bluuebunny/crossref_metadata_2025 huggingface dataset:
An advanced noise source identification technique using the inverse boundary-element method
Authors: Martinus Ferdy
Published: October 2013

The application of the inverse BEM method as an advanced, non-contact noise source identification technique will be discussed. In the first and most conventional experiment, the inverse BEM is used to reconstruct the vibration pattern on the surface of a motorcycle engine oil pan cover. In the second experiment, the inverse BEM is used to determine the distribution of particle velocity on the open end of a rectangular duct. Measurements of the particle velocity using the two-microphone method are compared to those predicted using the inverse BEM. In the third experiment, the inverse BEM is used to identify the mechanism of an aeroacoustics noise problem (a vortex tone) created by flow over a circular rod. The spectrum of the tonal sound within the flow field is reconstructed using the inverse BEM, and a near field spatial reconstruction of the sound pressure shows clearly the nature of the vortex source. This paper will also show that only a relatively small number sound pressure measurements are required for the inverse BEM and that these measurements need not be in the near field of the source nor conformal to it to obtain good results.
Two-microphone nearfield acoustical holography
Authors: Cho Yong Thung , Bolton J. Stuart , Kim Yong-Joe , Kwon Hyu-Sang
Published: October 2013

In conventional Nearfield acoustical holography (NAH), a large number of measurements is required to cover the entire source area. In addition, when the complete source comprises several incoherent sub-sources, the sound field must be decomposed into coherent partial fields before projection. The latter operation is made possible by using a fixed array of reference microphones and computing the reference cross-spectral matrix and the transfer functions between the reference microphones and the field microphones. Here it is shown that by combining the transfer functions from the reference to the field microphones obtained from one measurement with reference cross spectra measured in another, the sound field radiated any combination of different level (fixed-directionality) subsources can be visualized from measurements made with only enough reference microphones to represent the incoherent sources. The implementation of the procedure will be illustrated using an array of two loudspeakers, each fed by an independent white noise source. Comparisons are made of directly measured partial fields and those generated using only the reference information. By using this procedure, it is possible to avoid repetitive measurements when visualizing the sound fields radiated by different combinations of subsources having different levels, so long as the directionality of each subsource is fixed.
Meeting 2006, outdoor noise directive (OND) noise levels for a diesel engine driven air compressor: A case study in noise reduction
Authors: Rowe David F.
Published: October 2013

In January 2006, the noise limits for many products in the European Union will drop by 2–3 dBA, as directed by 2000/14/EC ‘‘Noise Emission in the Environment by Equipment Used Outdoors,’’ commonly called the ‘‘Outdoor Noise Directive,’’ or ‘‘OND.’’ Air compressors are among the products addressed by this directive. At Ingersoll-Rand, significant effort has been directed at meeting the challenge of reducing noise on a variety of diesel engine driven air compressor platforms, ranging from 15 to 350 kW diesel engine power ratings. This paper presents a case study of the noise reduction on a 750 cfm (21 m3/min) air compressor operating at 300 psig (21 bar), to meet the 2006 OND noise limit of 100 LwA.
Evaluation of transmission loss using the boundary element method for mufflers with two inlets
Authors: Jiang C. , Wu T. W. , Cheng C. Y. R.
Published: October 2013

Mufflers with multiple inlets and multiple outlets are commonly used in exhaust systems which provide the benefits of lower restriction and higher engine performance. In this paper, the direct mixed-body boundary element method (BEM) is used to predict the transmission loss (TL) of mufflers with two inlets and one or two outlets. To do this, the impedance matrix of the muffler is first computed by the BEM. The transmission loss (TL) can then be evaluated from the impedance matrix which relates the sound pressure at the inlets and the outlets to their corresponding normal particle velocities. A complex-number ratio of the sound pressure at the second inlet to the sound pressure at the first inlet will need to be supplied before the TL can be evaluated. However, the exact value of this ratio may not be known a priori in real applications, let alone the ratio would be a function of frequency. Therefore, an estimate has to be made and the TL needs to be presented with different possible values of the ratio. Numerical test cases are given in the paper, and results are verified by comparing to the five-point method and the six-point method.
Aircraft sound quality for passenger comfort and enhanced product image
Authors: Wakefield Gregory H. , Bultemeier Eric J. , West Erik , Angerer James R. , Bhat Waman V.
Published: October 2013

Passenger cabin noise requirements for commercial airplanes are being expanded beyond the traditional focus on noise annoyance and speech intelligibility. There is increasing recognition that the passenger response to the cabin soundscape is much more complex; affecting perceptions of product quality, and impacting fatigue and comfort. Tailoring the soundscape for a preferred cabin environment requires the development of metrics that capture a range of passenger responses. In a preliminary exploration of potential metrics, a series of experiments were undertaken to investigate passenger preference for several classes of stationary and transient sounds within the passenger cabin. The design, implementation, and data analysis for these experiments is discussed, along with the application of results to enhance cabin comfort and to convey product quality. Key findings confirm what has been found in sound quality studies in other industries: sound level alone does not fully account for passenger preference.
Acoustical comfort of vehicles: A combination of sound and vibration
Authors: Genuit Klaus , Schutte-Fortkamp Brigitte , Fiebig Andre
Published: October 2013

