bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic spectral envelope synthesis of trumpet tones
Authors: Beauchamp James W. , Horner Andrew
Published: October 2005

It is well known that spectral envelopes of brass tones vary with performed dynamic [D. Luce and M. Clark, J. Acoust. Soc. Am. 42, 1232–1243 (1967)]. In this study average spectral envelopes were computed as functions of normalized instantaneous rms amplitude using time-variant spectral data from a group of 15 trumpet swell tones with fundamental frequencies extending over a 2-octave range. It was found that 10 spectral envelopes, defined by amplitudes in each of 24 standard critical bands spanning the frequency range 0 to 10 000 Hz, were sufficient to characterize the tone set. Time-variant spectra were synthesized using the original rms amplitude-versus-time envelopes as driving functions to dynamically select and interpolate between the appropriate spectral envelopes for each moment of time. The time-variant spectra were then converted into sound signals using conventional additive synthesis. Since the synthetic tones sound almost identical to the originals, it appears that dynamic spectral envelopes are an important defining characteristic of trumpet tone behavior.
Ultrasonic tomography for materials characterization
Authors: Hutchins David A.
Published: October 2005

Ultrasonic tomography may be used as a method for imaging the internal structure of a wide range of solid materials. To do so requires tomographic reconstruction programs that can deal with irregular geometries, acoustic raybending and the possible presence of velocity anisotropy. Image reconstruction techniques are now available to deal with such problems, and have been applied to several situations of interest to materials characterization. The first of these involves the study of samples in bulk solid form, where a scanning system involving sliding contact transducers has been used to collect ultrasonic data and image materials that have been subject to thermal cracking. Additional studies have investigated the failure of fiber-reinforced polymer composites under applied load. In both cases, correlation with acoustic emission (AE) data has been performed. Other work has used immersion and noncontact ultrasonic transduction to image the structure of thin plate material using Lamb waves. In all cases, images will be presented and conclusions drawn on the type of information available from such images. [Work supported by SERC.]
Measurement of elastic properties of transversely isotropic plates using Rayleigh–Lamb waves
Authors: Rogers Wayne P.
Published: October 2005

This paper presents a novel method to experimentally determine the elastic constants of a transversely isotropic plate using measurements of phase velocity of Rayleigh–Lamb waves. The forward problem, i.e., to calculate the phase velocity versus frequency curves given known elastic constants, has been solved by numerical solution to the appropriate dispersion equations. The problem attacked here is the inverse problem, i.e., to determine the elastic constants given experimental measurements of phase velocity as a function of frequency. These elastic constants may be found by simultaneous solution of five distinct dispersion equations corresponding to particular measurements of phase velocity and frequency. This approach yields accurate solutions provided that appropriate Lamb waves modes, frequencies, and plate directions are chosen. The experimental method employs a pair of variable-angle-beam-contact transducers used in a pitch–catch mode with a harmonic wave phase comparison technique to measure phase velocity over the frequency range of 30 kHz–1 MHz. Results are presented for several isotropic plates and for a unidirectional-continuous-glass-fiber-reinforced epoxy plate. The elastic constants calculated using this inverse procedure are then used in the forward problem in order to compare experimental results to theoretical predictions of the dispersion curves for the first few modes. [Work supported by NASA—Langley.]
Hearing abilities of killer whales (Orcinus orca)
Authors: Bain David E. , Kriete Birgit , Dahlheim Marilyn E.
Published: October 2005

A study of hearing abilities of killer whales was conducted to help assess the impact of noise produced by vessels. The study had five objectives: (1) determine the range of frequencies that killer whales can hear; (2) determine the ability to hear these frequencies in the presence of bandlimited masking noise; (3) determine whether vessel noise affects the ability to hear pure tones; (4) determine whether noise from different directions has different masking properties; and (5) determine the ability to detect simulated killer whale sounds in the presence of vessel noise. Data were collected using conditioned responses of four captive killer whales. Conclusions reached include: killer whales are sensitive to a wide range of frequencies (0.5–105 kHz); noise reduces the ability to detect signals of similar frequencies; very loud, low frequency, noise reduces the ability to detect signals even at much higher frequencies; noise has the strongest effect when it comes from in front of the whale, and the least effect when it is from the side or behind; and the ability to detect broadband signals such as killer whale calls and clicks is not substantially affected by low levels of vessel noise.
Broadband impulse transducer for measurement of backscattering by objects in water
Authors: Kwiatkowski Christopher S. , Kaduchak Gregory , Marston Philip L.
Published: October 2005

