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Proceedings of Meetings on Acoustics

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POMA - 159th Meeting  Acoustical Society of America/NOISE-CON 2010
Conference Location: Baltimore, Maryland Conference Date: 19 - 23 April 2010
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Horizontal focusing/defocusing due to shallow-water internal waves

Luo Jing, Mohsen Badiey, and Ying-Tsong Lin

POMA Volume 9, pp. 005001 (May 2010); (11 pages)

Online Publication Date: May 13, 2010

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During the New Jersey Shallow Water 2006 (SW06) experiment, an acoustic source was towed by the Research Vessel Sharp and followed the front of an internal wave packet. The source was transmitting broadband acoustic signals (50-450 Hz) in different angles with respect to the internal wave front. The receptions of transmitted signal on a vertical hydrophone line array are analyzed to study the horizontal focusing/defocusing that occurred when the internal wave front and acoustic track aligned closely. Based on shipboard radar images and temperature data collected on the environmental moorings at various locations along the acoustic track, a detailed three-dimensional (3D) environment is reconstructed for a 3-D parabolic approximation model to study the unique propagation scenario. Data and model comparison are in good agreement.
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43.20.El Reflection, refraction, diffraction of acoustic waves
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.30.Es Velocity, attenuation, refraction, and diffraction in water, Doppler effect
43.30.Re Signal coherence or fluctuation due to sound propagation/scattering in the ocean
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An investigation of the combustive sound source

Andrew R. McNeese, Jason D. Sagers, Preston S. Wilson, and David P. Knobles

POMA Volume 9, pp. 005002 (December 2010); (13 pages)

Online Publication Date: December 30, 2010

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The Combustive Sound Source (CSS) is a versatile impulsive underwater sound source with an adjustable bandwidth and output amplitude. Unlike typical impulsive acoustic sources, CSS can maintain a wide bandwidth at low-amplitude, hence it is a more environmentally-friendly impulsive source for ocean acoustics experiments and surveys. The CSS consists of a submersible combustion chamber, open to the water, which is filled with a combustible fuel/oxidizer mixture. The mixture is ignited and a combustion wave propagates through the mixture. During this process the ensuing bubble expands due to an increase in temperature and can collapse to a smaller volume than before ignition. This bubble activity radiates acoustic pulses. The CSS can be used as a source for low frequency sediment characterization and TL measurements, and when deployed on the bottom, can produce seismic interface waves. In addition to stationary deployments in the water column, CSS can be deployed in a tow body and as an array. Discussion will focus on the latest CSS design including functionality, acoustic output, long-term operational stability and future development plans.
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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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Noise Dose for Aquatic Animals: Preliminary Estimates for Two Seismic Surveys

Nils Handegard

POMA Volume 9, pp. 010001 (October 2010); (13 pages)

Online Publication Date: October 19, 2010

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Two major air-gun exposure experiments have been conducted in Norwegian waters: The Nordkappbank experiment in 1992 [Can. J. Fish. Res. Aq. Sci., 1996, Vol. 53, pp. 2238-2249] and the Vesterålen experiment in 2009 [Fisken og Havet, 2010, Nr. 2, 76 pp. Inst. of Mar. Res.]. Although changes in catch rates and distribution of fish were observed in both cases, the responses were higher in the first experiment. Simple metrics such as number of exposures by time and area reveal large differences between the experiments. This is further detailed in looking at the distribution of distances to air-gun emission positions throughout the experiments. The exposures were in general closer in the Nordkappbank experiment. Analyzing the noise level data for the Vesterålen experiment showed on average cylindrical spreading, which is used in a simple acoustic spreading model estimating the integrated sound exposure levels at a central point in both areas. The analysis shows that the total noise energy exposed to an imaginary fish in these central locations are similar, but that the daily maximum total energy is higher for the Nordkappbank experiment. This gives some indication that the initial simple metrics gave a fair assessment of the exposures between the two cases.
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43.50.Rq Environmental noise, measurement, analysis, statistical characteristics
43.50.Sr Community noise, noise zoning, by-laws, and legislation
43.80.Nd Effects of noise on animals and associated behavior, protective mechanisms
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A Musician's Guide to Venue Acoustics