As vehicles become more and more quiet, the customer’s sensitivity to acoustical comfort increases. The acoustical comfort is not independent of the vibrations the driver can feel in the seat and at the steering. The passenger of a vehicle must be regarded as part of a vibro-acoustic system. Correspondingly, the subjective judgement which passengers make about their impression of levels of acoustic comfort encompasses both sound and vibration. Achievement in this field depends on obtaining knowledge about the interaction between sound and vibration and how these factors impact subjective evaluation. To save time and money prediction tools for the estimation of sound and vibration contributions into the vehicle cabin are very important in order to simulate the final comfort with respect to sound and vibration. Based on the binaural transfer path analysis in combination with the binaural transfer path synthesis a sound and vibration reproduction in a so-called SoundCar can be realized with a very good simulation of a real situation of a car. First research tests completed for the European research project OBELICS (Objective Evaluation of Interior Car Sound) have shown that the use of SoundCar may result in more reliable sound characteristic and quality evaluation.
Multimodal interaction in the perception of impact events displayed via a multichannel audio and simulated structure-borne vibration
Authors: Martens William L. , Woszczyk Wieslaw
Published: October 2013

For multimodal display systems in which realistic reproduction of impact events is desired, presenting structure-borne vibration along with multichannel audio recordings has been observed to create a greater sense of immersion in a virtual acoustic environment. Furthermore, there is an increased proportion of reports that the impact event took place within the observer’s local area (this is termed ‘‘presence with’’ the event, in contrast to ‘‘presence in’’ the environment in which the event occurred). While holding the audio reproduction constant, varying the intermodal arrival time and level of mechanically displayed, synthetic whole-body vibration revealed a number of other subjective attributes that depend upon multimodal interaction in the perception of a representative impact event. For example, when the structure-borne component of the displayed impact event arrived 10 to 20 ms later than the airborne component, the intermodal delay was not only tolerated, but gave rise to an increase in the proportion of reports that the impact event had greater power. These results have enabled the refinement of a multimodal simulation in which the manipulation of synthetic whole-body vibration can be used to control perceptual attributes of impact events heard within an acoustic environment reproduced via a multichannel loudspeaker array.
The acoustical design of vehicles—a challenge for qualitative evaluation
Authors: Schulte-Fortkamp Brigitte , Genuit Klaus , Fiebig Andre
Published: October 2013

Whenever the acoustical design of vehicles is explored, the crucial question about the appropriate method of evaluation arises. Research shows that not only acoustic but also non-acoustic parameters have a major influence on the way sounds are evaluated. Therefore, new methods of evaluation have to be implemented. Methods are needed which give the opportunity to test the quality of the given ambience and to register the effects and evaluations in their functional interdependence as well as the influence of personal and contextual factors. Moreover, new methods have to give insight into processes of evaluation and their contextual parameters. In other words, the task of evaluating acoustical ambiences consists of designating a set of social, psychological, and cultural conditions which are important to determine particular individual and collective behavior, attitudes, and also emotions relative to the given ambience. However, no specific recommendations exist yet which comprise particular descriptions of how to assess those specific sound effects. That is why there is a need to develop alternative methods of evaluation with whose help effects of acoustical ambiences can be better predicted. A method of evaluation will be presented which incorporates a new sensitive approach for the evaluation of vehicle sounds.
Proposed piezoceramic excitation for rotational and translational structural mobility measurements
Authors: Kankey Andrew T. , Koopmann Gary , Hambric Steven , Fahnline John
Published: October 2013

A piezoceramic array is proposed that will allow for more accurate measurement of translational and rotational structural mobility compared with current methods. This lightweight, compact array could be attached to a structure and would excite a normal force as well as bending and torsional moments in the structure. This paper focuses on verifying the ability of piezoelectric ceramic patches, when aligned in certain formations, to create normal forces and moments to excite a structure and allow easy measurement of structural mobility. A simple method for calibrating the patches is suggested using reciprocity. The test structure used is a 0.125 inch thick, fixed-fixed 12 x 1 inch aluminum beam to which two 1 x 0.5 inch piezoelectric ceramic patches are attached. Depending on the orientation of the patches, a normal force, bending moment, or torsional moment is created. Accelerometers are used to measure the mobility at the center point of the beam. This method combined with the proposed array could be moved to any point on a structure to excite the structure and measure the point structural mobility. Experimental results are compared to numerical results from a finite element program to verify the representation of the piezoceramic patches.
Investigation of accelerometer mass loading using a laser Doppler vibrometer
Authors: Carroll Gerard P. , Craun Matthew A.
Published: October 2013

