bluuebunny/crossref_metadata_2025 huggingface dataset:
Signal detection as a function of relative acoustic entropy.
Authors: Stilp Christian E. , Kiefte Michael , Kluender Keith R.
Published: March 2010

Natural sounds are far from random. Instead, they possess structure that reflects physical constraints on sound-producing objects and events. Listeners likely exploit such structure (predictability and redundancy) when perceiving complex natural sounds. The present experiments investigate listeners’ ability to discover and use structure in novel sounds to identify a repeating target sound against a competing background of sounds. Complementary signal-processing strategies independently varied acoustic entropy (complement to redundancy) in frequency or time. Novel sounds were generated by stretching the entropy in a restricted frequency band (instantaneous frequency dilation) or temporal slice (phase vocoding) of pink (1/f) noise across the bandwidth or duration, respectively, of an unstretched noise sample. Listeners matched a probe sound to a target sound (1%, 3.2%, or 10% entropy of pink noise) that repeats amidst distractor sounds (1%, 10%, or 100% entropy) at 0-dB SNR. In separate experiments varying entropy in frequency or time, identification of target sounds depended critically on the difference in entropy across targets and distractors. Listeners were more proficient identifying lower-entropy targets against higher-entropy distractors but not lower-entropy distractors. Similarly, higher-entropy targets were better identified amidst lower-entropy distractors. Potential implications for cochlear implant processing will be discussed. [Work supported by NIDCD.]
Non-intrusive audio notification in emotion classified background music.
Authors: Jung Ralf
Published: March 2010

In human-computer interaction, audio signals are generally used for warnings and acoustic feedback. Especially in environments with many people, such signals often affect intrusively and distractive because of their differentness compared to the natural sound environment. In this paper, a novel audio notification system is presented that provides methods to notify persons individually in multi-user environments. The used audio cues are unnoticeable for others since they can be embedded seamlessly in ambient background music. A novel notification hierarchy with three signal classes is introduced to realize a personalized and a context-aware notification within the background music. For the self-composed background music, perceptual constraints such as auditive Gestalt laws as well as results from musicology were taken into account to influence the listeners perception. A classification model for the emotional expression of non-vocal music is also introduced in this paper. The effectiveness of the novel notification method and the plausibility of the classification model are confirmed by empirical studies. This novel non-intrusive audio notification method let users become aware of individual events while at the same time other present persons will not get distracted by the notification.
Sensor network analysis for fatigue crack characterization in the vicinity of fastener holes.
Authors: Lissenden Cliff J. , Cho Hwanjeong , Kim Chung Seok
Published: March 2010

A network of surface mounted piezoelectric disk transducers is used to detect, locate, and eventually size a growing fatigue crack in an aluminum plate with multiple fastener holes. The results will be used as input to a probabilistic fatigue crack growth model in order to predict structural reliability and remaining useful life. The target application is built-up aircraft wing and fuselage structures. Since the transducers are bonded to the surface and available upon demand, this is structural health monitoring. A tomography algorithm based on a priori knowledge that a fatigue crack will initiate near to the centerline of the fastener holes is used to determine at which hole the crack initiated using Lamb wave modes. In that vicinity, both through-transmission and pulse-echo modes are then used to interrogate many guided wave propagation paths. Use of both modes enables evaluation of transmission and reflection coefficients. Training data are acquired from simpler geometries to facilitate characterization of crack length from received signal features. Characterization of fatigue crack size is in progress. The presentation will conclude with a description of the link to probabilistic modeling. [Support from the Ben Franklin Center of Excellence in Structural Health Monitoring is acknowledged.]
Ultrasonic nondestructive characterization of inhomogenieties and stress concentrations in the porous materials.
Authors: Tavossi Hasson M.
Published: March 2010

