bluuebunny/crossref_metadata_2025 huggingface dataset:
The Lloyd-Berry effective wave number in multiple scattering
Authors: Dacol Dalcio K. , Orris Gregory J.
Published: September 2008

The scattering of an acoustic field by an ensemble of many discrete objects is a phenomenon observed in many different contexts. In underwater acoustics, one finds examples in propagation through bubbly water, fish schools, non-homogeneous sediments (embedded shells for example), etc. The effective wave number associated with the propagation of the statistically averaged acoustic field scattered by an ensemble of many scatterers is a quantity of physical interest that is also experimentally accessible. Theoretically, this quantity can be evaluated only approximately. Typically, it is evaluated as an expansion in the average density of scatterers. In the literature, one finds two distinct expressions for the second-order contribution, one, the oldest, due to Waterman and Truell, and another by Lloyd and Berry. A new derivation of the Lloyd-Berry formula is provided using an approximation similar to the one used by Waterman and Truell and also by Foldy and Lax. This derivation should shed light on the origin of the different expressions and lend support to the contention that the Lloyd-Berry expression is the correct second-order term in the density expansion.
Scattering by a sphere illuminated by a Bessel beam: Finite-element modeling
Authors: Thiessen David B. , Marston Philip L.
Published: September 2008

The recent analytical solution for the scattering of an acoustic Bessel beam in water by a sphere centered on the beam [P. L. Marston, J. Acoust. Soc. Am. 121, 753–758 (2007)] gives insight into the processes associated with excitation of target resonances and provides a benchmark for numerical approaches. For example, it is possible to suppress the excitation of certain modes of an elastic sphere by appropriate selection of the beam parameters [P. L. Marston, J. Acoust. Soc. Am. 122, 247–252 (2007)]. The present work demonstrates that computation of the scattering for steady state illumination by a Bessel beam using the finite-element method (FEM) reproduces the analytical result for the scattering. The dependence of the mode coupling on beam parameters is also present in the FEM results. Some aspects of FEM-based scattering calculations for acoustic beams will be noted. [Work supported by ONR.]
Enhanced decay rate for the depth dependence of the backscattering of sound by simulated buried targets with evanescent wave illumination
Authors: Marston Philip L. , Espana Aubrey L. , Osterhoudt Curtis F. , Thiessen David B.
Published: September 2008

Sound incident, with a sufficiently small grazing angle on a smooth sediment, produces an acoustic evanescent wave in the sediment, which decays exponentially with increasing depth. A system consisting of an immiscible liquid in contact with a second liquid, has been used in the laboratory to explore the backscattering of sound by a cylinder illuminated by an evanescent wave [C. F. Osterhoudt, Ph.D. Thesis, Washington State University (2007)]. In that work the organ-pipe mode of an open-ended liquid filled metal cylinder was excited. The backscattering was found to decay with increasing depth at a rate approximately twice the spatial decay rate of the incident wave in the simulated sediment. Reciprocity predicts the decay rate is doubled in the case of localized acoustic coupling at the target. Recent supporting measurements of the backscattering, associated with a low-frequency circumferential mode of a plastic cylinder, are noted. Finite-element-based computations of the far-field low-frequency backscattering by a rigid cylinder in the simulated sediment show a decay rate approximately double that of the incident evanescent wave. [Supported by ONR.]
In situ estimation of acoustic impedance on the surfaces of realistic interiors: An inverse approach
Authors: Pablo Nava Gabriel , Sato Yoichi , Sakamoto Shinichi , Yasuda Yosuke
Published: September 2008

In situ measurement of acoustic impedance is traditionally performed using pairs of microphones located close to the test surface. However, this method becomes troublesome if inaccessible complex-shaped surfaces, such as those in a real room, are considered. To overcome this problem, a method to estimate the normal acoustic impedance on the interior surfaces of a room is proposed. As input data, the algorithm takes: (1) The 3-D shape of the room; (2) the strength of the sound source; and (3) a set of sound pressures measured at random locations in the interior sound field. The estimation of the acoustic impedance at each surface is achieved via the solution of an inverse problem, which arises from the boundary-element method applied to the discretized interior boundaries of the room. Unfortunately, the solutions of this kind of problems are known to be unstable and sensitive to noise, due to a rank-deficient linear system. Dealing with such a system is avoided in the proposed method by formulating an iterative optimization approach, which is shown to be more robust to noise. Previous work has reported examples with numerical simulations. This paper goes further and presents results obtained with real data from experiments.
Acoustical renovation of rooms for music instruction in schools to improve teaching and listening conditions
Authors: Paek Hyun , Siebein Gary W.
Published: September 2008