Laser Doppler vibrometer (LDV) measurements were used to quantify the effects of accelerometer loading and attachment methods on the response of a shaker driven submerged damped and stiffened plate. The complex plate transfer admittance over a frequency range from 5 to 40 kHz was first measured using the LDV without the accelerometers or the accelerometer mounting pads attached to the plate. The accelerometers and the mounting pads were then attached and the LDV measurements were repeated to determine their mass loading effects. With the accelerometers attached the complex plate transfer admittance was measured using both the accelerometer and the LDV outputs. These results were compared with the intention of developing a complex correction term to be applied to the accelerometer data to correct for data errors associated with accelerometer resonances and loading effects. This however was not carried out due to observed irregularities on the LDV measurement data possibly due to acousto-optic phase modulation of the laser signal.
Microflown based sound pressure microphone suitable for harsh environments
Authors: Yntema D. R. , de Bree Hans-Elias
Published: October 2013

There are several cases where a sound field reconstruction or prediction is required under harsh conditions such as high temperature, humidity or chemical attack. A regular pressure microphone will not last long under these conditions. Electret based pressure microphones stop working well above 70 degrees centigrade and other type of pressure microphones often operate with a built in amplifier that does not function above 120 degrees centigrade. The functionality of a MEMS based Microflown acoustic particle velocity sensor in air lies in the use of two heated platinum wires that are resistant to high temperatures and chemical attack. The wires are supported by silicon that has no other function than provide support. A pressure microphone is made based upon the Microflown principle by putting it in the opening of an enclosure. In this paper a silicon and platinum based sound probe for harsh environments is created, combining particle velocity and pressure measurements in a harsh environment. Use of this sensor is possible up to 250 degrees centigrade, in humid and under most chemical environments. The probe realization as well as calibration measurements are presented.
Sound pressure mapping with a hand held sound level meter/real time analyzer
Authors: Anderson Roger J. , Kertzman Zack
Published: October 2013

For the past twenty years or so we have been using acoustic intensity to map out the surface of an object in order to have a visual representation of that noise source. More recently the trend has been to use large microphone arrays and acoustic holography. Acoustic intensity is reasonably easy to do but requires an intensity probe, a two channel analyzer some training and special software. In total the system cost can easily exceed $20,000. Acoustic holography systems provide more information but are much more expensive and need trained personnel. However, a low cost single channel SLM/RTA can be used to generate very good sound pressure contour maps that help noise control engineers understand noise sources. The other advantage is that it is simple to use requiring only an hour or less of training. Several example pressure maps will be presented and compared to acoustic intensity maps.
Estimation of room absorption of acoustic cones based on impedance tube measurements
Authors: Dreyer Jason , Rao Mohan D.
Published: October 2013

Acoustic cones are often the primary absorption treatment choice for constructing anechoic chambers. Reverberation chamber estimation of room absorption will most accurately represent the actual effect of three-dimensional treatments, such as cones. However, for low frequencies, large reverberation chambers are often required, which may not be available due to space and cost constraints. Impedance tubes measurements are more accurate than reverberation chamber measurements in terms of sound absorption coefficient. Conversely, due to the two-dimensional nature of impedance tubes, room absorption of three-dimensional objects is difficult to estimate. Absorption coefficient of the material is a function of not only surface area but also material thickness. This paper proposes a technique to estimate the room absorption of three-dimensional treatments based on measured absorption coefficient of different thickness treatment specimens by impedance tube. This extrapolation of impedance tube measured absorption coefficient to actual room absorption can be used to evaluate the effectiveness of absorptive acoustic room treatments, including effects of adhesives and air gaps, without the need of constructing the actual treatment prototypes. The validity of this impedance tube room absorption estimation was verified for a tetrahedral cone treatment using a large reverberation chamber room absorption measurement.
The effects of receiving room dimensions and absorption in the measurement of impact insulation class (IIC) rating
Authors: Su Rose Mary , Tocci Gregory
Published: October 2013

The measurement of the Impact Insulation Class (IIC) rating of any floor/ceiling construction requires the use of a certified laboratory space. In a recent investigation into the IIC rating of a new floor system, several tests were conducted in a certified laboratory. In many tests, the IIC rating was controlled by the 100-Hz 1/3-octave frequency band, despite changes in the floor/ceiling construction. The base floor/ceiling construction included a wood structural floor on open-web wood joists and a GWB ceiling below. This paper will investigate the possibility that room resonances influenced the IIC ratings of the several floor systems tested. These data will be compared with IIC data collected for the same floor construction with the GWB ceiling removed. The removal of the GWB ceiling increased the receiver room volume and exposed the glass fiber insulation to the receiver room, thus eliminating the control of the 100-Hz 1/3-octave band over the IIC rating.
Properties of thermoacoustic engines desirable for space applications
Authors: Backhaus Scott
Published: October 2013

