bluuebunny/crossref_metadata_2025 huggingface dataset:
Sonic well logging—acoustic propagation and signal processing
Authors: Porter R. P. , Marzetta T.
Published: October 2005

Oil and gas wells are logged for mechanical properties with acoustic tools that excite elastic waves in the rock formation. Wide-band signals (5 to 20 kHz) are generated near the axis of a fluid-filled borehole. These signals propagate a few feet through the fluid and rock where they are detected by hydrophones also located near the axis of the borehole. The excited wave field consists of compressional and shear head waves, trapped fluid modes and a surface wave or Stoneley mode. The frequency dependence of the head waves and the Stoneley mode are strongly influenced by the formation surrounding the borehole. The higher order trapped modes are dispersive with phase speeds between the shear and fluid speeds. Because the borehole penetrates a complicated geometry of rock layers, the waves traveling in the formation undergo reflections and mode conversions at the bed boundaries. We shall show how the elastic parameters of the rock formation can be extracted from these complex waveforms. Implications of borehole acoustics for the analysis of waveforms will be discussed with emphasis on theoretical and experimental comparisons for both head waves and trapped fluid modes. We will describe coherent signal processing techniques based on many downhole receivers and describe the performance of various spectral estimators and beamformers.
Digital methods for suppression of acoustic noise from speech and music
Authors: Boll Steven F.
Published: October 2005

For the past five years considerable research has been directed towards the study and development of digital methods for acoustic noise suppression. This research has been supported primarily by the needs of the Department of Defense to provide secure narrowband digital speech in high ambient noise military platform environments. In such environments the added noise signal may be of sufficient intensity to prevent the coding algorithm from correctly estimating pitch, voicing, and formant information. These distortions in turn degrade the transmitted speech intelligibility. A variety of methods for removing noise from speech will be discussed. Included will be methods based on spectral subtraction, maximum likelihood, and perceptual modeling. Also considered will be adaptive two-microphone techniques which removes noise from one microphone which is highly correlated with the noise recorded from a second microphone. Finally applications of noise removal in wideband music signals will be discussed.
Effect of aircraft noise on children's reading and hearing levels in Brooklyn and Queens
Authors: Green Kendall , Pasternack Bernard , Shore Roy
Published: October 2005

The percent of students reading below grade level from 1972 to 1976 was regressed on racial, socioeconomic, educational, and noise variables for each school. Schools were assigned noise exposure scores based on Noise Exposure Forecast (NEF) contours. After adjustment for confounding factors, an additional 5% of the students in the noisiest schools read at least one year below grade level with 95% confidence limits from 2% to 8%. In a companion study, 201 cases of permanent bilateral high-frequency hearing loss and 208 controls with normal hearing were identified from school records. Information on residence and confounding factors was obtained from birth certificates and questionnaires. Noise exposure was estimated for each residence from NEF contours and other noise sources. No statistically significant association between noise exposure and the risk or severity of hearing loss was observed. The point estimate of the effect suggested a doubling of risk for residents of the noisiest region with 95% confidence limits from 0.7 to 7.
Active adaptive “Helmholtz resonator.”
Authors: Burgess J. C.
Published: October 2005

The effectiveness of noise reduction by active sound cancellation can be enhanced by using closed-loop control. The classical Helmholtz resonator in a duct acts as a passive filter with fixed stop-band characteristics. Active sound control systems described in the literature for use in ducts have open-loop control (externally set parameters). Such systems can lose effectiveness (and may even become amplifiers) as a result of changes in uncontrollable system parameters, such as temperature and flow rate. An active “Helmholtz resonator” with closed-loop control is not subject to the foregoing limitations. Computer simulation of such a system in a duct implies that it can completely cancel one or more pure tones. The theory supporting the simulation implies that the system can track moderate changes in amplitude and frequency, and that it can cancel narrow-band sound in the presence of spectrally overlapping broadband sound. The method can be applied more widely. [Work performed on sabbatical leave in the Acoustics Research Department, Bell Laboratories, Murray Hill, NJ.]
The attenuation of sound propagating through a radial diffuser with absorptive walls
Authors: Holger David K.
Published: October 2005

An analytical model for acoustic propagation through an idealized radial diffuser under zero flow conditions has been developed. The model has been used to generate a computer program which is capable of predicting radial attenuation for a variety of diffuser wall impedance combinations. Numerical results are presented for the following three cases: (1) one hard diffuser wall—one finite impedance wall, (2) equal finite impedance diffuser walls, and (3) unequal finite impedance diffuser walls. The results for cases (1) and (2) are found to be in good agreement with analytical results from the literature. [Work supported by The Trane Co.]
Feasibility of a three-dimensional finite element scheme for aeroengine duct acoustics
Authors: Abrahamson A. Louis
Published: October 2005

