bluuebunny/crossref_metadata_2025 huggingface dataset:
A constrained tracking algorithm to optimize plug patterns in multiple isocenter Gamma Knife radiosurgery planning
Authors: Li Kaile , Ma Lijun
Published: October 2005

We developed a source blocking optimization algorithm for Gamma Knife radiosurgery, which is based on tracking individual source contributions to arbitrarily shaped target and critical structure volumes. A scalar objective function and a direct search algorithm were used to produce near real‐time calculation results. The algorithm allows the user to set and vary the total number of plugs for each shot to limit the total beam‐on time. We implemented and tested the algorithm for several multiple‐isocenter Gamma Knife cases. It was found that the use of limited number of plugs significantly lowered the integral dose to the critical structures such as an optical chiasm in pituitary adenoma cases. The main effect of the source blocking is the faster dose falloff in the junction area between the target and the critical structure. In summary, we demonstrated a useful source‐plugging algorithm for improving complex multi‐isocenter Gamma Knife treatment planning cases.
Photon and electron collimator effects on electron output and abutting segments in energy modulated electron therapy
Authors: Olofsson Lennart , Karlsson Magnus G. , Karlsson Mikael
Published: October 2005

In energy modulated electron therapy a large fraction of the segments will be arranged as abutting segments where inhomogeneities in segment matching regions must be kept as small as possible. Furthermore, the output variation between different segments should be minimized and must in all cases be well predicted. For electron therapy with add‐on collimators, both the electron MLC (eMLC) and the photon MLC (xMLC) contribute to these effects when an xMLC tracking technique is utilized to reduce the x‐ray induced leakage. Two add‐on electron collimator geometries have been analyzed using Monte Carlo simulations: One isocentric eMLC geometry with an isocentric clearance of and air or helium in the treatment head, and one conventional proximity geometry with a clearance of and air in the treatment head. The electron fluence output for electrons is not significantly affected by the xMLC if the shielding margins are larger than . For small field sizes and electrons, the isocentric design with helium in the treatment head or shielding margins larger than is needed to avoid a reduced electron output. Dose inhomogeneity in the matching region of electron segments is, in general, small when collimator positions are adjusted to account for divergence in the field. The effect of xMLC tracking on the electron output can be made negligible while still obtaining a substantially reduced x‐ray leakage contribution. Collimator scattering effects do not interfere significantly when abutting beam techniques are properly applied.
Low-frequency sound field statistics in nonrectangular reverberation chambers
Authors: Geddes Earl , Tichy Jiri
Published: October 2005

The low-frequency sound field in nonrectangular enclosures was examined by using the finite element method. Five rooms were examined; one of which was rectangular and was used as a benchmark for comparison. The other four rooms were perturbations of the Louden room. Progressively complicated changes were made in order to assess the effect on the low-frequency sampling statistics of a change in boundary shape. All of the rooms had parallel floors and ceilings to represent a real life constraint. The source and receiver averaged response fluctuation statistics for the three lowest one-third octave bands defined in the narrow-band qualification standard (ISO-3742) were computed for each room. Further, the receiver averaged response was calculated in order to determine the effect of source position. The statistics were tabulated for twelve source positions in each room for each one-third octave band considered. The results of this study show that the low-frequency sampling statistics of rectangular reverberation chambers can be improved by relatively simple boundary modifications.
Field testing of wood joist floor/ceiling assemblies and comparison with laboratory test results
Authors: Campanella Angelo J.
Published: October 2005

New construction of multifamily living units often includes noise insulation performance testing. The degree and source of deviation of field test (FSTC and FIIC) values from those of the prototype laboratory specimen are generally not predictable. Field testing according to ASTME336-77 (FSTC) and ISO140 VII-78 (FIIC) were performed. In this test series, flanking and the site background noise was controlled and octave-band data was used to reduce test time [A. J. Campanella, J. Acoust. Soc. Am. Suppl. I 69, S8 (1981)]. Testing was conducted in partially completed units including wood framing, windows, doors, wiring, limited HVAC ducting. Wall FSTC tests generally agreed with laboratory tests, but the wood floors of rooms of reduced dimensions exhibited serious FSTC and impact sound level deficiencies amounting to as much as 10 to 14 dB in the 125-Hz octave band. Additional 63-Hz octave-band data indicated that the floor/ceiling structures exhibited low TL values in either the 63- or 125-Hz octave bands. This phenomenon was linked to bar-like resonance in short joist lengths (8 to 10 ft vs 14 ft in the lab test). Accelerometer measurements on exposed joists showed significant joist vibration in the free-end mode for the 125-Hz band under impact excitation. A layer of gypsum board was added to the subfloor sandwich to effect mass loading and added damping of the free-bar joist vibrational mode so that the 125-Hz FTL was greater than that of the 63-Hz octave band. Acceptable FSTC values were achieved by in addition placing the ceiling gypsum board on separate 2×4 subjoists with an added layer of R-11 insulation.
Field measurement of the effect of painting acoustic tile ceilings
Authors: Angevine Eric Neil , King Frances S. M.
Published: October 2005

