bluuebunny/crossref_metadata_2025 huggingface dataset:
Rumble strip sound level evaluation—Comparison of three designs
Authors: Braslau David , Terhaar Edward
Published: May 2015

Results of sound level monitoring from three types of longitudinal rumble strips installed along the edge of two-lane rural roads are discussed. This study was in response to objections by landowners about unwanted noise caused by vehicles traveling over rumble strips. The ultimate study goal is to provide maximum tactile and tonal sound levels at the driver position while minimizing exterior sound levels. Both exterior and vehicle interior sound levels were measured for three longitudinal edge-of-pavement rumble strip designs—California, Pennsylvania, and Minnesota. Simultaneous digital audio files were also recorded. Three vehicles types were tested at 30, 45, and 60 mph. Comparison of exterior levels and interior sound levels showed that the Pennsylvania design is the quietest, both interior and exterior. Interior levels from the Minnesota and California designs are similar but exterior levels are higher for the Minnesota design. The California design generates two tonal peaks. The Minnesota design generates only one higher tonal peak. Studies to date have not accurately addressed the distance at which a rumble strip signal can be heard. Sound levels were projected perpendicular to the roadway suggesting detectability at over a mile from the Minnesota design in a typical rural environment.
Reverberation increases perceptual calibration to reliable spectral peaks in speech
Authors: Stilp Christian , Anderson Paul W. , Assgari Ashley , Ellis Gregory , Zahorik Pavel
Published: May 2015

Preceding acoustic context influences speech perception, especially when it features a reliable spectral property (i.e., relatively stable or recurring across time). When preceding sounds have a spectral peak matching F2 of the following target vowel, listeners decrease reliance on F2 and increase reliance on changing, more informative cues for vowel identification. This process, known as auditory perceptual calibration, has only been studied in anechoic conditions. Room reverberation smears spectral information across time, presumably giving listeners additional “looks” at reliable spectral peaks, which should increase the degree of perceptual calibration. Listeners identified vowels (varying from [i] to [u] in F2 and spectral tilt) presented in isolation, then following a sentence filtered to share a spectral peak with the target vowel’s F2. Calibration was measured as the change in perceptual weights (standardized logistic regression coefficients) across blocks. Listeners completed sessions where stimuli were diotic or processed by virtual room acoustics to simulate high reverberation (T60 = 2.97 s). Perceptual calibration was significantly greater (larger decreases in F2 weight, larger increases in tilt weight) for reverberant stimuli than diotic stimuli. Interestingly, hearing reverberant stimuli first attenuated calibration in subsequent diotic stimuli. Results demonstrate perceptual sensitivity to the persistence of reliable spectral peaks across time.
When does binaural hearing benefit from ongoing envelope fluctuations?
Authors: Stecker G. Christopher , Diedesch Anna C.
Published: May 2015

A number of classic and recent studies suggest that listeners’ access to ongoing binaural information in sounds with steady envelopes is significantly poorer than for sounds with stochastic or slowly modulated ongoing envelopes. For some types of binaural cues—e.g., envelope interaural time differences (ITD)—that result is consistent with the requirement of salient envelope features for accurate cue encoding. For interaural level differences (ILD) and fine-structure ITD, however, no such requirement exists and the result is therefore more surprising. Regardless, the overall results suggest that binaural-cue encoding-in general-relies heavily upon the occurrence of infrequent envelope fluctuations, such as sound onsets and slow (e.g., syllabic-rate) amplitude modulations. Here, the results of relevant studies are reviewed, along with conceptual and physiological models of sampling binaural cues during envelope fluctuations. Potential advantages for binaural hearing in reverberation and competing backgrounds are considered, as is the impact of such mechanisms on the localization of strongly modulated targets such as speech. Overall results suggest a general degradation of binaural information-regardless of cue type-in the absence of envelope fluctuations. Instead, the binaural system emphasizes representations of temporally sparse, but highly localizable, onset-like events in the auditory scene. [Work supported by NIH R01-DC011548.]
Rate effects in interaural and sequential level difference perception
Authors: Laback Bernhard , Dietz Mathias , Ewert Stephan
Published: May 2015

The relative weighting of post-onset interaural level difference (ILD) cues decreases with increasing modulation rate of a signal. It is unclear, however, whether overall ILD sensitivity decreases with increasing rate, particularly if stimulus duration and loudness are kept constant. Moreover, it is unclear if the rate effect arises also in monaural sequential level discrimination. In experiment 1, ILD-based lateralization discrimination thresholds and sequential level difference (SLD) discrimination thresholds were measured using bandpass-filtered pulse trains (4 kHz) with rates of 100, 400, and 800 pulses/s. From 100 to 400 pulses/s, both ILD and SLD thresholds decreased, contrary to a rate limitation. From 400 to 800 pulses/s ILD thresholds increased while SLD thresholds remained constant. The latter result is consistent with a high-rate limitation being specific to binaural hearing. Experiment 2 evaluated whether this rate limitation is due to the loss of transmitted modulation at high rates. The ILD thresholds for an unmodulated 4-kHz pure tone were indeed higher than those for pulse-trains. An auditory nerve model (Zilany et al., 2014, JASA 135, 283–286) combined with an interaural discharge rate comparison stage qualitatively predicted the nonmonotonic pattern of ILD thresholds. Overall, the results suggest that modulation can be beneficial for ILD perception.
A Bayesian framework for the estimation of head-related transfer functions
Authors: Romigh Griffin D. , Stern Richard M. , Brungart Douglas S. , Simpson Brian D.
Published: May 2015

