connected digit strings
Authors: Bush Marcia A. , Hamilton Marie , Hata Kazue
Published: January 2006

To date, relatively few attempts have been made to explicitly incorporate coarticulatory information in the design of automatic systems for connected digit recognition. One reason for the limited progress in this area has been the lack of a convenient description of the relevant coarticulatory phenomena, culled from systematic analyses of large amounts of real speech data. This paper describes the initial stage of an ongoing project aimed at remedying this situation. The paper is based on computer-aided analyses of waveforms and spectrograms of 1180 isolated digits and connected digit strings, as produced by two male and two female speakers of American English. The acoustic data were supplemented with phonetic transcriptions by trained linguists. Coarticulatory phenomena are categorized according to: (1) word-boundary effects (e.g., phoneme insertions and deletions); (2) within-word effects (e.g., context-dependent changes in vowel formant frequencies); and (3) consistent speaker-dependent effects (e.g., allophonic variations of /r/). Implications of the acoustic data for system design are also discussed. In particular, the view is advanced that certain coarticulatory phenomena may serve as important sources of information in identifying “difficult” digit sequences (e.g., those containing the digit “oh”).
An improved word detection algorithm for telephone quality speech
Authors: Wilpon J. G. , Rabiner L. R. , Martin T.
Published: January 2006

Accurate location of the endpoints of spoken words and phrases is important for reliable and robust speech recognition. The endpoint detection problem is fairly straightforward for high-level speech signals in low-level stationary noise environments (e.g., signal-to-noise ratios greater than 30 dB). However, this problem becomes considerably more difficult when either the speech signals are too low in level (relative to the background noise), or when the background noise becomes highly nonstationary. Such conditions are often encountered in the switched telephone network when the limitation on using local dialed-up lines are removed. In such cases the background noise is often highly variable in both level and spectral content due to transmission line distortions, transients, and tones from the line and/or from signal generators, etc. Conventional speech endpoint detectors have been shown to perform very poorly (on the order of 50% word detection) over these conditions. In this talk we present an improved word detection algorithm which incorporates both vocabulary and task information, leading to word detection accuracies close to 100% for isolated digit detection over a wide range of telephone transmission conditions.
A pretty good formant tracker
Authors: Cole Ronald A. , Brennan Robert A.
Published: January 2006

Algorithms were developed for estimating formant frequencies on a time frame by time frame basis. The algorithms incorporate acoustic phonetic knowledge about formants. The algorithms are based on knowledge of acoustic phonetics, and do not merely rely on spectral peaks. Thus two formants will be identified even when the first and second formants merge or when the second and third formants merge to form a single peak. The algorithms were evaluated by comparing formants drawn on a speech spectrogram by a trained phonetician to those drawn automatically. The data base consisted of both male and female speakers speaking phonetically balanced sentences. In addition, synthesis derived from the formant frequencies and amplitudes was tested for intelligibility. Results will be presented for these two procedures. [Supported by NSF and DARPA.]
Reclaiming temporal information after dynamic time warping
Authors: Fitch Hollis L.
Published: January 2006

Template matching methods use dynamic time warping to eliminate differences in duration between the template and the unknown speech. These differences may be linguistically relevant. It has been demonstrated for one test word that the relative durations of certain segments in that word can be used to distinguish it from most “false alarms”—stretches of speech other than the test word that score well on the spectrally-based template match [H. L. Fitch, Proc. ICASSP 82, 1247–1250 (1982)]. Here, a more general procedure is described for segmenting, and testing the relative durations of the segments. This procedure has now been applied to ten words, and shows promising results.