A broadband impulse pressure transducer was developed using a 15×15 cm sheet of PVDF in water. Both sides of the sheet were in contact with the water and subsequently larger sheets were used. A planar transient wavefront was achieved by applying a step voltage across the sheet. Prior to the arrival of waves from the edge of the sheet, the radiated wave was nearly unipolar and impulsive for frequencies up to 1 MHz. The transducer is useful for measuring the backscattering or reflected impulse response of objects in water because the backscattered or reflected wave is nearly completely transmitted through the sheet. Thus a small broadband receiver can be placed behind the sheet transducer. The transmission was demonstrated by measuring the impulse reflected by a plate and the transducer was used to measure the short-term impulse response by an elastic shell. After a sufficiently long time, the received impulse response is contaminated by edge contributions. [Work supported by ONR.]
Understanding coupling between flexural disk transducers from near field measurement
Authors: Cortambert Jean-Marc , Baker Steven R.
Published: October 2005

Both in civilian and military applications of underwater acoustics the need of high-power, directional low-frequency sources has stimulated the development of volumetric arrays of closely spaced transducers. Understanding the coupling between transducers in the array becomes fundamental to proper beamforming in the active sonar array. The paper presents the study of two flexural double bilaminar disk transducers by the method of finite elements using the ATILA code. The modification of the vibration behavior and the near-field radiation distortion of an element induced by an adjacent element are computed. The results are compared with the measurement of the displacement on the flexural disk using surface mounted strain gages and the pressure field near the transducers. [Work supported by the French Delegation Generale pour l’Armement and the Naval Postgraduate School.] a)French Naval Engineer. Permanent address: DCN Toulon/SDET/BP77, Toulon 83000, France.
A 350-m depth capable, air-compensated baffled transponder for the deep water portable tracking system
Authors: Menoche R. K. , Reid R. J. , Stein P. J.
Published: October 2005

This presentation describes the design and testing of a novel baffled central up-link subsurface link (SSL) for the deep water portable tracking system (PTS). The central SSL is deployed at depths up to 350 m and collects the acoustic information from the bottom moored tracking transponders. These transponders can be deployed to depths down to 6000 m. Degradation of the up-link SSL performance is generally due to support ship radiated noise and surface generated ambient noise. These sources of interference can be suppressed with a downward looking receiver. This receiver must have a wide beamwidth (140 deg) and its response must fall off rapidly outside the beam to reject ambient noise. The device built consists of a hydrophone and projector mounted on the face of a steel signal conditioning plate (SCP). The plate is designed to have low vibration sensitivity. Behind the plate, and extending beyond the SCP edges, is a fiberglass air chamber. To prevent crushing, it is fed by an air-compensation bag. Extension of the air-backing beyond the SCP is important to ambient noise rejection. This soft surface helps to reject noise which diffracts around edge of the battle. The air-chamber design was chosen over material solutions because it was uncertain if, at the deeper depths, the latter could provide the pressure release surface required.
Adding pulsed noise to a flute physical model
Authors: Chafe Chris
Published: October 2005

Pulsed noise has been detected in the residual of steady flute tones after elimination of purely periodic components. LMS adaptive linear periodic prediction was used to trace the waveform through its slight period-to-period fluctuations. The predicted signal was removed from the original leaving a breathy sounding residual to examine. Noise pulses in musical oscillators result from period synchronous gating of the driving means. Bowed string instruments exhibit noise pulses arising from alternating stick-slip motion, where noise is introduced only when the string is slipping. Distinct pulses are also exhibited by the saxophone in which the reed modulates air friction. Flute noise is more continuous than in string or reed tones. Short time Fourier transformation of the residual signal reveals that pulses are present, but spectrally weighted toward higher frequencies. A physical model of the flute incorporating a corresponding noise synthesis method is presented. Results of the simulation are compared for pulse quality and effect on frequency jitter.
Acoustic features of tonal ‘‘grunt’’ calls in baboons
Authors: Owren Michael J. , Linker Christopher D. , Rowe Matthew P.
Published: October 2005

The acoustic features of ‘‘grunt’’ calls recorded from free-ranging baboons (Papioursinus) in Botswana were investigated. Analysis parameters typical of those used to analyze human speech were employed and these sounds were found to closely resemble speech vowels in several respects. They were brief (approximately 97 ms) and highly tonal with a stable fundamental frequency (approximately 122 Hz.) Like adult human males, baboons are estimated to have a vocal tract length of 17 cm (glottis to lips) and this concordance was reflected in the formant structure of the grunts. Three formants (range 2 to 7) were typically found between 0 and 5 kHz, in a pattern resembling that of the vowel ‘‘schwa.’’ Variation due to individual caller and behavioral context are discussed, as well as the implications of these findings for relationships between nonhuman primate vocal communication and human speech.
Time-frequency description of signals—A review
Authors: Cohen Leon
Published: October 2005

The frequency content of many natural and man-made signals changes drastically with time and standard Fourier analysis does not fully describe such highly nonstationary signals. Among such signals are speech, sonar and radar, optical images, and biological and geophysical signals. In the past 10 years there have been dramatic strides made in our ability to understand and process such signals. The basic idea is to develop a method that describes the intensity of a signal jointly in time and frequency. This would give the frequency content at each instant of time and hence describe how the spectrum is changing in time. A review is presented of the ideas and methods that have been developed to describe a time-varying spectrum and their application is illustrated with concrete examples from a wide variety of fields.
Decomposition of scattered waves from an isolated elastic object with time-frequency representation
Authors: Yen Nai-chyuan
Published: October 2005