While high-fidelity spatial auditory displays require individualized head-related transfer functions (HRTFs), much of the physical structure contained within an HRTF is similar across most individuals. This suggests that a Bayesian estimation technique, which uses sample observations to bias an a priori model towards an individual, may provide benefits in terms of efficiency. Therefore, the current work proposes a Bayesian HRTF framework that utilizes HRTFs in the form of their real spherical harmonic representation. When combined with assumptions of normality, the resulting technique is shown to enable the accurate estimation of an individualized HRTF from a small set of spatially distributed measurements. Moreover, the model provides a convenient way to analyze which components of an HRTF vary most across individuals, and can therefore be used to create very efficient HRTF measurement strategies. A perceptual localization test confirmed that similar localization performance could be attained with an HRTF estimated from as few as 12 spatial measurements, even when confined to the median-sagittal plane.
Acoustic radiation from an infinite submerged, line-driven plate with attached finite plate
Authors: Koch Robert M.
Published: May 2015

The structural acoustics and vibration related to submerged, structurally driven elastic plates is germane to a wide range of applications in U.S. Navy undersea vehicle and system designs. Of particular interest to a recent specific Naval design application was the examination of effects on the acoustic radiation from a very large, fluid-loaded elastic plate joined with a “welded,” or strongly attached, smaller elastic plate subjected to force-loading excitation somewhere on the large plate. This paper presents the results following an examination of several theoretical approaches to predicting the radiated sound level (both levels and directivity) of an idealized infinite plate and perfectly attached thin, finite plate submerged in a heavy fluid and driven by a line-load at varying locations on the infinite plate. Parametric studies are also presented to both highlight the underlying basic physical mechanisms and also to investigate the effect on sound radiation of varying system parameters. Specifically, results of parametric variations in (a) location of the line force on the plate with respect to the attached finite plate, (b) length/size of the attached plate, (c) mass and/or stiffness of the attached plate, (d) frequency of the harmonic line-load, and, time permitting, and (e) the mechanical theory of the attached thin plate, are all presented herein.
Causal and passive interpolation of structural acoustic matrices
Authors: McDaniel James G. , Wixom Andrew S.
Published: May 2015

The present work investigates the causal and passive interpolation of structural acoustic matrices in the frequency domain. Interpolations significantly ease computational burdens involved in computing these matrices from models. For example, one may wish to compute a small admittance matrix, relating forces to velocities at points on a structure, from a large finite element model with over one million degrees of freedom. In many structural acoustic systems, the elements of such matrices vary smoothly with frequency and therefore interpolation can be accurate and effective. In the time domain, causality requires no effect before its cause. In the frequency domain, this takes the form of Hilbert transform relations that relate the real and imaginary parts of scalar transfer functions. Passivity requires that the net power dissipated by the structure over a cycle of vibration be positive semidefinite. The present work develops series expansions in which these conditions may be implicitly satisfied by the proper choice of basis functions. Coefficients of in the series expansion are found by matching the series to the known values at the interpolation points. Examples demonstrate situations in which the satisfaction of these physical conditions yields more accurate interpolations.
A hybrid method for predicting heavy fluid loading of structures
Authors: Shepherd Micah R. , Fahnline John B.
Published: May 2015

Measuring the resonance frequencies and damping of structures in heavy fluids can be difficult and time consuming. To alleviate this burden, a hybrid approach is proposed by combining in-air experimental modal analysis with a boundary element estimate of the acoustic resistance and reactance matrices. The method was validated on a rectangular metal plate by comparing the natural frequencies estimated using the hybrid method to the natural frequencies measured in water. The modal parameters were first measured in air with the mass-normalized mode shapes estimated using the complex mode indicator function. The modal parameters were then updated using rational polynomials curve fitting. The measured modes were then used as in-vacuo basis functions to compute modal resistance and reactance matrices in water and the fluid-loaded vibration and sound radiation was estimated. The natural frequencies of the plate submerged in water were then measured and compared to the frequencies predicted by the hybrid method showing good agreement.
Magnetic excitation and identification of flexural modes of a circular plate
Authors: Daniel Timothy D. , Marston Phil L. , Abawi Ahmad T. , Kirsteins Ivars
Published: May 2015