The advantages of a technology that are promoted at its inception are not always those that may eventually allow it to win out over its competition. A collaboration with Northrop Grumman Space Technology on a small thermoacoustic-Stirling electric generator has shed some light on certain advantages of thermoacoustic-Stirling engines beyond ‘‘no moving parts’’ or ‘‘less moving parts.’’ Some of these advantages will be discussed
Electronic speckle pattern interferometry for modal analysis
Authors: Moore Thomas
Published: October 2013

Electronic speckle pattern interferometry is a common method for determining resonant frequencies and visualizing mode shapes of relatively small objects; however, the apparatus required for this type of interferometry is typically expensive and extremely sensitive to ambient vibrations. A design is presented for a low-cost electronic speckle pattern interferometer, and methods to alleviate the strict requirements on limiting ambient vibrations are discussed.
Effect of multiple compression channels on vowel spectra
Authors: Bor Stephanie , Wright Richard , Souza Pamela
Published: October 2013

Multichannel wide-dynamic range compression (MCC) is a common amplification strategy, but whether using more channels provides an advantage for speech recognition is disputed. Some researchers have hypothesized that MCC with a large number of compression channels can reduce spectral contrast and degrade recognition, but this has not been empirically tested. A detailed acoustic analysis was undertaken to determine (1) whether vowel spectra are altered by multichannel compression relative to single-channel compression, and (2) to quantify changes to vowel spectra as a function of the number of compression channels. Stimuli were eight naturally spoken vowels produced by five males and five females in an /hVd/ context. A series of compression conditions (1 through 16 channels) was created using clinically representative parameters. After compression processing, F1, F2, and F3 were measured using spectrograms, LPC, and FFT analysis. A quantitative measure was developed to represent spectral changes after compression. Preliminary data show spectral smoothing with more than four channels. Smaller numbers of compression channels have minimal effects on vowel spectra. These data will be related to vowel recognition scores.
Knowledge-based formant tracking with confidence measure using dynamic programming
Authors: Manocha Sandeep , Espy-Wilson Carol Y.
Published: October 2013

In this study, we report on refinements to a formant tracking technique originally reported in [Xia et al., ICSLP (2000)]. The formant tracker operates in two phases. First, it finds optimal formant track estimates in oral sonorant regions by imposing frequency continuity constraints using dynamic programming. Second, post-processing is performed to make the estimates more robust and accurate, and to extend formant tracks in nasal and obstruent regions. In recent work, we have improved on our initial estimates of the formants by combining the outputs from a 12th-order LPC analysis and a 16th-order LPC analysis. Additionally, we have added a confidence measure for each formant track in each frame. The confidence measure is based on formant continuity, competing formants, short-time energy, context information, and formant information over the entire utterance. The experiments show that most of the tracking errors are associated with a low confidence value, while the correct formants have high confidence values. The performance of the algorithm in the sonorant regions was tested using randomly selected male and female speech from the TIMIT database. [Work supported by NSF Grant No. BCS0236707.]
The relationship between the articulation index spectrogram and off-diagional confusion matrix performance-intensity functions
Authors: Lobdell Bryce , Allen Jont
Published: October 2013

Confusion matrices (CM), similar to those of Miller Nicely 1955, as a function of the speech-to-noise ratio (SNR), have been collected for 16 consonants and 4 vowels, from 18 talkers and 14 listeners. The goal is to quantify perceptual features (denoted events) in the acoustic waveforms, from the articulation index (AI) spectrogram, and the off-diagonal ‘‘PI-functions’’ Ph,s(SNR), indices 0≤s,h≤64 (h=hear≠s=spoken). Near ‘‘threshold’’ SNRs (i.e., where the off-diagional PI functions show confusion slightly greater than 1/64), the AI spectrograms show interesting transitions. The AI spectrogram is closely related to an information-theory measure called the channel capacity (and to jnd’s). Examples of events in the ‘‘CCgrams’’ will be given for a variety of speech sounds at threshold SNRs. A cool sound-morphing demonstration will be presented, where the dominant confusion depends on SNR.
Auditory and visual biasing for sentence recognition in noise
Authors: Main Jennifer J. , Carney Arlene E.
Published: October 2013

Previous research [A. E. Carney et al., J. Acoust. Soc. Am. 106, 2270 (1999)] showed that listeners have a range of visual biasing when presented with stimuli that have conflicting auditory and visual cues (e.g., visual /gi/ and /auditory /bi/). Further, individuals with strong visual bias had substantially changed labeling for synthetic continua with visual cues added in noise conditions, while those with auditory biases did not [B. R. Clement and A. E. Carney, J. Acoust. Soc. Am. 106, 2271 (1999)]. The purpose of the current study was to determine if listeners with strong auditory or visual biases had different patterns of auditory sentence recognition in noise with and without added visual cues. Two groups of ten listeners (one with auditory biases and one with visual biases on a screening task) were presented with lists of CID sentences at varying signal-to-noise ratios in auditory-only (AO) and auditory + visual (AV) conditions. Speech reception thresholds for both groups improved in the AV condition; visually biased listeners did show somewhat greater improvement when visual cues were added. In both groups, some listeners were much more adversely affected by the addition of noise than others. Results will be discussed in terms of individual differences among listeners. [For Speech Technical Committee Best Student Paper Award.]
Intelligibility of foreign-accented speech: Effects of listening condition, listener age, and listener hearing status
Authors: Ferguson Sarah Hargus
Published: October 2013

