bluuebunny/crossref_metadata_2025 huggingface dataset:
An experimental study of changes in the impulse response of a wood plate that is subject to vibrational stimulus
Authors: Grogan Jared , Braunstein Michael , Piacsek Andrew
Published: October 2013

It is a well-known dictum among players of stringed instruments that the tone of a new instrument improves with playing and that a fine instrument needs to be played if it is to maintain its optimum sound quality. This process is sometimes referred to as ‘‘playing in’’ an instrument. There is scant mention in the scientific literature, however, of a quantitative analysis of this phenomenon. As a first step in rigorously testing this hypothesis, measurements were made of tap tones of rectangular pieces of thin spruce before and after they were subjected to vibrational stimulus. Four spruce rectangles (20x28 cm) were cut from a single sheet obtained from a luthier supplier; three of these were stimulated at different amplitudes, while the fourth was a control plate. The stimulus (provided by a harmonically driven guitar string connected to the plate via a bridge) lasted approximately 10 weeks, during which time tap tones of all four plates were periodically recorded. Spectrograms of the tap tones are compared among the plates and over time. A preliminary analysis of the data does not reveal any significant changes in the acoustic response of the plates.
In situ measurement of geoacoustic sediment properties: An example from the ONR Mine Burial Program, Martha’s Vineyard Coastal Observatory
Authors: Kraft Barbara J. , Mayer Larry A. , Simpkin Peter G. , Goff John A.
Published: October 2013

In support of the Office of Naval Research’s Mine Burial Program (MBP), in situ acoustic and resistivity measurements were obtained using ISSAP, a device developed and built by the Center for Coastal and Ocean Mapping. One of the field areas selected for the MBP experiments is the WHOI coastal observatory based off Martha’s Vineyard. This area is an active natural laboratory that will provide an ideal environment for testing and observing mine migration and burial patterns due to temporal seabed processes. Seawater and surficial sediment measurements of compressional wave sound speed, attenuation, and resistivity were obtained at 87 stations. The ISSAP instrument used four transducer probes arranged in a square pattern giving acoustic path lengths of 30 and 20 cm with a maximum insertion depth of 15 cm. Transducers operated at a frequency of 65 kHz. The received acoustic signal was sampled at a frequency of 5 MHz. A measurement cycle was completed by transmitting 10 pulses on each of the five paths and repeating three times for a total 150 measurements. Resistivity measurements were obtained from two probes mounted on ISSAP following completion of the acoustic measurements. [Research supported by ONR Grant Nos. N00014-00-1-0821 and N00014-02-1-0138.]
Assessing the sediment volume contribution to scattering in SAX99 sediment: Sound-speed fluctuations
Authors: Briggs Kevin B. , Tang Dajun
Published: October 2013

A simulation experiment using Monte Carlo realizations has been undertaken based on real variations in sound-speed and bulk density data from SAX99 sand sediment. In this investigation, sound-speed profiles measured from cores are used to estimate the sound-speed power spectra and sound-speed correlation lengths. Due to the manner in which sound speed is measured from 6.1-cm-diam cores at 1-cm intervals, measured sound speed is an average value across the core. Thus, the values of the measurements as well as the estimates of the correlation lengths may be a function of the sampling interval and estimation of correlation lengths may be distorted. After realizations are generated from the sound-speed power spectrum and correlation length, the virtual core is sampled to obtain a sound-speed profile and then the power spectrum is re-estimated. Because actual sound speed is known from the original data in the simulation, the difference between the parameters used to generate the simulation and the virtual parameters is a measure of the distortion by averaging or smoothing. In addition, the cross-correlation between sediment bulk density and sound-speed fluctuations in the same cores is shown. [Work sponsored by ONR.]
Shape optimization: Good looks and acoustics too!
Authors: D’Antonio Peter , Cox Trevor J. , Haas Steve
Published: October 2013

One of the challenges in the architectural acoustic design of museums and other public spaces is to develop contemporary scattering surfaces that complement contemporary architecture in the way that statuary, coffered ceilings, columns, and relief ornamentation complemented classic architecture. Often acoustic surfaces satisfy the acoustics, but may or may not satisfy the aesthetics. One approach that has been successful employs a combination of boundary element and multidimensional optimization techniques. The architect supplies the desired shape motif and the acoustician supplies the acoustical performance requirements. The optimization program then provides an Arcousthetic surface, which simultaneously satisfies the architecture, the acoustics, and the aesthetics. The program can be used with diffusive or diffsorptive surfaces. Photos of installations using these acoustic tools and a description of the design of the National Museum of the American Indian will also be presented to illustrate the usefulness of these devices and their impact on architectural acoustics.
Comparison of ultrasound-induced bioeffects in glass catfish after injection with optison and liquid perflourocarbon droplets
Authors: Maruvada Subha , Hynynen Kullervo
Published: October 2013

