bluuebunny/crossref_metadata_2025 huggingface dataset:
Categories of repeatability and reproducibility in acoustical laboratories
Authors: LoVerde John J. , Dong David W.
Published: May 2015

There are many categories of variability in acoustical laboratory testing. The repeatability of acoustical testing is generally defined based on repeated testing of the same assembly in the same laboratory and conditions over a short time period, while the reproducibility is based on testing a (nominally identical) assembly in a different laboratory. However there is a spectrum of uncertainties between these points. The authors previously documented “long term repeatability,” the repeated testing of the identical specimen in the same laboratory with the same equipment and operator, but over an extended time period [J. Acoust. Soc. Am. 130, 2355 (2011)]. The current study examines the “long term rebuild repeatability,” a nominally identical assembly rebuilt in the same laboratory over a long time period. The results are compared with previously measured variability, and the implications for manufacturers and designers are discussed.
Simple mechanical model reproduces complex calls in a fish vocal system: Implications for the evolution of vertebrate acoustic communication systems
Authors: Rice Aaron N. , Han Sang Min , Land Bruce R. , Bass Andrew H.
Published: May 2015

A mathematical model has been developed for vocalizations of the three-spined toadfish (Batrachomoeus trispinosus) and the plainfin midshipman (Porichthys notatus); acoustically active fish species that have served as model systems for studying acoustic communication mechanisms among vertebrates. The toadfish has a vocal organ comprised of a pair of bilaterally separated swim bladders that generate acoustic nonlinearities similar to those found in tetrapods. Midshipman have one swim bladder with sounds lacking the nonlinearities. We modeled the toadfish mechanism as a system of two harmonic oscillators coupled with a tendon-like string, and the midshipman one by the same system without the coupling. The coupling in the toadfish model, along with nonlinear oscillator position and velocity dependent terms, generates signatures of nonlinearity such as deterministic chaos and bifurcating harmonics. The system generates sounds that simulate naturalistic calls of both toadfish and midshipman depending on the input parameters. We built an optimizer to minimize the difference between the power density spectra of the simulated call and an empirical recording. We successfully computed optimal toadfish and midshipman calls and simulated transection experiments, together leading to a deeper understanding of the diversity of vertebrate vocalization mechanisms. [Research support from Rawlings Cornell Presidential Scholars and NSF IOS 1120925.]
Measuring rapid adaptation to complex acoustic environments in normal and hearing-impaired listeners
Authors: Aspeslagh Sofie , Clark Fraser , Akeroyd Michael A. , Brimijoin W. O.
Published: May 2015

Listeners can move from room to room while conversing, encountering changes in the acoustics of their surroundings. In order to maintain speech intelligibility when faced with changing noises and reverberation listeners may rapidly adapt by building and updating a model of their surrounding auditory space. We have previously demonstrated rapid adaptation to a change in the acoustic environment, consisting of a brief decrease and then a recovery in intelligibility. In the current study we investigated whether the amount and time-course of this adaptation changes as a function of age and/or hearing impairment, and whether the amount of reverberation or the complexity of the background noise would affect adaptation time. We asked 29 normal-hearing and 37 hearing-impaired listeners to identify an ongoing stream of random target words, presented at a rate of one every 1.5 seconds, while the acoustic environment was switched every nine seconds. On average, intelligibility dropped by 16% upon entering a new environment before recovering to ceiling performance within 2.3 seconds. These results were not affected by hearing impairment or age. Preliminary analyses suggest that listeners may require additional time to adapt noises of greater complexity. [Work supported by MRC (U135097131) and the Chief Scientist Office (Scotland).]
Virtual auditory display validation using transaural techniques
Authors: Zahorik Pavel , He Zijiang J.
Published: May 2015

Validation of headphone-based virtual auditory display technology is inherently difficult, given the potential for display hardware to interfere with normal sound field listening conditions due to occlusion of the pinna. This difficulty is eliminated if loudspeaker-based transaural techniques are instead used for the virtual auditory display. Transaural techniques also offer the advantage of being able to use the display loudspeakers, or other additional loudspeakers, as individual reference locations in order to validate the display under natural listening conditions in the same sound field. Such validation can also include explicit comparison to visual localization of the sound sources. In this way, the accuracy and precision of virtual source localization can be directly compared to real source localization, and optionally to visual localization. Results of a validation experiment of this type using non-individualized head-related transfer functions are reported and compared to analogous data from a headphone-based virtual auditory display. [Work supported by NEI.]
Using multidimensional scaling techniques to quantify binaural squelch
Authors: Ellis Gregory M. , Zahorik Pavel , Hartmann William M.
Published: May 2015