A spatially localized, oscillating, magnetic field was used to induce resonant vibrations in an aluminum circular plate without direct mechanical contact. Experiments were done with the plate in air, at a free surface, and fully submerged in water. This allowed the effect of fluid loading on the plate's spectrum to be examined for both the fully loaded and half loaded case. Since the magnetic field is spatially localized, identification of the mode shapes is possible by scanning the source along the target and measuring the varying response of the plate. Additional experiments were done with an open-ended fluid filled copper circular cylinder in which both resonant frequencies and mode shapes were identified. Both targets responded at twice the oscillation frequency of the applied field [B. T. Hefner and P. L. Marston, J. Acoust. Soc. Am. 106, 3340–3347 (1999)]. The response corresponds to the oscillation frequency of the Maxwell stress associated with combined applied field and induced eddy-current field. Excitation of both plate and cylinder was found to be measurable with a steady state and a tone burst source. [Work supported by ONR.]
Vibrational analysis of hollow and foam-filled graphite tennis rackets
Authors: Vayur Kritika , Russell Daniel A.
Published: May 2015

The game of tennis is plagued with wrist and elbow injuries. Most players use light, stiff hollow graphite rackets. A recent foam-filled racket design appears to reduce the risk of wrist injury. A vibrational analysis of a wide variety of rackets was conducted in attempt to understand the science behind this racket’s apparent success. Damping rates were measured for the bending and torsional modes for a wide variety of hollow and foam-filled rackets. No significant difference among the rackets was found, suggesting the benefit of the foam-filled racket design is not due to damping. An extensive modal analysis was conducted for several rackets over the frequency range of 100 Hz to 1.5 kHz to identify the bending, torsional, and string modes. In this paper, the damping rates, mode shapes, and frequencies, will be compared for several hollow and foam-filled rackets. Results will be interpreted in light of the relevant forces between the racket, ball, and arm.
Frequency eigenvalues of the breathing mode of a submerged empty thin spherical shell: Variation with the ratio of shell thickness to radius
Authors: Hall Marshall V.
Published: May 2015

The frequency eigenvalues of the breathing mode of a submerged empty thin spherical shell are the three roots of a cubic algebraic equation. Compared with the quadratic equation for an in-vacuo shell, the polynomial contains two imaginary terms in the ratio of sound-speed in the ambient fluid to plate velocity of the shell material. All three roots of the equation are complex, due to radiation into the ambient fluid. For a shell submerged in a fluid similar to water, two of the eigenvalues’ real parts, and two of their imaginary parts, do not vary monotonically with shell thickness. To illustrate this phenomenon, an example of a steel shell submerged in water is considered. For a thickness to radius ratio of 0.1, one of the non-dimensional eigenvalues has a real part of 1.57, close to the in-vacuo result of 1.61. As the thickness ratio decreases to 0.0143, this real part decreases to zero and remains there for lower ratios. Another eigenvalue, whose real part is always zero above 0.0143, has a positive real part at ratios less than 0.0141, with a maximum at 0.009. Over the interval from 0.0141 to 0.0143, however, the real parts of all three eigenvalues are zero.
Bias of vibrational energy at high frequencies in circular and rectangular plates
Authors: Boyer Thomas D. , Shepherd Micah R.
Published: May 2015

Experimental modal analysis can be used to measure the modal parameters and vibrational energy in structures. This presentation will compare biases in the total vibration energy at high frequencies for a circular and rectangular aluminum plate that are freely supported. Both rectangular and cylindrical coordinates were used to create the set of excitation points for the circular plate, while only rectangular coordinates were used for the rectangular plate. Singular value decomposition was then used to obtain the natural frequencies and mode shapes in each of these plates. The obtained modes were used to synthesize the vibration response and to compute the vibration energy. Biases were found at high frequency using a direct integration method to compute the vibration energy. The dependencies of the bias on the plate geometry and set of excitation points will be discussed.
Ken Stevens and linguistic phonetics
Authors: Keating Patricia
Published: May 2015

While almost all of Ken Stevens’s research has been influential in linguistic phonetics—especially his work on the quantal nature of speech and on enhancement theory—this presentation will focus more on aspects not covered by others in this session. A noteworthy aspect of Ken’s career is that he frequently collaborated with linguists, notably in research on phonetic features and their structure. In work with Blumstein and with Halle, he provided acoustic correlates of place of articulation, laryngeal, and nasalization features. Much of this work is summarized in his 1980 paper in JASA, “Acoustic correlates of some phonetic categories.” In work with Keyser, he suggested an overall organization of features to define major classes of sounds. This work was published in linguistics journals, e.g., their 1994 paper in Phonology, “Feature geometry and the vocal tract.” Ken’s importance to linguistics, as an engineer interested in linguistic sound systems and eager to work with phoneticians and phonologists, cannot be overestimated, and is a legacy continued by many of his students.
Distinctive features, quantal theory, and enhancement
Authors: Hanson Helen
Published: May 2015