This work is an investigation of ultrasound-induced bioeffects in vivo. Glass catfish were used for these experiments because they are optically transparent. Anaesthetized fish were injected with either optison (OPT) or liquid perflourocarbon droplets (LPD), using microinjection techniques. Shortly after injection, the fish were insonified with one of two single element focused transducers (1.091 MHz and 0.747 MHz). An inverted microscope combined with a digital camera was used to optically monitor ultrasound interaction with the blood vessels in the tail of the fish at 200x magnification. The entire interaction was videotaped and digitized. The fish were insonified at power levels between 1–80 W, which translated into acoustic pressures from 0.45–15 MPa. Sonications were pulsed with burst lengths of 10 ms and 100 ms and a repetition frequency of 1 Hz. The entire length of one sonication at a specific pressure was 20 seconds. The effects of the sonication were analyzed at each pressure level. The ultrasound-induced bioeffects due to OPT and LPD were compared. Threshold values for damage were lower after OPT injection than after LPD injection, especially at lower frequencies.
Acoustic characterization of liposome suspensions and Optison® at 3.5 MHz
Authors: Coussios Constantin-C. , Holland Christy K. , Jakubowska Ludwika , Huang Shao-Ling , MacDonald Robert C. , Nagaraj Ashwin , McPherson David D.
Published: October 2013

Liposomes—phospholipid vesicles that can encapsulate both gas and fluid—are currently being developed as contrast agents and vehicles for targeted drug delivery. The backscattering coefficient and attenuation of liposome suspensions were measured at 3.5 MHz as a function of liposome concentration and compared to those of Optison®. The backscattering coefficient of liposomes at concentrations in excess of 1.15×108/ml exceeds that of Optison® at the clinical dose (5.0−8.0×104/ml). On the other hand, the attenuation of ultrasound through liposome suspensions is negligible relative to the attenuation through Optison® (0.25 dB/cm), suggesting that liposomes have a much higher scatter-to-attenuation ratio and could be more efficient as contrast agents. A theoretical model that treats the gas within the liposomes as a free air bubble was used to estimate the backscattering coefficient and correlated well with experimental results. Church’s model [J. Acoust. Soc. Am. 97, 1510–1521 (1995)] for Albunex® was also found to provide an accurate estimate of the backscattering coefficient of Optison®. These models suggest that the marked difference in attenuation between the two agents can be attributed to the fact that liposomes are sub-resonant in size at 3.5 MHz, but Optison® microspheres act as resonant scatterers. a)Currently at Boston University.
Simulation and experiment of nonlinear scattering mechanisms producing difference frequencies from two distinct primary frequencies incident on a target
Authors: Thierman Jonathan S. , Makris Nicholas C. , Ratilal Purnima , Hynynen Kullervo
Published: October 2013

Our theoretical derivation of nonlinear wave propagation with scatterers is compared with simulated and experimental results regarding the production of difference frequency signals from targets insonified by sources radiating at two distinct primary frequencies. The previously presented nonlinear wave equation derived from first principles using coherent wave theory is applied to the problem of focused ultrasound transducers and various target types and geometries. First, with computer simulation, we explore the relative contribution of each term of the theoretical derivation as applied to the geometry of focused sources. The terms of this equation represent different physical mechanisms responsible for the production of a difference frequency. Their relative magnitude reveals which mechanisms are more likely to produce the measured difference frequency signal in experiments. Next, we measure the difference frequency field in experiments to demonstrate the correlation of theory with simulation and experiment. The experiments reveal the profound effect various scattering phenomenon have on the produced difference frequency field.
Ultrasound phase-contrast transmission imaging of localized thermal variation in a breast tissue model
Authors: Clement Greg , Hynynen Kullervo
Published: October 2013

The present numeric study examines an ultrasound phase contrast method for imaging localized temperature rises in tissue, such as heating experienced in thermal ablation treatments. We tested the method’s ability to produce thermal images by simulating the signal from a planar ultrasound source directed through tissue containing skin, fat, and muscle layers. Phase-contrast imaging only requires phase shifts a fraction of a wavelength for detection, thus we tested for the feasibility of imaging at low (submegahertz) frequencies, allowing greater depth penetration and reduced scattering away from the image plane. The tradeoff for lower frequencies was a reduced spatial resolution. It was therefore necessary to determine the lowest possible frequency that could still provide information about the tissue structure and information about the temperature rise in the heated volume. After studying a tomographically reconstructed 4-mm cylindrical heated region in a 100-mm-thick section breast tissue model, thermal effects were detected at frequencies as low as 0.4 MHz, which allowed reconstruction resolution of about 2 mm2 over the image plane. This method may have applications for example in controlling focused ultrasound surgery of breast.
From acoustics to perception: How to listen to meaningful sounds in a meaningful way
Authors: Gygi Brian
Published: October 2013