David Zartman

POMA Volume 9, pp. 015001 (May 2010); (10 pages)

Online Publication Date: May 06, 2010

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Whether in High School or the Vienna Symphony, musicians have little control over their performance venues. An instrument can be upgraded or replaced if there is an undesirable aspect, but replacing a venue is often far too expensive to be a tenable solution. A musician's perfect venue will also change piece to piece - an incredible venue for lush Wagner operas can cause issues for someone performing an intricate Paganini concerto and vice versa. What then are these effects? Why do they take place? How can a performer anticipate and combat undesirable aspects of venues while drawing out their featured characteristics for an optimized performance?
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43.55.Fw Auditorium and enclosure design
43.55.Hy Subjective effects in room acoustics, speech in rooms
43.75.Cd Music perception and cognition
43.75.St Musical performance, training, and analysis
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Acoustics for reproducing sound at the visualization labs at the King Abdullah University of Science and Technology: A case study

Steve Ellison and Peter Otto

POMA Volume 9, pp. 015002 (August 2010); (11 pages)

Online Publication Date: August 06, 2010

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Researchers at the newly opened King Abdullah University of Science and Technology are developing new ways to visualize and auralize complex data sets in immersive environments. These environments include the Multipurpose Room, a 100 seat multipurpose facility, and Cornea, a 10' × 10' × 10' six-sided stereoscopic cave. Both facilities are equipped for multichannel audio generation and playback in various standard and custom formats, as well as electronically variable acoustics utilizing active acoustics. Concurrent viewing and dialogue between participants in the two spaces is supported. Fully immersive environments present unique challenges due to physical properties of projection screens and the geometries that characterize these structures. Explorations of Cornea at KAUST and StarCave at UCSD are presented, along with strategies for reproducing sound and varying acoustics in these environments. Multiuse facilities such as the MPR also have conflicting acoustical goals. For instance, the optimal acoustic for multichannel or cinematic reproduction is less reverberant than optimized classroom environments. The use of active acoustics to improve the listening and overall immersive experience at both Cornea and the Interactive Media Room is discussed. Examples are presented including an experimental VR emulation of the acoustics of the King Abdullah Grand Mosque on the KAUST campus.
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43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response
43.55.Jz Sound-reinforcement systems for rooms and enclosures
43.55.Lb Electrical simulation of reverberation
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High resolution absorption mapping with a pu surface impedance method

Emiel Tijs, Hans-Elias De Bree, and Eric Brandão

POMA Volume 9, pp. 015003 (August 2010); (10 pages)

Online Publication Date: August 13, 2010

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The in-situ surface impedance method with pressure-velocity probes is documented in many publications (see e.g. 1-6). The method is based on the measurement of sound pressure (p) and particle velocity (u) close to an acoustic absorbing material. A loudspeaker at a defined distance is used to generate a sound field with a known radiation impedance. The impedance of a small area (a few square centimeters) with a known impedance is scanned with an ultra miniature pu probe very close to the surface. The area is made of steel with a cut-out, and behind this a material with a known impedance is placed. In this paper the method is explained, the spatial accuracy of the measurement is examined and a visualization technique is presented with a display of the spatial distribution (2D picture) of the damping properties as function of frequency.
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43.58.Bh Acoustic impedance measurement
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Acoustic calibration of the Exterior Effects Room at the NASA Langley Research Center

Kenneth J. Faller II, Stephen Rizzi, Jacob Klos, William L. Chapin, Fahri Surucu, and Aric R. Aumann

POMA Volume 9, pp. 015004 (August 2010); (10 pages)

