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Proceedings of Meetings on Acoustics

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POMA - 157th Meeting Acoustical Society of America
Conference Location: Portland, Oregon Conference Date: 18 - 22 May 2009
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Transverse coherence lengths, processing limits and implications

William M. Carey

POMA Volume 6, pp. 005001 (August 2009); (15 pages)

Online Publication Date: August 28, 2009

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How does scattering in sound channels(deep and shallow waters) limit coherent array processing or what is the limitation of resolution in terms of the mutual coherence function and its temporal and spatial coherence lengths? The resolution of an array is limited by the mutual coherence function; but estimation in a partially coherent noise background with a multipath signal is difficult using the normalized cross power spectral density, magnitude squared coherence, because of the properties of both signals and noise. The measurement of magnitude-squared coherence is a poor statistical estimator since it is a function of the signal-to-noise ratio and multipath interference with large confidence bounds. Array gain measurements and a wave-theoretic coherence functional form can provide estimates of temporal and spatial coherence lengths defined as the 1/e value of this function. This paper reviews single path coherence results and those derived from array measurements over the low- to mid-frequency range in deep and shallow water. Representative coherence lengths are discussed in terms of boundary interactions, internal wave scattering, and coastal mesoscale features. The implications for arrays used to estimate geoacoustic properties,mammal locations, and scattering from the boundaries are presented.
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43.30.Bp Normal mode propagation of sound in water
43.30.Re Signal coherence or fluctuation due to sound propagation/scattering in the ocean
43.30.Wi Passive sonar systems and algorithms, matched field processing in underwater acoustics
43.60.Gk Space-time signal processing, other than matched field processing
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Modeling Correlation for Passive Sonar Bayesian Localization Techniques

Colin W. Jemmott, Richard L. Culver, N. K. Bose, and Brett E. Bissinger

POMA Volume 6, pp. 005002 (August 2009); (11 pages)

Online Publication Date: August 14, 2009

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Low frequency acoustic signals in shallow water are strongly affected by interference between multiple paths resulting from boundary interactions. As an acoustic source or receiver moves through this interference pattern, the spatial variation in transmission loss can result in strong temporal modulation of the received signal, which can be used to localize the source. Acoustic propagation models can produce accurate transmission loss predictions, but are sensitive to ocean environmental parameters such as bottom composition, bathymetry and sound speed profile. If the uncertainty in the undersea environment can be described by probability density functions of these parameters, Monte Carlo forward models can be used to produce an ensemble of possible transmission loss realizations. A probabilistic model representing this ensemble must include a density function of transmission loss at each location, as well as correlation of transmission loss between locations. In addition, the choice of probabilistic model has a large impact on the form of the resulting Bayesian localization algorithm. Previous results have shown that including spatial correlation of transmission loss can result in improved detection. This paper introduces a non-Gaussian probabilistic model for representing uncertainty in transmission loss predictions that includes correlation.
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43.60.Gk Space-time signal processing, other than matched field processing
43.60.Jn Source localization and parameter estimation
43.60.Uv Model-based signal processing
43.60.Wy Non-stationary signal analysis, non-linear systems, and higher order statistics
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An autonomous, near-real-time buoy system for automatic detection of North Atlantic right whale calls

Eric Spaulding, Matt Robbins, Thomas Calupca, Christopher W. Clark, Christopher Tremblay, Amanda Waack, Ann Warde, John Kemp, and Kris Newhall

POMA Volume 6, pp. 010001 (February 2010); (22 pages)

Online Publication Date: February 19, 2010

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A moored buoy system for automatic detection of endangered North Atlantic right whale (NARW) contacts was developed to provide near-real-time information on the presence of vocalizing whales. The marine components include the WHOI buoy platform (mooring, hydrophone, power system, surface expression, antennae) and Cornell buoy electronics (housing, analog interface hardware, GPS, embedded computer, detection engine, and telemetry hardware). Shore-side Cornell components include telemetry equipment, server hardware and processing software, database, and interfaces for data annotation, access, and visualization. The buoy hardware/software system is capable of capturing and ranking NARW contact candidates as 2s, 2000Hz sampled audio clips. Location, timestamp and other metadata associated with each audio clip are assembled and uploaded via satellite for processing. Human analysts regularly annotate incoming data, resulting in a curated database of NARW detections. Periodic 'health and status' data allow for confirmation that buoys are functional. Regular voltage reporting helps predict required maintenance. Following initial implementations of the system in 2005, a series of successes and failures have led to system improvements in the buoy mooring, electronics, and server components. Deployments have progressed from prototype near-shore units to an operational network continuously monitoring the shipping lanes off Boston to meet ship strike mitigation requirements.
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43.30.Sf Acoustical detection of marine life; passive and active
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Using multifractals to quantify diffuseness in rooms

