bluuebunny/crossref_metadata_2025 huggingface dataset:
Oto-acoustic emissions and remote masking
Authors: Bilger Robert C. , Matthies Melanie L.
Published: October 2005

The explanation of remote masking assumes that, at high levels, the random envelope of a band of noise is converted to a propagated noise by distortion in the region of maximum stimulation. If this assumption is correct, then there is a chance that that noise will be “emitted.” To this end, ear-canal measures were obtained from young, normal-hearing adults using a miniature receiver (Knowles, ED-1932) and an electret microphone (Knowles, BT-1842) coupled to a speculum (impedance probe). This assembly was sealed into the ear canal with a soft plastic tip. A band of noise (1000–5600 Hz) was presented at 40, 60, 80, 90, and 100 dB SPL via the miniature receiver and the filtered (1000 Hz low-pass) microphone output was analyzed (Hp-3582A) into one-third octave levels. The procedure was repeated for a 0–1000 Hz band, in which case the microphone output was high-pass filtered at 1000 Hz. For levels above 80 dB SPL, the third-octave levels below or above the noise band were appreciably greater in the ear canal than in a 2-cc cavity. [Work supported by grant NS-17273.]
An abbreviated procedure for obtaining performance intensity functions with a single administration of the Edgerton-Danhauer NST (1979)
Authors: Johnson Carole E. , Asp Carl W. , Danhauer Jeffrey L.
Published: October 2005

An abbreviated procedure for obtaining performance intensity functions with a single administration of the Edgerton-Danhauer Nonsense Syllable Test (1979)—a 25-item consonant-vowel-consonant-vowel (CVCV) open-response test of phoneme identification—was developed. Consecutive series of five CVCV items from a single administration of NST List A were presented at 15, 25, 35, 45, and 55 dB SL re: SRT to normal-hearing and hearing-impaired listeners in addition to administration of the entire NST List A at each of the same sensation levels. Results indicated no significant differences between performance intensity functions obtained with either procedure for both listener groups. The abbreviated procedure shows promise as a reliable and time efficient method of obtaining performance intensity functions. with a single administration of this test.
Loudness indicators for speech
Authors: Longinotti Cheryl
Published: October 2005

This study compared four measures to equate speech signals for loudness: VU level, A-weighted sound level, sones computed via Stevens' Mark VI, and sones via Zwicker (ISO, R532-1966). Monosyllabic speech tokens were equated for loudness and for indicated magnitude to a stationary reference, a synthesized [a]. Equal loudness was determined with normal listeners in sound field at two levels. Attenuation of each monosyllable was varied until its indicated magnitude (as measured electrically or via digital computation) equaled that of the reference. Attenuation for equal loudness was compared to attenuation for equal indicated magnitude. Results from fast and slow time constants were highly correlated. Presentation level did not alter relative ranking of the indicators. The VU meter performed best in equating speech to the reference; average error was less than the range described by the 95% confidence limits of the loudness judgments (+/−1 dB). Stevens' and Zwicker's procedures performed best in equating loudness among speech signals with an average error of less than 2 dB.
Amplification systems in a classroom for hard-of-hearing listeners
Authors: Nábělek Anna K. , Donahue Amy , Letowski Tomasz
Published: October 2005

Listening systems are used for hearing-impaired listeners as an alternative to public address systems (PA) used for the general public. These listening systems allow for individual control of sound pressure level and minimize the effects of background noise and room reverberation. Three listening systems: an audio induction loop (AL), frequency modulation of radio frequencies (FM), and modulation of infrared light (IR) were compared among themselves and with a PA system in a medium-size classroom. Listening groups were normal hearing, hearing impaired, hearing aid users, and elderly. Word-identification scores were obtained with the Modified Rhyme Test at two conditions: with a babble of 12 voices at speech-to-noise ratio (S/N) of + 8 dB and without the babble at S/N of + 20 dB. Analysis of variance indicated that the main effects of systems, groups, and S/N were significant. Also significant were interactions of systems by groups and systems by S/N. For all groups, the three listening systems provided better scores than the PA system. It can be concluded that all three tested listening systems are suitable for listeners with various degrees of hearing losses. [Work supported by NIH.]
Child and adult vibrotactile thresholds for sinusoidal and pulsatile stimuli
Authors: Bernstein Lynne E. , Kroshinsky Miriam B. , Goldstein Moise H.
Published: October 2005

As part of our effort to develop a tactile aid for hearing impaired children, we have obtained vibrotactile sensitivity thresholds from 6- and 10-year-old children and from adult subjects. In agreement with Rothenberg, Verrillo, Zahorian, Brachman, and Bolanowski [J. Acoust. Soc. Am. 62, 1003–1012 (1977)], we have found that pulsatile stimuli result in flatter threshold functions in comparison with sinusoids. Developmental data on tactile sensitivity are scant and are generally from children approximately 10 years or older [e.g., Verrillo, Sens. Processes 3, 49–59 (1979)]. The research literature suggests that vibrotactile sensitivity declines with age. Subjects were tested with either sine or pulse waveforms. A 2IFC adaptive procedure was used. Test and retest thresholds were obtained at intervals of at least one week. Equal numbers of trials were required to obtain thresholds across age. Results suggest that children's thresholds improve with practice and that they are able to detect lower levels of stimulation than adults. [Work supported by NIHR and NSF.]
Effects of anterior corpus callosotomy on central auditory function
Authors: Baran Jane A. , Musiek Frank E.
Published: October 2005