Binaural squelch is a perceptual phenomenon whereby the subjective strength of reverberant sound is attenuated under binaural listening conditions relative to monaural or diotic listening conditions. Although the effect is well known, only a few studies have explicitly quantified the effect and all used uni-dimensional objective measures such as word recognition or echo detection. Here, multidimensional scaling techniques were used to more directly quantify the perceptual attributes of binaural squelch. In a series of experiments, listeners were asked to rate the perceptual similarity between pairs of sound sources that varied in distance (1–12 m), level (±3 dB), and presentation mode (binaural versus diotic). Sounds were presented using virtual auditory space techniques to simulate sound-field listening to a frontal source in a reverberant room (broadband T60 = 2 s) and in anechoic space. The source signal was a brief sample of speech from a female talker. Multidimensional scaling (INDSCAL) results revealed that effects of binaural squelch are most evident on a perceptual dimension strongly related to the ratio of direct-to-reverberant sound energy, although individual differences were observed. Additional effects, unrelated to sound level, were also evident on a second perceptual dimension.
Influence of ground impedance on the sound radiation of a railway sleeper
Authors: Zhang Xianying , Squicciarini Giacomo , Thompson David J.
Published: May 2015

A railway track consists of rails attached to sleepers (cross ties) which are laid in ballast. The sleeper provides support for the rail and transfer loads to the ballast and subgrade. Due to the wheel/rail interaction the rail is induced to vibrate and this vibration is transmitted to the sleepers; both the rail and the sleepers radiate sound. Existing models used to predict the sound radiation from the sleeper consider this to be completely embedded in a rigid ground; in reality, however, the sleeper is surrounded by, or embedded to some extent, in the ballast. It is therefore necessary to take these conditions into account in order to obtain a more realistic model. This paper investigates the influence of the ground in close proximity to the sleeper on its sound radiation. A 1/5 scale concrete sleeper is analyzed by using the boundary element method in 3-D. Ground absorption is introduced in terms of its acoustic impedance using the Delany-Bazley model and its effects on the sleeper radiation are predicted. Finally, the numerical results are validated by experimental results using a 1/5 scale model.
Microphone cross-array beamformer processing to reduce noise and reverberation
Authors: Elko Gary W. , Meyer Jens , Backer Steven
Published: May 2015

Hands-free audio communication systems that are designed to allow audio and speech communication between remote parties are known to be sensitive to room reverberation and noise when the source is distant from the microphone. A common solution to the problem of room reverberation is to use an array of microphones to spatially filter the acoustic field. The maximum array gain is only attainable with specific microphone geometries and the gain of realizable microphone arrays is typically significantly lower than the maximum. The algorithm described in this talk attempts to address the rather slow growth in linear processing directional gain as a function of the number of microphones. One possible approach to attain higher directive gain is to use a processing scheme based on nonlinear multiplicative processing. An obvious candidate is the coherence function since it is a bounded and normalized multiplicative measure. A technique is presented for reverberation reduction processing using at least two beamforming microphones and a function of the estimated short-time coherence between the beamformer outputs. Each beamformer should have a different directional response or spatial position, or both, but with overlapping responses in the direction of the desired source.
Study and design of robust differential beamformers with linear microphone arrays
Authors: Benesty Jacob , Chen Jingdong , Pan Chao , Zhang Hao
Published: May 2015

Differential beamformers can generate frequency-invariant spatial responses and therefore have the great potential to solve many broadband acoustic signal processing problems such as noise reduction, signal separation, dereverberation, etc. The design of such beamformers, however, is not a trivial task. This paper is devoted to the study and design of differential beamformers with linear array geometry. The objective is to design robust differential beamformers that can form frequency-invariant beampatterns. The major contribution consists of the following aspects. (1) It discusses a general approach to the design of linear DMAs that can use any number of microphones to design a given order DMA as long as the number of microphones is at least one more than the order of the DMA. (2) It presents a method that can maximize the white noise gain with a given number of microphones and order of the DMA; so the resulting beamformer is more robust to sensor noise than the beamformer designed with the traditional DMA method. (3) It discusses how to use nonuniform geometries to further improve robustness of differential beamformers. (4) It investigates the possibility to improve the robustness of differential beamformers with the use of the diagonal loading technique.
Experimental verification of a Fisher Information Model for azimuth estimation in broadband active sonar
Authors: Ryan Colin J. , Buck John R. , Kloepper Laura N.
Published: May 2015

Bats easily identify targets of interest and reject clutter in the wild. A bat's transmit and receive beampatterns are frequency dependent, so it is possible that they exploit spectral cues to distinguish on-axis targets from off-axis clutter. The frequency dependent beampattern can also be interpreted as a different lowpass filter for each angular arrival. Given the known transmitted signal, the angle of arrival can be estimated from the high frequency attenuation in the received signal. The broadband Fisher information (FI) for azimuth in active sonar predicts a maximum FI at a slightly off-axis location, suggesting bats might target their sonar beam askance of a target to maximize the precision in estimating azimuth. This paper tests the FI model in a laboratory with a baffled tweeter as the sonar transmitter and an omnidirectional receiver. The experimentally measured beampatterns are used in Monte Carlo simulations with a maximum-likelihood estimator for azimuth over a range of SNR. The experimental results gained from the laboratory tests are compared with the model to assess the agreement between the predicted azimuth of maximum FI and the observed azimuth minimizing experimental error variance. [Funded by UMass Dartmouth Office of Undergraduate Research, College of Engineering, and ONR.]
Developing an audio network system for teleconferencing with evaluation of audio quality
Authors: Lim Hansol , Jang Hyung Suk , Imran Muhammad , Jeon Jin Yong
Published: May 2015