Noel Hart and Ning Xiang

POMA Volume 6, pp. 015001 (June 2009); (6 pages)

Online Publication Date: June 08, 2009

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Diffuseness, an important room acoustics parameter, is not easily quantified. Most current methods that attempt to define a single number to describe a room's level of diffuseness require highly specialized equipment or broad estimations. Multifractals present a recent mathematically robust method that may allow diffuseness to be quantied by analyzing a single room impulse response [S.J. Loutridis, "Quantifying sound-field diffuseness in small rooms using multifractals", JASA (125)(3)(2009)]. This method will be verfied by measuring a room in several states generally considered to affect diffuseness. The method has only thus far been demonstrated in small rooms, and its applicability towards a large concert hall is tested. Frequency dependence is investigated as well as the effects of the measuring location within the room.
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43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response
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Analysis of in-situ acoustic absorption using a spherical microphone array

Jonathan Rathsam and Boaz Rafaely

POMA Volume 6, pp. 015002 (June 2009); (9 pages)

Online Publication Date: June 15, 2009

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Acoustic absorption of materials typically depends on the characteristics of the incident sound field. Differences in the incident sound field between one laboratory and another, or between the laboratory and in situ, may therefore lead to differences in the measured absorption for the same material. To overcome this problem, a new method is proposed to measure acoustical absorption using a spherical microphone array. With this method one measures simultaneously the acoustic absorption as well as the incident sound field. The incident sound field and the reflected sound field are separated by the spherical microphone array using spatial filtering, or beamforming. The acoustic absorption is then determined from the amplitudes of the incident and the reflected fields. The measurement method may also be useful for verifying sound field diffusivity in a reverberation chamber when measuring diffuse-field absorption. Furthermore, absorption coefficients measured under in-situ sound fields may yield more accurate computer-based sound field simulations than diffuse-field absorption coefficients when the in-situ sound field is not diffuse.
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43.55.Dt Sound absorption in enclosures: theory and measurement; use of absorption in offices, commercial and domestic spaces
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Measuring the uniform diffusion coefficient: Synthesized aperture goniometer measurements

Philip Robinson, Ning Xiang, and Peter D.Antonio

POMA Volume 6, pp. 015003 (October 2009); (14 pages)

Online Publication Date: October 20, 2009

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There are currently two methods to measure the diffusion / scattering from acoustical surfaces: reverberation chamber measurement and in-situ measurement using a semicircular array of microphones called a goniometer. Each of these methods has advantages and drawbacks. The reverberation chamber method accounts for random incidence, but produces inconsistent results for materials of the same profile but different absorption. It does not distinguish between one-dimensional and two-dimensional surface topologies, since the sample is rotated, and is also inapplicable to high absorption materials. The goniometer measurement quantifies directivity as well as diffusion, but presents challenges related to processing power, as many microphones are required to achieve reasonable resolution. Using a procedure akin to synthesized aperture radar, a 2.5 deg. resolution polar plot of the 180 deg. response is achieved by scanning eight microphones rather than employing a full array of 72. Also, since the direct sound and reflected sound arrive at the receiver in close succession when measuring low incident angles, special processing must be exercised in order to resolve the relationship between the sounds. This research addresses the challenges of the goniometer measurement and attempts to use a synthesized aperture goniometer to derive accurate diffusion and directivity properties of materials.
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43.20.Fn Scattering of acoustic waves
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Acoustofluidics: theory and simulation of radiation forces at ultrasound resonances in microfluidic devices

Rune Barnkob and Henrik Bruus

POMA Volume 6, pp. 020001 (July 2009); (11 pages)