A suburban school district experimented with painting acoustic ceilings in a 25-year-old elementary school building in an attempt to improve the appearance of the deteriorating tiles. Several ceilings were painted using a latex primer and acrylic semigloss paint. Following complaints by teachers the painting program was suspended and other approaches were tried to increase absorption in rooms with painted ceilings and/or decrease the effect of painting in rooms still to be painted. Measurements of reverberation were made for each condition in an effort to correlate the effect of painting acoustic ceilings.
Speaker independent recognition of isolated digits in a telephone environment
Authors: Wilpon J. G. , Rabiner L. R.
Published: October 2005

A field study was initiated to learn about the effects of various telephone transmission and switching conditions on the algorithms currently used in the Bell Laboratories, LPC-based, isolated word recognizer. Digit recordings were obtained from customers over a variety of transmission facilities. During a 23-day recording period a total of 11 035 isolated digits were recorded. For each recording statistics were recorded about the line condition, the background environment, and the customer's ability to speak his telephone number as a sequence of isolated digits. Also recorded was information about the ability of the automatic work endpoint detector to find each spoken digit and to accurately determine the correct endpoints. The results of several recognition tests are presented—one in which a previously defined set of laboratory created digit reference templates was used, and several others where new sets of reference templates were created from a subset of the recorded digits. It is shown that the performance of the recognizer is poor (average digit accuracy of 77.4%) using the laboratory template set, but improves substantially (average digit accuracy 93.1%) for a template set created from the field recordings. An explanation of the reasons for this improvement in digit recognition accuracy is presented along with their implications to future work in isolated word recognition.
Knowledge-based recognition of voiceless stop consonants
Authors: Kopec Gary E. , Bush Marcia A.
Published: October 2005

Recent experiments [M. Bush et al., Proc. 1983 IEEE ICASSP] have demonstrated the ability of a trained spectrogram reader to identify initial stops in /CVb/ syllables from a table of numerical acoustic measurements with approximately 80% accuracy. This paper discusses an automatic system for discriminating between the voiceless plosives (/p,t,k/)which is based on the features and rules identified in these experiments. Ten binary features are extracted from two linear prediction spectra which are computed during the 35 ms following the consonant release. Typical features include “back-k-release-spectrum” and “compact-release-spectrum.” The features are detected by examining the frequencies and amplitudes of the local maxima and minima of the two LPC spectra, in a manner motivted by the actions of the human spectrogram reader. A simple statistical classifier is used to combine the outputs of the ten feature detectors. The classifier was trained on the 108 /p,t,k/ tokens of the multi-speaker corpus used in the spectrogram reading experiment. When tested on the training data, the system achieved 96% correct recognition. When tested on two additional data sets of similar composition, the system achieved scores of 94% and 92%, respectively.
Signal detection analysis of voice recognition at two delay intervals
Authors: Papcun George , Kreiman Jody
Published: October 2005

Ten male talkers who were raised in Southern California were recorded with a high-quality dynamic microphone while making survey calls on public attitudes towards crime. A week later they were recorded again. A recording of one of the talkers made during the first recording session was played to the listeners. After delays of either one or two weeks the listeners returned and heard all ten second recordings of the talkers. The listeners were told that the voice of the talker they heard the first time might appear once, more than once, or not at all. Listeners were asked to say whether each voice they heard was the voice they heard in the first listening session, and how confident they were in their decision. If they decided a voice was not the voice they had heard earlier, they were asked to indicate how similar it was to that voice. Signal detection analysis showed that listeners maintained an essentially stable hit rate at the cost of an increasing false alarm rate in the two week as opposed to the one week interval.
Reading speeds for visual speech displays
Authors: Weiss Mark , Levitt Harry , Halprin Marilyn S.
Published: October 2005

Design criteria for a visual speech display system for the deaf are being investigated. Of particular interest is reading speed for displays of the type that could be produced by an automatic speech recognition device. An adaptive procedure has been developed for measuring reading speed at a prescribed level of performance (e.g., 70% of displayed sentences interpreted correctly). This technique has been used in measuring reading speed as a function of sentence length, (3, 6, or 12 words), display format (stationary, flowing, accumulative), and mode of representation (Standard English text, phonetically based symbols). Extremely high reading speeds (>500 words/min) were obtained using standard English text and very short sentences. Reading speeds comparable to normal speech rates were obtained with a simple, phonetically based representation and moderate sentence lengths (e.g., 6 words/sentence). Experiments are currently in progress on the effects on reading speed of eliminating word boundaries and adding stress markers. [Research supported by PHS Grant ♯PO1-NS 17764.]
An evaluation of certain assumptions underlying articulation index testing
Authors: Pavlovic Chaslav V. , Studebaker Gerald A.
Published: October 2005