A teleconference system was developed to transmit speech signals for audio communication with remote users. The hardware system was composed of 3-D microphone arrays to capture directional sound and a wireless headset to provide freedom of movement for users. An application programming interface (API) was used for interaction between the computer and the audio devices, including the microphone, headphone, and ADDA converter, transferring input/output audio signals in real time through the network. For the evaluation of the system, a latency test was performed with a simultaneous recording system in capturing and reproduction positions. The latency from the network procedure was calculated with different buffer sizes, and the lower-delay and smaller-deviation buffer was selected. In addition, the transmitted audio signals were compared with the input signals in terms of signal patterns and frequency responses. The resulting audio qualities in the time and frequency domain were suitable for a teleconferencing system.
Ultrafast frame rate microscopy of microbubble oscillations: Current studies employing the UPMC-Cam
Authors: Helfield Brandon , Chen Xucai , Qin Bin , Villanueva Flordeliza
Published: May 2015

Ultrasound-stimulated microbubbles are clinically employed for diagnostic imaging and have been shown to be a feasible therapeutic strategy for localized drug and gene delivery applications. In order to investigate microbubble oscillation dynamics, the University of Pittsburgh Medical Center has developed the UPMC-Cam—an ultrafast imaging system capable of recording 128 frames at up to 25 million frames per second, one of only two in the world currently in use. Current studies include elucidating the effect of fluid viscosity on microbubble behavior. At lower pressures (0.1–0.25 MPa), an increase in fluid viscosity from 1 to 4 cP alters the fundamental and second-harmonic oscillation amplitudes in a bubble size-dependent manner, related to resonance. At higher pressures (0.5–1.5 MPa), a significant decrease in the propensity for microbubble fragmentation was observed in the more viscid fluid environment. Additionally, studies aimed at gaining physical insights into sonoporation have been conducted in which individual bubbles lay adjacent to a cell monolayer. These studies have revealed a maximum microbubble expansion threshold above which sonoporation occurs, likely related to the associated shear stresses exerted by a microbubble on the adjacent cell membrane. The UPMC-Cam has shown to be an invaluable tool for investigating biophysical-related phenomena over a wide range of ultrasound-microbubble applications.
Heat and mass transfer effects on forced radial oscillations in soft tissue
Authors: Barajas Carlos , Johnsen Eric
Published: May 2015

Cavitation has a vast array of biomedical purposes such as histotripsy, used to mechanically fractionate soft tissue. Alternatively, cavitation can cause unwanted biological damage in diagnostic ultrasound, e.g., when using ultrasound contrast agents. These benefits and harmful effects make it desirable to develop models to better understand cavitation in viscoelastic media. We numerically model cavitation in a viscoelastic (Kelvin-Voigt) medium using the Keller-Miksis equation to describe the radial bubble motion. We specifically focus on the effects of heat and mass transfer, through numerical solution of the full energy and mass equations, reduced models, and theoretical analysis. We will discuss how thresholds on the driving pressure and frequency where thermal and mass transfer effects become significant can be determined, as well as ranges of amplitudes for which reduced models can be used accurately. We will also present theoretical investigations on how oscillation properties depend on these effects. Our findings will provide guidelines to determine regimes when heat and mass transfer are dominant. [This work was supported in part by NSF grant number CBET 1253157 and NIH grant number 1R01HL110990-01A1.]
Microbubble behavior during long tone-burst ultrasound excitation
Authors: Chen Xucai , Wang Jianjun , Pacella John , Villanueva Flordeliza S.
Published: May 2015

Ultrasound-microbubble mediated therapies have been investigated to restore perfusion and enhance drug/gene delivery, using both short (~μs) and long (~ms) ultrasound tone-bursts. Microbubble oscillation behavior can be observed with ultra-high speed microscopy; however, due to the high frame rate required and limited number of frames available, microbubble dynamic behavior can only be observed for a few acoustic cycles (~μs). In this report, the fate of microbubbles throughout long tone-burst ultrasound exposures (5 ms) was explored via direct microscopic optical observation in conjunction with passive cavitation detection, over a range of acoustic pressures (0.25, 0.5, 1.0, and 1.5 MPa) and microbubble concentrations (2e6, 2e7, and 2e8 MB/ml). The ultrasound system was triggered from UPMC Cam, the ultra-high speed camera system at the University of Pittsburgh Medical Center, such that microbubble activity at various time points (0–5 ms) within the long tone-burst was captured. Microbubbles first underwent stable or inertial cavitation depending on the acoustic pressure used, and then formed gas-filled clusters that continued to oscillate, break up, and form new clusters. Cavitation detection confirmed continued, albeit diminishing acoustic activity throughout the 5 ms ultrasound excitation. This discovery suggests that persisting cavitation activity during long tone-bursts may confer additional therapeutic effect for ultrasound-microbubble mediated therapies.
High-frequency scattering from a sand sediment with an overlying mud layer
Authors: Hefner Brian T. , Ivakin Anatoliy , Jackson Darrell R.
Published: May 2015