In observing the scattering phenomena from an isolated elastic object, one would like to understand the composition of the scattered waves so the characteristic structure of the scatterer can be estimated. This paper reviews such an inverse scattering problem in terms of wave packet decomposition. Particularly, the focus is on a heuristic approach that has been developed from the study of acoustic scattering. The basic scheme of this approach is to examine the coherence property of the wave signature of the scattered waves and to compute its energy distribution in a joint time and frequency representation. Also shown is how to apply signal synthesis techniques to determine the dominant components, namely wave packets, expressed as the natural frame (basis), the building block for the formulation of the scattered wave. The magnitude and the phase of each wave packet are evaluated by algorithms that treat them as the independent nonorthogonal components from a set of linear equations. Examples of the response of the scattered waves from shell type elastic objects are used to illustrate the physical implication of this decomposition method in resolving the inverse scattering problem. It is concluded that the wave packet decomposition by means of the natural frame (basis) can be considered as a generalized Gabor and/or wavelet transform. Their relationships are discussed through the fundamentals of linear functional analysis.
Adaptive wavelet analysis of transient signals in structural acoustics
Authors: Stepanishen P. R. , Huynh Q. , Greene T.
Published: October 2005

Linear and quadratic time-frequency transforms are used to investigate and characterize transient signals from several wave propagation problems in structural acoustics. The transforms include: the short-time spectrum, Wigner type representations, and wavelet methods. Advantages and disadvantages of the various representations within the present context are presented. Particular emphasis is placed on using the wavelet packet method of Coifman to analyze and characterize complex transient signals from various structural-acoustic transmission paths with dispersive characteristics. Adaptive procedures are used to determine optimal time-frequency localization by using the best basis functions for the class of dispersive signals of interest. Various features and parameter extraction methods based on the local maxima of the wavelet transform at each scale are presented for several complex transient dispersive signals. [Work supported by ONR.]
Acoustic aspects related to the performance of teleconference facilities
Authors: Basnett Bradley P.
Published: October 2005

Room acoustic design and electroacoustic system integration are paramount to the performance, and therefore effectiveness, of teleconferencing facilities. Some key elements that need to be considered during the design and implementation stages are (a) the effects of room acoustics on transmitted, received, and in-room speech communications; (b) the effect of transmission bandwidth on intelligibility and audio quality in the teleconference suite; (c) the naturalness of interaction over a telephone network; (d) the impact of acoustic and electroacoustic devices in a visual communications medium; (e) room ambient noise and potential noise sources. These elements are examined in light of the recent design, implementation, and operation of 12 teleconference (audio and video) suites. Details of design choices and acoustic measurements of these teleconference suites will be presented.
Model calculation for deviation of ambient noise statistics from signal statistics in shallow water
Authors: George Jacob
Published: October 2005

It has been reported that cumulative distribution functions (CDFs) of a signal in shallow water obey normal distributions, while those of ambient noise deviate from this, in both cases independent of depth [J. George, J. Acoust. Soc. Am. 92, 2304 A (1992)]. One cause of intensity fluctuations is internal waves, studied by path integral and moment methods in deep water [B. J. Uscinski etal., J. Acoust. Soc. Am. 74, 1474 (1983)]. In shallow water, internal waves have been shown to behave as solutions [J. Zhou and X. Zhang, J. Acoust. Soc. Am. 90, 2042 (1991)]. For the time spans considered in the CDFs mentioned above (25–320 s) intensity fluctuations caused by surface waves cannot be ignored. Results of a model calculation designed to contrast the effects of a stable signal source below the surface with the effects of ambient noise sources moving with the surface will be presented. [Work supported by ONR.]
Ambient noise predictions from deep to shallow water
Authors: Breeding J. Ernest , Bradley Marshall , Hebert Melanie
Published: October 2005

The RANDI-III noise model is used to make predictions of the omni noise level, horizontal noise field, and the vertical noise field for real world examples of broad and narrow transects from deep to shallow water. For comparison, some noise predictions are also made with the ANDES-II noise model. This is of interest since these two noise models are fundamentally different in several ways, including the methods used to propagate noise and the approaches used to treat ship sources. It is found that at the deeper water portions of the transects, the RANDI-III and ANDES-II predictions of the omni noise levels and the horizontal noise fields can be similar. However, the RANDI-III and ANDES-II predictions of the vertical noise field at these same water depths are quite different. At the shallow water sites the predictions of noise are not possible with ANDES-II. Examples illustrating the differences and similarities of the RANDI-III and ANDES-II predictions, as well as the RANDI-III predicted variations in the noise along the transects from deep to shallow water will be presented. [Research supported by The Office of Naval Research, Program Element 62435N with technical management provided by the Naval Research Laboratory, Stennis Space Center, MS.]
Tracking zooplankton at sea with a three-dimensional acoustical imaging system
Authors: McGehee Duncan , Jaffe Jules S.
Published: October 2005