Development of two-dimensional finite element solution schemes for seroengine duct acoustics was initiated in the mid-1970's and has achieved considerable success. Analyses of acoustic propagation in axi-symmetric ducts with nonuniform flow are now possible (A. L. Abrahamson, AIAA Paper, 77–1301) and schemes for increasing computational efficiency have progressed to the stage where repeated analyses for duct liner optimization are feasible (A. L. Abrahamson, AIAA Paper, 79–0662). The payoff, from development of a three-dimensional model, is the ability to analyze axial and circumferential liner segmentation simultaneously. This paper examines the feasibility of a three-dimensional duct acoustics model using Galerkin or least-squares element formulations combined with Gaussian elimination, successive over-relaxation, or conjugate gradient solution algorithms on conventional scalar computers and on a vector machine. A least-squares element formulation combined with a conjugate gradient solver on the C.D.C. Star vector computer initially appeared to hold great promise, but severe difficulties were encountered with matrix ill-conditioning. [Work supported by NASA-LaRC.]
Acoustical radiation from nonaxisymmetric duct inlets
Authors: Posey Joe W. , Clark Lorenzo R.
Published: October 2005

The radiation of isolated spinning modes from two nonaxisymmetric duct inlets each characterized by having a long side and a short side, is examined experimentally to determine the effectiveness of their geometries at redirecting acoustical energy. One is a flight-worthy turbofan inlet, known as a scarf inlet, and the other is a static test inlet. In each case, farfield radiation patterns in the inlet's plane of symmetry are compared with patterns from appropriate axisymmetric inlets. The data shows that the angle of maximum radiation on the short side of either nonaxisymmetric inlet is about the same as for the corresponding axisymmetric geometry, but that the level may be as much as 6 dB higher. The radiation peak on the long side, however, is essentially eliminated in some cases and in others is shifted toward the duct axis, resulting in much reduced levels at and beyond the angle of peak radiation for the associated axisymmetric inlet. This no-flow study shows that significant redirection of turbofan inlet noise can be effected by inlet geometry, aside from any refraction due to asymmetrical inflow.
Microbending fiber optic acoustic sensor
Authors: Lagakos N. , Trott W. J. , Bucaro J. A.
Published: October 2005

Microbending induced mode coupling in optical fibers has been utilized to detect pressure, displacement, acceleration, etc. The acoustic and mechanical design considerations of such an intensity modulated microbending optical fiber sensor is discussed. An illustrative example of how an external force, acceleration, etc., can couple to the sensor is given. All the relevant design parameters are studied and the acoustic frequency response of the sensor is determined. The minimum detectable pressure, acceleration, and displacement are predicted and compared with the latest experimental results. Finally, optimization of the sensor is discussed.
Schlieren multimode fiber-optic hydrophone
Authors: McMahon D. H. , Spillman W. B.
Published: October 2005

A multimode fiber-optic hydrophone based upon a Schlieren intensity modulation mechanism is described. The device possesses sufficient sensitivity to detect the Knudson sea noise levels in the frequency range 100 Hz to 1 kHz and to detect static displacements as small as 2.5 × 1013 Å. It is not susceptible to phase noise and is relatively insensitive to static pressure head variations. The hydrophone is electrically passive. Ease of fabrication, potential low cost, and compatibility with present multimode fiber-optic technology make this device an attractive candidate for incorporation into practical fiber-optic acoustic sensing arrays.
Integrated optical effect of finite beams of ultrasound reflected from planar-liquid solid interfaces
Authors: Cook Bill D. , Fray Charles
Published: October 2005

In studying the reflection of finite beams ultrasound reflected from planar liquid-solid interforces, many investigators have used optical techniques, namely the Schlieren, to demonstrate certain novel features. Of importance is the beam displacement that occurs when the waves generated in solid are near their critical angles. We have previously reported a procedure for calculating the integrated optic effect of a finite beam and the resulting Schlieren pattern. Now we present the results of incorporating the angle dependent reflection coefficient into these calculations. We find that the optical problem is “exact” in two dimensions and is virtually the same as the other two-dimensional theories commonly used to calculate beam displacements. With the numerical procedure, it is possible to include a variety of transducer geometries, i.e., circular, square, or Gaussian, etc., in the modeling, and the answers can be calculated in both the nearfield and farfield of the transducer.
Strain-induced phase noise in an acoustically sensitive fiber-optic interferometer
Authors: Stowe D. W. , Tekippe V. J. , Beasley J. D. , Krueger H. H. A.
Published: October 2005

An acoustic interferometer subjected to random accelerations may experience strain-induced phase noise which exceeds the photon shot-noise limit. In order to minimize strain-induced noise originating in the fiber leads to the interferometer, the leads may be closely juxtaposed so thal they experience the same strain. Experimental results using this technique are presented which show phase-noise cancellalion of 40–60 dB. The observed residual phase noise is in close agreement with theoretical predictions and is shown to be dominated by terms arising from the nonlinearity of the optical indicatrix. Dependence of residual phase noise on lead length and on the static strain imbalance between the leads is discussed.
Forward masking and suppression in the midbrain of an anuran
Authors: Hillery Cynthia M. , Fay Richard R.
Published: October 2005