In the spring of 2014, multibeam echo sounder time series data were collected in St. Andrew’s Bay, FL, in an area of the bay where the sand sediment was covered by a mud layer. As part of the environmental characterization at the experiment site, the In-Situ Measurement of Porosity (IMP2) system collected conductivity probe data 25 cm into the seabed along 3 m tracks. The mud layer appears clearly in the conductivity probe data and had a mean thickness of 13 cm. The roughness power spectrum of the sand/mud interface was 10–20 dB higher than that of the mud/water interface and, more significantly, was 5–10 dB higher than that of sand/water interfaces measured in the Gulf of Mexico during the Target and Reverberation Experiment 2013. The mud layer appears to be preserving the roughness of the sand interface, an effect observed during the Sediment Acoustics Experiment in 2004 following the passage of Hurricane Ivan. The impact of both the increased roughness and the presence of the mud on 180–420 kHz scattering will be assessed through data/model comparisons using the sediment properties measured at the experiment site. [Work supported by ONR and SERDP.]
Comparison of headphones for audiometric screening and hearing protector fit-testing
Authors: Byrne David C. , Schmitt Laura , Murphy William J.
Published: May 2015

Accurate hearing screening in hearing loss prevention programs is entirely dependent upon sufficient isolation of the subject from any surrounding noise as well as adequate acoustical performance of the headphones that are used. Assessment of hearing protector attenuation by newly developed individual fit-test systems uses many elements borrowed from standard audiometric testing. To assess the suitability for this type of testing, the National Institute for Occupational Safety and Health evaluated the attenuation characteristics, maximum output levels, linearity, and total harmonic distortion of three different circumaural headphones: the FitCheck headphone with a TDH-39 driver, the Sennheiser HDA-200, and Sennheiser HDA-300 headphones. Attenuation measurements were obtained with a laboratory-based real-ear attenuation at threshold system, and the electroacoustic measurements were conducted on a standard IEC318 coupler. The long term goal of this effort is to determine whether attenuation differences or the performance characteristics of the different styles of headphones affect the resulting earplug attenuation values when measured with an earplug fit-test system.
Publish or perish and funding or failure—The dark side of a career in academia
Authors: Muehleisen Ralph T.
Published: May 2015

A career in academia can be extremely rewarding. It can be intellectually stimulating, financially rewarding, provide an extremely flexible work schedule, and give an opportunity for one to truly impact the world in a positive way. But, there is a dark side to academia that one should be aware of before jumping in. Academia can also be full of petty and insignificant politics, enormous egos, and unrealistic expectations. Perhaps the darkest side relates to the need to “publish or perish” and “find funding or fail” that can be found at many research universities. This presentation will provide an honest discussion of the ups and downs of academia from someone who found both success and failure.
Tonal noise in heating, ventilation, and air-conditioning equipment in commercial and residential buildings
Authors: Eichelberger Curtis , Bender James E. , Bauch Paul F. , Giraud Jarom H.
Published: May 2015

All heating, ventilation, and air-conditioning (HVAC) equipment that moves air or compresses refrigerant produces noise with tonal content. The challenge for the equipment manufacturer and building designer is to make sure that this tonal noise is isolated from the occupied spaces in a building. This paper provides an overview of the tonal content in airborne and structureborne sound produced by heating, cooling, and ventilation equipment. Examples of the tonal noise in HVAC components and packaged equipment will be presented. The challenge to manufacturers in measuring and rating equipment sound will also be covered. An overview of methods for testing and rating HVAC equipment sound will be presented, with emphasis on the uncertainty in characterizing the tonal content.
Front-back confusions when sources and listeners rotate
Authors: Yost William , Zhong Xuan
Published: May 2015

Tonal stimuli presented from directly in-front or directly in-back of a stationary listener are often miss-located in that sounds presented from in-front are occasionally perceived as being in-back of the listener; and often sounds presented in-back of a listener are perceived as being in-front. These types of front-back/back-front confusions in the azimuth plane were investigated as a function of the type of stimuli (e.g., tones, speech, and wideband noise) used and as a function of the sound or listener rotating around an azimuthal 24-loudspeaker array. Front-back confusions/back-front confusions depended on the type of stimulus; and on the number of loudspeaker positions the sound rotated through and the rate of sound or listener rotation. For example, if the sound rotated through two loudspeakers from in-front to in-back, there were a large number of confusions; if the sound rotated through each of the 24 loudspeakers on the circular array there were almost no confusions. [Research supported by an AFOSR grant.]
Perceptual effects of update-delay in room auralization
Authors: Clapp Samuel W. , Seeber Bernhard U.
Published: May 2015