Ken’s background in physics and engineering and keen interest in phonetics gave him a rare ability to suggest a quantitative basis for distinctive features. His awareness that the acoustic correlate of a smoothly varying articulatory parameter might have a sudden change in value led to his development of Quantal Theory. In addition to providing a basis for distinctive contrasts, it provides a means for a continuous-time signal to reflect the discrete nature of the underlying representation of speech sounds. Later work led to two types of quantal relations: those based on aeromechanical properties of the vocal tract, which lead to manner features, and those based on coupling between cavities, which lead to articulator-bound features. Ken also suggested that each feature has a defining articulatory state, and thus, a defining acoustic correlate. Neighboring segments or higher-level phenomena may threaten the salience of defining acoustic correlates. Enhancement theory was developed to account for the fact that the defining articulatory or acoustic correlates are threatened in some environments. At such times, enhancing gestures that bolster the salience of the defining acoustic correlates are brought into play. Much of the work produced by Ken’s students was aimed at finding support for these theories.
The role of subglottal resonances in speech processing algorithms
Authors: Alwan Abeer , Lulich Steven , Ariskere Harish
Published: May 2015

Inspired by Ken Stevens’ work on speech production, we investigated the role of the subglottal resonances (SGRs) in several machine-based speech processing algorithms. The subglottal acoustic system refers to the acoustic system below the glottis, which consists of the trachea, bronchi, and lungs. The work is based on the observations that the first and second subglottal resonances (Sg1 and Sg2) form phonological vowel feature boundaries, and that SGRs, especially Sg2, are fairly constant for a given speaker across phonetic contexts and languages. After collecting an acoustic and subglottal database of 50 adults and 48 children, analyzing the database, and developing algorithms to robustly estimate SGRs, we were able to use these resonances to improve the performance of a variety of speech processing algorithms including: recognition of children's speech in limited-data situations, frequency-warping for adult speech recognition, speaker recognition and speaker verification, and automatic height estimation. [Work supported in part by the NSF.]
Influences of Ken Stevens on research in speech production
Authors: Perkell Joseph S.
Published: May 2015

Ken Stevens has had a profound influence on many aspects of speech research. His contributions to the understanding of speech range from the theoretical through a vast body of hypothesis-driven studies to important developments in methodology. His theory of the quantal nature of speech has important implications for our understanding the nature of sound structures of languages. It embodies the concept that sounds are specified by combinations of distinctive features, which are based on universal properties of the production and perception mechanisms. Over a period of five decades, he, the many people he mentored and others tested hypotheses stemming from this theory using modeling and running experiments on relations among vocal-tract configurations, articulatory movements, tissue properties and aerodynamics—and the influences of these factors on perceptually relevant characteristics of the resulting speech sounds. Investigators who spent time in Stevens’ Speech Communication Group also learned valuable principles for the conduct of scientific research. Examples of research on speech production will be presented to illustrate some of these points. [Research supported by the NIDCD, NIH.]
Ken Stevens' contributions to the field of communication disorders
Authors: Kent Ray D.
Published: May 2015

Speech is a robust faculty and most people rely on it daily, overcoming temporary difficulties such as laryngitis, dental work, or stage fright. Even slips of the tongue are relatively rare, occurring once in about a thousand spoken words. But for all its robustness, speech is vulnerable to a number of disorders that can be severe enough to interfere with efficient and natural communication. A communication disorder can be defined as a disruption or limitation in the production of speech that is fluent, intelligible, and natural. Through direct and indirect influences, Ken Stevens became a valued ally in the effort to bring relief to people with these disorders. In a highly selective account of the contributions of Ken and his colleagues, this talk examines three general areas: technological advances for the assessment and treatment of speech and voice disorders, basic theories that illuminated the path to understanding speech communication in health and disease, and quantitative research focused on speech communication in individuals with hearing loss or dysarthria (both of which have multisystem consequences on the production of speech and both of which can result in serious communication difficulties).
Analysis by synthesis techniques
Authors: Idsardi William
Published: May 2015

In the late 1950s and early 1960s, Ken Stevens and Morris Halle proposed analysis by synthesis (A-by-S) as a general model for speech perception by humans and machines. The leading idea in A-by-S is that people can generally both speak and listen, and therefore speech is both action and perception. Thus, the perception of a speech fragment can be the answer to the question, “how would I have said that?,” that is, to recover the action that would produce that event (or an appropriately scaled version of the event). This idea has had lasting influence in speech perception models and systems (even if they employ other terms), as well as in more general accounts of perception. In this talk, we will offer a brief history of the idea of A-by-S, focusing on the general architecture of such systems and in what space (auditory or articulatory) signal comparison is carried out. In doing so, we will briefly compare and contrast A-by-S with other influential ideas, including the motor theory of speech perception, modularity and the special nature of speech, mirror neurons, the memory-action-perception loop, Bayesian inference, and general auditory cognition.
Ken Stevens, motor theory, and infant MEG brain data
Authors: Kuhl Patricia K.
Published: May 2015