Online Publication Date: July 06, 2009

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Theoretical analysis is combined with numerical simulations to optimize designs and functionalities of acoustofluidic devices, i.e. microfluidic devices in which ultrasound waves are used to anipulate biological particles. The resonance frequencies and corresponding modes of the acoustic fields are calculated for various specific geometries of glass/silicon chips containing water-filled microchannels. A special emphasis is put on taking the surrounding glass/silicon material into account, thus going beyond the traditional transverse half-wavelength picture. For the resonance frequencies, where the largest possible acoustic powers are obtained in the microfluidic system, the time-averaged acoustic radiation force on single particles is determined. Schemes for in situ calibration of this force are presented and discussed.
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43.20.Ks Standing waves, resonance, normal modes
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.25.Qp Radiation pressure
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Transient processes in acoustic resonators

Armen Sarvazyan, Lev A. Ostrovsky, and Andrey Rubyanets

POMA Volume 6, pp. 020002 (November 2009); (15 pages)

Online Publication Date: November 10, 2009

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The use of ultrasound in resonators for manipulating particles in various biomedical applications is a relatively well studied topic. These studies were mostly concerned with steady-state processes. However, in certain important applications, such as stirring and mixing fluids in microfluidics and biosensors, the time scale of a process plays a crucial role. Here we consider some of these applications. In particular, the radiation force-induced motion of microparticles and micro-bubbles in a swept-frequency ultrasonic resonator is considered. The particles are forced to move due to switching the resonance modes in a resonator cell, thus providing effective stirring of the fluid. Another field of potential medical application where transient processes are of crucial importance, is ultrasonic treatment of tissues. In this new field of ultrasonic therapy, standing waves can be used for producing lesions in the tissue with simultaneous monitoring the lesion formation by automatic controlling the field parameters. Dynamics of temperature changes in the tissue under the action of a standing ultrasound wave, which is important for optimizing tissue treatment regimes, is evaluated. Experimental data illustrating theoretical results are presented.
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43.20.Ks Standing waves, resonance, normal modes
43.80.Gx Mechanisms of action of acoustic energy on biological systems: physical processes, sites of action
43.80.Sh Medical use of ultrasonics for tissue modification (permanent and temporary)
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Why we have two ears - A hands-on experiment comparing monaural and binaural hearing

Ralph T. Muehleisen

POMA Volume 6, pp. 025001 (July 2009); (9 pages)

Online Publication Date: July 23, 2009

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Whether they fly, swim, crawl, or walk, vertebrates have binaural auditory systems. Two ears provide redundancy in case of injury to the auditory system, improve the ability to detect quiet sounds, and perhaps most importantly, improve the ability to localize sound. This paper describes an all ages experiment to study the binaural and monaural sound localizing abilities of a human using headphone based auralizations. The experiment utilizes computer generated binary impulse response measurements that are convolved with computer generated noises to create a set of binaural directional directional audio tracks. The tracks are randomly presented over headphones to a subject who indicates the perceived direction of the source. The experiment is repeated with one only one audio channel to test monaural hearing. The perceived directions are then compared to the true source directions.
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43.66.Pn Binaural hearing
43.66.Qp Localization of sound sources
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A simple analytical demonstration of transient and steady-state response in a dissipative closed waveguide based on the d'Alembert solution

Jerry H. Ginsberg

POMA Volume 6, pp. 025002 (July 2009); (16 pages)

Online Publication Date: July 22, 2009

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The author previously [J. H. Ginsberg, J. Acoust. Soc. Am. 119, 1954-1960, 2006] used virtual images of waves to describe the response to initial conditions of a one-dimensional waveguide whose terminations have an arbitrary real (dissipative) impedance. The images are virtual, in that they are defined behind each wall, thereby converting the closed waveguide to one of infinite extent. The present work extends the development to cases where an arbitrary velocity is applied to one wall. The image construction allows one to visually track the evolution of the spatial pressure profile and its relation to temporal waveforms at various locations. The relatively low level of mathematical skills entailed in the formulation makes the method accessible to students at all levels. Application of the technique to periodic excitation of the boundary leads to visual representation of various effects, including various resonance effects.
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43.20.Bi Mathematical theory of wave propagation
43.20.El Reflection, refraction, diffraction of acoustic waves
43.20.Mv Waveguides, wave propagation in tubes and ducts
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Vibration analysis of a low pressure turbine bladed disk in 500MW fossil power plants

Dooyoung Lee, Yongchae Bae, Heesoo Kim, Yookryun Lee, and Hongil Choi

POMA Volume 6, pp. 030001 (June 2009); (8 pages)