Averaged evoked potentials (AEPs) recorded in the torus semi-circularis of the southern grey treefrog were used as a measure of forward masking and two-tone suppression. These experiments demonstrate the value of the AEP as a measure of acoustic response in complex stimulus situations. A series of functions were generated by measuring the peak-peak potential produced by a probe tone relative to: (1) the sound pressure level (SPL) of the probe tone, (2) frequency of a forward masking tone at a given SPL, (3) frequency of a “suppressor” tone simultaneously presented with the masking tone at a given SPL, and (4) the cessation of a simultaneous masking tone during continued stimulation by the probe tone (“off” response). The effects of maskers of differing duration and variable intervals between masker and probe tones were also investigated. Preliminary results show that the midbrain AEP can produce reliable forward masking “tuning” curves which resemble those from peripheral fibers innervating both the amphibian and basilar papillae. Further, both paradigms for measuring the two-tone suppression effects in the midbrain (3) and (4) give results which are consistent with results from eighth nerve single unit studies in other anuran species.
Diminution of vocal response in treefrogs due to the presence of masking noise
Authors: Narins Peter M.
Published: October 2005

The neotropical treefrog, Eleutherodactylus coqui produces a two-note advertisement call: the first (Co) note plays a role in spacing of calling males and the second (Qui) note serves to attract conspecific females [P.M. Narins, and R. R. Capranica, J. Comp. Physiol. 127, 1–9 (1978)]. Acoustic playback experiments were performed in which simulated Co notes were presented to isolated calling males in their natural habitat. When presented with a Co note stimulus at an appropriate level, males produced a characteristic one-note response. This response could be totally suppressed by the simultaneous addition of broad-band masking noise. The noise levels necessary for total suppression of the one-note response increased with the stimulus level required to evoke a threshold response. In some cases, wide-band noise of low to moderate levels significantly increased the one-note response rate of a particular male. In another experiment, noise of various bandwidths geometrically centered around 1 kHz, and with total noise power held constant, was added to a Co note of fixed level and presented to a calling male. The average one-note response rate for all males tested was an increasing function of noise bandwidth, for a constant S/N ratio at the animal. Thus the noise energy was more effective at masking when concentrated in a narrow band around the stimulus tone.
The effects of extended reinforcement schedules on the receiver operating characteristic (ROC) of an echolocating bottlenose dolphin (Tursiops truncatus)
Authors: Murchison A. Earl , Patterson S. A.
Published: October 2005

A bottlenose dolphin was conditioned to report via two manipulanda the presence or absence of a solid steel sphere suspended 80 cm beneath the water's surface, 7 m (minimum) from his position. The dolphin's biosonar target detection and trained binary reporting behavior were tested utilizing variable primary reinforcement schedules (VR) from VR1 (fish reward every correct response) to VR100 (fish reward on one trial, randomly selected from 100 trials). Tests were also conducted with a fixed reinforcement schedule (FR) of FR100 (6.8 kg of fish reward after correctly responding on the last trial of a 100-trial session). The probability of target presentation was 0.50 for all schedules tested and the number and amount of reinforcement was kept equal for “present” and “absent” responses during all tests. The dolphin's ROC remained essentially unchanged and Neyman-Pearson at all reinforcement schedules. However, if reinforcement was kept at the more extended schedules (VR20 to VR100 and FR100) for more than eight consecutive 100-trial sessions all responses became “target-absent.” Response topography clearly showed the difference between detection and response bias.
Echolocation sameness-difference discrimination by the Atlantic bottlenose dolphin (Tursiops truncatus)
Authors: Nachtigall Paul E. , Patterson Sue A.
Published: October 2005

A dolphin was trained to differentially respond to two simultaneously presented stimulus objects depending on whether the objects were identical or different. The development of the concept of sameness-difference was then examined by successively presenting novel stimuli. Once these transfer tests indicated concept development, concept formation was tested by presenting two pairs of novel stimuli. Following the successful completion of this test, sensory information was limited to the echolocation modality by requiring the animal to wear rubber eyecups. Animal performance continued at a high level and two further transfer tests were conducted, each with two novel stimulus pairs. Performance on the first test initially declined to below 70%, but rapidly recovered. Performance on the second test indicated perfect transfer with initial performance levels at 100%. All stimuli were constructed to be aspect independent and differences between pairs were made as obvious as possible by varying size, shape, and materials. Reflective characteristics were examined for both target strength and frequency cues using a monostatic sonar measurement system projecting a simulated dolphin echolocation pulse.
Hearing levels of guinea pigs exposed to elevated noise levels in utero
Authors: Cook R. O. , Konishi T. , Salt A. N. , Hamm C. W.
Published: October 2005