Ultrasonic nondestructive bulk testing of porous materials is difficult to achieve due to the high attenuation of ultrasonic waves in these materials. It is shown experimentally that ultrasonic wave attenuation and pass-band frequencies in the porous materials are some functions of average pore size, when other material parameters are kept constant. In most theoretical effective-media models for the porous materials, pore ratio is included but not their average size. The average pore size has a significant effect on both wave attenuation and pass-band frequencies of the porous materials. The goal of this study is to determine optimal criteria for nondestructive flaw detection in the porous materials. Experimental results are obtained on ultrasonic wave attenuation for different samples, as a function of frequency and the average pore size. Flaws in the form of inhomogenieties and localized stress concentrations are then introduced in the samples and the NDT techniques are applied to detect them. Experiments are performed to identify the type of flaw, size, and location in the porous samples. Data on location and sizing of the inhomogenieties and stress concentration will be presented. Results of this study can be used to determine the most effective ultrasonic NDT techniques for flaw detection in the porous materials.
Coherent versus incoherent modulation filtering.
Authors: Brennan Marc A. , Souza Pamela E. , Atlas Les E. , Greenhall Adam R.
Published: March 2010

Understanding how amplitude modulations are used for speech recognition is essential for improving speech signal processing techniques. Previous studies using vocoding or incoherent modulation filtering indicated that slow amplitude modulations are essential for speech recognition [e.g., Drullman (1994), Shannon (1995)]. Each method had limitations that constrain our understanding of how speech is decoded. These methods did not account for a product model which has the modulating signal multiply the carrier signal in speech or used modulation filtering which retained inherent carrier components. Coherent modulation filtering [C. & Atlas (2009)] is a modulation filtering method that uses a product model with more effective modulation filtering. The purpose of this study was to establish differences in speech recognition performance with coherent versus incoherent modulation filtering and assess the importance of slow amplitude modulations in speech recognition while preserving the carrier signal. Subjects were adults with normal hearing. Consonant recognition scores were measured for 16 nonsense syllables at different modulation filter cutoff frequencies. Speech was presented at a conversational level in a closed-set task. Recognition improved at high modulation filter cutoff frequencies for both conditions. At low-modulation filter cutoff frequencies, performance was substantially poorer with coherent compared to incoherent modulation filtering.
Age effects in the understanding of noisy speech denoised by estimated ideal binary masks.
Authors: Divenyi Pierre , Livingston Nicholas , Lammert Adam , Hu Ke , Wang DeLiang
Published: March 2010

An algorithm was developed to denoise speech presented in matching speech-spectrum noise by estimating the ideal binary mask (IBM) that retains the time-frequency (T-F) regions with favorable local signal-to-noise ratio (SNR) and removes the remaining regions [Hu et al., in Proceedings of the 4th SAPA Workshop, Interspeech 2008]. With this method sentence intelligibility was tested in 20 elderly and 20 normal-hearing young listeners. The elderly group had, at worst, moderate SNHL between 0.5 and 4 kHz. Speech material consisted of IEEE sentences spoken by a single female talker. Intelligibility was tested at two SNRs in the elderly (−2 and −4 dB) and three SNRs in the young group (−4, −6, and −8 dB). Subjects listened to 50 sentences at each SNR in three conditions: denoising by the estimated IBM by the algorithm, denoising by the IBM calculated from premixed signals, and the sentences presented in the original noise without processing. With this last condition taken as the baseline, both keyword- and phonemic intelligibility of the sentences processed with the algorithm showed a slight improvement for the young but no improvement for the elderly listeners, while both groups performed substantially better than the baseline in the IBM condition. [Work supported by the VA Medical Research.]
Automatic scoring of responses to the hearing in noise test using utterance verification based on hidden Markov models.
Authors: Lilley Jason , Aronoff Justin M. , Soli Sigfrid , Bunnell Tim , Pal Ivan
Published: March 2010