Several music classrooms were renovated because music instructors complained of excessive noise levels during classes. Instructors also could not hear students well and commented on harsh reflected sounds. The rooms were trapezoidal shaped with relatively low, angled gypsum board ceilings with few sound absorbing materials installed. Acoustical measurements of reverberation times, overall sound levels, and reflected sounds were used to identify the causes of the perceived problems. Renovation schemes included floating planes of sound-diffusing panels or prefabricated-diffusing panels suspended in a ceiling grid to allow students to hear each other; raising the ceiling height to reduce excessive sound levels; and strategically placing sound-absorbent materials to reduce reverberation and acoustic defects. Post-construction acoustical measurements, as well as discussions with music instructors, revealed that while both reverberation times and loudness levels decreased, the early sound energy reflected across the room increased and resulted in improved musical communication among students and instructors.
Perception and performance of hearing-impaired versus normal-hearing persons under noise
Authors: Ronsse Lauren M. , Wang Lily M.
Published: September 2008

Examining the effects of mechanical system noise on worker performance and perception for normal-hearing persons has been an area of previous research; this study extends this research area to include hearing-impaired subjects. The goal is to determine if persons with hearing impairments respond similarly to seven different mechanical system background noise conditions as persons with normal hearing. The seven noise signals vary in terms of level and spectral quality, but are all within the range of background noise conditions found in commercial offices. Performance is gauged on three types of tests (math, verbal and typing), while subjective perception is measured via a subjective questionnaire. The results of this investigation will show if significant differences are present between the two groups, and if so, they may lead to the development of different standards for noise criteria levels in spaces designed for the hearing-impaired. [Work supported by a Univ. of Nebraska Layman Award and an ASHRAE Graduate Student Grant-in-Aid.]
Residential wall construction transmission losses and home office productivity
Authors: Wagner Alicia J. , Wang Lily M.
Published: September 2008

With advances in technology, the office worker finds herself in a changing work environment; there are now more opportunities to work from home. While recent research has addressed variations in worker productivity due to existing sound conditions within a space, home office performance has a greater dependence on isolation from exterior sound sources than conventional office work. This project investigates how sound levels produced by walls with different levels of transmission loss (TL) affect an individual’s performance. Performance on math, verbal, and typing tests was assessed for sound signals played across four residential wall constructions ranging from a sound transmission class of 35 to 55. Correlations between the TLs and math, verbal, and typing productivity will be shown and used to determine if there is a minimum acceptable TL level.
Evaluation of accoustic comfort in classrooms of the Federal University of Parana
Authors: Ferreira Andressa M. C. , Zannin Paulo H. T.
Published: September 2008

This research is a case study developed to evaluate and compare the classroom acoustics of two different buildings from the Federal University of Paran, built in different times: Building CP (from the 1960s) and building JB (built in 2000). Acoustical parameters have been measured in eight classrooms of the CP building, and seven classrooms of the JB building: Sound pressure level, reverberation time, and sound insulation. The methodology employed followed standard procedures for acoustical evaluation of classrooms. Results showed that the classrooms of the CP building, from the 1960s, display satisfactory acoustical conditions, especially in their reverberation times. On the contrary, classrooms of the more recently built JB building yielded poor results with respect to reverberation times, either in empty classrooms, or in partially or even totally occupied classrooms, not meeting the values set by the standards. Thus, despite the evolution of the studies and research on room acoustics, older classrooms of the Federal University of Paran have better acoustics than more recently built classrooms.
An exploration of virtual 3-D sound
Authors: McDermott Scott , Chu Cheehung Henry
Published: September 2008

Many of the applications, virtual environments, and video games available to average computer users embrace stunning 3-D graphics and real-world visualizations. Developers spend an extraordinary amount of time and effort creating these immersive, realistic virtual environments, primarily focusing on the graphics components. Within these virtual realities, the user should be able to easily and accurately perceive the locations of sound sources, as well as the acoustic nature of the environment. However, for reasons of economy and simplicity, most developers apply readily available industry standards for generating pseudo-3-D sounds in their applications. This research explores the shortcomings of these standards and proposes an effective alternative. This project includes a number of computationally efficient, physics-based 3-D acoustics simulations, each of which will produce realistic aural reproductions. The goal is to evaluate and compare these algorithms against each other, non-3-D sound reproduction, and the current industry standards (e.g. Microsoft’s DirectX’s pseudo-3-D algorithm). Two hypotheses will be tested. First, users will find true, physics-based 3-D algorithms to render improved auralization reproductions compared against DirectX and/or OpenAL. Second, localization and spatialization improve with user training when using these algorithms.
Prediction of sound around a corner in long corridors
Authors: Fung William W. S. , So Sai Tung , Leung Chun Wah , Li Kai Ming
Published: September 2008

An L-shape section is a prime consideration in the design of corridors in modern buildings. Similar to a straight corridor, the direct sound field dominates the sight-line region in the near field. However, there is no contribution from the direct sound field when the receiver locates around the corner at the shadow zone. The reflected sound field becomes more important as the receiver moves further from the bend. The present study examines the propagation of sound along a long space with an L-shape section. A numerical model using an image-source method is developed for the prediction of sound transmission along the L-shape section of a long corridor. The reverberation times are predicted by the proposed numerical model. In particular, the respective sound fields at two octave bands (500 Hz and 2,000 Hz) are obtained. The noise levels at these two octave bands are needed for the computation of the rapid speech transmission index. This information is often used to conveniently assess the speech intelligibility of a communications channel. The proposed image source model is validated by comparing with field measurements conducted in an L-shape corridor and also conducted in a scaled model in an anechoic chamber.
Stable cavitation description and characterization
Authors: Church Charles C.
Published: September 2008