Pregnant guinea pigs were exposed to loom room noise at 115 dBA SPL for 7.5 h per day for various periods during the last trimester of pregnancy. When the hearing of their offspring was tested by brain stem evoked response techniques at 6-dB intervals, 5th peak latencies of exposed pups were found to be significantly longer than those of otherwise similar control pups. The latency differences corresponded to some 5 dB at medium levels and 10–12 dB near threshold. The results indicate that it is possible for noise-induced hearing loss to occur in utero in mammals whose auditory maturation process is complete, or nearly so, before birth.
Musical instrument transducers—Present applications and future potential
Authors: Berry John
Published: October 2005

Since their introduction several years ago, transducers designed to function with specific musical instruments have continued to receive increasing acceptance and widespread use for critical sound reinforcement and direct-feed recording applications. Sensors are now available for virtually all band and orchestral instruments and, through constant advances in this field of research, these transducers have achieved a level of design sophistication and performance capability which, in many instances, makes them a viable alternative to the use of traditional microphone technique. The parameters which can be used to determine the most appropriate pickup method for a given situation are discussed. The influence which this expanding transducer technology can be expected to have upon the development of new musical instruments is also considered.
The bass flute: A systematic exploration in using new acoustic and electronic sound possibilites
Authors: Andrus Donald G. , Shanley (Andrus) Gretel
Published: October 2005

Recent investigations were made by Donald Andrus with flutist Gretel Shanley in adapting “new” flute techniques to the bass flute. The study attempted to find what material in T. Howell's The Avantgarde Flute (Univ. of Calif., 1974) and R. Dick's The Other Flute (Oxford U.P., 1975) could be effectively adapted to bass flute composition. Of Howell's 1826 multiphonics, most cannot be used due to design limitations in the bass flute. Other sounds worked with include: pitch bending, microtones, fluttertonguing, percussion tones, whistle tones, harmonic sweep, and singing into the instrument. As might be expected, some of the original examples gave different but equally interesting results: in playing what Howell refers to as a tongue ram, an 11-tone scale emerges one octave below the bass flute's lowest written pitch. There is a short illustrative composition by Dr. Andrus which can be performed acoustically or fed as input to a synthesizer for processing. Waveform spectra slides of some multiphonics have been prepared.
Improving human engineering of violin playing
Authors: Mathews M. V.
Published: October 2005

Several changes in violin technique have been tried and will be described. These include holding the instrument vertically as a cello or viol is held, supporting the instrument with a bar which is gripped between the knees, and putting a set of small frets or finger guides on the fingerboard. For a violinist trained in a normal technique, it was found advantageous to reverse the order of the strings in order to reduce relearning of right-hand reflexes. The finger guides do not stop the string as does a guitar fret. Rather, they help locate the gross position of the finger. Fine pitch adjustments by ear are still possible and necessary. One violinist (the author) was able, in two years, to learn to play better in the new position than he had previously played. The new left-hand technique is much easier than the old. The new right-hand technique is comparable to the old. The new technique is well adapted to the new violins developed by C. M. Hutchins, many of which need to be held vertically.
Perception of the oral-nasal distinction in vowels: A cross-language study
Authors: Beddor Patrice Speeter
Published: October 2005

Cross-language research with isolated vowels has shown that accuracy of vowel discrimination, unlike consonant discrimination, is not affected by linguistic experience [K. N. Stevens, A.M. Liberman, M. Studdert-Kennedy, and S. E. G. Öhman, Lang. Speech 12, 1–23 (1969)]. The present study extends cross-linguistic investigation of vowel perception to the oral-nasal contrast. Speakers of French, Hindi, and English were tested on identification and discrimination tasks using several oral-nasal vowel series to determine the effect of phonemic status of nasal vowels on accuracy of discrimination. (The contrast between oral and nasal vowels is phonemic in French and Hindi, but allophonic in English.) Stimulus materials were generated by articulatory synthesis and involved three 11-step /ba/-/bā/ series in which size of velopharyngeal port opening increased in equal increments from the oral to nasal endpoints. Results of three-step oddity discrimination tests for a series incorporating 2.4 sq mm increments showed similar performance for all three language groups. However, performance was generally poor for all subjects. The effect on discrimination accuracy of, two modifications in the series—increased discrimination step size and increased port aperture at the nasal end of the series—was investigated. [Work supported by NICHD, NIMH.]
Analysis and display techniques for correlating articulatory and phonetic features in speech production
Authors: Nelson W. L. , Fujimura O. , Alfredson S.
Published: October 2005

A large body of speech-articulation data is being assembled using the x-ray microbeam system [Fujimura, Kiritani, and Ishida, Comp. Biol. Med. 3, 377–381 (1973)]. Once the phonetic elements of the speech utterances have been aligned with the articulatory data [Nelson, J. Acoust. Soc. Am. Suppl. 1 65, S22 (A) (1979)], it is possible to access and analyze the articulatory and acoustic data by phonetic feature. This paper discusses several techniques which have been developed for both statistical and detailed analyses of articulatory-phonetic relationships. In particular, two-dimensional histograms of x-ray pellet positions for many occurrences of a phonetic feature are useful for testing various assumptions and hypotheses concerning the principal articulatory conditions for that feature. For example, the retraction of the back of the tongue characterizing /1/ in different phonetic environments [Fujimura, Miller, and Escolar, J. Acoust. Soc. Am. Suppl. 1 61, S48 (A) (1977)] can be easily and quantitatively demonstrated.
Anticipatory labial coarficulation: Extent and influencing variables
Authors: Lubker James , McAllister Robert , Linker Wendy
Published: October 2005