The implications of various assumptions utilized in different approaches to the articulation predictions were tested utilizing several filtered speech, interfering noise and low level listening conditions. The monotonicity principle, basic to the AI theory, was examined and found valid when certain plausible adjustments were made in the speech signal and auditory sensitivity levels. The possibility of different intelligibility-articulation index transfer functions for amplitude distortion and noise interference was evaluated. An analysis of prediction results obtained by using different calculation techniques revealed that they did not agree. The band independency principle was investigated, both as related to the general validity of the AI concept and also as related to the test materials and calculation procedures used. Variations of certain assumptions within a given calculation technique (e.g., real peaks versus 12 dB across all frequencies) were found to have only minor effects on the accuracy of predictions. [Work supported by NINCDS.]
Comparison of interconsonantal differences and initial-syllable error responses for words heard in quiet and noise
Authors: Young Keith A.
Published: October 2005

Consonants, heard incorrectly, are replaced in error by speech sounds that are similar to the target sound. The Interconsonantal Difference (ID) [J. W. Black, Report 17, Proj. 2928, The Ohio State University Research Foundation, Columbus, OH, 1974] offers a method by which errors in aurally perceived words, graphically transcribed, may be compared. A sample of 6000 words was recorded, and reproduced to listeners under conditions of “quiet” and “noise,” yielding 250 000 errors. The frequency of error occurrence was correlated with the respective ID, for each of 54 consonants or consonantal clusters. Results indicated high correlation values where error phonemes were associated with front placement, voicing, and plosiveness, in “quiet.” Addition of “noise” resulted in an increase of correlational values, despite the larger overall number of errors made in transcription.
Intelligibility of fluent synthetic sentences: Effects of speech rate, pitch contour, and meaning
Authors: Slowiaczek Louisa M. , Nusbaum Howard C.
Published: October 2005

Previous research comparing the perception of natural and synthetic speech has demonstrated that the intelligibility of synthetic speech is significantly worse than natural speech. The present experiment was designed to investigate the effects of speech rate, pitch contour, and sentence meaning on the perception of fluent synthetic speech. The stimuli were sentences that were either syntactically correct and meaningful or syntactically correct and semantically anomalous. The sentences were generated by a Telesensory Prose-2000 text-to-speech system. The system produced the sentences at either 150 words per minute or 250 words per minute. Half of the sentences were generated with a flat pitch (monotone) and half were generated with “normal” clausal intonation. Subjects were instructed to identify the sentences by writing down what they heard. The percentage of words correctly identified was determined for each of the experimental conditions. In addition, the distribution of identification errors in each condition was examined. The results indicate that intelligibility of synthetic speech is primarily influenced by the speech rate and the meaningfulness of the sentences. These results have important implications for the design and application of text-to-speech systems, as well as theories of fluent speech perception. [Work supported by NIH.]
Adaptive staircase methods—A comparison using Markov theory
Authors: Kollmeier Birger , Gilkey R. H.
Published: October 2005

Adaptive techniques have been widely used for rapid estimation of psychophysical thresholds. This study considers two of the adaptive staircase rules described by Levitt [J. Acoust. Soc. Am. 49, 467–477 (1971)]. A “three-step rule,” in which the level of the signal is increased after an incorrect response and decreased after three successive correct responses, is compared to a “two-step rule,” in which the level is decreased after only two successive correct responses. Each of these rules was modeled in combination with both 2AFC and 3AFC psychophysical procedures using Markov theory. The time required to achieve a certain level of accuracy was then calculated using a digital computer. Both rules in combination with the 3AFC procedure were found to require less time than either rule in combination with the 2AFC procedure. In addition, for a given psychophysical procedure the three-step rule always required less time than the two-step rule. These results will be discussed and compared to the performance of human subjects. [Work supported by NINCDS, Grant NS 03856, and Fulbright Commission, Federal Republic of Germany.]
Adaptive estimation of frequency-gain characteristics for binaural hearing aids
Authors: Levitt Harry , Sullivan Jean , Neuman Arlene
Published: October 2005

A first estimate of the optimum frequency-gain characteristic for each ear was obtained using psychoacoustic data. The frequency-gain characteristic was then adjusted systematically so as to obtain an improved estimate of the optimum frequency-gain characteristic. A paired-comparison procedure was used with running speech against a noise background as the test stimulus. An estimate of the optimum binaural condition was then obtained by using the estimated optimum monaural condition in each ear. The frequency-gain characteristics in the two ears were then adjusted systematically and the paired-comparison procedure was used to compare conditions. For six of the eight hearing-impaired subjects tested, the best binaural condition was the combination of the two best monaural conditions. This result was found for both the SoNo and SoNπ-conditions. The two subjects who did not fit this pattern also showed high test-retest variability in their paired-comparison judgements. [Research supported by PHS Grant No. P01-NS 17764.]
Effects of context and hearing status on word recogniticm in noise
Authors: Matthies M. L. , Yuchtman M. , Bilger R. C.
Published: October 2005