Online Publication Date: August 25, 2010

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The Exterior Effects Room (EER) at the NASA Langley Research Center is a 39-seat auditorium built for psychoacoustic studies of aircraft community noise. The original reproduction system employed monaural playback and hence lacked sound localization capability. In an effort to more closely recreate field test conditions, a significant upgrade was undertaken to allow simulation of a three-dimensional audio and visual environment. The 3D audio system consists of 27 mid and high frequency satellite speakers and 4 subwoofers, driven by a real-time audio server running an implementation of Vector Base Amplitude Panning. The audio server is part of a larger simulation system, which controls the audio and visual presentation of recorded and synthesized aircraft flyovers. The focus of this work is on the calibration of the 3D audio system, including gains used in the amplitude panning algorithm, speaker equalization, and absolute gain control. Because the speakers are installed in an irregularly shaped room, the speaker equalization includes time delay and gain compensation due to different mounting distances from the focal point, filtering for color compensation due to different installations (half space, corner, baffled/unbaffled), and cross-over filtering.
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43.55.Jz Sound-reinforcement systems for rooms and enclosures
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Ambient noise levels and reverberation times in Mississippi school rooms

Megan N. Lucus, Edward L. Goshorn, and Brett E. Kemker

POMA Volume 9, pp. 015005 (January 2011); (5 pages)

Online Publication Date: January 30, 2011

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Nine elementary school classrooms at three Mississippi public schools were selected at random for noise and reverberation time measures to monitor voluntary compliance with ANSI standard S12.60-2002 (Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools). One-hour equivalent dBA noise levels and reverberation times (T60) were measured with SpectraPLUS Version 5.0 software. Measures were taken on separate days at each school in unoccupied classrooms with the HVAC system operating. For ambient noise measures an Audix TR40 omnidirectional microphone was placed in a 12 inch stand on a student's desk near the middle of the room and oriented toward the teacher's desk at a 45 degree angle. For the reverberation time measure a 400 watt loudspeaker (Yamaha BR15M) was placed on the teacher's desk about 3 meters from the microphone. Results showed that noise levels varied from 28 dBA to 51 dBA with broad spectra containing peaks at 120 Hz and harmonics. Five of nine classrooms had noise levels that exceeded the ANSI recommended level of 35 dBA. Reverberation times varied from .21 to .62 seconds; only one classroom exceeded the recommended minimal reverberation time of .6 seconds. Acoustical modifications to reduce noise levels and reverberation times will be addressed.
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43.50.Jh Noise in buildings and general machinery noise
43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response
43.55.Cs Stationary response of rooms to noise; spatial statistics of room response; random testing
43.55.Gx Studies of existing auditoria and enclosures
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Distilling the Acoustical Model from BIM Standard Architectural, Mechanical and Structural Models - Robust Acoustical Templates, Limitations & Recommendations.

Richard Vedvik and Jon Mooney

POMA Volume 9, pp. 015006 (February 2011); (22 pages)

Online Publication Date: February 11, 2011

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The integration of architectural acoustics into building integration modeling (BIM) software and the implementation of such integration is discussed between available systems and platforms. The process of integrating the various platforms of building integration modeling software, in such a manner that the assigned properties can be shared, manipulated, and exported, is of great interest to acousticians. As the architectural model is created, a standardization of materials and generic construction methods is desirable so the relevant properties assigned to the various building components are able to be imported and adjusted by Robust Acoustical Templates (RAT). Additional complications are identified as the acoustical model is detached from the live model. Standardization is also important between the architectural, structural, and mechanical models in order to create a common shared model that is able to maintain the relevant properties, both physical and analytical. Finally, the operation of a RAT prototype is demonstrated in the distillation of an acoustical model from standard BIM architectural, mechanical and structural models.
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43.55.Ka Computer simulation of acoustics in enclosures, modeling
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Control Algorithms for Adaptive Time-Frequency Test Signal Synthesis for Architectural Acoustics Measurements during Music Concerts