In his now-famous work, ‘‘Physics of Acoustic Cavitation in Liquids,’’ [Physical Acoustics, Vol. 1-B, edited by W.P. Mason (Academic Press, New York, 1964), Chap. 9, pp. 57–172], Hugh Flynn coined two terms that have become commonplace in the lexicon of bubbologists, ‘‘transient cavitation’’ and ‘‘stable cavitation.’’ Although in routine use in the field of acoustic cavitation research, the original, rather precise meanings of these phrases have since been obscured. For example, ‘‘inertial cavitation’’ is now preferred owing to the perception that the former, ‘‘transient cavitation,’’ refers to motion that must inevitably result in the destruction of the bubble upon collapse, while in fact the original criterion was simply that the contraction must approximate that of a Rayleigh cavity until arrested by the internal pressure. Similarly, ‘‘stable cavitation’’ is often considered to be low-amplitude motion, but Flynn’s criterion was simply that the bubble oscillate nonlinearly about its equilibrium radius. This talk will describe the original and modern meanings of these terms, discuss various cavitational phenomena, and differentiate the effects likely to be induced by each type of bubble motion. [Work supported by DAMD17-02-2-0014.]
Subharmonic generation mechanisms in stable cavitation
Authors: Holt R. Glynn , Holzfuss Joachim
Published: September 2008

The observation of subharmonic emissions during an ultrasound experiment has often been taken as the sine qua non of stable cavitation. While the appearance of subharmonics is very likely the indication of the presence of bubbles, it leads to a thorny question: What do subharmonic emissions tell us about the nature of the cavitation in the experiment? The answer to that question will naturally be of pragmatic importance to the experimenter seeking to enhance, inhibit, or otherwise control the resulting bioeffect. In this talk, we review the physical mechanisms for bubble generation of subharmonics, giving where possible, examples of each mechanism and eliciting the consequences for biomedical experiments.
Ultrasound contrast agent microbubbles: Stable and transient subharmonic emissions
Authors: Masotti Leonardo , Biagi Elena , Breschi Luca , Vannacci Enrico
Published: September 2008

The paper describes a method able to perform an ultrasonic study of a single UCA bubble immersed in a tank filled with a liquid (water) by means of ultrasonic equipment able to insonify and acquire RF echo signals coming from an isolated bubble with a high frame rate. The work was focused on the study of subharmonic emission from an isolated bubble of SonoVue. In particular, the acoustic pressure threshold for a subharmonic stable emission was evaluated for a subset of 50 microbubbles at 3.3 MHz and at 5 MHz of insonation frequencies. An unexpected second pressure threshold, which caused the standstill of the subharmonic emission, was detected at 3.3 MHz and 5 MHz. A transient subharmonic emission, which is hypothesized as being related to the formation of new free gas bubbles, was detected during the ultrasound-induced destruction of microbubbles. Several sequences of RF echo signals and the related spectra, acquired from a set of 400 isolated microbubbles, is investigated at different acoustic driving pressures and excitation frequencies. Specific bubble behaviors concerning the stable subharmonic emission, the inhibition of subharmonic generation, and the transient subharmonic emission were detected during experimentation and discussed in this paper.
Effect of 810 kHz cw ultrasound on bacterial biofilms
Authors: Anguah Kofi , Velez Roby , Vollmer Amy C. , Everbach E. Carr
Published: September 2008

Biofilms of florescent E. coli bacteria were grown in protein-rich media on coverslips that served as the floor of an ultrasound exposure chamber. Two opposite walls of the chamber were strips of lead zirconate titanate (PZT-4) driven at their resonance frequency of 810 kHz in continuous wave mode, thereby setting up acoustic standing waves within the 12 mm by 16 mm by 0.5 mm chamber. A convolution confocal florescence microscope was used to visualize the biofilm before, during, and after 10-minute exposures at various acoustic pressure amplitudes, with and without Optison microbubbles present. Quantifiable changes to the biofilm structure suggest that stable cavitation is a mechanism of interaction that may provide a method of enhancing antibiotic action in medical applications. [Work supported by HHMI grant ♯52005202.]
Growth of gas bubbles by rectified diffusion at high supersaturation levels
Authors: Ilinskii Yurii A. , Wilson Preston S. , Hamilton Mark F.
Published: September 2008