The Acoustical Imaging Group in the Marine Physical Laboratory, Scripps Institution of Oceanography, has developed a real time, high-resolution three-dimensional acoustical imaging system for use in the ocean. The system, called Fish TV (FTV) is designed for the observation of macrozooplankton and small fish. FTV can synoptically examine a 16° by 16° volume of seawater with a 1-Hz frame rate. The sonar has recently been used at sea in two configurations. In the first experiment, the sonar was mounted 40 m deep, looking laterally from the research platform R/P FLIP. A video camera provided ground-truthing. In the second experiment, the sonar was attached to a Phantom DS4 remotely operated vehicle and deployed, again with video ground-truthing. Results indicate that the system can be used both to track animals in three dimensions and to estimate their density.
Focusing of sound power flow for sound incident on a structure in water
Authors: Hickling Robert
Published: October 2005

Computation of sound-power flow for sound waves incident on a solid sphere in water shows various degrees of focusing along the axis and in the wake of the sphere depending on the material properties of the sphere. This contrasts with a rigid immovable sphere that has no sound-power flow inside and a shadow zone in the wake. Visualizations are presented that show the focusing effect as a function of frequency for a number of different materials.
A comparison of structural intensity formulations
Authors: Zhang Yong , Mann J. Adin
Published: October 2005

Much past research concerning structural intensity has focused on the structural intensity formulation and measurement methods. For the structural intensity in a thin plate, different formulas were derived based on different assumptions. Pavic’s structural intensity formula [G. Pavic, J. Sound Vib. 49(2), 221–230 (1970)] was based on classical plate theory, which is described by Lagrange’s equation of motion. A more general derivation was perfomed by Romano etal. [Proceedings of the International Congress on Intensity Techniques, CETIM, 137–142 (1990)], which was based on three-dimensional elasticity. In this paper, a structural intensity formula is derived by simplifying Romano’s structural intensity formula using Mindlin’s assumption for thin plate theory that considers the rotary inertia and shear effect. The differences between the formulations will be discussed. From plate velocity measurements for an aluminum plate at single frequencies, the structural intensity is calculated based on the above-mentioned intensity formulas. In addition, the input mechanical force function is estimated. Results show that the input power from structural intensity and the input mechanical force match well with the experimental results.
A regression-based approach for simulating feedforward active noise control, with regression diagnostics for assessing the impact of measurement noise
Authors: Ruckman C. E. , Fuller Chris R.
Published: October 2005

Current numerical techniques for simulating feedforward active noise control in the frequency domain are mathematically equivalent to the techniques required for linear least-squares regression. Measurement error in the control system error sensors plays a role analogous to that of observation error in a statistical regression. In the statistics literature, regressions are always accompanied by regression diagnostics, i.e., computed statistics that help assess the impact of observation error. However, discussions in the acoustics literature typically fail to address this issue. The present workmodels feedforward active control as a regression of complex-valued variables, and shows how to apply two basic regression diagnostics: the F-test and the t-test. Also discussed are the physical significant of the ‘‘cost function’’ being minimized by the regression, and the assumptions that must be made regarding the variance of the measurement error. The techniques are demonstrated by numerically simulating a simple system in which radiation from an axisymmetric cylindrical shell is controlled by oscillating forces applied on the shell surface. [Work supported by David Taylor Model Basin and ONR.]
Feedforward control with the higher-harmonic, time-averaged, gradient (H-TAG) descent algorithm
Authors: Kewley Dorene , Clark Robert L. , Southward Steve C.
Published: October 2005

A novel adaptive filter structure has been proposed for the control of systems characterized by higher harmonic response. The control approach has been designated the higher-harmonic time-averaged, gradient (H-TAG) descent algorithm. In the H-TAG algorithm, a single frequency reference input is all that is required to implement the controller. The remaining harmonics are generated internally based upon simple trigonometric relationships. In addition, the algorithm is ideal for structures characterized by slowly time-varying parameters since no system identification is required to implement the algorithm. Results from simulations and experiments indicate that the proposed approach offers a unique method of achieving significant levels of attenuation in the harmonic vibration or acoustic response of structures.
Technology for people
Authors: Haggard Mark
Published: October 2005

Successful application of science and technology to improve human welfare, as seen in the career of Frank Cooper, requires a sensitive awareness of human needs and limitations. This talk illustrates how the drive for scientific understanding has interacted with concern for human welfare in producing two types of instrument (auditory warnings and auditory diagnostic or screening devices) in which the Medical Research Council of the UK has made major investments in recent years. Successful development requires a good grasp of engineering principles, well-judged investment in enabling technologies, correct description of the need to be met, and evaluation of the real life usefulness of the devices.
Reading, reading machines, and communications research
Authors: Liberman Alvin M.
Published: October 2005