Making sense of the sounds we encounter everyday requires a coupling between what we sense (acoustics) and what we ‘‘hear’’ (perception). Data will be presented suggesting that the psychological organization of familiar nonspeech, nonmusical sounds (‘‘environmental sounds’’) is closely aligned to the acoustic similarity of these sounds, as well as to the physical events that produced the sounds. Results of identification studies indicate that the particular acoustic features listened for include pitch salience, rhythmicity, and amplitude modulation. Far from being impoverished, the acoustic information available in the world is sufficient to quickly and reliably determine the source of a sound and allow for appropriate responses.
Appalachia meets the mid-south in Tennessee
Authors: McGowan Richard S. , Jackson Michel T-T.
Published: October 2013

The father of bluegrass and long-time member of the Opry in Nashville, Bill Monroe, had a number of musical influences, including blues, gospel, and the American versions of Anglo-Scots-Irish folk music endemic to Appalachia. (Although Bill Monroe was from western Kentucky, the Appalachian influence is apparent.) In 1946 he recorded a song for Columbia Records that he had written. This song was recorded again in 1954 at Sun Studios as a ‘‘B side’’ by the future king of rock and roll, Elvis Presley. Raised in East Tupelo, MS and Memphis, Elvis’ music derived from the mid-south’s blues and gospel music, but with a peculiar honkytonk-informed, Memphis style. We will compare these artists through this common song and their spoken interviews in terms of voice quality and English dialect. Some copy-synthesis of these artists will be attempted in our search for the high, lonesome and rock and roll sounds.
Acoustic correlates of Georgian stops
Authors: Wysocki Tamra M.
Published: October 2013

This paper presents results from an acoustic analysis of Georgian stops. Georgian is a South Caucasian language and has a three-way opposition among voiced, voiceless aspirated, and ejective stops for three places of articulation: bilabial, dental, and velar. Tokens consist of initial and medial stops in isolated words produced by two male and two female native Georgian speakers. Closure duration, VOT, and burst amplitude were measured using waveforms, spectrograms, and FFTs. The voice quality of adjacent vowels was examined for possible consonantal effects (e.g., creaky voicing adjacent to ejectives). Additional observations included noise characteristics during closure and following oral release. Results show much variation in the realizations of stops both within and across speakers. While a general trend exists for VOT and burst amplitude to differentiate initial voiced and voiceless stops, values of voiceless aspirated and ejective stops overlap. In intervocalic stops, VOT and burst amplitude are more variable. Closure duration remains fairly stable across the three stop categories. Noise quality following oral release and, to some extent, voice quality of a following vowel more consistently distinguish the three stop types in both positions than do the quantitative measures. These characteristics are further discussed in relation to similar cross-linguistic studies.
Affricate gemination in the English of Polish speakers: A study in second language variability
Authors: Thurgood Ela
Published: October 2013

This study investigates the nature of the acoustic variation in sequences of identical affricates produced by Polish learners of English. In both English and Polish sequences of identical affricates occur across word boundaries, but only in Polish do such sequences also occur root internally and across morpheme boundaries. In Polish sequences of identical affricates are manifested variably both by rearticulation of both affricates and by articulation of a single affricate but with lengthened duration of either the stop or the fricative. To investigate their English, the subjects performed two tasks: repetition of 12 English sentences and orally responding to 17 multiple choice questions. The task produced significant cross-speaker differences in the phonetics of the geminates, differences correlated with differences in their proficiency levels in English. The more Polish-like singly articulated long affricates were produced by 22% of the intermediate speakers but by 48% of the advanced speakers, the opposite of what one might expect. The intermediate speakers appear to have paid more attention to the phonetics of the English cues, thus producing more fully rearticulated affricates; the more advanced speakers appear to have paid less attention to the phonetics of the cues, thus reverting more to the norms of Polish pronunciation.
Padé approximations for boundary-layer losses in articulatory synthesis
Authors: Wilhelms-Tricarico Reiner , McGowan Richard S.
Published: October 2013

To build an articulatory synthesizer it is necessary to model acoustic propagation in tubes with variable area. Acoustic propagation entails viscous and thermal losses, which are strongest at the vocal tract walls. In the standard boundary-layer approximation irrational frequency laws containing the square root of frequency best represent these losses. Our immediate goal is, given a sound source distribution in the vocal tract, to efficiently calculate the sound output from the mouth. In order to use digital filter theory in this process, a rational approximation to the square root of frequency is sought in the form of Padé approximations. One implementation is obtained by modification of the Kelly–Lochbaum algorithm for calculating wave propagation in a tube, using a high over-sampling rate. However, frequency-dependent loss means that both the reflection coefficients and the time delays through a tube section are non-constant functions of frequency—an assumption used in the Kelly–Lochbaum algorithm. The reflection coefficients are replaced by digital filters and the delay elements by filters with frequency-dependent group velocities. We discuss implementation of a Kelly–Lochbaum algorithm in a digital filter design using a Padé approximation of the viscous and thermal loss terms. [Work supported by NIH Grant No. DC-01247.]
A new approach for isolated word recognition using dynamic synapse neural networks
Authors: Dibazar Alireza A. , Namarvar Hassan Heidari , Berger Theodore W.
Published: October 2013