This research is designed to investigate the temporal extent of anticipatory (right-to-left) co articulation as well as the variables which may influence it. Previous research in this and in other laboratories has suggested that anticipatory coarticulation in lip rounding extends for as much as six consonants or 600 ms prior to a rounded vowel. Some recent work, however, has suggested a more limited extent of such coarticulation. The present work is an attempt to resolve this issue and thus shed some light on cognitive representation and input units for the motor control processes of speech generation. Additionally a number of variables have been proposed to influence the precise location of the anticipatory boundary of labial coarticulation; for example front versus back tongue position for the rounded vowel, stress of the rounded vowel preceding the consonant string. In the present experiment these and other variables are controlled and their effect on the onset of coarticulation is described.
The relationship between jaw length and jaw opening for vowels
Authors: Ewan W. G. , Gay T.
Published: October 2005

Almost nothing is known about the physiological and acoustic aspects of speech adaptation among speakers whose oral structure is modified by trauma or surgical revision. For example, in speakers who undergo surgical shortening or lengthening of the mandible, it is not clear how the revised jaw length is related to articulatory compensation. Systematic changes in jaw position for speech due to surgical revision would provide insight into the biomechanics of normal jaw movement and speech motor control. The relation between “jaw length” and jaw opening for steady-state vowels has been investigated using both patients undergoing surgical changes in jaw length and a group of normal controls. Photographic and photoelectric transducing techniques were used to monitor jaw movement during the production of the steady-state vowels [i, e, æ, o, u, Λ]. Patients exhibited an increase in jaw opening with surgical shortening and a decrease in jaw opening with surgical lengthening. Controls (adults and children) with a large range in jaw size had a similar pattern in that a speaker with a larger jaw had less jaw opening for the steady-state vowel [a] than a speaker with a smaller jaw. The biomechanical and phonetic factors of this inverse relationship between jaw size and jaw opening will be discussed.
Modeling articulatory compensation in terms of physiological parameters
Authors: Ladefoged Peter , Wright James T.
Published: October 2005

An 18-section computer model of the vocal tract was used to investigate articulatory-acoustic relations by mapping from an articulatory feature space to an acoustic formant frequency space. The articulatory space was defined in terms of a five dimensional matrix in which the dimensions represented (1) degree of raising of the front of the tongue, (2) degree of raising of the back of the tongue, (3) extent of lip aperture, (4) degree of rounding, and (5) height of the larynx. The tongue dimensions and the lip dimensions were rescaled to satisfy a definition of equal articulatory step size in terms of similar differences in the total midsaggital section of the tongue and in the square root of lip area. Examination of the formant frequency space suggested that changes in tongue shape alone produce unique sets of values for the first three formant frequencies. However, variations in tongue shape combined with variations in lip area and larynx height result in articulatory compensation giving equivalent values for the first three formants. Changes in tongue shape alone failed to generate plateaulike regions of acoustic stability. [Work supported by NIH.]
Composite signals for simultaneous estimation of target range and bearing
Authors: Skinner D. P.
Published: October 2005

In a previous paper [J. Acoust. Soc. Am. Supp. 1 65, S62(A) (1979)] the design of large time-bandwidth product signals for simultaneous estimation of the range and bearing of stationary point targets from a moving platform was discussed. Examination of the range-bearing ambiguity functions produced by a number of simple FM signals indicated marginal gains in terms of interference suppression even for relatively large TW products. In this paper the performance of a class of composite (multi-carrier) FM signals which have desirable ambiguity, and interference suppression properties will be discussed and compared with the previous results. [Work supported by NAVMAT.]
Coherence degradation in active sonar systems
Authors: Higgins R. C.
Published: October 2005

This paper quantifies the degradation in performance of a quadrature receiver when the phase of the input target signal is time-varying and the background noise is additive Gaussian. The quadrature receiver, a conventional signal-processor in sonar applications. consists of a replica-correlator followed by a quadratic detector. In active sonar systems with narrowband transmit signals, direct path and multipath returns from a distributed highlight target add at the receiver to produce a composite echo which has a time-varying phase over the signal duration. As a result, a mismatch in phase exists between the received signal and the replica (replica-correlator) causing a degradation in processor performance. This paper measures the amount of processor degradation using a narrowband target signal model with Rayleigh distributed amplitude fluctuations and uniformly distributed phase fluctuations. First, an expression for the output signal-to-noise ratio of the quadrature receiver is derived using the postulated signal model. Second, the receiver's degradation is measured by defining a normalized signal-to-noise ratio and examining this parameter for the following three variations in the basic signal model: (1) the amplitude of the in-phase and quadrature signal components of the signal is constant, (i.e., complete correlation), (2) the amplitude of the in-phase and quadrature components of the signal is Gauss-Markov process (i.e., exponential autocorrelation function) and (3) the amplitude of the in-phase and quadrature components of the signal is a Gauss-peaked process (i.e., exponential-cosine autocorrelation function). The results for each case are presented functionally and graphically.
A measurement system for coherent analysis of target scattering data
Authors: Matthews A. D. , Nelander J. C.
Published: October 2005