In a recent presentation to the Acoustical Society, we reported the effects of signal-to-babble ratio on speech recognition as a function of hearing status for several groups of normal-hearing and hearing-impaired listeners. In that report, we were able to demonstrate that the difficulty hearing-impaired persons display in background noise is not a straightforward defecit. To resolve some of these difficulties, we report further analysis of these data in which the ratio of performance at one S/B to another i.e., +4dB/ +7dB, +1dB/ +4dB and +1 dB/ +7dB, is investigated. We have assumed that an ordered sequence of contextual cues can be constructed from the Modified Rhyme Test, CHABA sentences and the Speech Perception in Noise test. By taking the ratio of the performance at two signal-to-babble ratios, we observed that the normal-hearing subjects and hearing-impaired subjects perform more similarly as context increases (e.g., low-context SPIN versus MRT). This results belies a simple “signal-to-noise defecit” as an explanation for the difficulties that hearing-impaired subjects have recognizing speech in noise. [Work supported by NINCDS.]
Directivity of the human vocal source
Authors: Studebaker Gerald A.
Published: October 2005

The directivity affects of the voices of one male and one female talker were observed in several environments including an anechoic room. Measurements were made at all frequencies between about 200 Hz and 10 kHz at 45°, 90°, 135°, 180°, and 270° azimuths. All measurements were made in the horizontal plane at the level of the mouth opening and at one meter from the center of the head. The results agreed well with the only other known comparable studies [Dunn and Farnsworth, 1939; Moreno and Pfretzschner, 1979] and also agree well with results obtained by Olson (1972) who designed and used a simplified manikin source. Some loudspeaker types produce results very different from those of human talkers. A search is underway to determine whether there are any widely available or easily created loudspeaker configurations that reasonably closely replicate the observed directivity of human sources. [Work supported by NINCDS.]
Scattering from random surfaces
Authors: DeSanto John A.
Published: October 2005

We summarize the status of the scattering of scalar waves from random surfaces for both coherent and incoherent applications. The usual surface descriptor is via a Gaussian probability distribution in height and, for homogeneous statistics, a correlation function (or its Fourier transform, the surface spectral function). For isotropic surfaces, this leads to a parametric surface description in terms of two independent dimensionless length scales involving wavelength, surface rms height, and correlation distance. For coherent scattering, Kirchoff and perturbation methods are valid for only small roughness. Integral equation methods (Dyson equation} extend the range of validity to larger roughness but further extensions face computability problems. Applications include long range propagation in waveguides with rough walls. Incoherent scattering is described using a Bethe-Salpeter formalism which requires extensive approximations to be tractable. Some comparison with experiment will be given as well as a brief discussion of recent developments.
Stochastic bathymetric scattering and oceanic refraction
Authors: Baer R. N. , Berman D. H. , Perkins J. S. , Wright E. B.
Published: October 2005

The bathymetric scattering model of Betman and Perkins [J. Acoust. Soc. Am. Suppl. 1 72, 585 (1982)] has been incorporated into a propagation algorithm. It is now possible to compute the array angular response to a signal that has propagated through a refracting water column, scattered off a probabilistically described ocean floor, and is received by the array. The propagation algorithm used is the split-step solution to the parabolic equation. The coherence function approach and propagation along characteristics is used in the vicinity of the boundary scatter and the array. The code has been exercised on several model spectra. For these spectra, at 100 Hz, typically 50% of the incoming energy is incoherently scattered and array response is substantially degraded. The array 3-dB width varies inversely with the transverse coherence length of the bottom and is virtually independent of the longitudinal scale. It decreases with frequency and increases with the rms residual roughness. Future work will incorporate real two-dimensional bathymetric spectra. [Work supported by ONR.]
A piecewise-constant random fluctuation model for sediment scattering
Authors: Besieris Ioannis M. , Kohler Werner , Yordanov Oleg I. , Freese Herbert
Published: October 2005

A transversely homogeneous model of abyssal plain sediments is considered. In the depth direction, density and sound-speed variation consists of slow, nominally linear increase upon which is superposed a finite state, piecewise constant random fluctuation. The reflection of time-harmonic plane waves is studied. Ordinary differential equations are derived for the conditional moments of the process. The mutual coherence function for the complex pressure in the water column is obtained. [Work supported by ONR.]
Time spreads incurred by multipath reflections from a random surface
Authors: Brill Michael H. , Zabal Xavier , Adams Stanley L.
Published: October 2005

The complexity of formalisms that deal with broadband acoustic channel distortions suggests temporary retrenchment to a “zeroth-order” model that can be easily compared with experimental data. Such a model is provided by the present work, which characterizes—via a ray-acoustic approach similar to that of J. J. Martin. [J. Acoust. Soc. Am. 47, 1303–1309 (1970)]—distortions of broadband acoustic signals reflecting from a planar surface with random roughness. The essence of the approach is to require that a ray-path reflect specularly from each surface element. A ray arrives at a receiver if and only if the position and slope of a surface element provides the requisite specular path given the incident beam angle. In this way, the probability of reception of a ray with a given incident angle is tied to the distributions of slope and height at the reflecting surface. Whereas Martin has characterized the reflected beam's angle spread, we will assess the arrival-time spread of a pulse due to pathlength differences between the rays arriving at the receiver.
Model tank measurements of underwater acoustic scattering functions
Authors: Zapinsky A. , Zornig J. G.
Published: October 2005