In this paper we introduce a hybrid system for robust automatic speech recognition. We first present a new architecture for dynamic synapse neural networks (DSNNs) for a speech recognition task and then we extend the quasi-linearization algorithm to estimate the DSNNs parameters. This algorithm converges quadratically to the extemal solution of a given set of nonlinear differential equations. In our application, the DSNN parameters and or the signals spectrums estimated by DSNN are classified using a hidden Markov model (HMM) based classifier. Our results indicate that the features obtained from DSNN are robust with respect to state of the art frequency features in the presence of a high level of noise. [Work supported in part by DARPA, NASA, and
Spatial and temporal coherence of broadband acoustic transmissions in the Straits of Florida
Authors: DeFerrari Harry A. , Williams Neil , Nguyen Hien
Published: October 2013

Month-long time series of broadband coherent measurements of channel pulse responses in the Florida Straits allow for estimation of signal coherence under a great variety of signal parameters and environmental conditions. Two 32-element arrays, one vertical and another horizontal (bottomed) along the path of propagation allow for comparison of spatial coherency and single phone temporal coherencies. The transmitted signals cover 5 octaves from 100 through 3200 Hz. Coherencies for single resolved SRBR arrivals are compared with those for unresolved multipath BRB focused arrivals. Many factors are at play including the complication of coherent reception from nearby shipping and multipath interference. However, the time series are long enough to sort out and explain most relations to the environmental variability. Vertical and horizontal coherence lengths are compared over a wide range of frequencies. Generally, SBRB paths are found to be far more stable and coherent than RBR paths especially at higher frequencies suggesting that sound-speed variability near turning RBR rays/modes is more destructive to coherency. The loss of signal coherency for RBR paths is accompanied by a significant loss of signal intensity—as much as 10 to 15 dB.
Physical oceanography and acoustic propagation during LADC experiment in the Gulf of Mexico in 2001
Authors: Vinogradov Sergey , Caruthers Jerald W. , Rayborn Grayson H. , Udovydchenkov Ilya A. , Sidorovskaia Natalia A. , Rypina Irina I. , Newcomb Joal J. , Fisher Robert A. , Ioup George E. , Ioup Juliette W.
Published: October 2013

The Littoral Acoustic Demonstration Center (LADC) deployed three environmental and acoustic moorings in a downslope line just off the Mississippi River Delta in the northern Gulf of Mexico in an area of a large concentration of sperm whales in July 2001. The measurement of whale vocalizations and, more generally, ambient noise, were the objectives of the experiment. Each mooring had a single hydrophone autonomously recording Environmental Acoustic Recording System (EARS) obtained from the U.S. Naval Oceanographic Office and modified to recorded signals up to 5859 Hz continuously for 36 days. Also, self-recording, environmental sensors were attached to the moorings to obtain profiles of time series data of temperature and salinity. Satellite imagery and NOAA mooring data were gathered for an analysis of eddy formations and movement in the Gulf. This paper will discuss the possible environmental impact of two events that occurred during the experiment: the passage of Tropical Storm Barry and the movement of the remnants of an eddy in the area. Discussed also will be the expected effects of these events on acoustic propagation based on modeling, which are carried out for long range and low frequency (300 km and 500 Hz) using the normal-mode acoustic model SWAMP (Shallow Water Acoustic Modal Propagation by M. F. Werby and N. A. Sidorovskaia) and for short range and high frequency (10 km and 5000 Hz) using the parabolic-equation acoustic model RAM (Range-dependent Acoustic model by M. Collins). [Work supported by ONR.]
Studies of horizontal refraction and scattering of low-frequency acoustic signals using a modal approach in signal processing of NPAL data
Authors: Voronovich Alexander G. , Ostashev Vladimir E. ,   The NPAL Group
Published: October 2013

In our previous paper [J. Acoust. Soc. Am. 112, 2232], we obtained a time dependence of the horizontal refraction angle (HRA) of acoustic signals propagating over a range of about 4000 km in the ocean. This dependence was computed by processing of acoustic signals recorded during the North Pacific Acoustic Laboratory (NPAL) experiment using a ray-type approach. In the present paper, we consider the results obtained in signal processing of the same data using a modal approach. In this approach, the acoustic field is represented as a sum of local acoustic modes with amplitudes depending on a frequency and arrival angle. We obtained a time dependence of HRA for a time interval of about a year. Time evolution of HRA exhibits long-period variations which could be associated with seasonal trends in the sound speed profiles. The results are consistent with those obtained by the ray approach. Different horizontal angles within arrivals were impossible to resolve due to sound scattering by internal waves. A theoretical estimate of the angular width of the acoustic signals in a horizontal plane was obtained. It appears to be consistent with the observed variance of HRA data. [Work supported by ONR.] a)J. A. Colosi, B. D. Cornuelle, B. D. Dushaw, M. A. Dzieciuch, B. M. Howe, J. A. Mercer, R. C. Spindel, and P. F. Worcester.
The two-frequency third moment with internal wave induced fluctuations
Authors: Henyey Frank S. , Ewart Terry E.
Published: October 2013