This paper presents auditory findings for patients with anterior corpus callosotomies. Peripheral (pure tone and speech discrimination) and central auditory tests were administered to each subject pre- and postsurgery. The central tests included a low-pass filtered speech test, three dichotic speech tests, and the pitch pattern perception test. Mean scores for the peripheral tests fell grossly within the normal range preoperatively, and showed little change postoperatively. Similarly, scores on the central tests, though somewhat more variable, did not show any obvious differences upon pre- and postsurgical comparison. A comparison of these results with those for patients with posterior callosotomies [F. E. Musiek et al., Sem. Hear. 5, 219–229 (1984)] revealed that in general, the anterior group showed fewer postsurgery deficits on all central tests than did the posterior group. The lack of an “auditory” effect in the anterior group is believed to have an anatomical correlate. Animal studies have demonstrated that the auditory area of the corpus callosum is located in its posterior half [D. Pandya et al., Brain Res. 32, 31–43 (1971)]. Therefore, greater auditory effects would be predicted with posterior sectioning than with anterior sectioning.
Ultrasonic detection of oral markers for tongue scanning
Authors: Hamlet Sandra L. , Neubauer Werner G.
Published: October 2005

Using real-time ultrasonic scanning a certain amount of success can be achieved empirically in locating metal markers on the tongue or elsewhere in the vocal tract. Metallic objects can produce a distinct artifact on ultrasonic scans, which has been described as appearing like a beacon or comet-tail. The artifact “points” to the marker, which may otherwise not have a distinct echo. Problems in using such an artifact for orientation markers for tongue scanning were mentioned in an earlier paper [Hamlet, J. Acoust. Soc. Am. Suppl. 1 74, S47 (1983)]. Since the cause for the artifact is the complex ultrasonic rigid itself, its location and replication in this field are further complicated by the vagaries of the tissue as an acoustic medium. Our aim was to approach this problem from a physical acoustics perspective so as to better understand the optimum conditions required for more reliable detection. A linear array real-time ultrasonic scanner at 5 MHz was employed. Approaches attempted thus far include transducer masking for field simplification, receiver probe verification of the field, developing a method for creating a cigar indication of beam direction on the scan, testing marker location and angulation, and feasibility checks with human subjects. The field and marker conditions for the purpose of orientation, being rather like a calibration, need not be the same as for data collection, so that certain simplifications can be tolerated when they produce reliable results. [Work supported by NIH.]
A tongue pellet for use in ultrasound imaging
Authors: Stone Maureen , Shawker Thomas H. , Sonies Barbara C.
Published: October 2005

A 5-mm stainless steel ball bearing was affixed to the tongue using dental impression material and imaged visually with real time ultrasound. The pellet was used to measure movement at a single point on the tongue surface during speech and swallowing gestures. The pellet was placed at midline, a measured distance posterior to the tongue tip. Methodological validation of the visibility and positioning of the pellet was determined from phantom measurements. Pellet movements during speech were found to define superior/inferior and anterior/posterior tongue movements. Our data suggest, however, that these movements do not always represent the point of maximum interest on the tongue surface. Measurements made during swallowing indicate that for both single swallows (20 cc H2O) and continuous swallows pellet movement over time contains transverse and longitudinal wave components. Greater tongue excursion occurred during continuous swallowing. The advantages and limitations of using a pellet will be discussed. Future applications will be mentioned.
Voice discrimination by two listener populations
Authors: Kreiman Jody , Papçun George
Published: October 2005

The ability of two groups of listeners (over and under 45 years of age) to discriminate among the voices often young male Southern Californians was examined with a paired-comparison task. Listeners heard both orders of all possible pairs of voices, plus 30 pairs where voices were the same. They indicated for each pair whether the voices were the same or different and how sure they were of their response. Discrimination scores across groups ranged from nearly perfect (Az = 0.97) to near chance (Az = 0.69). Overall, the older group of listeners performed significantly less well than did the younger group: They made fewer correct identifications (24.65 vs 26.58), more false identifications (25.45 vs 17.75), and had a lower group discrimination score (Az = 0.85 vs 0.92). (All comparisons were significant at p < 0.05.) Two explanations are suggested. Aging may affect the ability to discriminate among voices as it does the ability to discriminate among phonemes [P.J. Price and HJ. Simon, L Acoust. Soc. Am. 76, 405–410 (1984)]. Alternatively, younger listeners may discriminate better because they have more experience with the voices of their peers than do older listeners.
Model for the peripheral processing of sound in bony fish
Authors: Rogers Peter H. , Cox Mardi , Popper Arthur N. , Saidel William M.
Published: October 2005