It is well known that, for listeners with normal hearing, speech produced by non-native speakers of the listener’s first language is less intelligible than speech produced by native speakers. Intelligibility is well correlated with listener’s ratings of talker comprehensibility and accentedness, which have been shown to be related to several talker factors, including age of second language acquisition and level of similarity between the talker’s native and second language phoneme inventories. Relatively few studies have focused on factors extrinsic to the talker. The current project explored the effects of listener and environmental factors on the intelligibility of foreign-accented speech. Specifically, monosyllabic English words previously recorded from two talkers, one a native speaker of American English and the other a native speaker of Spanish, were presented to three groups of listeners (young listeners with normal hearing, elderly listeners with normal hearing, and elderly listeners with hearing impairment; n=20 each) in three different listening conditions (undistorted words in quiet, undistorted words in 12-talker babble, and filtered words in quiet). Data analysis will focus on interactions between talker accent, listener age, listener hearing status, and listening condition. [Project supported by American Speech-Language-Hearing Association AARC Award.]
Examining explanations for fundamental frequency’s contribution to speech intelligibility in noise
Authors: Schlauch Robert S. , Miller Sharon E. , Watson Peter J.
Published: October 2013

Laures and Weismer [JSLHR, 42, 1148 (1999)] reported that speech with natural variation in fundamental frequency (F0) is more intelligible in noise than speech with a flattened F0 contour. Cognitive-linguistic based explanations have been offered to account for this drop in intelligibility for the flattened condition, but a lower-level mechanism related to auditory streaming may be responsible. Numerous psychoacoustic studies have demonstrated that modulating a tone enables a listener to segregate it from background sounds. To test these rival hypotheses, speech recognition in noise was measured for sentences with six different F0 contours: unmodified, flattened at the mean, natural but exaggerated, reversed, and frequency modulated (rates of 2.5 and 5.0 Hz). The 180 stimulus sentences were produced by five talkers (30 sentences per condition). Speech recognition for fifteen listeners replicate earlier findings showing that flattening the F0 contour results in a roughly 10% reduction in recognition of key words compared with the natural condition. Although the exaggerated condition produced results comparable to those of the flattened condition, the other conditions with unnatural F0 contours all yielded significantly poorer performance than the flattened condition. These results support the cognitive, linguistic-based explanations for the reduction in performance.
Contributions of gross spectral properties and duration of spectral change to perception of stop consonants
Authors: Alexander Joshua , Keith Kluender
Published: October 2013

All speech contrasts are multiply specified. For example, in addition to onsets and trajectories of formant transitions, gross spectral properties such as tilt, and duration of spectral change (both local and global) contribute to perception of contrasts between stops such as /b,d,g/. It is likely that listeners resort to different acoustic characteristics under different listening conditions. Hearing-impaired listeners, for whom spectral details are compromised, may be more likely to use short-term gross spectral characteristics as well as durational information. Here, contributions of broad spectral onset properties as well as duration of spectral change are investigated in perception experiments with normal-hearing listeners. Two series of synthesized CVs, each varying perceptually from /b/ to /d/, were synthesized. Onset frequency of F2, duration of formant transitions, and gross spectral tilts were manipulated parametrically. Perception of /b/ was encouraged by shorter formant transition durations and by more negative spectral tilt at onset independent of the rate of change in spectral tilt. Effects of spectral tilt at onset were contextual and depended on the tilt of the following vowel. Parallel studies with listeners with hearing impairment are ongoing. [Work supported by NIDCD.]
Field-calibrated source tracking using channel measurements from high-frequency mobile platform transmissions
Authors: Hursky Paul , Porter Michael B.
Published: October 2013

Modern signal processing methods for acoustic arrays in a waveguide use acoustic propagation models to construct signal replicas that capture channel effects such as multipath and refraction. However, such model-based techniques require a detailed map of the propagation environment (often unavailable) and impose the significant computational burden of modeling the channel. We propose an alternative approach to this problem, in which mobile platforms such as AUV’s and gliders act as acoustic beacons for calibrating the field, replacing modeled signal replicas with directly measured channel impulse response functions. Key issues are whether channel estimates made in a (typically) high-frequency communications band and at a limited set of points can be extrapolated to lower frequency and to the entire field. Furthermore, the channel response may change with time, depending on the variability in the ocean waveguide, requiring periodic refresh of the calilbration. We will demonstrate this approach in simulation and with experiment data from two high-frequency experiments, KauaiEx and the Makai Experiment, in which a variety of acoustic communications waveforms were transmitted from towed and fixed systems.
Horizontal refraction of sound by random internal gravity waves
Authors: Godin Oleg A. , Zavorotny Valery U. , Wolfson Michael A. , Voronovich Alexander G.
Published: October 2013