A real-time auralization system, permitting sources and receivers to move about a simulated acoustic space, offers the opportunity to study auditory perception in realistic listening scenarios. However, such a system requires substantial computing resources to achieve the low latency needed for the simulation to adjust to new conditions without introducing artifacts. To use computing resources most efficiently from a perceptual standpoint, the perceptual effects of the simulation update delays must be understood. Simulated early reflections are typically determined via the image source method. When the source or receiver moves, the positions of the image sources relative to the receiver must be updated, with higher orders requiring longer calculation times. The aim of this study is to examine the perception of sound sources in simulated reverberant rooms when a source moves to a new position with only a partial update of image source locations. The parameters tested are perceived localization and apparent source width, as a function of the highest order of image sources updated and the distance traveled by the moving source. The results are meant to aid designers of real-time auralization systems by providing a perceptual basis for the necessary update rates for image source locations. They also aim to provide insight into the perception of auditory images that are incongruous with a real room, where there is a dissociation between source and reflection positions. [Funded by BMBF 01 GQ 1004B.]
Reconstructing excitation forces acting on a baffled plate using near-field acoustical holography
Authors: Zhou Pan , Wu Sean F. , Li Wanyou
Published: May 2015

This paper presents numerical simulations of using nearfield acoustical holography technology to reconstruct the excitation forces acting on the surface of a baffled plate. The reason for choosing a baffled plate is that analytic solutions to the vibration responses and acoustic radiation are readily available. To acquire a better understanding of the interrelationship between excitation forces and vibro-acoustic responses of the plate, the structural intensities and power flows due to individual excitation forces and their interactions are calculated. The relative contributions of the excitations toward overall structural vibration responses of the plate are analyzed by taking the normal modes transform into the wavenumber domain. Results show that the wavenumber contents of vibration responses of a plate due to a line, point, and distributed forces have very distinct characteristics. Therefore, by analyzing the vibration responses in the wavenumber domain, it is possible to reveal the impacts of individual excitation forces on the resultant structural vibration of a plate.
Ken Stevens’ influence on the development of paradigms for speech synthesis
Authors: Story Brad H.
Published: May 2015

Synthetic speech has long been used as a means of understanding both speech production and speech perception, as well as for technological applications such as text-to-speech devices. Paradigms for developing speech synthesis systems have included electrical circuits, digital filters, and computational models that replicate either the structure or acoustic characteristics of the voice source and vocal tract. This presentation will focus on how Ken Stevens’ investigations of speech, spanning more than five decades, have directly influenced essentially every paradigm of speech synthesis, including formant synthesis, articulatory synthesis, and speech production modeling. [Work supported by NIH R01-DC011275 and NSF BCS-1145011.]
Decision-feedback equalizer based on channel estimation in the signal subspace
Authors: Yang Tsih C. , Huang San Ho
Published: May 2015

The performance of a channel-equalizer is determined by how well the equalizer knows about the channel. For a decision-feedback equalizer based on explicit estimation of the channel impulse response (CIR), the symbol soft-decision-error (SDE) can be directly linked to the channel-estimation error. Due to channel fluctuation and the presence of noise, conventional channel-estimation lacks the required accuracy to achieve minimal SDE (< −10 dB) for a single-receiver channel. One of the approach is to use spatial diversity, where the (effective) CIR for maximum-ratio combining of the multiple-channels, often referred to as the q function, is well-structured and behaved, and relatively accurately estimated. An alternative approach, as proposed in this paper, is to explore the signal subspace for a single-receiver channel, when the multi-paths are cross-correlated as in many underwater acoustic propagation channels. Since the signal occupies a small fraction of the total space, tracking the signal in the subspace has been shown to yield much smaller (by 10–15 dB) signal prediction error (the error between the received-data and predicted-data based on the estimated CIR) and SDE in the training mode. This paper extends the method to the decision mode for a semi-time invariant channel.
Improving headphone spatialization for stereo music
Authors: Usmani Muhammad Haris , Cepeda Ramón , Sullivan Thomas M. , Raj Bhiksha
Published: May 2015