ASA meetings provided a special time to talk to Ken Stevens and share data and opinions about topics of mutual interest. On one of these occasions, Ken uttered a sentence that stuck with me, “I hate to tell you this, but I think I’m becoming a motor theorist!” He then explained Analysis by Synthesis. In this talk, I’ll share newly published MEG brain data (Kuhl et al., PNAS, 2014), suggesting that young infants may indeed be engaging in something like analysis by synthesis as they listen to us speak. I'll use this and other findings to discuss Ken’s important contributions to Speech Communication.
The MIT Lexical Access Project: A window into Stevens’ model of feature-cue-based processing
Authors: Choi Jeung-Yoon , Shattuck-Hufnagel Stefanie
Published: May 2015

In his JASA (2002) paper, Ken Stevens proposed a model of human speech recognition based on extracting acoustic cues to the distinctive feature contrasts of the speaker's intended words. Following Halle (1995), he distinguished between cues to manner features (e.g., abrupt spectral events associated with constrictions/widenings of the vocal tract, called landmarks) vs. cues to other features related to voicing and place, and proposed that landmark detection is an early step in perception. Landmark cues are particularly useful: they are reliably produced, robustly detectable, and highly informative about the structure and lexical content of an utterance; they also identify adjacent regions rich in cues to additional features. During his working life, Ken's students developed many of the modules required to detect feature cues, meanwhile discovering important aspects of their systematic context-governed variation. Current work aims at (1) completing the speech analysis system based on detection of feature cues and parameter values, (2) evaluating its performance, and (3) comparing its performance to human perceptual behavior. A system based on Ken's insights will have implications for human speech processing models, for knowledge-based approaches to ASR, and for a deeper understanding of the mechanisms underlying clinical speech problems as well as language learning.
Ken Steven’s research and influence on automatic speech recognition
Authors: Espy-Wilson Carol Y.
Published: May 2015

This talk will address Dr. Kenneth Steven’s considerable influence in the area of speech recognition. Central to Ken’s model of lexical access is the relationship between acoustics and articulation. Binary distinctive features are identified from the continuous signal based on acoustic cues that are tied to articulation. As such, variability in this parameterization is reduced from that seen in the physical signal. The acoustic features are then matched against the lexicon where there is generally only one representation for each word. This lexical representation consists of a bundle of distinctive features. In contrast, state-of-the-art recognizers use acoustic features that are not tied to articulation. Consequently, they are highly variable, resulting in the recognizer’s over-reliance on sophisticated machine-learning tools and statistical signal processing methodologies that are data intensive and often fail to generalize. Further, multiple lexical representations of each word in terms of acoustic units called tri-phones are needed to cope with pronunciation variability. While Ken’s model has not been fully realized, it has motivated research into extraction of the distinctive features, investigations of alternate articulation-based representations, and marrying these representations with well-established recognition back-ends to study gains in robustness. Examples from studies and their promise relative to state-of-the-art methods will be given.
Random linear packet coding for half duplex underwater channels
Authors: Ahmed Rameez , Stojanovic Milica
Published: May 2015

Random linear packet coding is considered for underwater acoustic communications in situations where reliability is essential, i.e., where data packet delivery has to be guaranteed with some probability. We develop an adaptive power and rate control strategy for a half duplex acoustic channel in which the receiver can inform the transmitter about the channel state. We consider transmission in cycles, each long enough to conform to the channel’s coherence. In each cycle, the receiver feeds back the channel gain and the noise power, and the transmitter adjusts its settings accordingly. Based on the experimental measurements, we model the channel gain as a log-normally distributed fading process, and provide a system optimization procedure based on a chosen criterion, such as minimum average energy per bit or maximum average throughput. System performance is compared analytically and numerically to that of a non-adaptive system, showing benefits of closed-loop, channel-aware transmission.
Determination of material parameters to recreate realistic audio quality for sounding materials in virtual sound reproduction based on modal analysis
Authors: Imran Muhammad , Jeon Jin Yong
Published: May 2015

The modal synthesis method has been investigated to synthesize realistic virtual sounds for rigid bodies. The current methods to create realistic audio quality of sounding materials lack the ability to automatically determine material parameters. In this study, an approach is introduced to estimate material parameters that capture the inherent quality of sounding materials and extract perceptually significant features from the recorded example impulse responses. This approach is based on modal analysis using extracted material features to identify the best material parameters for linear modal synthesis (LMS). The synthesized audio produced from LMS preserves the same quality of material sound as recorded sound clips. A perceptual study was also conducted, revealing that the results of this approach are comparable with real recorded sounds in terms of perception of the materials.
Six decades of evolution in Underwater Acoustics at the Applied Physics Laboratory, University of Washington
Authors: Williams Kevin L. , Tang Dajun , Dahl Peter H. , Thorsos Eric I. , Jackson Darrell R. , Ewart Terry E.
Published: May 2015