Internal gravity waves (IWs) previously have been shown to be the main cause of horizontal refraction of sound at long-range propagation in deep water. In this paper, statistical properties of IW-induced bearing perturbations and acoustic travel-time corrections associated with horizontal refraction are studied within the geometric acoustics approximation. Two versions of the Garrett–Munk spectrum describing random IWs are considered: a model based on summation of numerically calculated normal modes of the IWs and their dispersion relations, and a traditional model that relies on analytical approximations of the modal shape functions and dispersion relations. Frequency dependence of 3D acoustic effects is modeled by varying the minimal spatial scales of IWs contributing to refraction of sound. Predictions of a theory that allows propagation of statistical moments of acoustic observables are compared to results of large-scale Monte Carlo simulations of horizontal refraction. The comparison provides an insight into significance of various assumptions underlying the theory, and demonstrates the sensitivity of acoustic quantities to the accuracy of modeling the IW field. [Work supported in part by ONR.]
Comparison of experimental and theoretical forward scattering by the Kermit-Roosevelt Seamounts
Authors: Baggeroer Arthur B. , Schmidt Henrik , Sikora Joseph , Luo Wenyu , Scheer Edward K.
Published: October 2013

In the SPICEX-LOAPEX-BASSEX experiments conducted in Fall 2004 forward scattering from the Kermit Roosevelt Seamounts was measured. There were four sources insonifying the seamounts: Kauai, S1 (a moored source), S2 (another moored source), and a ship suspended source at ranges from hundreds of kilometers to 1600 km. The signals were M sequences and LFMs centered at 75 and 250 Hz. These data were presented in J. Acoust. Soc. Am. 117, 2549, which indicated clear convergence zones and horizontal refraction by the seamounts as well as a gradual ‘‘fill in’’ of the scattering with increasing distance from the seamounts. Here, we compare the experimental results to a model of layered conic sections with both point excitations and a modal vertical line arrays. This Kauai, moored and ship suspended sources were deployed by Scripps Institute of Oceanography and the University of Washington, Applied Physics Laboratory as part of the joint experiment.
The new science of fiber safety: Assuring the safety of fiber-based materials for acoustic and noise control applications
Authors: Hadley John
Published: October 2013

In 2001, the International Agency for Research on Cancer (IARC) assembled a group of 18 international experts on the health effects of fibers. Their task was to review the available science on the health aspects of glass, rock, and slag wool fibers. The group of experts determined that glass, rock, and slag wool insulation fibers should be removed from the IARC list of possible carcinogens. That decision was based fundamentally on the development of new science that has led to an understanding of those properties of fibers which affect their potential biological activity. This presentation will provide both an overview of this new science and provide guidelines to assure the safety of fiber-based materials used in acoustic and noise-control applications.
Diel and spatial patterns in the singing behavior of humpback whales off Oahu, Hawaii
Authors: Lammers Marc O. , Stimpert Alison K. , Au Whitlow W. L. , Mooney T. Aran
Published: October 2013

The singing behavior of male humpback whales on the winter breeding grounds is still a poorly understood phenomenon. Previous work indicates that the chorusing levels of singing whales off west Maui are higher at night than during the day. However, the cause of this variation is not known. To investigate whether more whales sing at night or whether the same number simply move closer to near-shore recorders following sunset, the abundance and location of singing whales off Kaena Point, Oahu was examined. A bottom-moored recording system was used to establish that the same diel pattern observed off Maui also occurs off Oahu. The location of singing whales was determined by localizing singers along a preset transect track using a towed hydrophone array. More whales were found singing along the coastline examined at night than during the day. There was no indication of a shoreward migration. These results suggest that, at night, singing displays may be a more effective behavioral tactic than direct competition in a pod. Also, more singers were found along the northern part of the coastline, which is dominated by a shallow bank, indicating that singers were selective with respect to where they chose to sing.
Sound production patterns from humpback whales in a high latitude foraging area
Authors: Stimpert Alison K. , Wiley David N. , Barton Kira L. , Johnson Mark P. , Lammers Marc O. , Au Whitlow W. L.
Published: October 2013

Numerous studies have been conducted on humpback whale song, but substantially fewer have focused on the acoustic properties of non-song sound production (i.e., feeding and social sounds). Non-invasive digital acoustic recording tags (DTAGS) were attached to humpback whales on the western North Atlantics Great South Channel feeding grounds during July 2004. Acoustic records totaling 48.4 data hours from four of these attachments were aurally analyzed for temporal trends in whale signal production. A custom automatic detection function was also used to identify occurrences of specific signals and evaluate their temporal consistency. Patterns in sound usage varied by stage of foraging dive and by time of day. Amount of time with signals present was greater at the bottom of dives than during surface periods, indicating that sounds are probably related to foraging at depth. For the two tags that recorded at night, signals were present during a greater proportion of daylight hours than night hours. These results will be compared with previously published trends describing diel patterns in male humpback whale song chorusing on the breeding grounds. Data from the continuation of this research during the summer of 2005 will also be included.
Periodic nonlinear oscillations of a bubble between rigid parallel plates
Authors: Cui Jianying , Hamilton Mark F. , Wilson Preston S. , Zabolotskaya Evgenia A.
Published: October 2013