Many moments of the pressure field that results from sound propagation in the random ocean, for example the first moment, fall rapidly with range due to phase fluctuations associated with travel time ‘‘wander.’’ As a result, such moments are not of much experimental interest. However, just as with intensity moments, the third moment 〈p2(ω)p*(2ω)〉 is free from wander effects. In the Mid-ocean Acoustic Transmission Experiment (MATE), data was taken from which this moment can be extracted, both for ω=2 kHz and ω=4 kHz. The standard theory (assuming the Markov approximation) is developed for this moment and compared to the MATE results. The imaginary part of this moment describes the frequency dependence of travel time, while its real part can be thought of as an intensity moment. [Work supported by ONR.]
Doubly-focused echos from spheres unfold into a hyperbolic umbilic diffraction catastrophe
Authors: Dzikowicz Ben , Marston Philip L.
Published: October 2013

An underwater spherical target resides in an Airy field formed by reflection off a curved surface representing the sea floor or sea surface. In prior work [B. Dzikowicz and P. L. Marston, J. Acoust. Soc Am. 110, 2778 (2001)] direct returns of a tone burst from the surface reflection focused toward the target were shown to have a dependence on the target position described by an Airy function. The return echo can also be focused again by the surface onto the source and receive transducer. This gives the square of an Airy function for the case of a point target. With a finite sized target (as in the experiment) this goes over to a hyperbolic umbilic catastrophe with symmetric arguments. The arguments of the hyperbolic umbilic function are derived from only the relative return times of a transient pulse. Experiment confirms the predicted merging of transient echoes in the time domain, as well as the hyperbolic umbilic diffraction integral amplitudes for a tone burst. This method would allow for the observation of a target at a greater distance in the presence of a focusing surface. [Research supported by ONR.]
On the relationship between signal bandwidth and coherence for ocean surface forward scattered signals
Authors: Culver R. Lee , Bradley David L. , Keranen Joe G.
Published: October 2013

The relationship between the signal bandwidth and the coherence of high frequency, surface forward scattered underwater acoustic signals has been investigated experimentally and compared with available theory. Acoustic measurements were made under ONR sponsorship (the ARL Program) during 2000 [J. G. Keranen et al., J. Acoust. Soc. Am. 109 (2001)] and again in 2002, both times in deep water off the coast of San Diego. Transmitted signals consisted of 0.1 to 1.0 ms CW pulses and 500 Hz to 22 kHz wide linear frequency modulated sweeps using center frequencies of 18 to 46 kHz. Concurrent environmental measurements included water temperature, current speed and direction, directional wave height and wind speed. An analysis of the data is focused on how the coherence of the surface forward scattered path depends upon the signal bandwidth. We evaluate the usefulness of the frequency coherence bandwidth parameter [P. H. Dahl, IEEE J. Oceanic Eng. 26(1) (2001)], and compare measurements with time spread-based theoretical predictions [J. C. Reeves, Ph.D. thesis, UCLA, 1973; M. H. Brill et al., J. Acoust. Soc. Am. 75 (1984)]. [Work supported by ONR under Award No. N00014-02-1-0156.]
A plano-concave, 1–3 piezocomposite transducer for swept-frequency calibration of ultrasound hydrophones below 2 MHz
Authors: Harris Gerald R. , Gammell Paul M.
Published: October 2013

Rapid calibration of hydrophones used in biomedical ultrasound is possible with swept-frequency techniques such as time-delay spectrometry. However, the range below 2 MHz has largely been neglected because of insufficient source transducer bandwidth [P. M. Gammell and G. R. Harris, J. Acoust. Soc. Am. 106, L41–L46 (1999)]. Calibration in this range is important when recording pressure waveforms distorted by nonlinear propagation, especially for accurate measurement of the peak rarefactional pressure. Therefore, a 1–3 piezocomposite transducer designed for this range has been developed and tested (poled piezocomposite element, Smart Material Corp., Sarasota, FL; transducer assembly, UTX, Inc., Holmes, NY). The element has plane front and spherically concave back faces. The nonuniform thickness disperses the thickness resonance, and the composite structure suppresses radial-mode resonances. Also, the composite’s lower acoustic impedance provides a more efficient match to water. A 4-cm-diameter transducer having maximum and minimum thicknesses of 1.5 cm and 1 mm produced a smooth pressure spectrum at an axial distance of 35 cm that varied <15 dB from 0.1–2 MHz. Compared to plano-concave, single-element designs having similar dimensions, the new transducer had equivalent transmit sensitivity, and its response was significantly more uniform, possibly due in part to decreased contributions from radial modes.
Causal energy absorption by point-attached substructures
Authors: McDaniel J. Gregory , Li Xianhui
Published: October 2013