Professor Joe Henderson of the University of Washington physics department formed the Applied Physics Laboratory during WWII. The lab’s initial efforts were to redesign the magnetic influence exploders used in US torpedoes. One of the lab’s first Underwater Acoustics (UA) successes was development of transducers used in the Bikini Atoll Able test (1946). Those transducers, used to trigger other instrumentation, proved critical. Combining UA and torpedo expertise brought APL-UW to the forefront of tracking range design, construction and deployment in Dabob Bay, Nanoose, and St. Croix in the 1950s and 1960. Understanding the torpedo behavior seen in tracking ranges required measuring both the ocean environment and the acoustics within that environment. Making those measurements, as well as development and testing of models based on those measurements, also became standard operating procedure at APL, led in the 50’s by Murphy and Potter. This blueprint of applied research motivating basic research, and the pursuit of basic research via ocean experiments and high fidelity modeling, continues to this day. The presentation will follow this evolution. APL-UW ocean experiments carried out during that time, as well as notable APL-UW research papers, technical reports, computer codes and textbooks, will be used as guideposts.
Underwater acoustics at Applied Research Laboratories, The University of Texas at Austin
Authors: Muir Thomas G. , Penrod Clark S. , McKinney Chester M.
Published: May 2015

Several University of Texas physicists and acousticians served at the Harvard Underwater Sound Laboratory during World War II. Among them was Associate Director Paul Boner who founded Applied Research Laboratories (ARL:UT) upon his return to Texas in 1945. The underwater acoustics program began in 1949 under sponsorship of the Naval Ordnance Laboratory in support of passive sea mine sensors. The talk will focus on growth of the program in the early years including basic research, advancements in sonar engineering and signal processing, torpedo, mine and mine countermeasures (for both ocean and riverine environments), work on ship signatures, sediment physics and properties, target strength, submarine and anti-submarine sonar for both active and passive modes, in-situ calibration of ship transducers, environmental acoustics, long-range propagation and modeling, and nonlinear acoustics. ARL:UT’s participation and support of the university’s missions of research, education, and public service will also be discussed.
Penn State's Applied Research Laboratory contributions to underwater acoustics
Authors: Liszka Edward G.
Published: May 2015

The Applied Research Laboratory (ARL) at the Pennsylvania State University has had a rich history of research and development in the field of underwater acoustics dating from its founding in 1945. The author reviews some of the important contributions made over the intervening decades in sub-fields such as sound propagation, scattering, transducers and arrays, signal processing, autonomous systems decision making, structural vibration and sound radiation, and hydro acoustics. The Laboratory was established by the US Navy as a derivative of the Harvard Underwater Sound Laboratory following World War II. Dr. Eric Walker, the first Director, was charged with continuing research and development on acoustically guided torpedoes following his highly successful effort during the war. In 1949, the Garfield Thomas Water Tunnel was constructed to further the understanding of flow-driven underwater acoustic phenomena, such as cavitation and flow induced vibration as examples of early achievements. Due to a growing need for scientists and engineers educated in acoustics, the Navy encouraged Penn State to establish its Graduate Degree Program for Acoustics in 1965. While the Program covers a broad scope of acoustic disciplines, it has a served a significant role in the development of the underwater acoustics field.
Acoustical optimization of curvilinear shapes used in modern architecture
Authors: D'Antonio Peter , Talaske Richard H.
Published: May 2015

Classic architecture is characterized by beautiful statuary, coffered ceilings, columns, and relief ornamentation. These beautiful features coincidentally also provided excellent sound diffusion. As architecture evolves into using less ornate surfaces, the acoustic fallout is that modern rooms may not have good sound diffusion. As a result, there is a need for scattering surfaces that compliment contemporary architecture, the way that the afore-mentioned surfaces complemented classic architecture. In order to generate these modern sound diffusing surfaces, a software program called the Shape Optimizer was developed utilizing an accurate prediction method, a diffusion coefficient metric to evaluate performance and an intelligent search engine which can quickly and efficiently navigate through the myriad shape possibilities. One of the authors (Talaske) will also present an acoustician’s perspective on how to successfully meet the challenge of marrying the acoustical scattering requirements with the aesthetic goals expressed by the architect and/or interior designer. Several examples will be given by both authors illustrating the use of curvilinear diffusors and the potential of providing diffusing and absorbing surfaces with the same topology.
The effects of materials on the performance of acoustic diffusers
Authors: Lenz Richard L.
Published: May 2015