What knowledge or habit of mind must would-be readers command that mastery of speech will not have taught them? Surely, that is the first question one must answer if one is to understand the reading process and the ills that attend it. Yet the question could hardly be accommodated, let alone answered, within the theory of speech that was almost universally accepted when Frank Cooper entered the field. It therefore counts as a major achievement of his research that others were able to gain from it a critical insight into the relation between the biologically primary processes of speech and the biologically secondary processes of reading, and thus to see more clearly the difficulties that beset the progressions from the one to the other.
Measurements of the azimuthal distributions of very low-frequency noise with high resolution in a shallow water site in the Mediterranean
Authors: Newhall Bruce K.
Published: October 2005

An extremely long horizontal towed array was used to perform high-resolution noise measurements at very low frequencies. The directional measurements in one shallow site are compared with more extensive measurements in deep water. The very low-frequency noise at all sites is highly anisotropic due to the high azimuthal resolution of the discrete merchant shipping sources that dominate underwater noise at these frequencies. The deep water measurements were performed at sites in three oceans, covering an extreme range of shipping density conditions, however, the shapes of the azimuthal distributions of the noise levels are relatively insensitive to shipping density. The shallow water noise exhibits azimuthal spreading not apparent in the deep water. From the loudest sources this spreading may partly obscure the spatially quiet regions that are otherwise present in directions between loud ships. Although they have different shape parameters, both the shallow and deep water data fall between Weibull and gamma distributions, and are well fit by generalized gamma distributions. The effects of multipath fading are diminished by the spatial averaging across the long aperture. Low-resolution noise distributions, obtained from subapertures of the array, are dominated more by multipath fading, and approach gamma distributions.
Modeling of echoes from extended targets in shallow water
Authors: Baus T. , Rosario M. , Chang W. , Deavenport R.
Published: October 2005

Echoes are generated and compared for extended targets in a shallow water environment using the total target-medium broadband frequency response function and the frequency representation of the transmitted signal. The two-way medium response is calculated using a hybrid SAFARI/generic sonar model (GSM) environmental model. The target frequency response is found using a model of distributed targets and elastic spheres. The combination of the target and medium frequency responses gives the full frequency response, or form function, for the target, medium system. The product of the total form function with the frequency spectrum of the incident signal is computed and on inverse FFT is performed to predict the received signal, or echo, from the object. [Work supported by ONR Code 231.]
Quantitative ultrasonic imaging for tissue characterization
Authors: Miller James G. , Wickline Samuel A. , Perez Julio E. , Barzilai Benico , Holland Mark R. , Handley Scott M. , Sobel Burton E.
Published: October 2005

This presentation will illustrate relationships between physical acoustics and ultrasonic imaging for medical diagnosis. Ultrasonic tissue characterization is designed to complement two-dimensional echocardiography by providing information in addition to that derived from an assessment of tissue dimension and motion. The hypothesis is that indices based on (frequency-dependent) backscatter and attenuation can provide a noninvasive tool for the early diagnosis of diverse disease processes including ischemia and cardiomyopathy. Differentiation between mature infarct and acutely ischemic myocardium, which might benefit from reperfusion by angioplasty or thrombolysis, appears to be feasible on the basis of the frequency dependence of backscatter, which is lower in zones of infarct than in acutely ischemic or normal myocardium. Two-dimensional images are formed from scans made with the direction of propagation of ultrasound at varying angles relative to the local fiber orientation of the myocardium. Backscatter and attenuation vary substantially with the angle of insonification relative to myofibers. This research is designed to lay the groundwork for exploiting the anisotropy of myocardial ultrasonic properties to achieve improved understanding of cardiac mechanical properties (elasticity and compliance) in normal and diseased hearts. [Work supported by NIH HL40302, HL17646, HL42950.]
The influence of frequency resolution on the detection of spectral contrast by hearing-impaired listeners
Authors: Summers Van , Leek Marjorie R.
Published: October 2005

Abnormal frequency resolution associated with sensorineural hearing impairment produces a smearing of spectral detail in the internal representation of complex acoustic stimuli. As a result, listeners with hearing loss may have difficulty locating spectral peaks that provide important cues to speech understanding. This study examined the relationship between frequency separation of peaks in a complex sound and the degree of spectral contrast preserved in normal and impaired auditory systems. Five hearing-impaired subjects (HI) and five normal-hearing subjects (NH) discriminated a flat-spectrum bandpass stimulus from a stimulus containing a sinusoidal ripple across its frequency range. The peak-to-valley amplitude (in dB) necessary for detection of the ripple was measured for ripple frequencies ranging from 1 to 9 cycles/oct. Auditory filter characteristics in notched-noise were measured at 1 and 3 kHz in order to assess the relationship between frequency resolution and the ability to detect spectral contrast in complex spectra. There were clear differences between groups in both auditory filter characteristics and spectral contrast detection. Auditory filters tended to be both broader and more asymmetric for HI listeners than for NH listeners. Mean ripple amplitudes at threshold were approximately 4 dB lower for the NH group than the HI group at all ripple frequencies. However, excitation patterns based on auditory filter characteristics and threshold stimuli specific to individual listeners exhibited levels of peak-to-valley contrast that were nearly identical across listeners. This suggests that increased ripple detection thresholds of the hearing-impaired listeners were due to spectral smearing resulting from impaired frequency resolution. [Work supported by NIDCD Grant No. DC00626.]
Formant transition discrimination at varying frequency regions among normal hearing young and elderly adults as a function of noise, frequency region, and transition direction
Authors: MacNeil Jane F.
Published: October 2005