There is continued interest in possible effects of under-water sound on the growth of gas bubbles in capillaries of marine mammals and humans. [Houser et al., J. Theor. Biol. 213, 183 (2001)] showed that following a series of dives, gas supersaturation in capillaries of marine mammals can reach 300%. For such high supersaturation levels, standard mathematical models of both static and rectified diffusion underestimate the rate of bubble growth by 10%–20%. The discrepancy is demonstrated by comparing predictions based on existing mathematical models with direct numerical solutions of the differential equations for gas diffusion in the liquid and heat conditions in the bubble. The Rayleigh-Plesset equation is used to describe the bubble dynamics. Underestimation of bubble growth by existing mathematical models is due to the underlying assumption that the gas concentration in the liquid is given by its equilibrium state for a bubble of constant radius. This assumption is violated when high supersaturation causes the bubble to grow too fast in relation to the time scale associated with diffusion. Rapid bubble growth results in an increased concentration gradient at the bubble wall, and therefore a growth rate in excess of predictions based on quasistatic gas concentrations. [Work supported by ONR.]
Optimization of baffle configurations to prevent aeroacoustic instabilities in heat exchangers: Preliminary experiments
Authors: Moreira A. Miguel , Antunes Jose , Debut Vincent , Paulino Martins , Pina Heitor
Published: September 2008

Gas heat exchangers are prone to aeroacoustic instabilities, which often lead to severe noise levels, structural vibrations, and fatigue. Actually, this problem is solved by placing rigid baffles inside the container, which modify the acoustic modal fields and eventually inhibit the instability. For realistic industrial components using a restricted number of acoustical baffles, their optimal location is a challenging problem, as trial and error experimentation is often a costly and frustrating procedure. Recently, some strategies were proposed for the optimal location of a single baffle in a typical re-heater from a power station boiler, based on simulated annealing as well as genetic algorithm approaches. In this paper and using the above-mentioned optimization strategies, a more complex case of the problem—the optimal location of a given number (two or more) of baffles in a typical re-heater, was addressed. Some preliminary experiments were performed and compared with the simulation results. From the discussion, improvements in the developed optimization functional were proposed. [This work has been endorsed by the Portuguese FCT and POCI 2010, with funding participation through the EC programme FEDER (Project No. POCI/EME/5728/2004).]
The enigma of Vitruvian resonating vases and the relevance of the concept for today
Authors: Godman Rob
Published: September 2008

Anyone who has visited a Greek or Roman theatre cannot fail to be impressed by the overall clarity of sound without any form of enhancement. The seats arranged in curved rows around the circular orchestra form large horizontal reflecting surfaces. This ensures that the path of the sound waves travel from the source (the actor or singer) to each of the listeners in a direct path (i.e., without reflection). Vitruvius, however, claimed further enhancements could be made. ‘‘In theatres, also, are copper vases and these are placed in chambers under the rows of seats in accordance with mathematical reckoning. The Greeks call them Echeia. The differences of the sounds which arise are combined into musical symphonies or concords: The circle of seats being divided into fourths and fifths and the octave.’’ (Vitruvius, on Architecture, Book I,—on training of architects, Loeb). With the aid of modern-effect systems that attempt to mimic real and imaginary spaces, it may be difficult to imagine the importance of the Vitruvian idea. This paper demonstrates a number of digital reconstructions, examines the issue of intent, and questions an arguably more complex issue, that of a potential fusion between archaeology, science, and music.
Quantal computation of tonality in music
Authors: Sevgen Alpar
Published: September 2008

Each independent scale interval structure with N semitones and M notes contains a multiplet of N scales (for example, the major scale has the interval structure 2212221; and its twelve multiplet members are: C-major, D flat-major,..., B-major scales). Operators that step through these multiplet members (by sharping or flatting the notes of the multiplet members) are identical with those of N-level finite state quantum mechanics. It is possible to construct orthonormal basis states which represent the multiplet members of a given interval structure. A musical score can then be expressed as a mixture of various tonalities, using the density matrix formalism of quantum mechanics. Several examples help illustrate this quantitative approach.
Implementation of non-stringed instruments without bodies
Authors: Cho Sangjin , Chong Uipil
Published: September 2008

This paper describes the implementation of the non-stringed instruments using the TMS320F2812 DSP, which is possible to produce the sounds of musical notes. This basic concept of the instrument comes from the non-stringed instruments, which is not necessary to tune the string of the instruments before starting the play. In this paper, this system chose the guitar as an example for implementation. The system does not need a guitar body, but the pickup part is needed. The pickup of the system plays an important part in representing the up/down strokes and arpeggios. Therefore, the proposed system consists of three parts: Chord glove, pickup, and processor. Mapping between guitar chord and the glove takes place on the values of the force sensing resister and FLEX sensors. The extension of this system can be applied to stringed instruments in the future. [Work supported by KOSEF, R01-2005-000-10671-0.]
Experimental investigation of the effects of extra mass on a piano soundboard’s vibration property
Authors: Xing Hao , Zhao Bonan , Zhao Haiyan
Published: September 2008

A soundboard, as an important resonance component of a piano has been continuously studied in the past several decades. It is known that the variation of mass distribution on a soundboard could affect its vibration properties and the sound quality of a piano. However, those effects have been seldom investigated until now. In this paper, an experiment is carried out to study the effects of additional mass-blocks on a soundboard. Small pieces of metal blocks are pasted on several different locations on a soundboard, and a laser vibrometer is used to extract its mode shapes and spectrum under the excitation of an acoustic source with frequency ranges from 10 Hz to 1 kHz. The results show a notable difference of spectrum between mass-added cases and original in low frequencies, but little difference in high frequencies. It could be concluded that additional mass-block could greatly affect the energy of the low-mode of a soundboard.
Reed vibration, pressure, and airflow in Western free-reed instruments
Authors: Toussaint Edward L. , Cottingham James P.
Published: September 2008