Online Publication Date: June 08, 2009

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Many failures of turbine blades are caused by the coupling of aerodynamic forcing with bladed disk vibration characteristics. Vibration analysis for an individual turbine blade does not include all the coupled characteristics of the whole bladed disk system. This paper shows the coupled vibration characteristics of a low pressure turbine bladed-disk in a 500MW fossil power plant for the purpose of confirming equipment reliability. In order to verify the finite element model, numerical and experimental modal analyses for a single blade were performed and reviewed with boundary conditions not only where both ends were free to move but also where its root was fixed. Natural frequencies and corresponding mode shapes were calculated for the bladed disk under the operating conditions, and then proximity of modes to sources of excitation was assessed by means of the interference diagram to examine resonances. The result of the analysis was ascertained by being compared with modal testing for the bladed disk at zero speed without centrifugal and aerodynamic forcing. Dynamic stresses were also calculated at dangerous modes of operation. It is expected that these dynamic characteristics will be used effectively to identify the root causes of blade failures and to make prompt maintenance.
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43.40.At Experimental and theoretical studies of vibrating systems
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Achieving publication excellence in the Journal of the Acoustical Society of America

Ning Xiang

POMA Volume 6, pp. 032001 (June 2009); (13 pages)

Online Publication Date: June 15, 2009

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Publications in refereed acoustics journals are of significant relevance for scientists and engineers in acoustics-related fields. The Journal of the Acoustical Society of America (JASA) encourages authors to submit papers to JASA for publication. JASA regularly publishes detailed updated guidelines and instructions in order to help potential authors achieve publishing excellence. As a frequent reviewer, an author of JASA papers, and an Associate Editor of JASA, this author will provide an outline and overview of the JASA peer-review process in order to clarify the standards used to assess both successful and unsuccessful publication efforts. This author also discusses how to prepare qualified manuscripts, how to avoid unnecessary delays for, and how to review manuscripts for JASA.
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43.10.Gi Editorials, Forum
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Preparing a submission to the Journal of the Acoustical Society of America on applied projects in architectural acoustics

Lily Wang

POMA Volume 6, pp. 032002 (June 2009); (11 pages)

Online Publication Date: June 15, 2009

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The Journal of the Acoustical Society of America (JASA) encourages authors to submit articles for publication that are based on more applied projects, such as those commonly found in the technical area of architectural acoustics. However, very few of this type have been published in the recent past. Suggestions on how such articles should be prepared and how they may meet the 'significance' criterion will be given, from the viewpoint of a current JASA associate editor in architectural acoustics. Additionally a review of such articles that have been published in JASA within the past few decades will be provided.
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43.10.Gi Editorials, Forum
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Important aspects of editorial procedures for the information of inexperienced authors

Keith Attenborough

POMA Volume 6, pp. 032003 (June 2009); (7 pages)

Online Publication Date: June 15, 2009

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Several matters concerning the quality of papers and the editorial process have emerged from editorial activities for three acoustically-related journals (Applied Acoustics, Acta Acustica combined with Acustica and the Journal of the Acoustical Society of America). Each of the journals suggests particular criteria to reviewers as the basis for their reviews and offers various editorial decision options. These options and the uses that are made of them are discussed. Two common factors that influence editorial and reviewer judgements on submission quality include (a) the use of English and (b) the provision of a comprehensive and critical literature review. An increasingly important consideration is the availability of good reviewers in areas related to the topic of the paper. The range of methods used in Reviewer selection is explored. The possibility of achieving publication success despite negative reviews is revealed. Two unwelcome and increasing problems are simultaneous submission and plagiarization. Sanitized examples illustrating some of these points are offered.
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43.10.Gi Editorials, Forum
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Realities of publishing in a journal: why should you submit, what should you submit, and what problems might you encounter

Allan D. Pierce

POMA Volume 6, pp. 032004 (July 2009); (14 pages)

Online Publication Date: July 13, 2009

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Attractions of a journal are its widespread availability, its archival (forever!) nature, priority in literature searches, and its prestige. Articles should be readable to others in the field, be significant, and be original. JASA is selective and imposes standards. Perceived quality is often measured by the "Impact Factor", which may have very little to do with the extent to which the Journal fulfills the mission of the Society. Of great frustration to the editors is that a substantial fraction of authors who submit papers seem to be somewhat clueless as to what is a reasonable topic and what is a reasonable scope for an article in JASA. Also frustrating is that most good work reported at Society meetings never gets submitted. The present talk critically discusses the selection process, its peer-review aspects, and its flaws. The selection process deals with realities, such as that willing and competent reviewers are hard to find and that submitted reviews are often inane, with carefully selected highly expert Associate Editors who can make authoritative decisions without absolute reliance on external reviews. Suggestions are given on how to prepare a suitable manuscript and on how to cope with the vagaries of the peer review process.
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43.10.Gi Editorials, Forum
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Optimization of valve tube lengths for brass instruments