A new hypothesis for the processing of acoustical information by bony fish is presented. The hypothesis proposes that the ear itself can perform most of the calculations required to localize a sound source, and discriminate frequency and beam form for signal to noise enhancement. Prior theories assume all of the analysis occurs in the central nervous system (CNS). A mechanism is demonstrated by which the ears may resolve the particle velocity into three vectorial components and determine the time derivative of the acoustic pressure. This information can be used to localize a sound source, assuming that the CNS is capable of evaluating the ratio of the appropriate velocity components. If localization is accomplished in this manner, it follows that the CNS would also be capable of finding the ratio between the magnitude of the acoustic particle velocity and the time derivative of the acoustic pressure. This ratio is shown to be proportional to frequency in the farfield, and the product of the frequency squared and the distance from the source in the nearfield. Thus discrimination between frequencies is possible at any distance, absolute frequency can be determined in the farfield, and some capability to discriminate range might also be possible. Supporting evidence from the literature is presented. [Work supported in part by ONR and NIH.]
The application of principal-components spectral analysis to sensory aids for the hearing impaired
Authors: Zahorian Stephen A.
Published: October 2005

In order to present speech information through an alternate sensory modality—such as touch or vision—extensive processing of the speech signal is required. This processing should represent a large amount of speech information with a small number of slowly varying parameters. These parameters should be relatively speaker independent, robust in the presence of noise, and closely linked to the perceptually important features of speech spectra. One such set of parameters are speech spectral principal components. In this paper we will discuss the application of principal-components analysis of speech spectra to speech recoding for use with sensory aids. A brief overview of the analysis procedure will be included. An interpretation of principal components, and a comparison with other speech parameters such as speech formants, will be presented. Both potential benefits and drawbacks of this analysis procedure will be discussed. In addition, the implementation of a vowel articulation training aid based on principal components will be presented. Although the vowel training aid utilizes a visual display format, with color as a primary information-bearing parameter in the display, the procedure used for obtaining principal components applies equally well to a tactile aid.
Vibrotactile sensitivity thresholds of hearing children and of profoundly deaf children
Authors: Bernstein Lynne E. , Schechter Miriam B. , Goldstein Moise H.
Published: October 2005

We investigated sensitivity thresholds for 1-s sinusoidal stimuli of 20, 40, 80, and 160 Hz with hearing 5- to 6- and 9- to 10-year-olds and adults. Stimuli were presented in a two-interval forced choice procedure according to an adaptive rule to estimate the 70.7% threshold [H. Levitt, J. Acoust. Soc. Am. 49, 467–477 (1971)]. Results showed that young children were somewhat less sensitive than older children and adults. The present results are not in complete agreement with published reports [R. T. Verrillo, Bull. Psychonomic Soc. 9, 197–200 (1977) and R. D. Frisina and G. A. Gescheider, Percept. Psychophys. 22, 100–103 (1977)]. Previously, we found no effect of age with haversine pulse trains. To explore whether hearing status might affect sensitivity, two prelingually profoundly deaf children were tested with 1-s haversine stimuli at 10, 50, 100, 160, and 250 pulses per second. The deaf children were at least as sensitive as previously tested normally hearing adults and children. [Work supported by NSF and NINCDS.]
The effects of phase randomization in the detection of interaural differences of time in five-component complexes
Authors: Dye R. H. , Yust W. A.
Published: October 2005

Threshold interaural differences of time (IDTs) were measured for two types of interaural delays. In the first case, the stimulus consisted of 550-650-750-850-950 Hz, and thresholds were measured for all possible combinations of one, two, three, four, and five delayed components. In the second case, threshold interaural envelope delays were measured for five-component waveforms whose carriers were 2 and 4 kHz and whose modulation frequencies ranged from 20–500 Hz. Comparisons were made between thresholds measured when all components were added in sine phase and those obtained when the starting phases were randomized between intervals of a two-interval task. The signals were 100 ms in duration, and the level of each component was 65 dB SPL. For the low-frequency waveforms in which a subset (m) of the five components was delayed, phase randomization had a negligible effect on performance. Regardless of the starting phases, d′m was approximately equal to d′1 m, where d′1 is the d′ when one of the five components was delayed. These data tend to support the contention that this task is performed by a component-by-component analysis, with the lateral position determined by a weighted average of the information at each frequency. For the high-frequency waveforms with envelope delays, phase randomization had only small deleterious effects on performance, rendering untenable explanations based on interaural comparisons of the outputs of simple envelope detectors. [Work supported by NSF, NIH, and AFOSR.]
Spectral dominance in sensitivity to interaural delay for broadband stimuli
Authors: Zurek P. M.
Published: October 2005