The hearing in noise test (HINT) is widely used in clinical settings to measure patients’ speech recognition thresholds (SRTs). The patient must repeat 20 sentences presented at signal-to-noise ratios (SNRs) that change adaptively throughout the test. HINT varies the SNR of the sentences according to the patient’s responses, so each response must be scored by a human judge before the next sentence is presented. An utterance verification engine (UVE) would remove both the need for a human judge and the subjectivity of human judgments. 2000 HINT responses were used from 25 listeners to develop a UVE based on hidden Markov models (HMMs), a lexicon of observed and likely words, and a grammar that generates utterances classifiable as correct or incorrect. An evaluation study is in progress with a planned enrollment of 25 normal-hearing listeners. HMMs, lexicon, and grammar are updated after every five listeners. In results with ten listeners tested to date, scoring accuracy averaged 88% per subject (range 81%–95%). The mean SRT determined by the UVE differed from the mean SRT determined by human scorers by an average of 0.56 dB (range 0.04–1.91). Complete results will be presented at the conference. [Work supported by NIDCD Grant R43DC008212.]
Speech intelligibility in cross-dialectal multi-talker babble.
Authors: Fox Robert A. , Jacewicz Ewa , Chang Chiung-Yun
Published: March 2010

This study examines speech perception in multi-talker babble by varying speaker dialect as a masker. Studies varying the language of the target speech and the babble masker show that the target is most intelligible when the masker is constructed from a non-native language and target represents exemplars from the listener’s native language. Does variation in speaker and listener dialect has a similar effect on speech intelligibility? In this study, central Ohio listeners listen to target sentences spoken by either native Ohio or native North Carolina talker. The sentences are masked by multi-talker babble consisting of speech from either Ohio or North Carolina talkers presented at several sound-to-babble (S/B) ratios. The same material is also presented to listeners in North Carolina. The results for Ohio listeners show significant effects of dialect at 0 dB S/B ratio. Intelligibility improved when the background babble featured the dialect that was different from the dialect of the target speaker. The performance of Ohio listeners was more than 20% higher when the target was presented in the North Carolina babble than in the Ohio babble. Results for North Carolina listeners will be discussed. [Work supported by NIH.]
Fricative perception with and without hearing aids, an event-related potential study.
Authors: Miller Sharon , Zhang Yang
Published: March 2010

The present study used auditory event-related potential (ERP) measures to investigate how the adult brain differentially processes fricative speech sounds with and without the use of a hearing aid. Synthetic stimuli for /sa/, /sha/, /as/, and /ash/ were created to control for the spectral cues in the vowel and consonant portions based on naturally recorded speech. ERP responses were recorded for each sound in an unaided and a hearing aid condition using a randomized block design. At least 160 trials per stimulus were averaged for each sound per subject. The results indicated that (1) the ERP responses in the unaided condition significantly differed from the aided condition, (2) N1 peak amplitudes and latencies to /s/ and /sh/ significantly differed in both unaided and aided conditions as well as in syllable-initial and syllable final positions, and (3) phonological context significantly affected N1-P2 responses. Despite some minor differences, these results are consistent with our previous ERP study using natural speech stimuli, which suggests that amplification through hearing aids alters neural coding of acoustic features in speech sounds. [This work was supported by the Graduate Research Partnership Program and Grant-in-Aid, University of Minnesota.]
Effect of reduced audibility on masking release for normal- and hard-of-hearing listeners.
Authors: Nelson Peggy B. , Anderson Elizabeth , Nie Yingjiu , Katare Bhagyashree
Published: March 2010

Listeners with sensorineural hearing loss show reduced benefit from fluctuating compared to stationary maskers. Our hypothesis is that the representation of the signal in the dips is the most important predictor of performance [Jin and Nelson (2006)]. Because the audibility of the signal is the most critical factor, we tested normal-hearing (NH) and hearing-impaired listeners at similar reduced audibility levels. Listeners with normal hearing and hearing loss were presented IEEE sentences at a range of overall levels (from 30- to 80-dB sound pressure level), signal-to-noise ratios, and low-pass filter settings, resulting in a range of signal AIs that varied from 0.1 to 0.95. For the NH listeners, there was a very systematic relationship between AI and performance, but the slope of the function for the higher level stimuli was shallower than that for the low-level stimuli, suggesting that the active mechanism is at work at low levels both in quiet and in noise. The relationship between AI and performance was less systematic for listeners with hearing loss. [Work supported by NIDCD R01-DC008306.]
Improvement of consonant identification in noise by spectro-temporal enhancement.
Authors: Liu Chang , Eddins David A.
Published: March 2010