Ren Gang, Justin Lundberg, Dave Headlam, and Mark Bocko

POMA Volume 9, pp. 015007 (February 2011); (15 pages)

Online Publication Date: February 11, 2011

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A system was proposed by G. Ren [158th Meeting of the ASA (2009)] to perform field acoustics measurements during ongoing music concerts. It addresses the long‐standing problem of performing architectural acoustic measurements with an audience present. In this system, an adaptive time‐frequency synthesis algorithm was employed to generate test signals with time‐frequency energy distributions that conform to predicted "masked measurement vacancies" to ensure that the acoustic response of the test signals can be separated from the music and that the test signals are inaudible to the audience by taking advantage of auditory masking phenomena. In the present paper, approaches utilizing higher‐level structure of music are exploited to reduce the number of conflicts between the test signals and the music. Three approaches are described: a music theory based probabilistic prediction algorithm, using prior knowledge of the score, and the third exploits the availability of previous recordings of the music being performed. These control algorithms are adapted to architectural acoustic measurement procedures conforming to ISO3382‐1∕2(2009). The proposed system achieves similar performance compare to conventional acoustic test procedures, which emit loud test signals in empty music halls.
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43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response
43.55.Mc Room acoustics measuring instruments, computer measurement of room properties
43.58.Ta Computers and computer programs in acoustics
43.60.Ac Theory of acoustic signal processing
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Feasibility study of superharmonic imaging using chirps

Paul Van Neer, Mikhail G. Danilouchkine, Guillaume Matte, Marco M. Voormolen, Martin D. Verweij, and Nico De Jong

POMA Volume 9, pp. 020001 (April 2010); (7 pages)

Online Publication Date: April 28, 2010

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Superharmonic imaging (SHI) targets a combination of the 3rd to 5th harmonics. It was proven to have certain advantages in comparison with the established imaging standards in medical utrasound. SHI enhances the spatial resolution and improves the quality of echographic images, mainly by eliminating reverberation artifacts at the chest wall. However, SHI suffers from ripple artifacts, originating from the spectral gaps in between harmonics, and degrading the temporal resolution. To solve this a chirp-based SHI protocol was employed and its characteristics investigated, i.e. point spread function (PSF). The protocol was implemented for an interleaved phased array probe (44+44 elements tuned at 1.0+3.7MHz), connected to a fully programmable ultrasound system. A linear chirp (center frequency 1MHz; bandwidth 40%) was used for excitation. To obtain the PSF, the RF traces were recorded at focus along the lateral axis and convolved with the decoding signal. This was computed using KZK simulations. A PSF comparison between a superharmonic chirp and the 3rd-harmonic of a 2.5-cycle Gaussian apodized sinus burst at 1MHz showed a decrease in axial pulse length of 46% at -6dB and 32% at the -20dB level in favor of SHI. Chirp based SHI is virtually free of ripple artifacts and therefore feasible.
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43.60.Fg Acoustic array systems and processing, beam-forming
43.80.Vj Acoustical medical instrumentation and measurement techniques
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Ultrasonic characterization of cancellous bone using three models of trabecular structure

Jerzy Litniewski, Andrzej Nowicki, and Janusz Wojcik

POMA Volume 9, pp. 020002 (May 2010); (9 pages)

Online Publication Date: May 14, 2010

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The semi-empirical scattering models of trabecular bone were developed and examined for their abilities to mimic the frequency dependent backscattering coefficient measured in the cancellous bone. In the simulation of the bone RF echoes the real properties of the bone and experimental conditions were taken into account. Three types of trabeculae mimicking scatterers were considered. First, the bone consisted of cylinders with varying thickness (Gamma distributed) within the population, was assumed. The next two cases accounted for the contribution of thick and thin trabeculae to the total backscattered signal. The second model assumed existence of two populations of the cylindrical scatterers significantly differing in the average value of Gamma distributed diameters. Finally, the mixed model composed of thick and thin trabeculae modeled respectively by cylindrical and spherical scatterers was examined. The last selection resulted from the similarity found between scattering on small sphere and finite cylinder. Calculated echoes demonstrated the usefulness of the mixed model. Frequency dependence of backscattering coefficient agreed well with the experimentally determined dependences. The study showed also that the amplitude histograms calculated using demodulated RF echoes deviate from the Rayleigh distribution when the variation of scatterers' diameters increases.
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43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
43.60.Cg Statistical properties of signals and noise
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Analytic and numerical modeling of ultrasonic B-scan and echo decorrelation imaging