One means of attempting global vibration control when a structure is excited by an unknown transient force is to attach a substructure that optimally absorbs energy by matching the structural dynamics. Frequency-domain analysis allows one to determine the substructural admittance for optimal absorption, however the resulting admittance is often noncausal. A classic noncausal example is when the substructural admittance is chosen as the complex conjugate of the structural admittance. This presentation will present a methodology for solving this problem by employing an implicitly causal Fourier series in frequency for the substructural impedance. The Fourier coefficients of this series are chosen to maximize the energy absorption of the attachment. This methodology also allows one to seamlessly incorporate a passivity requirement for the substructure.
Predicting noise in industrial workrooms using empirical models
Authors: Hodgson Murray
Published: October 2013

Sound fields in complex industrial workrooms can be predicted well using numerical procedures such as the method of images and ray tracing. However, this requires acoustical expertise, as well as computational resources and times which result in prediction methods only being used in special cases. This paper discusses alternative empirical prediction methods which have the potential to be sufficiently accurate in ‘‘typical’’ cases, and more readily accessible to practitioners, making them more likely to be used in practice. The first method discussed is a hybrid approach, whereby characteristic workroom sound-propagation curves are predicted using ray tracing. These are then input into an empirical model which sums the energy contribution of all sources at a receiver position based on those curves and the applicable source/receiver distances. Next, the development of empirical models for predicting frequency-varying sound-propagation curves and reverberation times using regression techniques is discussed. These were developed from data measured in actual workrooms when empty or fitted, without and with sound-absorptive treatment. Empirical methods for estimating workroom fitting densities and multisource noise levels, and the integration of the empirical models into the PlantNoise prediction system, are also discussed.
Effect of mean fluid flow on an acoustic standing wave in an open cavity
Authors: Anderson Michael , Line Kenneth , Budwig Ralph
Published: October 2013

Acoustic radiation pressure can be used to concentrate or remove small particles from an airborne aerosol. In this application, an ultrasonic transducer, mounted flush to one wall of a channel, is used to excite an integer half-wavelength standing wave of high amplitude that propagates perpendicular to the aerosol flow direction. An expression for the Fourier transform of the acoustic pressure in a semi-infinite channel, including the effect of mean fluid flow and finite transducer aperture, has been obtained. A parabolic (laminar) mean flow was assumed. The acoustic pressure was found to be governed by the Mach number of the flow, defined by the projection of the propagation direction relative to the mean flow velocity vector; and the aperture function of the transducer. Near a frequency of 50 kHz, numerical inversions of the acoustic pressure transform showed that the presence of mean flow in the velocity range 0-2 m/s caused changes in acoustic pressure on the order of 1%–4%. Corresponding experimental measurements showed changes in acoustic pressure up to 10%. The highest changes in measured acoustic pressure were found to occur up- and down stream relative to the transducer, and these patterns were in agreement with predictions of the analytical model.
Coherent versus diffuse surface and volume Reverberation in an ocean wave guide: Reverberation rings, modal decoupling, and possible fish scattering in Geoclutter 2001
Authors: Ratilal Purnima , Makris Nicholas C.
Published: October 2013

Conditions necessary for the field scattered from volume inhomogeneities and surface roughness in a wave guide to become diffuse in nonforward azimuths are derived from Green’s theorem. Diffuse scattering leads to a decorrelation of the wave guide modes that simplifies the expression for the intensity of the total scattered field. When diffuse scattering conditions are not satisfied, seafloor scattering becomes coherent and leads to the formation of ‘‘reverberation rings’’ sometimes observed in high-resolution sonar systems. The formation of these rings will be investigated both analytically and with simulations. The possibility that some prominent clutter events in the Geoclutter 2001 experiment are due to diffuse scattering from fish schools is investigated theoretically and experimentally.
Current status of standards for testing electroacoustic hearing protectors
Authors: Murphy William J. , Franks John R.
Published: October 2013

Electroacoustic hearing protectors encompass several classes of electronics: level limiting, amplitude compression and active noise control (ANC) devices. Each class of protector seeks to enhance performance by overcoming insertion loss and/or improving low-frequency attenuation. Level-limiting devices turn off the amplification when the external sound level exceeds a preset threshold. Amplitude compression devices apply variable gain and limit amplification of signals above the threshold. ANC devices create an out-of-phase signal under the protector to improve the low-frequency attenuation of earmuffs. ANC devices typically perform best in continuous noise that has strong harmonic components that can be predicted and cancelled. The different methods of enhancing protector performance require separate standards to understand both the static and dynamic performance. Testing of ANC devices has further requirements which require knowledge of both passive and active electronic conditions and in noise with different crest factors. This talk will review a variety of tests of the different protector classes.
Software development for NIOSH hearing protector testing
Authors: Murphy William J. , Franks John R. , Rohrer Douglas T.
Published: October 2013