Just-noticeable differences (jnds) in interaural delay of a target band were measured in the presence of a diotic spectral fringe. Stimuli were clicks or 100-ms bursts of noise with flat spectra from 0.1 to 9 kHz. The bandwidth of the target band was 0.4 times the center frequency. With either clicks or noise, the jnds for target bands having center frequencies between 0.5 and 1 kHz were roughly unaffected by the presence of the fringe: They were on the order of tens of microseconds. In contrast, the jnds for target bands at high frequencies were greatly degraded by the presence of the fringe: They increased from approximately 100 μs to greater than 600 μs. With noise, delaying a low-frequency target band causes the image of that band to separate from the image of the fringe. With clicks, delaying a low-frequency band (with about 3% of the total energy) causes the entire wideband image to lateralize. In general, the results suggest that the degree of the dominance region described by Bilsen and Raatgever [Acustica 28, 131–132 (1973)] is virtually total and that interaural delays at high frequencies are insignificant compared to those at low frequencies. [Work supported by NIH.]
Perception of modulations in pitch and lateralization
Authors: Beecher Laurel , Stern Richard M.
Published: October 2005

We compare the ability to perceive low-frequency sinusoidal modulations of monaurally and dichotically created pitch to the perception of modulations of the subjective lateral position of a binaural image. The stimuli used in the dichotic pitch experiments had a 0- to 2000-Hz lowpass spectrum, and they were created by modulating the time delay of a multiple-phase-shift filter [F. A. Bilsen, J. Acoust. Soc. Am. 59, 467–468 (1976)]. Stimuli with similar spectra and sinusoidally modulated interaural time delays (ITDs) were used for the lateralization experiments [D. W. Grantham and F. L. Wightman, J. Acoust. Soc. Am. 63, 511–523 (1978)]. We also examined the perception of monaural frequency-modulated pure tones, and monaural lowpass stimuli created by summing the signals to the two ears from the dichotic pitch stimuli. Subjects discriminated between sinusoidally modulated and unmodulated stimuli using 2IFC paradigms, and we determined the threshold frequency deviation or ITD as a function of modulation frequency. Preliminary results were similar for all three pitch experiments: Frequency deviation at threshold was constant for modulation frequencies up to approximately 10 Hz, and then increased as a power function of modulation frequency up to at least 32 Hz. Threshold ITDs in the lateralization experiments were constant for frequencies up to about 4 Hz, and then increased with increasing modulation frequency. [Work supported by NIH.]
Fundamental frequency and its relationship to Spanish stress
Authors: Massone M. I. , de Manrique A. M. B.
Published: October 2005

In the present work, we attempt to describe F0 movements and the amount of F0 change in the stressed syllables of Spanish sentences as a function of phonetic and linguistic effects. The material consisted of a list of 92 sentences with different syntactic structures which were recorded twice by a male speaker. Wideband spectrograms and F0 contours of all the sentences were obtained. F0 movements on the syllabic nucleus of each accented syllable were chosen as the parameters for the analysis of F0 contours. Results showed that the accented syllabic nucleus presents the following F0 movements: rise, fall, level, and rise-fall. These movements are correlated with effects such as the nature of the preceding consonant (level with voiceless, rise with voiced), position of the accented word (fall in the last accented word, rise in yes-no questions), and boundary (rise-fall or fall). Emphatic stress is correlated with increased F0 and larger F0 excursions. The amount of F0 change seems to follow a declination line. This general pattern is altered by different effects: lexical (adverbs, pronouns), syntactic (phrasal verbs, aposition, prepositional phrases, clauses, syntactic phrases), and semantic (modality operators, emphasis, prominent words).
The effects of sea surface roughness on the transmission of sound through an air-ocean interface
Authors: Barger J. E. , Sachs D. A.
Published: October 2005

This is a review of recent experimental and theoretical studies of the influences of the sea surface on the transmission of airborne sound into the ocean. Most applications will depend upon conditions where the refracted grazing angle is greater than approximately 30° since the loss is very large for smaller angles. For grazing angles larger than 30°, two parameters serve fairly well to characterize the transmission loss through the sea surface. The first is a roughness parameter R which is equal to the sea wave height measured in airborne sound-speed wavelengths. The second is a diffraction parameter DL which is equal to the Fresnel zone diameter measured in correlation lengths of the sea surface slopes. When R is less than unity and DL is less than 3, there is usually no effect due to surface roughness. When either condition is not satisfied, there is usually more transmission loss than there would be through a flat surface. Exceptions to this depend upon the refracted grazing angle and upon the angle between the wave crests and the incident sound.
The effect of vowel quality variations on stress-beat location
Authors: Fox Robert Allen , Lehiste Ilse
Published: October 2005

This study examines the effect which vowel quality variations have upon the location of vowel onsets—indicators of stress-beat location—in rhythmically produced lists of monosyllables. Three talkers produced 120 sequences consisting of seven monosyllabic tokens of the form /s___t/. These token sequences were either homogeneous (identical components) or alternating (stimulus syllables alternated with the token “sight”). Talkers produced the sequences in both a metronome and nonmetronome condition. Analysis of the obtained results shows that vowel quality variations had a significant effect upon the location of the vowel onset. Regression analysis demonstrated that the differences in vowel onset-to-vowel onset intervals were significantly related to vowel duration differences between the tokens. There was also a significant difference between talkers in terms of the location of the vowel onsets, suggesting either the use of different production strategies or differential capabilities in doing the rhythmic task. No evidence of preboundary lengthening was obtained. These data support the suggestions [R. A. Fox and I. Lehiste, J. Acoust. Soc. Am. Suppl. 1 77, S54 (1985)] that the location of the “stress beat” is determined on the basis of the acoustic structure of the entire syllable, rather than strictly upon the articulatory onset of the vowel and that subjects in such a task do not necessarily impose a hierarchical structure on the syllabic sequences. Perceptual data relevant to the importance of vowel durations to the stress-beat location will also be presented.
Perceptual cues to lexical accent contrasts in English and Japanese
Authors: Beckman Mary E.
Published: October 2005