Western free reed instruments, including the reed organ, harmonium, harmonica, and accordion, use asymmetric free reeds that are able to maintain sustained oscillation in the absence of a pipe resonator. Studies of the motion of air-driven American reed organ reeds and accordion reeds have been made that yield the volume air flow through the reed opening as a function of time. Reed vibration waveforms are obtained using a variable impedance transducer, and corresponding sound pressure waveforms are obtained from a probe microphone at positions near the reed opening on both sides of the reed tongue. The airflow waveform is obtained by integrating the pressure waveform and using a calculated area function and is calibrated using the measured average and minimum airflow rates. The results are compared with earlier preliminary studies as well as recent theoretical work. For pressure and airflow waveforms among different types of reeds or for the same reed at different blowing pressures, differences can be understood in terms of the configuration of the reed and reed frame system, as well as the amplitude of reed vibration. [Research supported by NSF REU Grant No. PHY-0354058.]
Empirical physical modeling based music synthesis and representation
Authors: Dong Xiaoxiao , Sterling Mark , Bocko Mark
Published: September 2008

We describe a method in which empirically-based musical instrument physical models are employed both to synthesize musical sounds and to form the basis of a compact representation of mono-timbral musical sound. Results are presented for a Bb clarinet. The physical model incorporates measured acoustic impedance spectra of a clarinet air column for all playable notes. Low bandwidth control parameter time histories, serving as inputs to the physical model, are inferred from audio recordings of actual clarinet music. The control parameters represent the fingerings, the blowing pressure of the player, and the mouthpiece clamping pressure of the player’s embouchure. It is shown that, given an appropriate physical model, the control parameter time histories can serve as a highly compact representation (compression by a factor of several hundred) of a source recording. To serve as an assessment tool, we also describe a distance metric emphasizing timbral aspects of musical audio. The metric provides a method to quantitatively evaluate the parameter extraction routines, to test the effect of minor alterations to the model, and also to compare the present physical modeling approach with other forms of musical sound synthesis. The framework described may be extended to other musical instruments and instrument families.
The influence of the acoustic feedback on the fluid-structure interaction within single-reed mouthpieces: A numerical investigation
Authors: da Silva Andrey Ricardo , Scavone Gary
Published: September 2008

The aim of this article is to complement a previous numerical study conducted to investigate the flow behavior in single-reed woodwind instruments during dynamic regimes with a moving reed [J. Acoust. Soc. Am. 120, 3362 (2006)]. The code uses a fully-coupled scheme based on the lattice Boltzmann method and on a finite-difference scheme to represent the interaction between the reed and the fluid field. The previous study had suggested that, during a dynamic regime and in the absence of acoustic feedback, the flow behavior diverges significantly from what is predicted by the current quasi-stationary models based on the Bernoulli obstruction theory. The present work provides a further investigation on the same topic by taking into account the influence of the acoustic feedback from the bores open end and its interaction with the mean flow within the mouthpiece-reed system. This is achieved by coupling the previous mouthpiece-reed model to a digital waveguide whose reflection function is described by a low-order digital filter to represent the open-end boundary condition. [The first author would like to thank CAPES for supporting his doctoral research.]
Vibration modes of the snare drum batter head
Authors: Larkin Barry , Morrison Andrew
Published: September 2008

Percussionists have always had to contend with an undesirable ringing sound while performing on the snare drum. It is usually referred to as the edge ring. A common method to eliminate this sound comes from placing some type of dampening material on the edge of the drum head. Manufacturers of drums have provided many ways of dealing with this problem, including internal dampening devices, customized drums heads, or material designed to be placed on the drum head. Using electronic television holography, was revealed the source of this ring to be the third mode of vibration that produces a pitch approximately one octave and a half-step above the fundamental. During this presentation, holographic images from the fundamental to the eighteenth mode will be displayed. Methods to dampen this mode will be displayed and demonstrated as part of this paper.
Animals, ordinary humans, and scientific experts: Noise(s) or sounds? How semantics may help understanding animal behavior and human cognition as well
Authors: Dubois Daniele S.
Published: September 2008

If an anthropomorphic conception of animal behavior is inescapable, cross cultural studies, situated cognition, as well as research in ethology, have recently pointed that contemporary cognitive models of information processing that pretend to be universal of any living system, could be misleading as relying on a specific conception of cognition. Actually, such models can account for the cognition of experts trained in an analytic processing of the world, grounded in contemporary scientific (physical) knowledge, but not for the ways ordinary humans perceive and react to environmental noise for behaving and acting in the world. In every day life, humans process multimodal incoming stimulations in a holistic manner that gives meaning to their ways of being. Within this frame, acoustic stimulations are not processed per se, but as cues pointing to categorical knowledge already stored in memory and structured according to adaptation purposes. Such a situated model of cognition has been fruitfully integrated in soundscape research and in environmental acoustics. It now challenges the traditional psychophysics paradigms in developing an ecological exploration of categorization for sounds. We would like to present such methodological issues, expecting to provide new insights for human as well as for animal behavior research.
Noise and noise effects on humans and its meaning for measurement decisions
Authors: Schulte-Fortkamp Brigitte
Published: September 2008