Our previous studies have shown that perception of vowels and consonants in long-term speech-shaped noise (LTSSN) by listeners with normal and impaired hearing is improved significantly by spectro-temporal enhancement resulting from modifications in the spectral modulation domain. The present study manipulated several parameters of enhancement processing including length of the analysis window and size of fast Fourier transform (FFT) analysis to determine which parameters produce the greatest improvement in stop consonant identification in the presence of LTSSN and cafeteria noise for normal-hearing listeners. The speech signals were presented at 70-dB sound pressure level and the signal-to-noise ratio was varied in fixed steps. Results indicated that identification of stop consonants increased by about 10 percentage points in LTSS noise and by about 25 percentage points in cafeteria noise when the length of analysis window was 200 ms and the FFT size was 512 points. Subsequent acoustic analyses showed that such perceptual improvement may be due to enhancement of formant transitions relative to background competition.
The speech scale.
Authors: Umesh S. , Cohen Leon , Nelson Douglas
Published: March 2010

Using the Timit database, we describe experimental results that lead to the concept that sounds made by different individuals and perceived to be the same that can be transformed into each other by a speech scale. The speech scale is empirically determined using only speech data. We show the similarity of the speech scale to the MEL scale of Stevens and Volkmann, which was derived only from hearing experiments. We thus argue that we have experimentally linked speech production and hearing.
Native and non-native speech database for children.
Authors: Bent Tessa
Published: March 2010

Language acquisition, performance in school, and social interactions all require the ability to compensate for the enormous amount of variability in the speech signal. Foreign-accented speech represents one common, real-world source of speech variability, which can be particularly challenging for accurate speech perception. Although maintaining perceptual constancy in the face of variability is necessary for effective communication, little is known about how listeners develop the skills to compensate for speech variability. As a resource for investigating this issue, I am developing a new database of foreign-accented speech with materials appropriate for children. The database includes 28 speakers with 4 from each of the following language backgrounds: American English, Spanish, Mandarin, French, German, Japanese, and Korean. In each language group, half of the talkers are female. Speakers were recorded reading words, sentences, and paragraphs in English, which have been used in previous research and clinical settings with children. The database also includes assessments of objective intelligibility, perceived comprehensibility, and strength of foreign accent by adult native listeners. With this database, I plan to assess the development of the cognitive-linguistic skills that underlie a listener’s ability to compensate for variability in the speech signal. [Work supported by NIH-NIDCD R21-DC010027-01.]
Cross-language perception of Mandarin affricates in conversational vs careful speech.
Authors: Woods Anna C. , Warner Natasha L.
Published: March 2010

Two affricates “zh” and “j” in Beijing Mandarin are often confused by English speakers learning the language [Dow 1972]. An experiment based on the work of Logan in 1989 training Japanese speakers to distinguish the difference between English /∈vr/ and /l/ was modified to include training tokens taken from native Mandarin speakers’ phone-conversational speech. “j” is described by Lee and Zee [2003] as laminal pre-palatal, and “zh” is described as apical post alveolar. In careful speech, the sounds are in complementary distribution, with “j” always followed by a high front vowel or a glide. A preliminary perception experiment shows whether native Mandarin speakers are able to distinguish between the pair of affricates simply by hearing the affricate alone, or if they are only able to distinguish them when hearing the vowel information as well. In conversational speech, the following high front vowel may be deleted, so natives’ perception of the two affricates may differ for casual speech. English speakers with no Mandarin experience also participate in a perception task to show the effects of training with conversational speech tokens. This study elucidates how learners acquire categories despite the variability of natural speech.
Effect of age on clear speech intelligibility.
Authors: Smiljanic Rajka
Published: March 2010