Frederick J. Young

POMA Volume 6, pp. 035001 (July 2009); (9 pages)

Online Publication Date: July 07, 2009

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The intonation deviations from the well-tempered scale are presented for valve brass instruments. Compensating and full double instruments are considered.The lengths of the valve tubes are optimized by minimizing the overall root mean squared (rms) intonation error using the method established by Robert Young^{[4]} in 1967. Open note detuning is considered in each case and improves the intonation. The worst three valve instrument without open note detuning has an rms deviation of 24 cents. The best of the three and four valve instruments is a three valve compensating euphonium tuned 3 cents sharp on the open notes and flat on valves 2, 1 and 3 by 3, 3 and 13 cents respectively. Although it lacks the extended range of the four valve instrument, it exhibits only 2 cents rms deviation on single valves and less than 3 cents on valve combinations. The comparisons also include several three and four valve systems including one having a switch valve that descends by 6 rather than 5 semitones. An intonation improvement for the triple waldhorn is presented also.
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43.75.Fg Brass instruments and other lip-vibrated instruments
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The input impedance of an alp horn including an Alexander mouthpiece

Frederick J. Young

POMA Volume 6, pp. 035002 (July 2009); (11 pages)

Online Publication Date: July 07, 2009

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The Alp horns built and sold by the late Joseph Littletown of Hammondsport, NY are analyzed. His dimensions of bore as a function of position are used in the solution of the Webster equation for impedance solved numerically earlier for the flügelhorn and the trombone[3]. In addition, the steady flow through the instrument is calculated by Laplace equation. The musical notation for the frequencies of the impedance peaks found by the solutions to the Webster equation are given below. Here the subscripts refer to the harmonic number. The fundamental, rarely used, is 12 cents sharp from Eb at 51.9 Hertz. The intonation errors for C1, C2, G3, C4, E5, G6, B7b, C8, D9, E10, F11, G12, A13, B14b B15, C16, C17# and D18 are 269, 30, 63, -39, -41 ,-25, -13, -7, -11, -1, 2, 11, 11, 15, 15, 20, 24 and 28 cents.
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43.75.Bc Scales, intonation, vibrato, composition
43.75.Fg Brass instruments and other lip-vibrated instruments
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The double bell descant euphonium

Frederick Young and Jeffrey K. Young

POMA Volume 6, pp. 035003 (November 2010); (6 pages)

Online Publication Date: November 08, 2010

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A euphonium is presented that has better intonation and is easier to play in the extreme registers. It is a complete double horn having five double valves in contrast to the incomplete normal double French horn having only three double valves. The valves descend 2, 1, 3, 4 and 5 semitones from the open tones. A switch valve activates the smaller alto bell in the key of high E and sends the air through the five shorter valve slides and out the small bell. The fundamental frequency of the E side is 82.4 Hz being six semitones above the fundamental of the Bb euphonium. The key of E rather than F or Eb enables all notes in the complete range (about 29 --988 Hz) to be played with single tunable valves thereby eliminating valve combinations. Either of the other keys would introduce a need for an additional valve or compromise the intonation.
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43.75.Fg Brass instruments and other lip-vibrated instruments
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The importance of incorporating signal characteristics in the evaluation of noise exposure impacts on marine life

Michael Stocker

POMA Volume 6, pp. 040001 (June 2009); (6 pages)

Online Publication Date: June 15, 2009

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Auditory thresholds are used to establish mitigation guidelines for anthropogenic noise exposure on marine animals. These thresholds are determined using either sinusoidal signals at specific frequencies or band limited, sinusoidal-derived Gaussian noise. Given that the preponderance of naturally occurring noise in the marine environment is sinusoidal, marine animals may have lower thresholds, and thus lower tolerance to non-sinusoidal noise. Fast rise time impulse noise, continuous non-sinusoidal noise, or a combination of these characteristics may induce biological responses at lower levels than sinusoidal noise with an equivalent power density. The author proposes a metric to evaluate and express signal characteristics as a component of determining noise exposure impacts on marine animals.
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43.80.Ev Acoustical measurement methods in biological systems and media
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Penetration depth for measurements with ultrasonic diffraction grating spectroscopy