T. D. Mast and Swetha Subramanian

POMA Volume 9, pp. 020003 (August 2010); (14 pages)

Online Publication Date: August 06, 2010

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An numerical model is presented for B-scan images of weakly-scattering,lossy media, based on ultrasound array beam patterns calculated analytically under the Fresnel approximation. Given these beam patterns and a 3D analytic or numerical tissue model, this method yields beamformed A-line signals from which B-scan images are constructed. This approach is further employed to model echo decorrelation imaging, a method for quantitatively mapping transient heat-induced changes in pulse-echo ultrasound images. In echo decorrelation imaging, a normalized decorrelation parameter is computed between A-line signals separated by milliseconds. Maps of this parameter comprise echo decorrelation images, which are potentially useful for monitoring of local tissue coagulation during thermal ablation treatments for cancer therapy. Following previous studies in which scattering cross section has been related to spatial-frequency spectra of tissue sound speed, density, and impedance variations, echo decorrelation is related quantitatively to the local decoherence of these spatial-frequency spectra. Decoherence estimates are validated by simulations employing analytic array beam patterns and random-media models for ablated tissue, and are further applied to quantify tissue structure changes caused by thermal coagulation during in-vitro radiofrequency ablation.
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43.20.Fn Scattering of acoustic waves
43.58.Ta Computers and computer programs in acoustics
43.80.Qf Medical diagnosis with acoustics
43.80.Vj Acoustical medical instrumentation and measurement techniques
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Numerical simulation of mechanisms of blast-induced traumatic brain injury

Jan Teland, Anders Hamberger, Morten Huseby, Annette Säljö, and Eirik Svinsås

POMA Volume 9, pp. 020004 (October 2010); (14 pages) | Cited 1 time

Online Publication Date: October 05, 2010

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Blast-induced traumatic brain injury caused by road bombs has lately become a larger part of allied injuries. The same mechanisms may also be responsible for milder injuries of similar nature, resulting from training with large caliber weapons and explosives. In this paper, blast effects from a weapon on the brain are investigated. Using the hydrocode AUTODYN, numerical simulations of shock wave propagation into the brain are performed. The shock wave similar to that of a howitzer or a rifle is calculated. An idealized head is placed in the position of personnel firing the weapon. The focus is on the qualitative mechanisms of the propagation of the shock wave through the skull and into the brain. The results are validated by comparing with experiments carried out on anesthetized pigs exposed to weapon noise.
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43.80.Nd Effects of noise on animals and associated behavior, protective mechanisms
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Multiscale structure-functional modeling of lamellar bone

Kay Raum, Quentin Grimal, Pascal Laugier, and Alf Gerisch

POMA Volume 9, pp. 020005 (March 2011); (15 pages)

Online Publication Date: March 25, 2011

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Bone is a natural example of a structure that has achieved a unique combination and range of stiffness and strength. One of the striking features bone tissue is the ability to adapt to variable loading conditions by multiple but well organized structural arrangements of mineralized collagen fibrils at several levels of hierarchical organization. A profound understanding of the structure-function relations in bone requires both experimental assessment of heterogeneous elastic and structural parameters and theoretical modeling of the elastic deformation behavior. A "bottom-up" approach for experimental assessment and numerical modeling of the hierarchical structure from the nanoscale to the macroscale will be presented. Experimental data are obtained by scanning acoustic microscopy between 50 MHz and 1.2 GHz and provide anisotropic elastic and structural information at the lamellar (nanoscale) and at the tissue matrix (microscale) level. These data are directly translated into a Finite Element (FE) mesh. By numerical deformation analyses the homogenized elastic stiffness tensor of the next hierarchical levels (microscale to macroscale) are derived. At each level the numerical results are cross-validated by experimental data.
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43.58.Bh Acoustic impedance measurement
43.58.Ls Acoustical lenses and microscopes
43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.80.Ev Acoustical measurement methods in biological systems and media
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Calculations of intensities for radiation force modeling with the software package FOCUS