In June 1998, NIOSH researchers recognized the necessity of rebuilding the NIOSH Hearing Protector Device Testing Laboratory. Several design requirements influenced the software development and hardware selection. First, the hardware must be commercially available and easily operated from personal computers that use the Microsoft Windows operating system. Second, software must have the flexibility to support not only the demands of a research laboratory and field studies but also be configurable such that a commercial laboratory could use the software for production testing of protectors. Finally, the complete package must ensure the use of standard operating procedures for the purpose of achieving and maintaining NVLAP certification for the ANSI S12.6 and S3.19 standards for the measurement of real-ear attenuation at threshold. The total system has been operational since May 2002 and has been installed in three laboratories to date. This paper will present how these competing needs were addressed in the development of the NIOSH HPD Lab software.
Spectral pattern and harmonic relations as factors governing the perceptual cohesion of low-numbered components in complex tones
Authors: Roberts Brian , Brunstrom Jeffrey M.
Published: October 2013

Mistuning a harmonic changes its pitch more than expected and also increases its salience. Both effects can be used to explore the auditory organization of complex tones. In this study we extend our findings indicating that the effects of a spectral pattern on grouping are not restricted to harmonic relations. Stimuli were either harmonic (F0=200 Hz) or frequency shifted by 25% of F0. Component 1 or 2 was replaced by one of a set of sinusoidal probes in the same spectral region. In experiment 1, listeners adjusted the frequency of a pure tone to match the probe pitch. Inflections of the pitch-shift functions were close to the two expected values in the harmonic condition. In the shifted condition, they were close to the suboctave (225 Hz) and the frequency (450 Hz) of component 2. In experiment 2, listeners matched the probe loudness by adjusting the level of a tone of identical frequency. Loudness minima corresponded closely to the pitch-shift inflections. Experiment 3 showed that a pitch-shift inflection close to 450 Hz requires the presence of component 1. These results suggest that the first component of a shifted complex is grouped differently from the others, based on harmonicity rather than spectral spacing.
Virtual auditorium concepts for exhibition halls
Authors: Evans Jack , Himmel Chad , Knight Sarah
Published: October 2013

Many communities lack good performance facilities for symphonic music, opera, dramatic and musical arts, but have basic convention, exhibition or assembly spaces. It should be possible to develop performance space environments within large multipurpose facilities that will accommodate production and presentation of dramatic arts. Concepts for moderate-cost, temporary enhancements that transform boxy spaces into more intimate, acoustically articulated venues will be presented. Acoustical criteria and design parameters will be discussed in the context of creating a virtual auditorium within the building envelope. Physical, economic, and logistical limitations affect implementation. Sound reinforcement system augmentation can supplement the room conversion. Acceptable control of reflection patterns, reverberation, and to some extent, ambient noise, may be achieved with an array of nonpermanent reflector and absorber elements. These elements can sculpture an enclosure to approach the shape and acoustic characteristics of an auditorium. Plan and section illustrations will be included.
Acoustic performance of roadside barriers in urban environments
Authors: Li Kai Ming , Tang Siu Hong
Published: October 2013

Extensive research has been conducted for assessing the acoustic performance of a barrier in a sub-urban area where the receivers are normally situated at a considerable distance from the barrier. However, in a typical urban community, a noise barrier is frequently erected in front of a tall building. It provides a shadow zone to listeners on the other side of the barrier. The size of this shadow zone depends on the height and position of the barrier away from the building facade. Sound waves are diffracted at the top edge of the barrier before they reach the receivers either directly, or on reflection from the ground and/or from the facade surface. Diffraction and multiple scattering play important roles in determining the sound pressure levels between the facade and barrier. Furthermore, the possibility of a direct wave between the source and the receivers higher up the building requires further evaluations when considering the total sound fields. In this paper, the theory behind the facade–barrier system is outlined. Indoor scale model experiments are conducted to validate theoretical predictions. [Work supported by Research Grants Council of the Hong Kong Special Administrative Region and The Hong Kong Polytechnic University.]
The propagation of sound in tunnels
Authors: Li Kai Ming , Iu King Kwong
Published: October 2013

The sound propagation in tunnels is addressed theoretically and experimentally. In many previous studies, the image source method is frequently used. However, these early theoretical models are somewhat inadequate because the effect of multiple reflections in long enclosures is often modeled by the incoherent summation of contributions from all image sources. Ignoring the phase effect, these numerical models are unlikely to be satisfactory for predicting the intricate interference patterns due to contributions from each image source. In the present paper, the interference effect is incorporated by summing the contributions from the image sources coherently. To develop a simple numerical model, tunnels are represented by long rectangular enclosures with either geometrically reflecting or impedance boundaries. Scale model experiments are conducted for the validation of the numerical model. In some of the scale model experiments, the enclosure walls are lined with a carpet for simulating the impedance boundary condition. Large-scale outdoor measurements have also been conducted in two tunnels designed originally for road traffic use. It has been shown that the proposed numerical model agrees reasonably well with experimental data. [Work supported by the Research Grants Council, The Industry Department, NAP Acoustics (Far East) Ltd., and The Hong Kong Polytechnic University.]
The development and use of a high frequency horizontal sonar to monitor channel catfish in shallow water commercial aquaculture ponds
Authors: Chambers James , Wren Daniel , Carpenter Brian , Minchew C. Douglas , Beecham Rachel
Published: October 2013