Analysis of acoustic scattering from submerged elastic targets of finite dimensions can be complicated by aspect dependence. A method is being developed for measuring and combining scattering data from adjacent frequency bands and aspect angles into a single phase-coherent transfer function. Detailed spatial analysis of a target response should be possible by means of synthetic aperture processing techniques. This will permit high resolution windowing of small parts of the target. These techniques require that measurements over different frequency bands and aspect angles be phase coherent. This necessitates high precision positioning equipment and an accurate computer controlled data acquisition system. Such a system is described, and calibration procedures and results are illustrated. The method for removal of transmit and receive characteristic of transducers and electronic hardware is discussed.
The signal to noise gain of sparse array processors
Authors: Earwicker Martin J.
Published: October 2005

In this paper general expressions are derived for the signal to noise gain of sparse array processors which take account of both broadband signal and noise fields and the finite averaging times of real processors. This is achieved by considering the covariance between the fluctuations in pairs of estimates of cross correlation functions between hydrophone outputs. In the case of sparse arrays comprising many hydrophones and for low input signal to noise ratios, it is shown that the signal to noise gain of such a processor is 4.3 dB less than that of a filled array “sum square” processor using the same number of hydrophones.
Vibrational characteristics of Saron Barong metallophones in the 1893 Field Museum Gamelan
Authors: Savage William R. , Kottick Edward L. , DeVale Sue Carol
Published: October 2005

The gongs used in Asiatic music frequently exhibit noticeable glides in pitch comprising a significant fraction of a semitone. Bar-form metallophones of the 1893 Gamelan also show a glide in pitch. This contrasts with western bar-form metallophones which are generally pitch stable. Measurements of the keys of two Saron Barong show that they have different lengths, widths, and cross sections but do not “scale” since they have nearly similar masses. The keys of lower pitch are longer and wider than those of higher pitch within a given seven note Saron. The upper surface of the keys is convex for both length and width aspects. The lower surface of the lower pitch keys is concave becoming convex for the upper keys. They are mounted with nails through holes at a distance one quarter the length from the end on resilient pads above individual air cavities. The holes are not symmetrically located and the bars are not straight. They were cast of bell metal in sand molds and roughly finished. The central part of the underside is hollowed. Torsional and flexural modes near the pitch frequency can be found by external excitation. These modes have frequencies consistent with those found by high-speed spectral analysis and pitch measurements. The pitch glide seems to be associated with a bar shape that favors excitation of both torsional and flexural modes at the initial strike with a more rapid decay of the torsional mode. This mechanism differs from that suggested for gongs where the moving mass associated with the mode decreases with decreasing amplitude of vibration.
The acoustics of timpani
Authors: Anderson Craig A. , Rossing Thomas D.
Published: October 2005

The frequencies of the vibrational modes of kettledrum heads have long been known to differ from those of an ideal unloaded membrane [Lord Rayleigh (J. W. Strutt), The Theory of Sound (Macmillan, 1894), 2nd ed., Vol. 1]. The three principal modes, under normal playing and tuning conditions, have frequencies nearly in the ratio of 4:3:2, thus giving timpani a musical pitch which is easily discernible. This favorable relationship of modal frequencies is brought about by membrane stiffness and air loading; our experiments indicate that air loading is the more important factor. We have measured the frequencies of ten or more modes of vibration under various conditions: high and low tension, with and without the kettle, in air and helium atmospheres. The kettle raises the frequency of the lowest symmetric mode, and also fine tunes some of the higher modes; its most important role is that of a baffle, however.
Experimental analysis of acoustically generated boundary cavitation
Authors: Clark J. A.
Published: October 2005

Cavitation can be produced by the inversion of large amplitude acoustic pressure pulses or shock waves which occurs during the reflection of waves at a soft boundary. In current experiments, acoustic pulses in water with peak pressures up to 25 atm and durations of 40 μs and longer are being used to generate cavitation near the free liquid surface. The cavitation process is being analyzed by optical, holographic interferometry which provides whole field measurements of the density of the medium at a series of time intervals. Acoustical measurements of the echo produced by the subsequent collapse of the cavitation region are also obtained. The echo pulses are observed to be nearly as strong as the incident pulses, but are delayed by about 200 μs relative to a small-amplitude, reflected pulse.
Application of linguistically-motivated rules. of syllabication to automatic speech synthesis
Authors: Kahn Daniel
Published: October 2005