Robert McGough and Matthew W. Urban

POMA Volume 9, pp. 020006 (June 2012); (7 pages)

Online Publication Date: June 15, 2012

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Rapid calculations of the intensity are required for models of the radiation force generated by linear ultrasound phased arrays. To determine the computation times and numerical errors produced by two medical ultrasound simulation packages, namely, FIELD II and FOCUS, comparisons of the calculated pressures and intensities are performed using a simulated Vermon L5 phased array probe with 128 active elements. In these simulations, the array generates a fixed focus 25 mm from the array for a 5MHz excitation, and the pressure field is computed on a 133 × 133 × 261 rectilinear grid that is centered at the focus. Half wavelength sampling is employed in all three directions. In FIELD II, this calculation takes approximately 4 hours on a 64bit laptop running Linux, and in FOCUS, the same calculation takes less than 4 minutes on the same computer. The numerical errors are also much smaller with FOCUS. Details of the simulation approaches employed for this transducer model are presented, including selection of FIELD II and FOCUS simulation parameters and calculations of the reference pressure field for error evaluations.
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43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
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Cooperative radiation and losses in bubble clusters

Derek Thomas, Yurii A. Ilinskii, and Mark Hamilton

POMA Volume 9, pp. 020007 (November 2012); (9 pages)

Online Publication Date: November 21, 2012

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In existing models for single bubble dynamics it is necessary to account for radiation damping, a consequence of fluid compressibility. A similar correction is necessary when modeling systems of coupled bubbles. The coupling alters the collective dynamics and therefore the acoustic power radiated. In the linear approximation and for compact clusters in which the bubbles pulsate in phase, the radiation damping per bubble increases in proportion to the number N of bubbles in the cluster, and the acoustic power is N times greater than is radiated by the cluster in the absence of bubble interaction. The latter effect is relevant to passive detection of cavitation noise as an indicator of the onset and degree of cavitation in therapeutic applications such as shock wave lithotripsy and high‐intensity focused ultrasound. The effect that collective radiation damping has on the dynamics of several simple systems is considered for both small and large pulsations. [Work supported by the ARL:UT McKinney Fellowship in Acoustics and NIH DK070618.]
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43.35.Ei Acoustic cavitation in liquids
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The Singing Shoebox: A $5 Loudspeaker Project

Scott Porter, Daniel J. Domme, and Jeffrey S. Whalen

POMA Volume 9, pp. 025001 (July 2010); (8 pages)

Online Publication Date: July 22, 2010

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Moving-coil loudspeakers typify the interdisciplinary nature of acoustics. In order to reproduce sound, these devices employ principles of electricity, magnetism, mechanics, and acoustics. The widespread use of loudspeakers has made them familiar to students and thus a valuable opportunity to introduce students to acoustics. In this paper, the authors demonstrate a loudspeaker-enclosure system that is easily built from scratch. The system is mostly constructed from common household supplies, making it low-cost and accessible to a wide audience. In addition, this project is well-suited for use by the K-12 educator as the content can be scaled to fit a variety of different academic levels. To this end, the speaker's design and construction will be presented and its relevance as an educational demonstration discussed. Finally, the loudspeaker will be auditioned and its performance demonstrated.
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43.38.Ar Transducing principles, materials, and structures: general
43.38.Ja Loudspeakers and horns, practical sound sources
43.75.Tv Electro-acoustic and electronic instruments
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The tin-can telephone: An example of sound propagation and communication for Project Listen Up