Earlier experiments have shown that Japanese and English differ in the extent to which they use duration and vowel amplitude patterns as acoustic correlates of lexical accent [M. E. Beckman, J. Acoust. Soc. Am. Suppl. 1 71, S23 (1982); J. Acoust. Soc. Am. Suppl. 1 75, S41 (1984)]. A new experiment examines the relative salience of various acoustic correlates as perceptual cues in the two languages. Minimally contrasting test utterance pairs from the earlier production experiments were used to synthesize test stimuli with all possible combinations of acoustic patterns (e.g., the F0 and amplitude patterns of contráct combined with the duration and spectral quality patterns of cóntract). Japanese, Americans with speaking knowledge of Japanese, and monolingual Americans judged the accent patterns of these test stimuli. Results showed differences correlated both with the source language of the stimulus, and with the language background of the subject. For all three groups, F0 was the dominant cue to the accent patterns of the Japanese stimuli, scoring significantly higher than it did in the judgments of the English stress patterns by the same group. In judging the English stimuli, the monolingual American subjects relied on acoustic cues other than F0 to a greater extent than did the bilingual Americans, although both American groups used them to a greater extent than did the Japanese subjects, most of whose scores for amplitude, duration, and spectral quality patterns were at chance.
Causality, caustics and the structure of transient wave fields
Authors: Brown Michael G. , Tappert Frederick D.
Published: October 2005

Transient acoustic wave fields in the vicinity of caustics in both two and three space dimensions are considered. In the vicinity of some possible caustics, the time history of the wave field due to an impulsive source includes a precursor. This noncausal behavior is reconciled with the physical principle of causality by requiring that such caustics be a part of certain higher dimensional caustics. With this constraint, all noncausal arrivals are preceded by a causal arrival and the total time history is causal. This constraint is used to derive some simple general properties of transient wave fields in the short wave limit, e.g., the number of arrivals must be an odd number.
Method for study of range-dependent time-differences-of-arrival between underwater sound eigenrays
Authors: Greene David C.
Published: October 2005

PASCAL language computer programs are described, which allow the calculation of eigenrays between an underwater source and receiver and the study of the range-dependence of time-differences-of-arrival (TDOAs) between eigenrays. The method uses a sound velocity profile from a disk file and user-supplied source and receiver depths. First, characteristics of rays which graze the surface and the bottom are calculated and presented to the user. Using this information, the user estimates eigenray angles. The program refines the user's estimate until the range error of the eigenray is smaller than a threshold value (typically 0.1 ft). Time of arrival for the eigenray is noted and the process is repeated for a set of range values. The process is repeated for other eigenrays. The range histories of arrival times of the eigenrays are used to calculate the range-dependent TDOAs. Using an 8-bit, 4-MHz microcomputer, less than 10 s are required to refine an estimate to an eigenray determination. Calculation of TDOA-versus-range data for ten pairs of five eigenrays takes about 30 min.
Accurate PE calculations for range-dependent environments based on c updates
Authors: Jensen Finn B. , Martinelli Giovanna
Published: October 2005

The standard parabolic approximation to the acoustic wave equation is known to have intrinsic phase errors, which will degrade the accuracy of any PE solution for long-range propagation in the ocean. Pierce recently suggested a remedy to minimize these phase errors by simply choosing an appropriate mean phase speed (c0), eventually updated with range, representing a weighted average of all phase speeds involved in a particular propagation problem. We have now extended Pierce's formalism to include the wide-angle parabolic equation of Thomson and Chapman [J. Acoust. Soc. Am. 74, 1848 (1983)], which inherently has smaller phase errors than the standard parabolic equation. The importance of using c0 updates in PE calculations for range-dependent environments is demonstrated through numerical results for a wedge-shaped ocean. Comparison with alternative solution techniques (coupled modes, intrinsic modes) shows that accurate PE solutions for the wedge problem can be obtained only for single-mode situations, even when using c0 updates with range.
Effects of random bottom structure and topography on transmissions in a shallow ocean
Authors: Ashley C. E. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

In a recent paper [C. E. Ashley, M. J. Jacobson, and W. L. Siegmann, J. Acoust. Soc. Am. 76, 1445–1455 (1984)], the authors studied the influences of stochastic horizontal bottom structure on underwater sound transmissions. Both bottom density and sound speed were taken to be random. Ray theory was used in an isospeed channel with horizontal boundaries. In this study, we add to random structural effects those of a lossy bottom interface consisting of large-scale random facets with curvature, on which may be superimposed small-scale roughness. Each facet is assumed to possess small random slope, depth deviation, and curvature. Initially, we take acoustic rays to be specularly reflected from a large-scale facet bottom, and derive formulas for the mean and variance of incoherent intensity at a point receiver for a transmitted cw signal. The results are sufficiently general to permit their use with different bottom-acoustic models. Relative effects of structure and topography are compared. Subsequently, small-scale roughness is added to the facets, and the consequences of scattering are considered. [Work supported by ONR.]
The stabilization of stepwise coupled modes
Authors: Evans Richard B.
Published: October 2005