Music is mixed and mastered for playback on near- and far-field speakers, which presents a problem to the growing population of listeners who listen to music primarily on headphones. Playing legacy stereo mixes on headphones places the stereo image inside the listener's head and makes the image appear ultra-wide. While this is helpful for separating the center and stereo content, it has a detrimental effect on the spatialization of the music. It makes headphone listening unnatural and uncomfortable, although listeners have learned to accept it. In this work, we develop a system that processes stereo signals to provide a better sound image to headphone listeners. The sound image is improved by adding the necessary cues to the signal so as to externalize the perceived soundstage by making it similar to the soundstage experienced inside a mixing studio. In order to work with all headphones, our system tries to maintain the mastering equalization curve of the original stereo content. We employ head-related transfer functions, de-correlation, models of reverberation, and 1/3-octave-band equalization to realize our system. The results of pilot subjective evaluations suggest that our system makes music more natural and comfortable to listen to, although with some loss of quality.
Multi-modal mapping of complex data using interactive visual and aural cues
Authors: Kuchera-Morin JoAnn C.
Published: May 2015

At the AlloSphere Research Facility at the University of California, Santa Barbara, our research encompasses multimodal mapping of big and complex data sets. Interactive visual and sonic cues are used to navigate through this complex information. Sonic cues are used to reinforce visual cues as well as used independently, depending on the nature and structure of the data being mapped. In this presentation, I will discuss various research projects and their different or similar mapping configurations depending upon the information being extracted form the data set. We have found that sonic representation is essential for expanding our field-of-view of a large and/or complex data set, as information outside of our visual field-of-view can be sonically represented, thus facilitating visual navigation to that area of the data.
Clay and Medwin: An intuitive approach to the math and physics
Authors: Badiey Mohsen , Stanton Tim
Published: May 2015

It is interesting to look back to the first encounter with a field that one would eventually make a career. This is frequently a combination of a mentor and some initial learning in an academic environment. Clarence (“Clay”) Clay and Herman (“Hank”) Medwin provided such an experience for numerous researchers in the field of ocean acoustics. Being active researchers and mentors, they published a sequence of two books, both entitled Acoustical Oceanography (1977 and the revised version in 1998), to introduce the field to those interested in using sound to remotely sense the oceans’ interior and boundaries. In addition to acousticians, readership includes marine biologists, geologists, and physical oceanographers. Although each book may look relatively simple at first glance, they present an intuitive approach to complex ocean acoustic problems with the right balance between physics, math, and real-world applications. There are also many references to more in-depth treatments of the topics. Each book provides a range of diverse topics including principles of underwater sound, sonar systems, signal processing, nonlinear acoustics, scattering from objects and creatures in the sea, the seafloor, acoustic waveguides, and many other subjects.
A historical perspective: Frank Andrews and acoustics at The Catholic University of America
Authors: Vignola Joseph F. , Ryan Teresa J. , Turo Diego , Guan Shane , Judge John
Published: May 2015

The Catholic University of America has a long history in the field of acoustics dating back to the 1930s. Some notable acousticians associated with Catholic University during the early development of the acoustics program there include Father Frances Fox, Karl Herzfeld, Theodore (Ted) Litovitz, among many others. Herzfeld and Litovitz are responsible for an enormous amount of pioneering work in the field of acoustic dissipation. Under the direction Litovitz, Acoustics moved from its original home in the Physics Department to Engineering in the early 1960s. Litovitz in turn recruited Frank Andrews. Andrews took the helm of acoustics at Catholic University and expanded the scope of the program from largely research focused to include a broader emphasis on both graduate teaching and developing the critical connection to practical Navy interests. This presentation will describe the history of acoustic research at Catholic University with a focus on Frank Andrews’ accomplishments and contributions to Catholic University and the acoustics community at large.
Diffusion and scattering: A critique of existing standards and data
Authors: Sauro Ronald
Published: May 2015

This presentation will look at the existing standards used to measure scattering and diffusion. It will point out scientific problems, unreasonable assumptions, and methodology problems in these standards. Scattering has been assumed to be a separate property of unevenly shaped materials, and therefore, a method was needed to “measure” this property. It will be pointed out that scattering is really a part of the sound absorption characteristics of materials, i.e., diffraction and can be measured as part of the sound absorption characteristic. Scientific problems and unreasonable assumptions in the standard will also be pointed out. Diffusion can be characterized by the directivity of the energy as well as the magnitude and phase of the energy radiating from the diffuser. The methodologies used to create diffusion can be described as geometric or diffractive. The existing standards do not measure the magnitude or phase of the radiated energy. The results derived from the existing standards approximate the energy losses using scattering and the directivity measured is only used to compare diffusers but cannot be used in acoustic simulation programs.
A design for a biomimetic dynamic sonar head
Authors: Caspers Philip , Fu Yanqing , Mueller Rolf
Published: May 2015