Using the model tank facility at Yale, a series of measurements were made on the surface scatter channel (specular scatter, single bounce). This is a doubly spread communication channel showing both multipath (delay spread) and frequency spread; the channel is underspread. The probing signal used was short in time to isolate separate paths and had a large bandwidth to measure many frequencies simultaneously [J. G. Zornig, J. Acoust. Soc. Am. 64, 1492–1499 (1978)]. Two different surfaces were examined: a wind-driven water surface and a mechanically agitated sinusoidal water surface (having nearly one-dimensional line waves). Previously reported theoretical work [J. F. McDonald and F. B. Tuteur, J. Acoust. Soc. Am. 57, 1025–1029 (1975)] indicated a correlation between longer delays and larger Doppler shifts. The results reported here show substantial agreement with the theory over the range of transducer geometries and water surfaces obtainable in the Yale Hydroacoustic Facility. The assumption of a one-dimensional water surface which was necessary for mathematical tractability appears to have been unnecessary in the model tank since both types of surfaces showed similar agreement with the theory. A test of the data acquisition and analysis system using solid moving targets is presented as confirmation of the method. [Work supported by NSF.]
Review of the path-integral theory of ocean acoustic fluctuations
Authors: Flatté Stanley M.
Published: October 2005

The path-integral theory of ocean acoustic fluctuations was systematically introduced in a book, Sound transmission through a fluctuating ocean, by S. M. Flatté, R. Dashen, W. H. Munk, K. M. Watson, and F. Zachariasen (Cambridge U. P., Cambridge, 1979). The theory establishes three regions of fluctuation behavior for acoustic fluctuations along a single deterministic ray caused by internal waves: unsaturated, partially saturated, and fully saturated. Emphasis in this talk will be placed on the saturated regions. A review of progress in comparison of the theory with experiment will be given. Discussion will include results involving second moments (the coherence function of space and time separations, and appropriate Fourier transforms thereof), fourth moments (the scintillation index and spectra of intensity), higher moments (corrections to Rayleigh statistics for the intensity p.d.f.), as well as spectra of phase and log intensity. [Work supported by ONR, Code 425UA.]
Transport of acoustic radiation along curved rays
Authors: Tappert F. D.
Published: October 2005

A distinguishing feature of sound propagation in the ocean is the existence of the deep sound channel. In consequence ray paths are curved, multipath propagation is prevalent, and caustics abound. This causes severe difficulties in the theory of stochastic wave propagation that have not been fully resolved even on the level of second-order statistics. We shall discuss two approaches to this problem based on radiation transport theory. The first uses ray coordinates to reformulate the wave equation yielding a parabolic equation valid near a single specified ray. After applying a statistical closure (weak Markov) approximation, we obtain a radiation transport equation along a curved ray. It is shown that when the strong Markov approximation is additionally applied, then this equation may be solved analytically and the results of Flatte et al. are recovered. In other limiting cases, our equation yields different results. The second approach begins with a derivation of a general multipath radiation transport equation. When this equation is expanded near a single specified ray, we obtain results comparable to the first approach but with a shift in the position of the mean ray. Thus the mean intensity on a single arrival is not equal to the unperturbed intensity, as predicted by Flatte et al. In addition, this approach allows calculation of the mean intensity and coherence at a caustic insofar as stochastic effects dominate diffraction.
Acoustic field probability density functions for the canonical sound channel
Authors: Bates Susan M. , Bates Bruce J.
Published: October 2005

The canonical deep ocean sound channel is parametrized by the sound-speed minimum, buoyancy frequency scale, and adiabatic fractional sound-speed gradient. Variations in the sound-speed parameters depend on spatial and temporal variations in temperature and salinity. These variations are described by probability density functions. The sound channel near the sound-speed minimum is approximated by a Hirsch sound-speed profile, and the low-frequency acoustic field is derived. Analytic field density functions for received frequency, intensity, wave vector, and arrival time are derived by the application of the transformation of random variables, assuming the sound-speed parameters are uncorrelated Gaussian random variables. The resulting field density functions are non Gaussian. Estimates for the sound-speed parameters and associated variances are used to evaluate the field density functions.
Fluctuations of sound propagating vertically through the ocean
Authors: Desaubies Yves
Published: October 2005

We consider internal wave induced fluctuations of sound propagating vertically through the ocean. Expressions are derived for the acoustic phase structure function, variance and spectra. In a number of important oceanic applications sound propagates essentially along the vertical, from the surface (or some depth) to the bottom, as for instance in acoustic depth sounding or tracking of moving objects by bottom mounted hydrophones. The limits imposed by ocean variability on the accuracy of such systems are discussed and are found to be generally small.
A comparison of the quasi-Rytov and smoothing methods
Authors: Wenzel Alan R.
Published: October 2005