A decoupling algorithm is derived to stabilize the calculation of the stepwise coupled modes. The stepwise coupled mode method reduces the elliptic wave equation in a discretely range-dependent environment to the solution of a matrix two-point boundary value problem. The solution of such boundary value problems can be unstable in the presence of modes whose amplitudes both grow and decay rapidly with range. This stability problem affects the accuracy of the stepwise coupled mode solution as range and frequency increase. The decoupling algorithm described here solves this stability problem. The algorithm makes it possible to decouple the growing solution from the decaying solution. Then each solution can be computed accurately by integrating in a direction in which the solution decays. The stabilized stepwise coupled mode method is more accurate at longer ranges and higher frequencies than the original method. [Work supported by NORDA.]
Measurement of the acoustic intensity in the nearfield of a fluid-loaded, point-driven cylinder using nonplanar nearfield acoustical holography
Authors: Williams Earl G.
Published: October 2005

Nearfield acoustical holography (NAH) is confined to the reconstruction of acoustic fields in parallel planes with a hologram consisting of a measurement of the acoustic pressure over a plane boundary. Although ideal for planar sources, such as vibrating plates, NAH encounters problems in dealing with nonplanar sources. Therefore, we have modified the technique to apply specifically to a cylindrical geometry with a hologram comprising a cylindrical contour. The cylindrical hologram consists of the measurement of the amplitude and phase of the pressure field at 4096 points on this cylindrical contour. This contour is located close, and concentric with, a radiating cylindrical source (in this case a finite, point-driven cylindrical shell submerged in our underwater tank facility). We show how this hologram is processed in a rigorous manner to map the pressure, vector velocity, and vector intensity (real and reactive components) from the surface of the source into the farfield. The vector intensity maps are shown to be helpful, in many cases, in identifying the location of the point driver attached inside the shell. Both the active and reactive intensity fields will be shown. Since the vector velocity is also obtained from the cylindrical hologram, we can identify the radial mode shape of vibration from the radial velocity component at the shell surface, and along with the reconstructed surface pressure (which provides the fluid loading) we can also map the surface intensity. This latter quantity is used to compute the total power radiated by this mode shape. This new technique provides a comprehensive method to study radiation from cylinders.
A nonlinear coherence function and its application to machine diagnostics
Authors: Coffin Tom , Jong Jen Yi
Published: October 2005

The harmonic content in dynamic measurements from rotating machinery contains much subtle information concerning equipment operational condition and component degradation. For this reason, the power density spectrum (PSD) has long been employed to assess the relative magnitude of fault-related spectral contributions. Measurements on high-performance rocket engine turbomachinery suffer from severe noise contamination from numerous extraneous sources, which impedes rotating element diagnostic evaluation. It is thus difficult to determine whether an apparent high-level harmonic contribution is indeed related to the fundamental rotational frequency, f1, or possibly due to an independent source. The ordinary PSD, being an absolute value, is of no assistance to this problem. In an effort to relate synchronous speed characteristics with an arbitrary harmonic component, an unique coherence spectrum was devised which we call the hyper-coherence function. The hyper-coherence function, Hn(f1), defines the nonlinear correlation between waves at the fundamental frequency and harmonics at nf1, n = 1,2…. The computation is straightforward by FFT methods, and results in a line spectrum of correlation coefficients as a function of harmonic number. This paper presents the hyper-coherence as a multiple-ordered correlation function and illustrates its utility through application to several idealized signals, and the assessment of an apparent high-amplitude harmonic signature in rocket engine vibration measurements.
Green's function analysis of free shear layer instabilities in jets of arbitrary cross section
Authors: Koshigoe Shozo , Tubis Arnold
Published: October 2005

Sound generation via the Kelvin-Helmholtz instability mechanism in jet shear layers is closely related to instability modes with the largest spatial growth rates [A. Michalke, J. Fluid Mech. 23, 521–544 (1965)]. Recently, there has been considerable experimental interest in noncircular jets [e.g., E. Gutmark et al., AIAA Shear Flow Control Conf., 12–14 March, Colorado Springs, CO, 1985; and R. A. Peterson et al., Bull. Am. Phys. Soc. 29, 1562 (1984)]. In order to theoretically describe these cases, we have used Green's function techniques to develop practical solution methods for the Orr-Sommerfeld linearized stability equations with arbitrary jet mean flow profiles. Some preliminary results are presented for critical Reynolds numbers, instability mode eigenfrequencies, and shape functions. [Work supported by NWC research grant.]
A simplified boundary element formulation for acoustic radiation and scattering for axisymmetric bodies and boundary conditions
Authors: Soenarko Benjamin , Seybert A. F.
Published: October 2005