This study investigated the perceptual abilities of young (18–28 years) and elderly (65–75 years) adults to discriminate suprathreshold short duration dynamic frequency transitions. Influences of frequency region (1 to 3 kHz), transition direction (upward or downward gliding), offset frequencies (converging or diverging), and background condition (quiet or noise) were examined. Signals were 60-ms transitions classified according to whether or not: they diverged to differing offset frequencies, converged on a common terminal frequency; and had an upward or downward trajectory. Young adults displayed smaller just-noticeable differences (jnds) relative to the elderly, and the elderly showed greater effects for frequency region, noise, and transition direction. Signals centered at 3 kHz were considerably more difficult for the elderly to distinguish even though hearing sensitivity levels were comparable across both groups at this region. However, among both age groups diverging signals produced smaller jnds than did converging signals. The results of the study showed that elderly subjects with comparable audiological profiles to young adults, or a mild sensorineural hearing loss, have greater difficulty distinguishing dynamic sounds, especially in background noise.
Modulation detection interference in subjects with a mild, high-frequency hearing loss
Authors: Opie Jane M. , Bacon Sid P.
Published: October 2005

Modulation detection interference (MDI) was measured in three normal-hearing subjects and in three subjects with mild, high-frequency sensorineural hearing impairment. Subjects detected 10-Hz amplitude modulation of a signal carrier in quiet and in the presence of a masker carrier that was unmodulated or amplitude modulated (depth of 100%) from 2 to 40 Hz. The carrier frequencies were 984 and 3952 Hz; either could serve as the masker, while the other served as the signal. Thus, for the hearing-impaired subjects, one carrier was in the region of hearing loss. In experiment 1, both the signal and masker were presented at equal sound pressure levels (SPLs). In experiment 2, the effect of sensation level (SL) was considered. In both experiments, there was generally little difference between the two groups when the signal carrier was in a region of normal hearing. However, the hearing-impaired subjects demonstrated more MDI than did the normal-hearing subjects when the signal was presented within the region of hearing loss. This suggests that even mildly hearing-impaired subjects may have difficulty processing complex, time-varying stimuli. Further, it appears that this may not be solely attributable to audibility but may be mediated by other factors. [Work supported by NIDCD.]
Vowel discrimination after multichannel compression
Authors: Yund E. William , Crain Thomas R.
Published: October 2005

The effect of full-range multichannel compression (MCC) on vowel discrimination was studied in hearing-impaired and normal-hearing subjects. For normal-hearing subjects MCC was fit to four hypothetical flat losses, with thresholds ranging from 60 to 90 dB SPL, and one hypothetical sloped loss, with thresholds normal at 500 Hz and 90 dB SPL at 4 kHz. Each hearing-impaired subject was tested with the flat MCC systems as well as one fit to the subject’s own hearing loss profile. Compression ratios varied from 1.75 to 7.00, in the flat MCC, and the number of channels varied from 2 to 31. Robinson–Huntington compression [C. E. Robinson and D. A. Huntington, J. Acoust. Soc. Am. 54, 314 (1973)] had a 10-ms time window in all channels. Unprocessed stimuli and frequency-equalized linear amplification were control conditions. The expected deleterious effects of MCC on vowel discrimination are clear for the most severe compression systems, but preliminary results indicate that they fall off rapidly as the number of channels and compression ratios decrease. Complete results and their implications for the application of MCC in hearing aids will be discussed. [Work supported by Department of Veterans Affairs.]
Design of a large-scale, in-home study of noise-induced sleep disturbance
Authors: Fidell Sanford , Pearsons Karl , Howe Richard , Finegold Lawrence
Published: October 2005

Pearsons, Barber, and Tabachnick (1990) have documented large differences in the findings of laboratory and home studies of the ability of noise to disturb sleep. More recently, preliminary analyses of data collected in a large-scale, in-home study of sleep disturbance [Ollerhead etal. (1992)] suggest a lower probability of awakening than indicated by a dosage–response relationship recommended by Federal Interagency Committee on Noise [FICON (1992)]. The U.S. Air Force is currently conducting an in-home study of sleep disturbance, intended in part to clarify several issues not fully resolved in prior work. These include the definition of sleep disturbance and the temporal linkage between noise exposure and sleep disturbance. The rationale, design, and progress of the Air Force study are described.
Approximate traveling wave solution for impulsively perturbed circular membrane
Authors: Powell Alan
Published: October 2005