To discuss advances in measurements of noise and noise effects on animals and humans is challenging. Usually, it is physics that dominates the approach in the studies about noise and noise effects on humans; indicators in use are based on A-weighted sound pressure levels. By extension, psycho-acoustics has contributed to understanding the limitations of the A-weighted sound level in dB as a metric criterion or a criterion for measurements. In addition, noise annoyance appears to be differently perceived, expressed, and experienced in different places. For this reason, supplementing the acoustics and psycho-acoustics approaches by a more qualitative approach, as in soundscape research, seems to be appropriate in order to consider more the perception, the way people experience noise, and relate this to their well-being. Research shows that perceived and expressed annoyance are explained not only by acoustics, but also by other factors, and their relationships can explain the links between populations and their environment. Therefore, the way people react and evaluate noise as the real experts has to be taken into consideration with respect to conceptualization of measurement approaches and measures. The diverse approaches will be introduced with respect to decisions for measurements in defined environments.
Documenting noise exposures for wildlife studies: Review of large studies over the past 18 years
Authors: Kull Robert
Published: September 2008

A couple of decades ago, researchers recognized the importance of improving understanding of noise exposure to wildlife for bioacoustic studies. Due to the differences in the ecology of species of concern, various approaches took place over these past 20 years to address this issue. The metrics used to determine effects and how the metrics were applied to observed behavioral and physiological responses also varied, based on several factors. This presentation will review methods used on several large projects, including big horn sheep, caribou, kit fox, Mexican spotted owls, peregrine falcons, and red cockaded woodpeckers. This review may help provide the direction for future bioacoustic studies.
The effects of helicopter noise on the reproductive success of the coastal California gnatcatcher
Authors: Hunsaker Don , Rice Jacque , Kern John
Published: September 2008

Our laboratory conducted a five-year study on the potential effects of helicopter noise on the reproductive success of the coastal California gnatcatcher (Polioptila californica californica) on Marine Corps Air Station Miramar (MCAS Miramar) in Southern California. Seven-hundred twenty-one nests were monitored for reproductive success, predation, noise levels, and habitat quality. An array of Larson-Davis sound level meters was used to monitor habitat on MCAS Miramar for a total of 6,176 days during 620 runs at 328 locations. Most sites were exposed to noise in excess of 60 dBA SPL for less than 5% of the monitoring period, but some nests experienced levels in excess of 70 dBA for more than 20% of the time. Statistical models of nest success, nest site selection, and number of fledges per pair showed that the factors best predicting reproductive success were measures of suitable nesting habitat, not noise levels. Helicopter and other noise sources did not affect the reproductive success of gnatcatchers. [Supported by the Marine Corps Air Bases Western Area and the Naval Facilities Engineering Command, SW.]
Marine wildlife behavior database for estimating environmental impacts
Authors: Vigness Raposa Kathleen J. , Frankel Adam S. , Sisson Geoff , Ellison William T. , Damon Christopher
Published: September 2008

Assessing the potential effects of underwater sound on the environment is an increasing concern. In order to predict an animal’s exposure from an acoustic source, it is necessary to know how it moves through the sound field. While a number of tools have been developed in recent years to estimate environmental impacts, they require an estimate of the species present at the time of the operation, their abundance and distribution, as well as their diving, movement, and acoustic behaviors. To determine whether a species might be susceptible to certain sound exposures, it is also necessary to consider the probable hearing range and sensitivity of the species. The marine wildlife behavior database (MWBD) is creating a worldwide standard for measuring and characterizing behavior. It includes geo-referenced baseline data on diving, movement, and acoustic characteristics of fishs, marine mammals, and sea turtles. The database is designed to capture the distribution of the values of a behavior in a way that is amenable to models that replicate the movement or other behaviors of an animal. The MWBD is publicly available over the Internet through a registered node on the National Spatial Data Infrastructure at http://www.edc.uri.edu/MWBD.
Update on exposure metrics for evaluation of effects of sound on fish
Authors: Hastings Mardi C. , Popper Arthur N.
Published: September 2008