A special formulation involving axisymmetric bodies and boundary conditions is presented using the boundary element method. For this special case, the surface integrals are reduced to line integrals and an integral over the angle of revolution. The integration over the angle is performed partly analytically in terms of elliptic integrals and partly numerically using simple Gaussian quadrature formula. This model allows simple discretization scheme for a desired degree of accuracy and less computing time as compared to the general three-dimensional boundary integral equation method. Examples are shown for problems involving spheres and cylinders.
Spectral analysis via lag reshaping of the correlation estimate
Authors: Nuttall Albert H. , Carter G. Clifford
Published: October 2005

The possibility of achieving maximally stable, low-sidelobe spectral estimates, without the need for overlapping or temporal weighting, is investigated both theoretically and via simulation. In particular, the (frequency domain) power spectral estimates of each of a sequence of abutting rectangularly gated time data segments are averaged, and then Fourier transformed into the lag (or correlation) domain. This correlation estimate is then reshaped, by dividing out the undesirable triangular autocorrelation of the rectangular temporal weighting, and by multiplying by a desirable lag-weighting function with low sidelobes. Another Fourier transform yields the final spectral estimate of interest. This technique includes, as special cases, the Blackman-Tukey technique and the weighted overlapped segment-averaging FFT technique. The general method has been analyzed in terms of the mean and variance of the spectral estimate, thereby revealing the fundamental dependence of its performance on the temporal weighting, lag weighting, amount of overlap, number of pieces, available data record length, and desired frequency resolution. The mean spectral estimate is equal to the convolution of the true spectrum with an effective window. In the case of lag reshaping, the effective window corresponds directly with the desirable lag-weighting function above, with its low sidelobes. More generally, the effective window is equal to the convolution of the lag window with the magnitude-squared temporal window. Analytic results for the variance of the spectral estimate with rectangular temporal weighting indicate that if the length of the temporal weighting is selected to be somewhat larger than the length of the lag weighting, the variance is at a near minimum. Furthermore, in this situation, the possibly deleterious sidelobes of the temporal weighting can be exactly compensated by proper choice of lag weighting, resulting in low sidelobes and good decay of the overall effective spectral window. Simulation results that confirm all these effects predicted theoretically are presented. The possibility of detecting a weak tonal via lag reshaping is demonstrated, both for a nearby frequency as well as a distant tonal.
Bubble-related ambient noise in the ocean
Authors: Prosperetti A.
Published: October 2005

Several mechanisms by which bubbles can contribute to ambient noise in the ocean are described and their effectiveness estimated. At low frequency, up to a few tens of Hz, bubbles are driven into oscillation by oceanic turbulence. The normal quadrupole radiation mechanism of turbulence thus acquires a monopole character. At frequencies from around 1 to a few kHz single bubbles formed by breaking waves radiate in free oscillation. In the range of hundreds of Hz the acoustic emission may be due to collective oscillations of systems composed of many bubbles. The efficiency of all these mechanisms is estimated on the basis of an adaptation of Lighthill's theory of aerodynamic noise. Finally, at frequencies above several kHz, drop impact and free oscillations of bubbles thereby produced appear to be responsible for the ambient noise. [Work supported by SACLANT ASWR, La Spezia, Italy.]
Autoregressive modeling of nonstationary multibeam sonar reverberation
Authors: Luby James C. , Lytle Dean W.
Published: October 2005

This work describes a technique for simulating nonstationary, multibeam Gaussian sonar reverberation sequences. The primary objective is to simulate quadrature-demodulated complex digital vector sequences that have a prescribed time variant covariance function. We use a first-order integral scattering model to relate the geometrical, environmental, and sonar parameters to the assumed locally stationary multivariate reverberation power spectrum for each of a set of ranges spanning the total observation range of interest. At each range we compute the multivariate autoregressive canonical factorization of the power spectrum. The resultant autoregressive models are used to generate multivariate, correlated, stationary realizations for each range. Next we combine stationary realizations adjacent in range with an overlapped windowing scheme. This scheme allows the spectral characteristics of the reverberation to change with time. Finally, a time variable gain is applied to the entire realization to adjust the average intensity.
Community response to low-frequency impulsive sources
Authors: Schomer Paul D.
Published: October 2005

Most army noise problems are the result of two types of sources: helicopters or large weapons (artillery, etc.). Through analysis of compaints and through attitudinal surveys, the U.S. Construction Engineering Research Laboratory (USA-CERL) has studied community response to these sources. The results show that large-amplitude impulsive noise is better assessed using C-weighting rather than A-weighting, and that building vibration and rattles are the primary adverse factors. Based on these results, USA-CERL, with FAA support, studied the role noise-induced vibrations and rattles play in human response to helicopter noise. A “laboratory” test was performed in the field, using almost 200 subjects. The test used paired comparisons in two real dwelling units. The source as a UH-1H (Huey) helicopter and the control was 500-Hz octave band of white noise with an amplitude (envelope) temporal pattern shaped to approximate a helicopter fly by. The general results show that with no rattles or vibration generated, the helicopter is correctly assessed using A-weighting. With only “a little” rattle, about 10 dB must be added to A-weighted levels for correct assessment, and with “a lot” of rattle, the offset exceeds 20 dB. Overall, these studies demonstrate the very important role noise-induced rattles and vibrations play in noise annoyance.
Piano string excitation
Authors: Hall Donald E.
Published: October 2005