It is instructive to transform the normal modes solution for a circular membrane (radius R) suddenly displaced ξ0 at the boundary into an approximatepurelyperiodic traveling waveform ξ=ξ0Σ ×An√r/R cos[(n −1/4)π(r/R ± ct/R) − π/4], where c=wave speed (although strictly good for n≫1, r/R≪1). The series evidently has period T=8R/c. Individual mode periods T/3,T/7,T/11,... account for the notable characteristic symmetry of the waveform about the center of the periods T and asymmetry about the quarter points. The −π/2 focal phase shift (finite Hilbert transform) and the simple sign reversal (±π shift) at the boundary are readily deduced. The result also applies to ideal supersonic jets, ξimplies pressure perturbation, ctimplies (axial distance) √M2−1. For cell length (axial period) one may take sM = 8R√M2−1 for the series, or sP =8/3R√M2−1 for the first term. The two-dimensional case is unambiguous sM=4(semiwidth) √M2−1. Of course, the exact solution is not periodic at all, the major discrepancy being in first term approximation (4/3 vs 1.307...), so a better approximation is to transform just terms n≥2: the characteristic periodic waveform remains a dominant feature.
Localization and delocalization in the response of a beaded string
Authors: Maidanik G. , Dickey J.
Published: October 2005

In a complex structure in which the substructures are fairly periodic the phenomenon of localization (à la Anderson) and delocalization may arise when the periodicity is disturbed. In this paper, the localization and delocalization that may manifest in the response of a beaded (taut) string are discussed. It is argued that this phenomenon is related to the phenomenon of pass and stop bands that arise in a beaded string in which bays are fairly identical. A bay is the portion of a string between adjacent beads. When the identity of the bays is disturbed, localization and delocalization occur at frequencies that lie in pass and stop bands, respectively. The disturbance may be in the form of changing fractionally and randomly the spatial extents of the bays. Both localization and delocalization may play a significant role in the response behavior of periodic structures.
Vibration damping of large structures induced by attached small resonant structures
Authors: Strasberg M. , Feit D.
Published: October 2005

It is well known that the observed vibratory behavior of large and complicated structures usually indicates much more damping than can be accounted for by the inherent dissipation in the structural material. Several investigators have pointed out that greatly increased damping may result from vibratory power dissipated by the numerous small resonant substructures usually attached to the large main structure; C. Soize called them the ‘‘structural fuzzy’’ [J. Acoust. Soc. Am. 92, 2365 (A) (1992)]. This paper presents a simplified procedure for estimating the effect of these substructures when they have many resonances at frequencies near the excitation frequency. In this case, the increased damping of the large structure depends mainly on the total effective mass of all the substructures resonating within a frequency band (say a half-octave) centered at the excitation frequency, and is relatively independent of the specific amount of dissipation in the individual substructures. The effect of the substructures on the frequency response and vibration pattern of the main structure can also be accounted for in simple fashion. The influence of nonuniform spatial distributions of the attached substrates on the estimates is also discussed in terms of specific examples. [Work supported by ONR.]
On the nonlinearity of exhaust system acoustics in firing spark-ignition engines
Authors: Selamet A.
Published: October 2005

An extensive amount of literature is available on the performance of automotive silencers subject to linear acoustic disturbances and no-mean or steady-mean flow conditions. The flow through the automotive exhaust system exhibits, however, a number of nonlinear phenomena including high sound pressure levels reaching 180 dB and varying mean flow, as well as spatially and temporally changing temperatures. These nonlinearities are difficult to treat with the linearized acoustic theory approach in the frequency domain. The present study provides experimental results as well as numerical predictions for a production vehicle full exhaust system (Ford 1.9L Escort engine) and investigates the nonlinearities. The study implements a time-domain finite-difference approach to predict the acoustic performance based on the work of Chapman etal. [Winter Annual Meeting of ASME (1982)], which solves the one-dimensional, variable cross-sectional area, nonlinear balance equations of mass, momentum, and internal energy coupled with the equation of state for compressible flows. Nonlinearities are discussed in view of the experimental data and by comparing the terms of the momentum balance from computational results.
Determination of the performance of sound intensity probes in standing wave fields
Authors: Frederiksen Erling , Christensen Jo/rgen I.
Published: October 2005

IEC and ANSI standards that specify the performance of instruments for the measurement of sound intensity are expected to be released in the near future. The drafted standards prescribe the minimum performance of sound intensity probes in standing wave fields. Generally, the measurement of sound intensity has the greatest interest in connection with reactive sound fields. Unfortunately, the more reactive the sound field, the higher are the requirements to the instrument for the same measurement accuracy. As well-defined reactive fields can be produced inside tubes, standing wave tubes have been selected for testing of intensity probes. The standing wave performance of intensity probes, equipped with pressure-sensing microphones, has been calculated and measured. Results obtained by the two methods will be shown. A description will be given of the calculation model and of the specially designed standing wave tube that has a frequency-independent standing wave ratio of 24 dB (±0.5 dB) between 40 and 500 Hz. This performance has been obtained by terminating the test tube with many long and narrow plastic tubes.
The role of finite-element analysis in mode studies of musical instruments
Authors: Rodgers Oliver E.
Published: October 2005