Over the years, many different theories about the effects of material mass, finishes, coverings such as fabrics, porosity, and other physical attributes of diffuser design have been put forth. These theories have included excess absorption and/or reduced diffusion being caused by different woods or other materials being used as well as different types of paints and finishes. This paper is a study on the veracity of those theories and the effects of assorted materials in the construction and implementation of acoustic diffusers. The study will include the use of a specific diffuser design utilizing a periodic design with specific frequency ranges better known as quadratic residue diffusers. Tests will be conducted to look at specific absorption results and the correlation to diffusion efficiency, if any. In addition, different styles of QRD's will be utilized to see if any designs can overcome the various attributes in design used in diffusion. Standard and customized testing procedures will be used to derive the information presented in the paper.
Particle simulations advance insight into diffusion device design, efficiency, and diffuse field development and propagation
Authors: DeGrandis James J.
Published: May 2015

After the development of a demonstration to illustrate acoustic diffusion using Ping-Pong balls (DeGrandis, 2011, “Sound Diffusion Explained,” http://acousticsfirst.com/educational-videos-acoustic-sound-diffusion.htm), the idea of virtualizing the concept to gain more insight into diffusion from a particle physics perspective became a goal. Using open-source, Ray tracing modeling, and physics simulation software, the efficiency of different diffusor designs was evaluated. Simulations included individual elements and arrays in varied distribution and varied environments, and their impact on the propagation of sound, as well as the visualization and prediction of the development of an acoustically diffuse field. Integrating a simulated particle emitter to model the excitation, environmental physics to model atmospheric conditions, and 3d models with adjustable surface dampening properties, usable simulations with calculable and predictable properties could be run. New data were collected based on spatial diffusion, isometry, and the speed of which the excitation was broken down from a contiguous wave front into a diffuse particle field. Simulations varied from individual unit efficiency to complex room modeling with multiple emitters and scattering surfaces. This is a collection of the findings from that exercise.
A better method or methodology for the measurement of diffusers
Authors: Sauro Ronald
Published: May 2015

This presentation is a follow-on to the presentation “Diffusion and Scattering: A critique of existing standards and data (Goodbye, Scattering).” In this presentation, we will present a method of displaying 3D directivity data for diffusers, pointing out the similarities between the directivity data for diffusers and loudspeakers, and how those similarities can be used to answer the problem of creating usable data for acoustical simulation programs. We will point out that other acoustic and electro-acoustic organizations have solved many of the problems with characterizing the spatial characteristics of sound sources and how diffusers can meet those same criteria. These solutions offer a roadmap for us to be able to characterize diffusers as well. We will also present a way of measuring these diffusers using generally accepted methods, and introduce a method of presenting this data in an easily understood way with a format that can be used in acoustic simulation programs.
The effect of mouth gape angle on beam size for echolocating Eptesicus fuscus
Authors: Kloepper Laura , Wojciechowicz Rebecca , Simmons James
Published: May 2015

The sonar beamwidth of mouth-emitting echolocating bats is hypothesized to change according to mouth gape angle, with a narrowing of the beam predicted with wider mouth openings. To investigate the relationship between mouth gape angle and beam size, we recorded both the emitted sonar beam as well as the mouth opening for four bats during a target detection task. Sonar signals were recorded with an array of microphones, and bat mouth dynamics was recorded with an action camera recording at 240 frames per second. The video frames corresponding to each pulse emission were extracted and the mouth gape angle was measured. Sound intensity, −3 dB beam angle, and frequency characteristics were calculated from the microphone array and compared to the mouth gape angles to determine the influence of mouth opening on echolocation signals.
Comparing the biosonar signals of free swimming dolphins with those of a stationary dolphin in a net pen
Authors: Au Whitlow W. , Copeland Adrienne , Martin Stephen W. , Moore Patrick W.
Published: May 2015

The biosonar signals of two free-swimming Atlantic bottlenose dolphins performing a complex sonar search for a bottom target in San Diego Bay were compared with the biosonar signals of a dolphin performing a target discrimination task in a net pen. A bite-plate device that the dolphins carried supported a hydrophone that extended directly in front of the dolphin. A biosonar measuring tootbox (BMT) attached to the bite plate measured the outgoing biosonar signals while the dolphins conducted sonar searches. Both of the free-swimming dolphins used different biosonar search strategy in solving the problem and their biosonar signals reflect the difference in strategy. The dolphin stationed in a hoop in the pen while echolocating on a target 6 m away and reported if the indentation on a spherical target was directed toward it. The signals were parameterized by determining the peak-to-peak source levels, source energy flux density, peaked frequency, center frequency, rms bandwidth, rms duration, and the Q of the signals. Some of the characteristics of the r signals were similar for the free-swimming and stationary dolphins while some were significantly different suggesting biosonar signals used by free-swimming animals may be different than signals used by captive dolphins in restrictive environments.
Hot topics in noise
Authors: Sommerfeldt Scott D.
Published: May 2015