Prediction of piano string motion is challenging for the theorist because the force from the hammer extends over a finite time. Abstract prescriptions for solving this problem with sequences of traveling waves become much more useful when a microcomputer can be assigned to generate all the proper terms and translate their total into graphical output. Sample results will be discussed for a program that includes hammer compliance and can handle any case where the hammer mass is not too much larger than the string mass. How to make adequate allowance for hammer nonlinearity and finite width, string stiffness, and bridge compliance will be considered, along with possible laboratory measurements that could clarify the application of this theory to piano hammer design.
Jitter in violin and singing-voice tones
Authors: Rasch Rudolf A.
Published: October 2005

Musical tones like those of the stringed instruments and the singing voice are not sequences of exactly repeated waveforms with constant frequency, amplitude, and spectrum. Frequency variations can be classified as jitter (random or pseudorandom period-to-period fluctuations), vibrato (quasiperiodic fluctuations with a frequency of 4–7 Hz), and trend (slow, long-term fluctuations). We have investigated a number of musical tones for the presence of jitter and will present the results of various types of measurements, like period-to-period differences, standard deviations of periods, autocorrelations of periods, etc. One of the main findings was the relation between jitter and the resonance of the sound radiating system (top plate, vocal tract). Tones with frequencies near to a resonance had considerably less jitter than tones with frequencies further removed from a resonance.
A Percusive sensor for playing a computer-controlled synthesizer
Authors: Mathews M. V. , Kohut J.
Published: October 2005

A sensor is described for performing a computer-controlled synthesizer. The sensor consists of an equilateral triangle-shaped surface, which is struck with a soft drumstick. Each time the sensor is hit, it sends four pieces of information to the computer—a trigger pulse, the two coordinates of the strike point, and the force of the blow. This information is used by the computer program to control the synthesizer. Several modes of control have been tried. In all modes, loudness is controlled by blow force. In one mode, the two coordinates control pitch and decay time of the sound. Another mode is a form of “conductor program” in which the sequence of pitches to be played is stored in the computer memory. Each stroke causes the next pitch in the sequence to be played. The two coordinates control decay time and spectrum of the sound. The sensor uses three strain gauges mounted at the corners of the triangle. The coordinates and force are computed from the strain gauge outputs by a simple analog circuit.
Evaluation of beam fields reflected at a plane interface
Authors: Ruan Y. Z. , Felsen L. B.
Published: October 2005

The complex ray method [L. B. Felsen, Geophys. J. R. Astron. Soc. 79, 77–88 (1984)] is employed to calculate the fields of a Gaussian beam reflected at a plane interface between two different media. A lateral wave is included in the region of total reflection. To simplify the calculation, a paraxial approximation is employed when the observer is located near the beam axis. These calculations all fail when the beam axis and observer simultaneously approach the critical angle, the criterion of failure being a parameter called the numerical distance. The correct solution in the transition region is generated by a parabolic cylinder transition function. Detailed numerical comparisons provide an assessment of the validity of the various formulations and approximations. [Work supported by NSF.]
Determination of surface wave velocities on single crystals from backscattering measurements
Authors: Adler Laszlo , Bolland Ken , deBilly Michel , Quentin Gerard
Published: October 2005

It was established in previous papers [Adler et al., J. Acoust. Soc. Am. 77, 1950–1953 (1985)] that the Rayleigh angle backscattering may be used to determine surface wave velocities. The method has been applied to single crystal silver, nickel, and copper. Several planes of symmetry have been considered. Simultaneously, an algorithm has been developed to calculate Rayleigh wave velocities on a single crystal surface. Experimental data agree well with theoretical predictions. [This work was supported by NATO Research Grant ♯637/84 to The Ohio State University and to the Universite Paris 7.]
Excitation of plate resonances by transient acoustic wave trains
Authors: Maze G. , Izbicki J. L. , Ripoche J. , Nagl A. , Überall H.
Published: October 2005

Experiments have been carried out with 30-μs-long sinusoidal wave trains incident on an aluminum plate submerged in water. The excitation of plate resonances by such pulses has been observed, in a fashion used previously for cylinders [G. Maze et al., J. Acoust. Soc. Am. 77, 1352 (1985)]. The pulse distortions (in the form of initial transients, a quasi steady-state regime, and a final transient) have been interpreted by the interference of reflected and multiple internally refracted pulses, as previously done by us for a layered ocean bottom [A. Nagl et al., Inverse Problems 1, 99 (1985)]. The final transient, showing a step structure, represents the ringing of the resonance. Overlapping resonances are shown to lead to beat effects in the ringing. [Work supported by the Direction des Recherches, Etudes et Techniques, France, and by the Office of Naval Research and the Naval Research Laboratory, U.S.]