Vibration analysis using finite-element methods of the mechanical systems of musical instruments have been and will continue to be an important and powerful tool for research and development workers studying musical instruments. If properly planned, executed, and interpreted, a finite-element calculation can describe all of the possible vibration modes, including some that might be missed in experimental studies because of complications in exciting and recording systems. It can be very useful for making studies of the effect of single design or tuning variables on mode-frequency placement. The method is especially valuable when the instrument under investigation is made of wood, an extremely variable and unpredictable material. (Knowledge of how to adjust the frequencies of important modes is very important when assembling and fine-tuning most stringed instruments.) Examples of successful use and opportunities for further use will be described.
Modal analysis of noncircular cylinders and bells
Authors: Rossing Thomas D. , Hansen Uwe J.
Published: October 2005

In oval cylinders, the familiar vibrational modes of a circular cylinder are split into doublets, one new mode having a node in the region of greatest curvature and the other having an antinode there. Since increasing the curvature increases the effective stiffness and thus raises the speed of bending waves, the bending wavelengths are generally longer (and the nodes further apart) in the region of greater curvature. This phenomenon is the basis of the ‘‘two-tone’’ phenomenon in ancient Chinese bells. The mode splitting in a variety of noncircular cylinders and bells, observed by means of holographic interferometry and experimental modal testing with impact excitation, is described. By using two mirrors, it is possible to view simultaneously the front, end, and top of a vibrating cylinder in holographic interferograms.
Extension of modal analysis techniques: Wind instruments and radiated sound fields
Authors: Hansen Uwe J. , Bork Ingolf
Published: October 2005

The study of normal modes of a vibrating structure using modal analysis involves the phase relationship between a large number of coherent signal pairs obtained over a predetermined geometrical grid covering the structure. From a set of transfer functions, resonance frequencies are obtained and an animated picture of the motion at the resonance frequency is displayed on a computer screen. Extending this technique to standing and traveling waves in air involves using an excitation source as reference and forming transfer functions between that reference source and sound pressure level measurements at predetermined locations in the sound field. The technique will be illustrated with animations of air modes in a flute and with animations of sound fields radiated by a piano at several frequencies [I. Bork, Acustica 75, 154–167 (1991)].
Brass instrument bell vibrations and coupling to air modes
Authors: Hoekje Peter L. , Payne Colby A. , Kjar David N.
Published: October 2005

The vibrations of brass instrument bodies are important to musicians. Three proposed mechanisms by which players might detect these vibrations are radiation, mechanical coupling to hands and mouth, and alteration of the acoustic response of the instrument bore as felt by the lips. The first mechanism has been demonstrated by other researchers [e.g., B. Lawson and W. Lawson, J. Acoust. Soc. Am. 77, 1913–1916 (1985)]. The mechanical coupling is strong, but this mechanism has minimal musical significance. For the third mechanism, the coupling between the instrument shell vibrational modes and the cross-sectional modes of the air in the bore is dependent on their relative symmetries. In the narrow main bore only plane waves propagate; in theory these should couple only to cylindrically symmetric shell modes. Trombone bell vibrational mode patterns, identified by holographic interferometry, exhibit symmetries similar to those in church bells, with nodal circles and nodal meridians. However, they may be indexed by the single number m of the nodal meridian planes. For m≳0, the frequencies fm are approximately described by a simplified Chladni’s law of the form fm=C(m)p. For a typical trombone bell, C=209 Hz and p=1.1, while f0=277 Hz.
Airport noise: The problem and some solutions and frustrations
Authors: Tauer Paul E.
Published: October 2005

Citizens of nearby communities, usually with little or no direct control over airport operations, bear the brunt of airport noise. Minimal concern for the impact of this noise has been shown by the airlines, the airports, and the F.A.A. Political pressure and legal action have both been used in attempts to force the parties responsible to address the problem. The author has worked for several years on these issues in his capacity as former Council Member and current Mayor of a city of 235 000 residents that borders both the soon-to-close Stapleton Airport and the new Denver International Airport, and as President of the National Organization to Insure a Sound-controlled Environment (NOISE). A significant project to reduce the impact of airport noise was the Stapleton Noise Insulation Program, which involved the expenditure of $20,000,000 to sound-insulate homes in Aurora, CO. Recent legislation regarding Stage III aircraft will reduce noise at the source, but does not adequately address noise impact. Thus, political conflict, prolonged litigation, and airport-capacity limitations will continue. There is a solution: communication and cooperation.