The biosonar system of horseshoe bats (family Rhinolophidae) has been shown to employ unusual dynamics upon the emission as well as the reception of the ultrasonic pulses. Non-rigid changes to the shapes of the noseleaves (emission baffles) as well as the outer ears (pinnae, reception baffles) have been demonstrated to affect the properties of the emitted and received ultrasonic signals. These effects have been found in the results of numerical simulations as well as experimentation with physical prototypes. In the present work, a next-generation prototype of a biomimetic sonar head inspired by horseshoe bats is being developed. The goals for this system are to create more comprehensive and life-like dynamic baffle shape geometries as well as a better acoustic coupling between the ultrasonic transducers and the time-variant baffle shapes. Particular attention has been paid to geometry of the transition between nostrils and the noseleaf baffle. A single biomimetic system that incorporates these dynamic emission and reception baffles will enable an experimental investigation of how these two dynamic stages could be used in an integrated fashion to enhance sonar performance in real-world sonar sensing scenarios.
Echolocation beam shape of the Risso's dolphin (Grampus griseus)
Authors: Smith Adam B. , Kloepper Laura , Yang Wei-Cheng , Huang Wan-Hsiu , Jen I-Fan , Nachtigall Paul E.
Published: May 2015

Studies have shown that echolocation signals of some odontocete species are projected in both single and sometimes vertically dual-lobed beam shapes. In this study, the echolocation beam of a Risso's dolphin (Grampus griseus) was measured from a captive individual ensonifying an underwater target. Clicks were recorded with an array of 16 hydrophones and the two dimensional beam shape was explored using frequency-dependent amplitude plots. Click source parameters were comparable to those already described for this species, while analysis revealed primarily single-lobed, and occasionally vertically dual-lobed, beam shapes. Center frequencies of click signals increased with increasing sound pressure level, while the −3 dB beam radius decreased with increasing center frequency. This study is the first to measure the beam shape of echolocation signals in G. griseus, which exhibits forms similar to those found in the bottlenose dolphin and false killer whale
Hot topics in speech communication: Acoustics of regionally accented speech
Authors: Fox Robert A. , Jacewicz Ewa
Published: May 2015

Pronunciation patterns of native speakers of American English vary across the country in a systematic way, being shaped in part by social and cultural factors in a particular geographic area. The detectable regional (or dialect) variation in speech can considerably alter speech recognition and perceptual processing. The intelligibility of regionally accented speech has its source in acoustic variation present in dynamic sound structures, which convey an unprecedented richness of acoustic phonetic details along multiple dimensions in space and time. The challenge for speech communication research is to understand which complex acoustic structures are essential in shaping auditory sensitivity to regional variation and which are coexistent and necessarily redundant. New directions in this research area include acoustic explorations of complex interactions among spectral, source, and temporal components whose unique balance is modified by regional and social influences. Recent advances in these acoustic explorations will be presented.
A full double tuba in F/BBb
Authors: Young Frederick J.
Published: May 2015

Described here is a design for an F/BBb tuba. The valves and keys needed for a full double tuba take a lot of space. There exists a full and complete double tuba in BBb/EEE built on a very large instrument frame and is more than 5 feet tall and 2 feet wide [1]. However, the sizes of F tuba frames are too small to accommodate 5 double and 2 switch valves and their associated tubing. Using a standard F tuba frame, the lack of space has been solved by having four double valves and two switch valves. The fourth double valve is unusual because it is descending on the F side and ascending on the BBb side of the instrument. An ascent to a BB □tuba is made by the ascending part of that valve. The valve slide lengths have been optimized to yield intonation such that −5< intonation error < 5 cents over a five semitone descent from an open note. Various acoustic measurements are reported for the instrument which will be exhibited. [1] F. J. Young, “Five valve compensating brass wind instrument,” Proc. Meetings Acoust. 11, 035004 (2011).
The impact of anthropogenic noise on wetland habitats
Authors: Hopson-Costa Adrienne , Antonioli Regis , Crispim da Fontoura Julia , de Szalay Ferenc
Published: May 2015

Impacts of anthropogenic noise is an important but poorly studied aspect of wetland ecology. Many aquatic animals use sound to attract mates, coordinate movements, defend territory, and detect predators. However, anthropogenic noise (e.g., from boat or automobile motors) are increasingly important in wetlands. Therefore, it is important to understand how anthropogenic noise pollution affects these habitats. I sampled wetland soundscapes in urbanized and rural areas in northeastern Ohio, and used Raven software to analyze the data. Above the water line, average sound power was 38.9db–73.9db, which was similar to below the water line (48.6db–78.5db). Frequencies in the band 0–5 kHz had the highest overall power both above and below the water. One of the most urbanized sites had above/below readings as high as 83.9/79.3 dB. In comparison, one of the most rural sites had readings as low as 47.6/66.8 dB. At both urbanized and rural sites, the 0–5 kHz band had the highest overall power. I further tested if wetland invertebrates could be impacted by anthropogenic sounds. I found that Procambarus acutus crayfish produced audible clicks (frequency range 6 kHz–45 kHz, average power 69–73.5 dB). Ongoing laboratory research is testing if motorboat noise affects P. acutus behavior and sound production.
Bayesian inverse analysis of multilayer acoustic porous media
Authors: Fackler Cameron J. , Horoshenkov Kirill V. , Xiang Ning
Published: May 2015