There are a number of diverse areas of interest in TC Noise. Many of these have developed in response to adverse human reaction to various noise sources. This paper will briefly overview some of these current topics to give some exposure to what is happening in “Noise.” These include wind turbine noise, which has become of concern with the development of wind farms near residents; soundscapes, which is focused on engineering a desirable environment in the settings where we live; high amplitude jet noise, which is becoming of greater concern as source levels increase, and humans and animals are exposed to higher sound pressure levels; and active noise control, which continues to mature and is beginning to show up in more applications in society.
Hot topics in physical acoustics
Authors: Mobley Joel
Published: May 2015

From the astronomical to the molecular, acoustics is central to phenomena across a vast spectrum of length scales. This talk provides an overview of recent developments in physical acoustics across the size continuum, while looking more in depth in three areas. At the larger end of the scale, the generation of the infrasound by cyclonic storms is considered, specifically looking at the infrasonic signatures that can be used to track and characterize these systems. At intermediate length scales, advances in acoustic metamaterial (AM) research are examined. Specific examples will include energy-harvesting metasurfaces and soft matter systems. Moving to the small end of the scale, phoxonic crystals (PxC) are discussed. PxC’s possess both optical and acoustic band gaps and can be used to trap light and sound together, enhancing the strength of acousto-optic interactions.
Acoustic characteristics of a guitar
Authors: Taylor Corey A. , Russell Daniel A.
Published: May 2015

A variety of tests were done on an acoustic guitar to help characterize and quantify the radiated sound. Modal analysis was performed to determine resonant low frequency modes of the guitar and the motion of the air in the sound hole. Mechanical impedance and mobility measurements were taken at the bridge. String decay and radiated decay times were measured at several fret positions to study the interaction between modal resonances and decay times. Many of these individual tests have been performed on acoustic instruments before. This paper will combine the analysis of all tests and measurements to show that the modal frequencies play a large role in affecting the sound quality of an acoustic guitar.
Using spectral analysis to evaluate flute tone quality
Authors: Yorita Ron , Clements John
Published: May 2015

Many skilled flutists place a high priority on “good” tone quality, or timbre. Unlike pitch and rhythm, timbre is difficult to objectively quantify. This project explores (1) how tone quality is described by skilled flutists, (2) whether the harmonic spectrum has some correlation with tone quality, (3) whether certain harmonic spectra are preferred, or considered “good.” Thirty-one flutists ranging from high school students to professionals were recorded. A set of samples was used in surveys and interviews to capture descriptors and ratings of tone quality. All of the recorded samples were analyzed using application programs, Harmonic Analysis Tools (HAT), created for this study. HAT uses digital signal processing techniques to produce “spectral signatures”. The signatures consist of the harmonic content, pitch, and amplitude of a sample. The outcome of this research is a baseline set of some often used descriptors. In addition, results showed some correlation between harmonic spectra and descriptors. There were also trends in preferences with respect to certain spectral characteristics. An unexpected finding was that University students showed divergent timbre preferences compared to highly experienced flutists.
Air columns for demonstration of upstream/downstream symmetry in reed wind instruments
Authors: Hoekje Peter L.
Published: May 2015

The acoustics of a reed wind instrument such as a clarinet or oboe, and including the lip-reed instruments such as the trumpet, are classically described by the input impedance of the instrument air column and the dynamical flow control characteristics of the reed valve. The behavior of the system is largely dependent on the resonances of the instrument air column. A fuller explanation however includes both the downstream (usually the instrument) and the upstream (usually the player's wind way) input impedances in symmetry. To demonstrate this, a clarinet-like instrument with no resonance peaks can be played using the resonances of the player's wind way. Another demonstration uses a resonant tube for the upstream air column, with the playing frequency or fundamental based upon a resonance of this upstream tube. The downstream air column has a resonance whose frequency and damping can be set independently of that other resonance. This allows exploration of the effect of a resonance at a harmonic of the playing frequency.
Visitor assessment of anthropogenic noise at Grand Canyon National Park
Authors: Pamidighantam Pranav K. , Schomer Paul
Published: May 2015

In the last decade, multiple studies have been conducted at national parks using the traditional uni-polar annoyance scale and the dose-response concept to determine the effects of aircraft noise on park visitors’ experiences. This survey instead uses a bipolar “pleasantness” scale and breaks each visitor’s hike into segments so as to understand the efficacy of the pleasantness scale as a metric for visitor perceptions of aircraft noise. This survey was conducted on three different trails at the Grand Canyon: the Hermit trail, a backcountry trail with a large amount of aircraft noise; the Widforss trail, a backcountry trail with minimal aircraft noise; and the Bright Angel trail, a maintained trail with a small amount of aircraft noise but many hikers. Many visitors began hiking before aircraft started flying so the use of segments allowed for a longitudinal study between segments with and without aircraft noise. Through the use of these segments, correlations are drawn and regression models fit between pleasantness and various metrics, such as Leq or percent time audible. The results to date show “pleasantness” to be a viable alternative metric to quantify visitor perceptions of aircraft noise in national parks.