Two techniques for studying wave propagation in random media, the quasi-Rytov method and the smoothing method, have been applied to a problem involving radiation by a point source in a one-dimensional random medium. Each method was used to calculate the mean field, and the results have been compared. It is found that the results are in substantial agreement outside a small region surrounding the source, but that inside this region they disagree. Some technical difficulties which are associated with the smoothing method, and which are related to this discrepancy, are discussed. It is concluded that, although the two methods yield essentially equivalent results (apart from the discrepancy in the near-source region, which is generally not of practical importance), the quasi-Rytov method is easier to apply than is the smoothing method. [Work supported by NORDA.]
Spectral distribution versus propagation path from deep ocean test data
Authors: McCammon Diana F.
Published: October 2005

The distributions of energy across the spectra received during a deep ocean sea test were determined using an unorthodox application of standard statistical analysis. These distributions have been grouped by their principle type of propagation path, e.g., convergence zone or bottom bounce, to enable frequency smearing paths to be identified. This grouping displays clearly the smearing effects of the bottom bounce paths. [Work Supported by NAVSEA, Code 63D-1.]
Discrimination of formant frequency with simulated low-frequency hearing loss
Authors: Collins M. Jane
Published: October 2005

The effects of simulated low-frequency hearing loss on formant-frequency discrimination were investigated for synthetic three-formant vowels. Hearing loss was simulated through the use of masking by low-pass filtered white noise. Percent-correct identification was determined in an AABA paradigm for 100 Hz differences in F1 and for 200 Hz differences in F2. Stimuli were presented at 15 dB above masked threshold in both quiet and in the presence of the masker and at 15 dB above threshold in quiet. Performance was differentially affectced by sound pressure level in quiet (15 dB SL re: masked threshold versus 15 dB SL: re: quiet threshold) and by masking (15 dB SL in noise versus 15 dB SL in quiet). On the average, poorest performance was observed with simulated hearing loss. F1 discrimination in the simulated-loss condition appears to be more dependent on the relation between F1 and F2 than in either quiet condition. F2 discrimination appears to be interactively dependent on the F2 frequency range and the relation between F1 and F2. The results have implications for the use of a pattern-recognition mechanism in discrimination of synthetic speech sounds.
Experiments on the identification of /s/ by the hearing-impaired
Authors: Dorman F. , Hannley M.
Published: October 2005

Clinical audiologists often observe that hearing-impaired listeners with moderate to moderately severe sensitivity losses in the 2–4 kHz region correctly /s/ within PB word lists. To assess the contribution of frequencies below those commonly thought important for /s/ identification, the /s/ in “sin” was filtered in five configurations: between 0.1 and 9.7 kHz; between 1 and 9.7 kHz; between 2 and 9.7 kHz; between 3 and 9.7 kHz; and between 4 and 9.7 kHz. Preliminary results indicate that the detection threshold for the 0.1-to 9.7-kHz stimulus was on the order of 12 dB lower than that of the other stimuli. Detection and use of the energy below 1 kHz appears to be one factor in accurate /s/ identification by the hearing impaired. In other experiments we have verified our previous result that errors for /s/ are highly systematic when referenced to the threshold of /s/ detection.
Visual, auditory, and auditory-visual recognition of consonants by deaf children
Authors: Gentil Michèle
Published: October 2005

It was reported [M. Gentil, J. Acoust Soc. Am. Suppl. 1 72, S8 (1982)] that, given coarticulatory effects, visual recognition of consonants (in nonsense words of consonant-vowel type) depended on the following vowel. The present study extends the previous one in that the recognition of consonants was explored in a more complete and systematic way. Sixteen consonants placed in initial or final position of French words of consonant-vowel or consonant-vowel-consonant type (V = a, i, u) had to be recognized under three observational conditions, that is visual, auditory, and auditory-visual. The experimental population consisted of 51 deaf children with a mean age of 16.5. Results indicated: (1) extremely low percentages of visual recognition, (2) for a given consonant, recognition was better when its occurrence in the word was initial rather than final, for each kind of tests, and (3) under auditory-visual conditions a substantial increase in intelligibility was observed. The results will be discussed in terms of coarticulatory effects and viseme groups which make lipreading difficult.
The pitch and acoustic characteristics of 30 words selected according to a tonality criterion
Authors: Hume Sue Bessel , Asp Carl
Published: October 2005

The relation between the pitch of words and their acoustic characteristics was measured in two separate studies. In the first study, listeners used a paired-comparison procedure to judge the pitch of 30 English monosyllabic words selected according to a tonality (pitch) model [J. Acoust. Soc. Am. Suppl. 1 64, S20 (1978)]. These judgments were used to rank order the words from high to low pitch. The rank order of the words agreed with the proposed pitch model. In the second study [J. Acoust. Soc. Am. Suppl. 1 67, S39 (1980)], these 30 words were analyzed with a spectrograph and a frequency analyzer for fundamental and formant frequencies, duration, and amplitude spectra. A significant correlation was found between the amplitude spectra and the rank order and between formant two and the rank order. Visual inspection of the spectra revealed specific patterns associated with the three pitch categories. The results of these two studies are compared, and the usefulness of a pitch criterion in evaluating speech perception of hearing-impaired persons is discussed.
Causal intonation in right-hemisphere brain damaged speakers
Authors: Cooper William E. , Soares Carlos , Kutik Elanah , Michelow Diane , Nicol Janet
Published: October 2005