One can derive a set of rules for the syllabication of English words and phrases using traditional linguistic argumentation—for example, simplicity of the resulting grammar, agreement with native speaker intuitions in clear cases, etc. In this paper, I describe a practical application of such rules, the automatic syllabification of phonetic strings as a component of a text-to-speech synthesis scheme whose basic unit of concatenation is the demisyllable [Fujimura, J. Acoust. Soc. Am. Suppl. 1 59, S55(A) (1976)]. Some important characteristics of these linguistic rules are the use of a “maximal-initial-cluster” principle, no constraints on final clusters, and the assignment of “ambisyllabicity” in certain cases (an “ambisyllabic” consonant is one which is simultaneously the final element of one syllable and the initial element of the next syllable). Informal listening tests have lent support to the hypothesis that these linguistically motivated rules are appropriate in the practical application of syllable-based speech synthesis.
Acoustic features of CFAV QUEST
Authors: Collier Arthur J. , George Arial W.
Published: October 2005

In 1969 the Canadian Forces Auxiliary Vessel QUEST was commissioned for use by the Defence Research Establishment Atlantic in Dartmouth, Nova Scotia. QUEST was specifically designed and constructed as a platform from which to conduct open ocean underwater acoustic experiments. The acoustic features built into the ship, some of the philosophy behind the design, and the performance of the vessel will be discussed in some detail.
Ultrabroadband target strength measurements of biological entities
Authors: Johnson R. A. , Friedl W. A. , Nelson D. E.
Published: October 2005

An ultrabroadband underwater echo-ranging system has been employed to collect echoes from biological entities off the coast of Southern California. The system uses an implosive impulse source and a broadband, constant beamwidth towed array. For these measurements, target strengths were calculated over the band of frequencies from 500 Hz to 50 kHz with minimal distortion due to transducer beamwidth effects. Averaged frequency spectra for echoes from many biological targets have been examined. Echoes from schools of fish exhibit Rayleigh scattering regions as well as resonances and have target strengths in excess of 0 dB with occasional schools exceeding 20-dB target strength over a portion of the band. [Work supported by the Naval Material Command.]
A numerical study of acoustic interaction effects in backscattering from linear arrays of gas-filled bubbles
Authors: Novarini J. C. , Bruno D. R.
Published: October 2005

The acoustic backscattering of spherical waves from a linear array of gas-filled bubbles in water is studied including interference and multiple scattering to all orders. These effects are studied through separate factors, one of which takes into account interference in the single scattering approximation, and the other accounts for multiple scattering effects. This allows the calculation of the total scattered field from the single scattering, incoherent field, which is easily calculated. The dependence of the effect on the array parameters and frequency is discussed. [Work supported by the Organization of the American States and Secretaria de Estado de Ciencias y Technología of Argentina.]
Bottom reverberation in the oceans
Authors: Mackenzie Kenneth V.
Published: October 2005

Bottom reverberation generally follows Lambert's law for grazing angles less than 50° [P. B. Schmidt, J. Acoust. Soc. Am. 50, 326–331 (1971)] with 10 log μ between −24 to −34 dB with an average near −28 dB obtained for 530- and 1030-Hz data [K. V. Mackenzie, J. Acoust. Soc. Am. 33, 1498–1504 (1961)]. For steeper angles, scattering varies as exp cot2φ, where φ is the grazing angles [Y. Y. Jitkovskiy and L. A. Volovova, E67, 5th Int. Acoust. Congr. (1965)]. Reflection loss at normal incidence follows Rayleigh. A practical equation for a deep-ocean bottom reverberation model is presented and compared with available data.
Source level measurements of an arctic sea ice pressure ridge
Authors: Buck Beaumont M. , Greene Charles R.
Published: October 2005

Ice pressure ridge activity occurred over a three-day period in the immediate vicinity of a research ice camp 180 miles from the pole in the Eurasian Basin of the Arctic Ocean in 1979. The ridge was instrumented with both horizontal and vertical calibrated hydrophone pairs at a distance of about 100 m and the acoustic output tape recorded. Dimensional surveys were made atop the ice of the active portions of the ridge. Correlation and spectral analyses were performed which allowed quantitative assessments of source level in the hand 3–1000 Hz. These data, along with previously measured arctic transmission loss, were used to derive a model of pressure ridge area distribution and density by matching previously gathered statistical ambient noise data. The observed ice ridge noise was abundant in fairly long-lasting tunais as low as 8 Hz attributed to a “slipping clutch” effect. These were the first known quantitative acoustical measurements of a nearby pressure ridge.
Speech reinforcement in a large cathedral, at the limits of D 2
Authors: Irvine L. K. , Fullmerr R. K.
Published: October 2005

A state-of-the-art point source speaker system was installed in a large (627 000 cu ft) cathedral, with 3.5 s RT60. Initial calculations using D. Davis' theory for articulation are compared with results of nonsense word articulation tests made in the building using the installed system. Also, results of octave band RT 60 measurements are plotted, showing results of pioneering acoustical corrections performed in 1916 using covered felt blankets applied to ceiling.
Rotary spectrum analysis of sodar Doppler signals
Authors: Underwood K. H.
Published: October 2005