A linear analysis of forced bubble oscillations between rigid parallel plates that was presented at the previous ASA meeting is extended to include periodic nonlinear oscillations of the bubble. An equation of Rayleigh–Plesset form is obtained that satisfies the boundary conditions on the plates. Compressibility of the liquid is taken into account with radiation damping, and with time delays associated with acoustic reflections from the plates. The equation is expanded to cubic order in the perturbation of the bubble radius, and the radius is expanded as a Fourier series in harmonics of the acoustic drive frequency. The result is a system of coupled nonlinear algebraic equations for the Fourier coefficients, the solutions of which describe the steady-state response of the bubble. Solutions were obtained numerically by iteration. An advantage of this frequency-domain approach is that the infinite sequence of pressure waves reflected from the plates can be summed analytically. Time histories and frequency responses are presented as functions of plate separation, the amplitude of the drive, and its frequency. This general approach can also be used to investigate moderate subharmonic generation. [Work supported by NIH Grant EB004047 and ARL IR&D funds.]
Destruction of contrast microbubbles used for ultrasound imaging and drug delivery
Authors: Jain Pankaj , Sarkar Kausik , Chatterjee Dhiman
Published: October 2013

Microbubble contrast agent destruction by ultrasound pulse is useful in real-time blood-flow velocity measurement, stimulating arteriogenesis, or targeted drug delivery. We investigated in vitro destruction of contrast agent Definity (Bristol Meyer-Squibb Imaging, North Billerica, MA) by measuring attenuation of ultrasound through it. The measurement is performed with single-cycle bursts for varying pressure amplitudes at 50-, 100-, and 200-Hz pulse repetition frequencies (PRF). At low excitation levels, the attenuation increases with time, indicating an increase in bubble size due to ingress of dissolved air from the surrounding liquid. With increased excitation levels, the attenuation level decreases with time, indicating destruction of microbubbles. A critical pressure amplitude (1.2 MPa) was found for all three PRFs, below which there is no significant bubble destruction. Above the critical excitation level, the rate of destruction depends on excitation levels. But, at high pressure amplitudes destruction becomes independent of excitation pressure amplitude. The results are interpreted to identify two different mechanisms of bubble destruction by its signature in attenuation, namely, slow dissolution by diffusion at intermediate pressure amplitudes and catastrophic shell rupture at high amplitudes.
Design and characterization of an anechoic aeroacoustic facility
Authors: Mathew Jose , Bahr Chris , Carroll Bruce , Sheplak Mark , Cattafesta Lou
Published: October 2013

The design and characterization of an anechoic wind tunnel facility at the University of Florida are presented. A previously existing and ISO 3745 validated 100-Hz anechoic chamber is upgraded to incorporate an open-jet anechoic wind tunnel facility suitable for airframe noise studies, including swept-wing trailing edge studies. For suitable modeling of landing conditions, a chord-based Reynolds number of 3 to 4 million is required. The wind tunnel is driven by a 224-kW centrifugal fan controlled by a variable frequency drive. The test section measures 0.74 m (29) by 1.12 m (44) by 1.83 m (6 ft). The estimated maximum velocity attainable in the test section is ∼ 76 m/s (250 ft/s). Preliminary measurements at 17 m/s indicate excellent flow uniformity and a turbulence intensity of 0.11%. Background noise level measurements with an empty test section reveal an overall SPL from 100 Hz 20 kHz of 49.9 dB, with a peak 1/3 octave-band level of 46 dB at 100 Hz that decreases to 29.9 dB at 1 kHz. Facility characterization experiments over a range of test section speeds are also reported, along with the results of preliminary trailing edge noise experiments.
Grating lobe reduction in 1-D transducer arrays by driving a bar
Authors: Anderson Brian E. , Hughes W. Jack
Published: October 2013

This presentation investigates the effect of placing a finite-length bar between eight transducer elements and water in order to reduce undesirable grating lobes. The transducer elements are mounted to the bar, with a thin polyurethane layer between the elements and the bar, and force the bar to approximate the radiation of a continuous line source (i.e., no grating lobes). Reductions in the grating lobe with the insertion of a bar, compared to the unmodified array, have been found numerically and experimentally. In addition the transducer array can still be steered and amplitude shaded, and the bar geometry may be scaled according to the design frequency. Freely vibrating bending modes in the bar create undesirable additional radiation. The benefits and limitations of retrofitting existing array systems with a bar for grating lobe reduction, in frequency and steer angle, will be presented. The insertion of the bar provides a very inexpensive and easily implemented approach to reduce grating lobes without increasing the number of array elements. [Work sponsored by ONR Code 333, Dr. David Drumheller.]
Free-field reciprocity calibration of microphones in ultrasonic frequency range
Authors: Bouaoua Nourreddine , Fedtke Thomas , Mellert Volker
Published: October 2013