Margaret S. Greenwood

POMA Volume 6, pp. 045001 (June 2009); (9 pages)

Online Publication Date: June 17, 2009

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The current status of ultrasonic diffraction grating spectroscopy (UDGS) was described at the Acoustics 08 Conference in Paris. An important question remains: What is the penetration depth of the ultrasound for such measurements? Although the spectral order m = 1 at 90º is of primary interest, much insight can be gained by investigating a range of angles. The first step was to measure the amplitude of the m = 1 transmitted beam in the liquid as a function of the transmitted angle. Data were obtained by sending a toneburst signal to the send transducer and measuring the response of a receive transducer immersed in the liquid. The angle of the receive transducer was varied in half-degree steps from about 50º to 90º. The data were compared with a formulation for the interference of N wavelets from N grooves and showed very good agreement. In addition, an experimental technique was developed to measure the penetration of ultrasound into the liquid. Experimental parameters that affect this penetration depth were also investigated. The results of these measurements will be discussed and compared with the theory.
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.35.Pt Surface waves in solids and liquids
43.35.Ty Other physical effects of sound
43.35.Yb Ultrasonic instrumentation and measurement techniques
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Parametric acoustic array development a the US Navy's New London, Connecticut laboratory

David G. Browning, Mark B. Moffett, and William L. Konrad

POMA Volume 6, pp. 045002 (June 2009); (22 pages)

Online Publication Date: June 26, 2009

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A brief history of the development of parametric acoustic sources at the US Navy Underwater Sound Laboratory (USNUSL), and its successor, the Naval Underwater Systems Center. Inspired by Robert Mellen, the Parametric Sonar Group was formed to explore the practical implications of Westervelt's idea for underwater acoustics. Spanning more than two decades, this research pursued various potential applications exploiting the unique characteristics of parametric sources, including echo-ranging in reverberant environments, communications involving voice, data, music, and video signals, target-strength measurements, bottom bathymetry, high-resolution sub-bottom profiling, and measurements of scattering and reflection from surfaces. Parametric source design procedures were developed, and guidelines were established for diagnosing and avoiding undesirable effects, such as difference-frequency instability and spurious nonlinearities, such as direct radiation from the projector, cavitation, and receiver nonlinearity. Theoretical models extended the Westervelt theory to realistic primary fields. For planar projector arrays, parametric source design curves, valid for levels in the primary far field, enabled designers to predict performance without resorting to computer calculations. To obtain source-levels and beam-widths within the primary near field, where the secondary signal is generated, a computer program, called CONVOL5 in its present configuration, can be used to obtain more detailed performance predictions.
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43.25.Lj Parametric arrays, interaction of sound with sound, virtual sources
43.30.Lz Underwater applications of nonlinear acoustics; explosions
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration
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Self-calibrating measurements of the density and velocity of sound from the reflection of ultrasound at two solid-liquid interfaces

Margaret S. Greenwood

POMA Volume 6, pp. 045003 (July 2009); (11 pages) | Cited 1 time

Online Publication Date: July 09, 2009

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This report describes a method to measure the density of a liquid and velocity of sound by observing two reflections of ultrasound from a solid-liquid interface: one for perpendicular incidence of a longitudinal wave and the second for incidence of a shear wave at an angle of 45 deg. In previous research [J. Fluids Eng. 126, 189 (2004)], transducers were mounted on the outside of a stainless steel pipeline, 6 mm thick. Multiple reflections within the wall yielded the acoustic impedance. This method is self-calibrating because each echo is affected in the same way by any change in transducer voltage. The velocity of sound was obtained from the time-of-flight (TOF) across the pipeline. The current research replaces the TOF measurement by using a triangular stainless steel wedge (45, 90, 45 deg). A 1-MHz shear wave transducer is mounted on a short side of the wedge, with the longer side immersed in the liquid. Multiple reflections from the opposide of the wedge are obtained. The two reflection coefficient can be used to solve for the density and velocity of sound. Greater precision can be obtained by using fused quartz instead of stainless steel.
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43.35.Ae Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in gases
43.35.Yb Ultrasonic instrumentation and measurement techniques
43.58.Bh Acoustic impedance measurement
43.58.Dj Sound velocity
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Research on parametric arrays in Russia: Historical perspective