Four right-handed adult patients with unilateral right-hemisphere lesions and four non-neurological patients read aloud sentences designed to test influences of clause and utterance length on fundamental frequency (F0) and timing. For single-clause sentences of varying lengths, two patients whose lesions involved the anterior region of the right hemisphere showed more normal differences in F0 as a function of utterance length than did two patients whose lesions involved the posterior region of this hemisphere. For two-clause sentences of varying lengths, the posterior-lesioned patients showed greater abnormality than the anterior-lesioned patients in both the pattern of F0 declination within each clause and the frequency and magnitude of declination resetting at the clause boundary. For both sets of sentences, peak values of F0 averaged about 25 Hz higher for the right-hemisphere patients than for the non-neurological group. Analyses of word and utterance durations revealed no systematic temporal differences among the speakers. The deficits in F0 versus timing for right-hemisphere patients is contrasted with the pattern of results obtained for aphasics. Individual differences and problems of generalizability in light of other studies are discussed in terms of specific area and extent of lesion, disorder complications, and possible differences in premorbid speech characteristics. [Supported by NIH NS 11408 and NS 15059.]
Respiratory and laryngeal movements associated with stutterers' delayed acoustic LRT
Authors: Watson Ben C. , Alfonso Peter J.
Published: October 2005

Most experiments assessing laryngeal reactinn time (LRT) report that stutterers, as a group, are significantly slower in initiating phonation than nonstutterers. We have extended these studies by assessing the effects of a variable foreperiod and stuttering severity on acoustic LRT. Sufficiently long foreperiods, the time between the warning cue and phonate cue, provide subjects time to prepare for a known response. We found that mild stutterers' LRT values approached nonstutterers as foreperiod increased while severe stutterers' LRT values remained significantly longer than nonstutterers throughout the range of foreperiods. These data suggest that differential deficits (i.e.,: respiratory and laryngeal prephonatory posturing and/or vibration initiation) may underly stutterers delayed acoustic LRT values. However, acoustic measures alone are insufficient for a detailed analysis of the deficits contributing to stutterers prolonged LRT values. Therefore, we have begun investigating respiratory and laryngeal movements occurring immediately before phonation onset. Results of preliminary simultaneous acoustic and movement LRT measures will be discussed in terms of the differential deficit hypothesis. [Supported by NINCDS grant NS13870 to Haskins Laboratories.]
Analysis of Lombard effect acoustics in normal and vocal nodule children
Authors: Bailey Jill , Stemple Joseph C. , Weiler Ernest M.
Published: October 2005

The Lombard effect is the increase in voice level as competing noise levels increase. In the present study, fundamental frequency, vocal intensity, and vocal muscle tension were recorded for eight children with bilateral vocal nodules, and 13 comparable normals. Competing noise levels were quiet, 70, 80, 90, and 100 dB, during vocal production. Significant interactions between group and noise levels would have implications for vocal nodule problems. Fundamental frequency was found to differ between groups and between noise levels. The interaction was significant. Intensity level was significant between groups and between noise levels, but there was no interaction. Vocal tension in microvolta was significant between groups and between noise, but there was no interaction. For all three measures the vocal nodule group had higher measures than the normals. Only for fundamental frequency did the interaction reveal that the vocal nodule group increased its distance from the normals with noise level. Implications will be discussed.
Stereophonic recording and listening; Modern techniques and devices used to preserve and to enhance the spatial attributes of sound
Authors: Trahiotis Constantine , Bernstein Leslie R.
Published: October 2005

Recently, several products have become available to consumers who wish to enhance the spatial qualities of their hi-fidelity audio systems in homes and automobiles. These products capitalize on the use of electronic circuitry and speaker design which allow for the extraction and synthesis of interaural temporal and intensitive disparities present in records and in listening rooms. While some of these products appear to widen greatly the “sound-stage” produced by two normally placed loudspeakers, others utilize four or more separate loudspeakers to increase the apparent front-to-back size of the listening room. In addition to presenting the theoretical basis for such devices, we will discuss both approaches and evaluate them in terms of their entertainment value and their ability to produce more “realistic” sound images.
Directional hearing in relation to hearing impairments and aids
Authors: Colburn H. S. , Zurek P. M. , Durlach N. I.
Published: October 2005