With increasing seafood demand and a declining capture in offshore fisheries, aquaculture is poised to become a major growth industry in the United States in the 21st century. A major portion of the costs associated with raising channel catfish is related to the cost of feed and aeration. These costs are directly related to the total number of fish being raised in each pond. Unfortunately, at the present time a pond would have to be totally harvested to get an accurate inventory. An alternate technique, discussed here, is the use of a high frequency (420 kHz) horizontally scanning sonar to size and count the fish in a pond. Commercial catfish ponds range in size 0.04 to 7.2 hectares. The most desirable size is about 4 hectares. These ponds will typically be about 100 m in length and 1 to 2 m in depth. This sonar is capable of 1 cm range resolution combined with an approximately 100 m maximum range. Results from field tests will be presented to show the systems effectiveness in determining the number and possibly size distribution of commercial catfish ponds. In addition design considerations and operating parameters for the shallow water environment will be discussed.
International documentary standards and comparison of national physical measurement standards for the calibration of accelerometers
Authors: Evans David J.
Published: October 2013

The documentary standards defining internationally adopted methodologies and protocols for calibrating transducers used to measure vibration are currently developed under the International Organization for Standardization (ISO) Technical Committee 108 Sub Committee 3 (Use and calibration of vibration and shock measuring instruments). Recent revisions of the documentary standards on primary methods for the calibration of accelerometers used to measure rectilinear motion have been completed. These standards can be, and have been, used as references in the technical protocols of key international and regional comparisons between National Measurement Institutes (NMIs) on the calibration of accelerometers. These key comparisons are occurring in part as a result of the creation of the Mutual Recognition Arrangement between NMIs which has appendices that document the uncertainties, and the comparisons completed in support of the uncertainties, claimed by the National Laboratories that are signatories of the MRA. The measurements for the first international and the first Interamerican System of Metrology (SIM) regional key comparisons in vibration have been completed. These intercomparisons were promulgated via the relatively new Consultative Committee for Acoustics, Ultrasound and Vibration (CCAUV) of the International Committee for Weights and Measures (CIPM) and SIM Metrology Working Group (MWG) 9, respectively.
Ancient celtic horns
Authors: Campbell Murray
Published: October 2013

There is considerable evidence from iconographic and documentary sources that musical lip-reed instruments were important in the early celtic communities of Scotland and Ireland. In recent years several studies have been undertaken with the aim of gaining a better understanding of the musical nature of these ancient horns, and of their place in the life and culture of the time. A valuable source of tangible evidence is to be found in the archaeological remains deposited across Scotland and the whole of Ireland. A project is now under way, under the auspices of the Kilmartin House Trust and the general direction of John Purser, which has brought together an international team of musicians, craftsmen, archaeologists, musicologists and physicists with the aim of analyzing ancient musical artifacts, reconstructing some of the original instruments, and analyzing the sounds they produce. This paper describes acoustical studies carried out on a number of recent reconstructions of wooden and bronze instruments, and discusses the role of acoustics in this type of investigation. [Work supported by Sciart and EPSRC.]
Room acoustic computer modeling: The effects of scattering on transient power flow
Authors: Campbell Richard H.
Published: October 2013

The CATT© room acoustic modeling program allows the computation of acoustic power projected to three mutualy perpendicular planes at a point in space integrated over a specified time period. By selecting successive time periods it is possible to observe the oscillatory nature of the transient power flow from first arrival to the long-term settled value during diffuse-field reverberant decay. The computation is normalized, and displayed as a fraction of the total power. Introducing scattering on the room surfaces results in a significantly smaller peak amplitude of power flow oscillation. Several cases are shown involving different room sizes and shapes and different orientations of source and receiver. Conclusions are made on the number of mean-free path intervals required to ‘‘settle’’ the computer-modeled acoustic field.
Helmholtz design for noise transmission attenuation on a chamber core composite cylinder
Authors: Li Deyu , Vipperman Jeffrey S.
Published: October 2013

This work explores the feasibility of using Helmholtz resonators to attenuate a subscale ChamberCore cylinder noise transmission. The ChamberCore cylindrical composite is an innovative new sandwich-type structure. It consists of an outer skin, an inner skin, and linking ribs. There are wedge-cross-section chambers along the axis direction between the outer and inner skins. These chambers provide a potential for the acoustic Helmholtz resonator design in order to reduce the noise transmission, which is dominated by the internal acoustic cavity. In this experimental work, the sound transmission behavior of the ChamberCore fairing is investigated and divided into four interesting frequency regions: the stiffness-controlled zone, cavity resonance-controlled zone, coincidence-controlled zone, and mass-controlled zone. It is found that the noise transmission in the low-frequency band is controlled by the structural stiffness and cavity resonances, where the acoustic Helmholtz design method has the potential to improve the noise transmission.