Lev A. Ostrovsky

POMA Volume 6, pp. 045004 (August 2009); (18 pages)

Online Publication Date: August 04, 2009

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This presentation is concerned with the "Russian part" of the history of parametric arrays (PAs). After the pioneering works of P. Westervelt in USA and V. Zverev and A. Kalachev in Russia and a decade of relative isolation, Soviet and Russian researches became involved internationally in the work on the PAs and, more generally, of nonlinear acoustic beams. Several Russian institutions have been involved, including Moscow University, Andreev Institute of Acoustics in Moscow, Radiophysics Research Institute and Institute of Applied Physics in Gorky (now Nizhny Novgorod), Gorky University, Pacific Oceanographic Institute in Vladivostok, and some others. Selected the Russian contributions of different years are to be outlined in this talk, including: The theory of nonlinear acoustic beams, e.g., the Khokhlov-Zabolotskaya- Kuznetsov equation and other models of nonlinear acoustic beams in application to the PA; The limitation of the PA efficiency by shock wave formation; Possible enhancement of the PA radiation by bubble "curtains"; Experiments in laboratory and in the ocean; Some new developments such as generation of low-frequency shear waves by ultrasound beams with biophysical applications.
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43.25.Lj Parametric arrays, interaction of sound with sound, virtual sources
43.25.Yw Nonlinear acoustics of bubbly liquids
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Acoustic Nonlinearity in Fluorinert FC-43

Cristian Pantea, Dipen Sinha, Curtis F. Osterhoudt, and Paul C. Mombourquette

POMA Volume 6, pp. 045005 (December 2009); (14 pages)

Online Publication Date: December 18, 2009

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Fluorinert FC-43 nonlinearity was investigated using two approaches: (i) a finite amplitude method with harmonic production; and (ii) a nonlinear frequency mixing in the fluid with consequent beam profile measurement of the difference frequency. The finite amplitude method provides information on the coefficient of nonlinearity, β, through the amplitudes of the fundamental and the second harmonic, at a certain transmitter-receiver distance. A calibrated hydrophone was used as a receiver, in order to obtain direct pressure measurements of the acoustic waves in the fluid. The role of transmitter-receiver distance in β determination is investigated. In the second approach, a single transducer is used to provide two high-frequency beams. The collinear high-frequency beams mix nonlinearly in the fluid resulting in a difference frequency beam and higher order harmonics of the primaries. The difference frequency beam profile is investigated at lengths beyond the mixing distance. The experimental data are compared with the KZK theory.
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43.25.Ba Parameters of nonlinearity of the medium
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Multidimensional perceptual scaling of musical timbre by hearing-impaired listeners

Kelly Fitz, Matt Burk, and Martin McKinney

POMA Volume 6, pp. 050001 (July 2009); (8 pages)

Online Publication Date: July 06, 2009

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We examine of the impact of hearing loss and hearing aid processing on the perception of musical timbre. Our objective is to identify significant timbre cues for hearing-impaired listeners, and to assess the impact of hearing aid signal processing on timbre perception. Hearing aids perform dynamic, level-dependent spectrum shaping that may influence listeners' perception of musical instrument timbres and their ability to discriminate among them. Grey (Grey, J. M. 1977. Multidimensional perceptual scaling of musical timbres. JASA 61: 1270) showed that sustaining instrument tones equalized for level, loudness, and duration, are distinguished primarily along three perceptual dimensions that are strongly-correlated with the acoustical dimensions of: 1) spectral energy distribution, 2) spectral fluctuation, and 3) precedent high-frequency, low-amplitude energy. Following the work of Grey, we ask listeners having mild to moderately-severe sensorineural hearing loss to rate pairs of synthetic musical instrument tones according to dissimilarity in aided and unaided conditions. We analyze the dissimilarity judgments to identify acoustical correlates for the significant dimensions of timbre discrimination. This analysis helps us to objectively estimate the impact of hearing aid signal processing on the ability of hearing-impaired listeners to discriminate among musical instruments, an important component of musical listening.
Show PACS
43.66.Jh Timbre, timbre in musical acoustics
43.66.Sr Deafness, audiometry, aging effects
43.66.Ts Auditory prostheses, hearing aids
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