Rotary spectrum analysis is a proven method for interpretation of geophysical data exhibiting inherent rotational characteristics. Computationally derived using a discrete Fourier transform, it shows the extent to which contributions to the total variance originate from clockwise or counterclockwise rotating components. The technique is well suited to the analysis of Doppler sodar signals which are sampled as the in (I) and quadrature (Q) phase components of a rotating phaser. The Penn State Doppler sodar system may be operated either in a “track” or I and Q mode. This paper demonstrates the advantages of I and Q sampling and rotary spectrum analysis for detailed interpretation of atmospheric wind and turbulence profiles. A comparison of Doppler-derived and 123-m tower measured winds will be presented.
Computerized sodar for network measurements of planetary boundary layer structure
Authors: Peters R. L. , Thomson D. W.
Published: October 2005

Local or regional scale analysis of planetary, boundary structure, such as is required for gravity wave or mixing depth analyses, can be greatly facilitated by using a network of sodar systems. Such a network will typically include three to twenty acoustic sounders and some supplementary sensors such as sensitive electronic microbarographs. Use of network observations is greatly simplified if the distributed sodars are controlled by the measurements logged on the display at a central minicomputer. This paper presents an inexpensive, telephone network system designed for sodar control and data acquisition. The combination digital and analog signal transmission was optimized for telephone transmission of sodar control and signal data. Features include automatic answering and hangup, simultaneous sodar triggering, data acquisition from all network sites, and automatic remote calibration of the interface system. The system requires only the availability of a standard-voice Bell system compatible circuit.
Velocimeter for quality control monitoring in rubber production
Authors: Corsaro R. D. , Jarzynski J. , Burns L. , Moniz W. B.
Published: October 2005

A velocimeter was designed for longitudinal sound-speed measurements on 3-mm-thick (ASTM) rubber samples. Batch-to-batch variations in sound speed are detected to 0.1% precision by operators without technical experience. Each measurement required five minutes with the prototype device, and substantial reductions are expected with minor design modifications. The device consists of two ultrasonic transducers with a rubber sample sandwiched between them. During device assembly, the sample is squeezed by the transducers such that a known and reproducible transducer-transducer separation distance is obtained. A 5-MHz cw signal is then applied to one transducer. The phase angle difference of the signal received by the other transducer is read on a meter face, and is related to the wave speed in the rubber. By performing a detailed theoretical analysis of this geometry, we are able to meaningfully compensate the value of the meter reading for variations in temperature, thickness (related to the degree of sample squeezing used), and sound absorption, and also use the device for absolute sound speed and attenuation measurements.
Stoneley waves at an imperfectly bonded interface
Authors: Schoenberg Michael
Published: October 2005

A model for an imperfectly bonded interface between two elastic media has been proposed. Displacement across this surface is not required to be continuous but it is taken to be linearly related to the stress traction which is continuous across the interface. For isotropic interface behavior, there are two independent interface compliances,ηN and ηT, where the component of the displacement discontinuity normal to the interface is given by ηN times the normal stress and the parallel component is given by ηN times the shear stress. Stoneley wave velocities (possibly complex) at such interfaces between two elastic halfspaces are calculated and are found to be dispersive even when the compliances, ηN and ηT, are real and frequency independent. When the interface is purely dissipative such that the stress traction is proportional to the velocity discontinuity, the compliances are pure imaginary and proportional to the inverse of frequency yielding complex, but in this case, nondispersive, Stoneley wave velocities.
Experimental studies of ultrasonic radiation from cylindrical shells in water
Authors: Fritsch K. , Allen C. W. , Carome E. F.
Published: October 2005

Studies are being made of ultrasonic waves radiated into water from air-filled cylindrical metal shells. A shell is directly excited by polyvinylidine fluoride thin film transducers mounted on its inside surface. By using arrays of such transducers it has been possible to excite various normal modes of the cylinder. Both schlieren and acoustic probe techniques are being used to examine the radiated acoustic fields. Data are presented to indicate the applicability of this new technique. [Work supported in part by ONR.]
The effect of envelope on fusion of tones with inharmonic partials
Authors: Cohen Elizabeth
Published: October 2005

Temporal envelopes for tones with an inharmonic partial structure were generated using the Systems Concepts Digital synthesizer. [E. Cohen, J. Acoust. Soc. Am. Suppl. 1, 65, S123(A) (1979)]. The reasons for choosing envelopes based on musical viability rather than a flat “psychoacoustically standard” pattern, will be discussed. Subjects were asked to make judgments on the degree of tone dispersion for single tones differing in degree of inharmonicity and temporal envelope. The importance of attack and decay times, as well as transients in the signal will be explained. A real-time experiment on the determination of subjective interval size of dyads using two different envelope patterns also revealed that duration of the “steady state” portion of signal has an effect on tone fusion.