The normal binaural auditory system provides the listener with a “spatial filter bank” that facilitates the detection, localization, and monitoring of acoustic sources and improves the understanding of speech in noisy environments. Since impairments often degrade binaural capabilities, it clearly is important to characterize and understand these degradations and to develop hearing aids that compensate for them. In the first portion of the talk, we present an analytic summary of normal binaural advantages. Next, we review past work on the effects of conductive and sensorineural impairments on binaural capabilities. Finally, we consider some results on the effects of hearing aids on these capabilites and some approaches to the problem of providing binaural benefits to the hearing impaired. [Work supported by NIH.]
A harmonic distortion standard
Authors: Frye George J.
Published: October 2005

All harmonic distortion analyzer instruments may not give the same reading when measuring a particular audio range signal. A design method is presented that can supply a signal with a precisely determined amount of harmonic distortion. Digital signal generation technique is used. Factors which determine the accuracy of the signal are examined. An instrument was designed using the outlined principles. With it, the operator can control the frequency of operation, the harmonic, and the percentage of distortion. Results from the sample constructed are presented. Performance of a number of distortion analyzers are shown.
A comparison of spatial spectra from a vertical line array using the maximum entropy method and the standard FFT beamformer
Authors: Lawrence Mimi Zebrick , Ramsdale Dan J.
Published: October 2005

Acoustic data were collected in the Northeast Pacific using a vertical line array placed near the bottom. Narrow-band data were provided by a cw source (54 Hz) which was towed at a nominal depth of 91 m radially away from the array. Time series from each hydrophone were converted to the frequency domain using an FFT with an 0.625-Hz processing band. Spatial spectra were obtained for the source frequency using both a standard FFT beamformer and the maximum entropy method (MEM), which was implemented using the Burg algorithm in complex form. Conventional power averaging was utilized for the standard FFT beamformer while the MEM beamformer displayed the best results when the averaging was performed over the filter coefficients. The MEM beamformer was exercised for different model orders, with the sharpness of the signal arrivals increasing with increasing model order as expected. The half-power width of typical signal arrivals was approximately seven times smaller with the MEM beamformer than with the standard FFT beamformer. The background noise level for directions away from the signal arrivals was correspondingly approximately 10 dB lower on the MEM beamformer. [Work supported by the Naval Electronic System Command.]
A computer system for aircraft flyover acoustic data acquisition and analysis
Authors: Boston D. W. , Cashar E. E. , Cope D. A. , Glover B. M.
Published: October 2005

A mini-computer-based system housed in a mobile trailer was designed for field measurements of aircraft flyover noise. The system was used to accomplish recent Federal Aviation Regulation Part 36 noise certification testing for the new Boeing model 757 and 767 aircraft. The multi-user system performed acoustic and telemetered data acquisition, analysis, and data storage. All data were made available to online color monitors and on hardcopy. One-third octave band acoustic data were acquired and analyzed via microcomputer controlled digital frequency analyzers. Ground weather data and telemetered data, which includes upper air weather and airplane position and performance information, was received, stored and displayed automatically. By integrating all of the data, fully corrected acoustic time histories, spectra, and EPNL values were calculated within minutes of an airplane flyover. Online data output were used to make test operational decisions and evaluate aircraft noise level predictions. This computer system increased test efficiency by providing high quality data to personnel for real time decision making.
Aeroacoustic theory for low Mach number flows
Authors: Crighton David G.
Published: October 2005

Recent experiments by Laufer and Yen offer the first chance yet for an examination in all detail of the predictions of Lighthill aeroacoustic theory. The experiments concern the internal flow structure and radiated acoustic field of discrete tone subharmonic instability waves associated with multiple vortex interactions on the laminar initial shear layer of a weakly excited round air jet at very low Mach number (0.05 < Mj < 0.2). This paper will review all aspects of low Mach number aeroacoustic theory in the light of these experiments. Linear and nonlinear hydrodynamic stability theory will be used to give a reasonable description of the subharmonic shear layer waves. However, what should then follow as a routine application of the Lighthill theory throws up several difficulties, from which it is concluded that the theory apparently cannot be used in its elementary form to predict the sound from air jets even with Mach numbers as low as 0.1. [Work carried out in collaboration with Dr. Patrick Huerre, Dept. of Aerospace Engineering, Univ. of Southern California.]
A comparison between the SR-6 propeller noise in flight and in a wind tunnel
Authors: Dittmar James H. , Lasagna Paul L. , Mackall Karen G.
Published: October 2005

High-speed turboprops offer an attractive candidate for future aircraft because of their high propulsive efficiency. However, one of the possible problems associated with these propellers is a high level at cruise that might create a cabin environment problem for future aircraft powered by these propellers. Models of these propellers have been tested for acoustics in the Lewis 8-by-6-ft wind tunnel and on the Dryden JetStar airplane. This paper shows comparisons between the airplane and wind tunnel data for the SR-6 propeller. The comparison of the maximum blade passing tone variation with helical tip Mach number taken in flight with that taken in the tunnel showed good agreement when corrected to the same test conditions. Directivity comparisons also showed fairly good agreement. These good comparisons indicate that the wind tunnel is a viable location for measuring the blade passage tone of these propellers.