Jason D. Sagers, Andrew R. McNeese, and Preston S. Wilson

POMA Volume 9, pp. 025002 (January 2011); (9 pages)

Online Publication Date: January 14, 2011

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The tin-can telephone can be used to illustrate the basic concepts of sound waves and sound-structure interaction. It can also be used to illustrate advanced concepts of frequency response and speech intelligibility in acoustic communications. For the proposed demonstration, students will construct a tin-can telephone from household materials and observe its performance from a variety of acoustic tests. Students will observe sound transmission and discover that some sounds are transmitted with greater clarity than others. A measured frequency response function for several tin-can telephones constructed from different materials will be provided to the student to illustrate the concept of frequency response and speech intelligibility.
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43.38.Ar Transducing principles, materials, and structures: general
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Use of compressively-stressed zinc oxide to increase microspeaker response

Lukas Baumgartel and Eun S. Kim

POMA Volume 9, pp. 030001 (May 2010); (7 pages)

Online Publication Date: May 19, 2010

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A micromachined piezoelectric speaker was fabricated on a 5 mm square silicon nitride diaphragm (1 micron thick). A 4 mm square zinc oxide (ZnO) piezoelectric transducer sits in the middle of the diaphragm, providing actuation. Two variations were fabricated: one with the compressively-stressed ZnO covering the region between the transducer and diaphragm perimeter -- causing wrinkling -- and another with the ZnO removed in this region. In both variations, the stress gradient causes curvature in the active-area, raising the resonant frequency to above 4 kHz. The displacement response is therefore approximately flat from 40 Hz to 4 kHz. The speakers are driven with a sinusoidal voltage, and the response is measured with a laser interferometer. The wrinkled device exhibits 11 times larger response and can be actuated by much smaller voltage, achieving lower THD while still having a larger deflection. The wrinkled device is driven at 2.2 V from 40 Hz to 4 kHz, demonstrating a response of 27.5 nm/V and an average THD of 5.1%. The unwrinkled device is driven at 15.0 V over the same range, yielding a response of 2.5 nm/V and an average THD of 8.6%. Sound and displacement responses are analyzed based on a simple piston model.
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43.38.Ar Transducing principles, materials, and structures: general
43.38.Fx Piezoelectric and ferroelectric transducers
43.40.Dx Vibrations of membranes and plates
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Temperature Characteristics of Electret Silicon Microphones

Yoshinobu Yasuno

POMA Volume 9, pp. 030002 (July 2010); (9 pages)

Online Publication Date: July 01, 2010

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The electret condenser microphone (ECM) has become an important component for various consumer equipment systems because of its stable sensitivity and frequency characteristics and its success in achieving small size and high sensitivity. A previous report described the method to design a microphone with stable temperature characteristics. The quality of the silicon material for the diaphragm was pointed out as important for improving robustness. Recently, microphones using micro-electro-mechanical systems (MEMS) have been practically applied and widely used for mobile equipment, such as cellular phones. The major reason for adopting MEMS is that a re-flow soldering process can be used in production, in addition to having desirable features such as being small and thin. However, almost no electret types have been commercialized since a guaranteed 300-degree C heat resistance is required. This report presents a new trial electret silicone microphone that contains a SiO2 thin-film electret. The report also evaluates the heat resistance of a SiO2 electret, the temperature stability of a silicon diaphragm, and the temperature change of sensitivity and frequency characteristics compared with those of a conventional ECM and the microphone for measurement.
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43.38.Bs Electrostatic transducers
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In-situ calibrated sound signals and hearing sensitivity

Robert Withnell, Patricia S. Jeng, William Shofner, and Jont Allen

POMA Volume 9, pp. 030003 (August 2010); (10 pages)