Exposure to airborne low-frequency ultrasound occurs in many industrial applications such as cleaning, welding plastics, measuring distances in buildings, and by using consumer devices such as camera rangefinders, automatic door openers, parametric ultrasound loudspeakers, etc. Exposure to ultrasound in air may be dangerous to the hearing and may have negative bio-effects on humans. Care should be taken in its use. In order to establish appropriate limits and to measure the output of ultrasound devices, there is a need to develop a sound-pressure standard in the frequency range from 20 kHz to about 160 kHz. A calibration project for quarter-inch microphones by the reciprocity method has been started in the PTB, and a new automated measurement setup for free-field reciprocity calibration of quarter-inch microphones has been established. A procedure for a free-field reciprocity calibration of quarter-inch microphones in the frequency range 20 to 160 kHz is described. First results of free-field calibration of quarter-inch microphones are presented, giving the sensitivities and the repeatability of results. The effects of reflections and cross talk on the accuracy of the measurements will be explained.
Sonic gas analyzer for microbiological metabolic measurements
Authors: Horta Miguel A. , Garrett Steven
Published: October 2013

A differential open-pipe resonator was built to track changes in gas-mixture concentration. A single miniature loudspeaker simultaneously drives two adjacent ducts at resonance and 180 deg out of phase. The resonant frequency is tracked with a phase-locked loop, using the difference signal from two electret microphones whose sensitivities are balanced by adjustment of the preamplifier gains to provide common-mode rejection of extraneous noise sources (for example, a magnetic stirrer) within the bioreactor. A small change of the gas concentration produces a proportional change of the driving frequency for a given binary mix of gases. This sensor is designed to measure the production of hydrogen or methane from metabolic processes of anaerobic bacteria. Results from an initial set of experiments using helium injection and hydrogen release from a HCl+Zn reaction will be presented. [For Engineering Acoustics Best Student Paper Award.]
A noncontact transportation in water using ultrasonic traveling waves
Authors: Nomura Shinfuku , Matula Thomas J. , Satonobu Jun , Crum Lawrence A.
Published: October 2013

A noncontact transport experiment in water using a traveling-wave-type linear motor was investigated. Acrylic disks were used as the floating objects. A vibrating plate was enclosed in acrylic plates, and a water tank was made that would allow the vibrating plate to be placed on the bottom. In order to propagate the traveling wave, two ultrasonic transducers were attached at both ends to the bottom of the vibrating plate. One side was used as the wave-sending side and the other side was used as the wave-receiving side. Comparing the transport experiments conducted in water with those conducted in air, the transport velocity becomes faster for floating transport in water than for floating transport in air. The occurrence of cavitation bubbles acts as a resistive force on the movement of the object being transported, and causes the transport velocity to be reduced. Transport velocity depends on the height of the water. If the height of the water surface is too shallow, the water surface freely deforms and the water surface forms bumpy standing waves, making it difficult for the object to be transported.
Three demonstrations of degeneracy lifting
Authors: Morrison Andrew
Published: October 2013

Two normal modes of vibration of a single object having exactly the same frequency are said to be degenerate modes. Certain simple systems, such as a circular membrane, have predictable degenerate modes. A lack of isotropy in the material or a geometric asymmetry can separate the frequencies and lift the degeneracy. Demonstration of this effect is easily accomplished in the classroom. Three methods of showing the effect are presented using a handbell, a short metal rod, and a coffee mug.
Auditory demonstrations simulating Mayan architecture
Authors: Lubman David
Published: October 2013

Fascination with the ancient temples and ball court at Chichen Itza provide rich opportunities for science education. Children of all ages are delighted to learn that the sound of handclaps scattered from long temple staircases are transformed into bird chirps. Their engagement in such seemingly magical phenomena provides magic moments for teaching acoustical principals, including the picket-fence effect (PFE). PFE transforms impulsive sounds scattered from spatially periodic structures into tonal sounds. PFE is demonstrated with a computer possessing a sound card and a simple sound editing program. The inverse relationship between tonal frequency and the time interval between periodic impulses is easily demonstrated. The number of impulses needed to produce an audible tone is easily demonstrated and compared with the number of steps on the staircase. Transformation of audible tones into downward-gliding chirps is simulated by monotonically increasing the time between impulses. The Great Ball Court also provides opportunities for acoustical demonstration. Observers clapping their hands while standing between the long, tall, and parallel walls of the playing field marvel at the profound flutter echo heard for about 1.5 s. The flutter echo sonogram demonstrates the speed of sound and frequency-selective atmospheric attenuation.