Several studies [A. R. Scholik and H. Y. Yan, Hear. Res. 152, 17–24 (2001); A. N. Popper et al., J. Acoust. Soc. Am. 117, 3958–3971 (2005); M. E. Smith et al., J. Exp. Biol. 209, 4193–4202 (2006)] indicate that the equal energy hypothesis does not apply when evaluating auditory effects in fish. This is not surprising, as similar results have been reported for mammals [R. P. Hamernik and W. Qiu, J. Acoust. Soc. Am. 110, 3163–3168 (2001)]. New data show that fish recover relatively quickly from large temporary threshold shifts (TTS) after exposure to impulsive sounds, but take several days to recover from smaller amounts of TTS due to exposure to band-limited noise. Recent studies [e.g., J. J. Govoni et al., J. Aquatic Anim. Health. 15, 111–119 (2003)] also validate that peak sound pressure is not an appropriate metric for effects on nonauditory tissues, even if the peak level is negative. Large negative pressures have been thought to be more harmful due to swim bladder expansion, but there are no data to support this hypothesis. Physical injury correlates with a cumulative energy index, as has been found in terrestrial mammals [J. H. Stuhmiller et al., J. Biomechanics 29, 227–234 (1996)].
An experimental study for the penetration of sound into a rigid porous medium
Authors: Chang Hoyt , Li Kai Ming
Published: September 2008

In a recent study, a new analytic solution for computing the penetration of airborne sound into a rigid porous ground has been derived. Modeling the lower medium as a modified fluid, a simple analytic solution can be obtained that can be cast in a form analogous to the Weyl-van der Pol formula for the sound field in the upper medium. The current study is devoted to an experimental validation of the analytical model. A layer of glass beads is used in the experimental study for modeling the rigid porous ground. To test the analytical formulation, measurements of excess attenuation spectra above and within the layer of glass beads were conducted. The impedance, propagation constant, and the index of refraction of the glass bead aggregate were deduced from the excess attenuation spectra. The experimental results are compared with other methods for finding the propagation of the rigid porous medium. The proposed method suggests a new way of finding the propagation constant and the index of refraction of a rigid porous medium.
Refraction and attenuation of sound in a rigid porous medium
Authors: Li Kai Ming
Published: September 2008

An investigation was conducted to predict the penetration of sound into a ground surface irradiated from a point source located in the air above the air/ground interface. To simplify the analysis, the outdoor ground surface is treated as a modified fluid in which its acoustical properties are characterized by using a complex density and a propagation constant of the porous medium. By modeling the porous ground as a modified fluid, the physical phenomenon for the refraction of sound from the upper medium (air) to the lower medium (porous ground) has been explored. It has been shown from the mathematical analysis that the refracted path can be determined by Snells Law. The sound field can be formulated in an integral form for subsequent evaluations. Two approaches are used to calculate the integral, numerically predicting the total attenuation of sound in the porous medium. A numerically intensive scheme, known as the fast field formulation, and an analytical method known as the steepest-descents integration, are used to calculate the sound fields in the lower medium. Numerical results computed from both schemes agree well with each other over the practical range of interest.
Theoretical modeling of active seismic detection of shallow buried tunnels
Authors: Küsel Elizabeth T. , Andrews Mark , Ratilal Purnima
Published: September 2008

Low-frequency seismic waves are widely used to detect oil/gas reservoirs, and study the properties of Earth’s interior. Here, we investigate the application of low-frequency active seismic waves (tens of Hz to a couple of hundred Hz) for long-range wide-area detection of shallow underground tunnels. The main objective is to image wide areas of the ground at the longest possible ranges to identify potential underground tunnel hotspots. The tunnel is modeled as a circular air-filled cylinder. The incident field at the tunnel is calculated in terms of the horizontal (u) and vertical (w) displacements by the elastic parabolic equation. The scattered field from the tunnel is modeled by application of Green’s theorem, approximating the radial dependence of the scattered field by the Hankel function, and satisfying the boundary conditions. Compressional and shear waves scattered from the tunnel will be calculated to determine which wave type is most suitable for detection purposes. Scattered field levels from the tunnel will be compared with seismic ambient noise and reverberation from surrounding medium heterogeneities. Tunnel detection ranges will be quantified as a function of tunnel diameter and length, seismic wave frequency, receiving array length and orientation, and medium properties.
Directivity pattern of footstep sound at ultrasonic frequencies
Authors: Ekimov Alexander , Sabatier James M.
Published: September 2008

The human footstep generates broadband frequency sound in air due to friction forces between the foot and the ground surface. An ultrasonic (25–26 kHz) footstep signal was measured on the ground at a distance of 17 m from the walker. Another aspect of footstep sound characterization is a directivity pattern. The sound wavelength at those frequencies corresponds to 13–14 mm, which is much less than the source size (the area of sound generation is approximately the size of a foot, 300 mm×120 mm). The results of the experimental investigations are presented and discussed. An analysis of test results shows that the directivity pattern of footstep sound has inhomogeneous dependence on the azimuthal angle. A maximum value of the pattern corresponds to the direction of walking, while the minimum value is in the opposite direction. [Work supported by Department of the Army, Army Research Office Contract No. W911NF-04-1-0190.]
Are there systematic movements of poles/zeros with sound source location for pole/zero models of acoustic directional transfer functions?
Authors: Al-Sheikh Bahaa , Matin Matin , Tollin Daniel
Published: September 2008