Online Publication Date: August 13, 2010

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The acoustic input impedance of the ear provides data on the acoustico-mechanical function of the ear and can be used diagnostically to assess outer and middle ear function. Sound signals delivered to the ear canal can be quantified in-situ if the complex reflectance of the ear has been determined. Hearing sensitivity can be expressed in terms of the forward-going sound pressure wave, or after correcting for acoustic delay, the fraction of the forward-going sound pressure wave transmitted to the middle ear. The latter is an estimate of the signal the cochlea receives. Data is presented examining the virtues of expressing hearing sensitivity in terms of an in-situ calibrated sound signal.
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43.64.Ha Acoustical properties of the outer ear; middle-ear mechanics and reflex
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A new loudspeaker design for the enhancement of sound image localization on flat display panels

Gabriel Pablo Nava, Keiji Hirata, and Yoshinari Shirai

POMA Volume 9, pp. 030004 (June 2011); (9 pages)

Online Publication Date: June 05, 2011

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In most audio-visual multimedia applications, conventional stereo loudspeakers have been used to implement auditory displays. However, a fundamental problem with this kind of displays is that only the listeners situated at the sweet spot and over the symmetrical axis of the loudspeaker array, are able to accurately localize the sound images. Although a number of audio signal processing algorithms has been proposed to expand the listening area, relatively less study on new loudspeaker configurations has been explored. This paper introduces a simple, yet effective, loudspeaker design to enhance the localization of sound images over the surface of flat display panels. In contrast to previous approaches, expansion of the listening space is achieved by attachment of rigid barriers which physically modify the sound radiation pattern of the loudspeakers. Moreover, numerical simulations, experimental sound measurements, and subjective tests have been preformed to validate a prototype of the proposed loudspeakers design using a display panel of an immersive teleconferencing system. Finally, an example of an interactive application was implemented involving real-time speaker tracking with a microphone and video cameras.
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43.38.Ar Transducing principles, materials, and structures: general
43.38.Ja Loudspeakers and horns, practical sound sources
43.38.Md Sound recording and reproducing systems, general concepts
43.38.Vk Stereophonic reproduction
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An Introduction to the Acoustics of Playing the Horn

David Zartman

POMA Volume 9, pp. 035001 (May 2010); (8 pages)

Online Publication Date: May 06, 2010

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In the art of music, a good performer can make a low-quality instrument sound passable, while a bad performer will not play well even on the best instrument in existence. Rather than merely focusing on the properties of the instrument, it is useful to provide the musician with some of the acoustical principles involved with playing the horn well. At the same time, this provides a medium to enable the acoustician to understand some of the intricacies a musician must balance well to create a pleasing sound.
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43.75.Bc Scales, intonation, vibrato, composition
43.75.Cd Music perception and cognition
43.75.Fg Brass instruments and other lip-vibrated instruments
43.75.St Musical performance, training, and analysis
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Novel computer aided design of labial flue pipes

Brian Moss, Elfed Lewis, Gabriel Leen, Kort Bremer, and Andrew Niven

POMA Volume 9, pp. 035002 (May 2010); (7 pages)

Online Publication Date: May 19, 2010

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A labial flue pipe is a well known tone generator, which is familiar and easily recognisable as the organ pipes seen in many concert halls and churches. However, the design and understanding of the sounding mechanism of such pipes is fraught with difficulty. Traditionally labial pipes are constructed from age-old lookup tables that are closely guarded intellectual secrets. This paper discusses a novel computer program that facilitates the design and construction of such labial flue pipes. The computer program allows almost all aspects of the labial flue pipes design to be varied, the resultant frequency is generated and in addition the Ising efficiency number is provided. Furthermore, a discussion is included related to the fact that even though an Ising number greater than 3 indicates that a pipe is overblown, the fundamental tone is still predominant. A comparison will also be made between a CFD simulation of the labial flue pipe jet mechanism and smoke trail plots typical of such analysis
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43.20.Ks Standing waves, resonance, normal modes
43.58.Wc Electrical and mechanical oscillators
43.75.Np Pipe organs
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