Porous materials provide sound absorption and noise control in various applications. In many scenarios, different porous materials may be combined into multilayer absorbers to enhance the absorptive properties. We apply the Bayesian inference framework to analyze such multilayer porous materials, developing a method to determine simultaneously the number of constituent layers as well as the physical properties of each layer in a multilayer porous material. The model-based analysis combines a measurement of the acoustic surface impedance or absorption coefficient of a potentially multilayered material sample with a transfer-matrix formulation of multilayer porous material acoustic propagation models. For each sample to be analyzed, the number of layers considered in the propagation model is varied, and Bayesian evidence is computed for each case. Selecting the model with the highest evidence parsimoniously determines the number of layers present in the sample. Once the number of layers has been determined, Bayesian parameter estimation inversely determines the physical properties of each layer by estimating the input parameters of the multilayer propagation model. The proposed method automatically determines the number of layers and physical parameters of a multilayer material without any a priori knowledge of these values.
Acoustical field and vibration in hearing aid devices
Authors: Salameh Michael
Published: May 2015

One of the main considerations in the hearing aid design is the feedback from the receiver (speaker) to the microphone. Transducer characteristics, mechanical design, material properties, and test setup are among the factors that affect the feedback in hearing aid devices. Characterizing the vibration and the acoustical field generated from different components of the hearing aid device is one of the main challenges in the feedback study and control. In this paper, the acoustical field and the vibration in a hearing aid device are evaluated. Simulation and measurement data are presented and analyzed.
Resonant ultrasound spectroscopy with large attenuation and arbitrary geometry
Authors: Remillieux Marcel , Ulrich TJ , Le Bas Pierre-Yves
Published: May 2015

Resonant ultrasound spectroscopy (RUS) is a powerful and established technique for measuring material properties. The first step of this technique consists of extracting resonance frequencies and attenuations from the vibrational frequency spectrum measured on a sample with free boundary conditions. An inversion technique is then used to retrieve the elastic tensor from the measured resonance frequencies. As originally developed, RUS has been mostly applicable to (1) weakly attenuating media where each resonance frequency can be clearly identified and (2) relatively simple geometries where analytical solutions exist. In this presentation, the possibility of using RUS in a highly attenuating medium and on a sample of arbitrary geometry is explored. The Kumaresan-Tufts algorithm is used to fit a sum of exponentially damped sinusoids with closely spaced frequencies to the measured frequency spectrum. The inversion of the elastic tensor is achieved with a genetic algorithm, which allows searching for a global minimum within a discrete and relatively wide solution space. The accuracy of the proposed approach is evaluated against numerical data for which the solutions are known a priori. [This work was supported by the U.S. Dept. of Energy, Fuel Cycle R&D, Used Fuel Disposition (Storage) campaign.]
“Negative” acoustic signal propagation in a media with resonant density and compressibility response functions
Authors: Burov Valentin , Dmitriev Konstantin , Sergeev Sergei
Published: May 2015

The properties of acoustical double-negative media strongly depend on the frequency of a propagating wave. Particularly, the effective density and compressibility of a medium can be negative only at the certain frequency band. So it is very important to consider nonstationary processes in such media. The numerical simulations of the medium characterized by resonant-type density and compressibility response functions was performed in the article. It was based on the deduced matrix equation of a Lippmann-Shwinger type. The layer of “resonant” medium was placed inside an infinite background with constant density and compressibility. The incident impulse had a gauss form modulated by a certain carrier frequency. The effective density and compressibility of the layer change from both positive to both negative values while the impulse propagates through it. The phase velocity also becomes negative and the group velocity remains positive satisfying the causality principle. In the case of long enough impulse duration the layer behaves like it is made of a double-negative medium.
Comparisons between the preferences of musicians and non-musicians in response to varying room acoustics using two different testing methods
Authors: Lawless Martin S. , Vigeant Michelle C.
Published: May 2015

Although the brains of musicians and non-musicians differ both on an anatomical and functional level, these groups tend to experience similar emotions in response to the same, unaltered musical excerpts (Bigand/Poulin-Charronnat Cognition 2006). Contrarily, preliminary results of the authors and colleagues suggest that the two groups have diverse preferences when presented with the same excerpt convolved with different room conditions. A more comprehensive investigation was conducted to determine differences in preference between musicians and non-musicians in response to stimuli of with different reverberation times, ranging from anechoic to very reverberant. Room acoustics models were used to create auralizations for a number of motifs. Subjects initially rated the stimuli in terms of overall preference, followed by rating their perception of reverberance. Two distinct subjective testing methods, successive and comparative, were utilized and compared. The successive method required the participants to rate each stimulus separately in succession, while the comparative method allowed the subjects to compare and rate each stimulus within a set with the rating scale for each stimulus on one screen. The comparison between methods was performed to validate future testing conducted with the same stimuli in more constrained settings, specifically in a functional magnetic resonance imaging (fMRI) scanner.