Humans and animals locate sound sources using three main acoustical cues: Interaural time (ITD) and level (ILD) differences and monaural spectral shape cues. The cues are generated by the spatial- and frequency-dependent filtering of the propagating sound waves by the torso, head, and external ears. These acoustic transformations can be captured in measurements of the directional transfer functions (DTFs), the directional components of the head related transfer functions (HRTFs). A set of DTFs can be used to create a virtual auditory environment by presenting over headphones arbitrary sounds filtered with DTFs. DTFs are generally measured at finite locations in azimuth and elevation, so models are needed to synthesize DTFs for source locations not measured. Here, we investigated the use of different pole/zero models with different orders to model DTFs measured in humans and cats. With models that successfully characterized the DTFs with little error, we examined the systematic movements of the poles/zeros in the unit circle with changes in source azimuth and elevation. The ultimate goal of this research is to find a simple relationship between the movements of the poles/zeros with source location. [NIH Grant No. R01-DC6865.]
A study on the input-output function of a nonlinear cochlear transmission-line model with the function of an outer hair cell model
Authors: Murakami Yasuki , Unoki Masashi
Published: September 2008

A nonlinear cochlear transmission-line model with the physiological function of an outer hair cell (OHC) model is presented to investigate how OHCs produce the nonlinearity in the input-output (IO) functions of cochlear filtering. As the physiological function of the OHC model, the pressure produced by the somatic motility of the OHCs was studied. The somatic motility is induced by the transducer currents that change with the displacement of the hair bundle. The pressure produced by the OHC model can be linearly approximated by the amount of current. The proposed model is comprised of a middle ear model and a cochlear transmission-line model, which includes a basilar membrane and lymph fluid model, a tectorial membrane model, hair bundles model, and the OHC model. The model’s parameters were set as estimates for a human obtained from animal data. In simulation results, this model could account for the IO functions of cochlear filtering obtained from both physiological and psychological experiments. These results suggest that the somatic motility of the OHCs, which depends on the transducer currents, produces the nonlinearity in the IO functions of cochlear filtering.
Does Norwich’s entropy theory of perception produce equal-loudness contours?
Authors: Nizami Lance
Published: September 2008

Norwich & Wong [Percept. Psychophys. 59, 1997; derived backwards in JASA, 97, 1995] modeled loudness L versus intensity I by L(I,k,γ,Ith,n)=(k/2)ln(1+γ(I/Ith)n). They assumed Lth=L(Ith) and L=L−Lth, producing two loudnesses, L or L=L−Lth, giving L(Ith)=Lth or 0, and L(0)=0 or (−k/2)ln(1+γ), a negative. They took dL/dI, called it ΔL/ΔI, and rearranged it, giving ΔI/I(ΔL,k,γ,Ith,n). New terms S∞(ΔL,n,k) and S0(ΔL,n,γ,k) were introduced, thus γ=S∞/(S0−S∞). The result was ΔI/I in S∞, S0, and n, identical to an equation of Riesz (Phys. Rev., 31, 1928). Riesz’s empirical S∞, S0, and n provided γ’s and n’s for L(I)=L(I,k,γ,Ith,n)−(k/2)ln(1+γ). Assuming k was constant, Norwich & Wong equated L(I)’s for comparison and reference tones, generating equal-loudness contours. The contours contradicted empirical ones; to adjust, they replaced Riesz’s n by Stevens’ Index, x. The present author curvefitted the Entropy Equation and Stevens’ Law to 37 loudness-growth plots. k depended on maximum loudness as k=0.173Lmax1.41 n≠x, rather, n=0.123+1.215x. Altogether, the derived contours are invalid. a)Research done at Univ. of Toronto in Mississauga, 3359 Mississauga Rd. N., Mississauga, ON, Canada.
Tonotopic map reorganization and spectral weights in high-frequency sensorineural hearing loss
Authors: Espinoza-Varas Blas , Akram Hammad , Oleyadun Titus , Jang Hyunsook
Published: September 2008

Owing to reduced afferent input from high characteristic-frequency hair cells, high-frequency sensorineural hearing loss (SNHL) reorganizes the tonotopic maps in the central auditory nervous system: Map expansion is observed in the midfrequencies and map contraction in the high frequencies. Does the relative weighting of mid and high frequency information depend on this reorganization? With complex tones consisting of a 1,000- and a 3,127-Hz sinusoid, 80 and 60 ms each, the resolution of simultaneous increments in frequency (IF) at 1,000 Hz and in duration (IT) at 3,127 Hz was studied in participants having either normal hearing or moderate-to-severe SNHL above 2,000 Hz. In both groups, the sensation level at 1,000 Hz (1.5–8 dB) was 17–38 dB lower than at 3,127 Hz (25–39 dB). In normal-hearing participants, IF resolution was inferior to that of IT, suggesting stronger weighting for the more audible component. In hearing-impaired participants, IF resolution was superior or equal to that of IT, suggesting stronger weighting for the lower sensation level 1,000-Hz component impinging on the expanded tonotopic map region; in addition, IT resolution improved significantly following extensive training. [Work supported by PHF and NIH grants.]