Previous work has established that elderly adult’s comprehension is more detrimentally affected by noise, multi-talker babble and the absence of contextual cues compared to younger adult’s comprehension. Elderly adult’s abilities to understand fast speech and to detect/recognize brief non-speech and speech sound sequences (e.g., stop gaps) also decline with age. These effects seem to persist even when hearing loss is taken into account. In this study, we explored whether there are parallel effects of age on speech production, i.e., whether elderly adult’s production patterns differ from those of younger adults. Specifically, we examined whether elderly and younger adult’s hyper-articulation clear speech strategies provide similar intelligibility advantage for younger adult listeners. The sentence-in-noise perception results revealed that elderly adult’s clear speech increased intelligibility for young adult listeners. Importantly, the overall elderly adult’s speech intelligibility and the clear speech intelligibility gain were smaller compared to that provided by the speech of younger adults. Acoustic correlates of the differences in the observed clear speech gain provided by older and younger adults are explored. These results suggest that, in addition to perceptual problems, cognitive and hearing changes due to age can affect elderly adult’s speech patterns and intelligibility.
American English adults’ perception of Spanish-accented conversational and clear speech.
Authors: Levy Erika S. , Garcia Paula B. , Leone Dorothy , Lew Jessica A.
Published: March 2010

Clear speech, an intelligibility-enhancing manner of speech production, has been shown to increase the transmission of information to various listener groups when uttered in the speaker’s native language. When clear speech is used in a non-native language, it is not evident whether this mode will also improve intelligibility. The present study examined the accuracy with which adult monolingual native American English (AE) listeners identified Spanish-accented vowels produced in conversational and clear speech modes. Consonant-vowel-consonant (CVC) words were presented in the carrier sentence “Touch the CVC please,” containing the AE vowels /æ, ʌ, ɑ, ε, i, ɪ/. The sentences were produced by a native speaker of AE and by a native speaker of Spanish judged as moderately accented by the AE listeners. Five pairs of photographs (cap-cup, map-mop, nut-knot; ship-sheep, pot-pet), representing the vowel pairs /æ-ʌ/, /æ-ɑ/, /ʌ-ɑ/, /ɪ-i/, /ɑ-ε/ were presented visually on a touch screen in a two-alternative forced choice paradigm. Listeners had the greatest difficulty with the /ɪ-i/ and /ʌ-ɑ/ contrasts. Clear speech mode was not as effective for non-native speech as it has been shown for native speech. Implications are considered for social and clinical settings in which a mismatch in language backgrounds is present.
Distilled sensing for sparse recovery.
Authors: Haupt Jarvis , Castro Rui , Nowak Robert , Baraniuk Richard G.
Published: March 2010

The study of sparsity in data-rich applications has recently garnered significant attention in the signal processing, statistics, and machine learning communities. Generally speaking, sparsity quantifies the phenomenon where, in a large collection of data, only a small fraction is significant. Techniques that exploit sparsity are currently utilized in a wide variety of applications, including conventional and medical imaging, rf communications, signal intelligence, and bioinformatics, to name a few. Recently a renewed emphasis has been placed on identifying techniques that make judicious use of sensing resources, with the goal of extracting only the relevant information in high-dimensional but sparse signals. Among these techniques, the most promising approaches typically employ some form of active sampling, or sampling with feedback. Distilled sensing highlights how active sampling can result in rather surprising (and dramatic) improvements over traditional sampling methods.
Hands-on demonstrations for Project Listen Up: Education outreach.
Authors: Allaire Hannah E. , Carlson Bethany L. , Devlin Julie , Dibiasie Alaina D. , Porterlott Krysta L. , Renzhofer Erica B. , Voneiff Janet S. , Carman Jessie , Korman Murray S.
Published: March 2010

Midshipmen from the General Science Major will be getting involved in an ASA education outreach effort by presenting a number of acoustical demonstrations geared to promote a hands-on learning experience for middle- and high-school age girl scouts. The demos are designed to visualize certain sound wave effects that will be explained by the Midshipmen (role models) who hands-off the controls of the apparatus to the students who will be free to participate and make their own scientific discoveries. The demonstrations will be (1) sympathetic vibrations of matched xylophone bars or matched tuning forks mounted in quarter-wave resonant open-ended boxes, (2) tuning fork excitation of standing waves in a sound resonance tube with a variable water column, (3) small inexpensive speaker placed in a hole in a baffle or inside a megaphone generating enhanced sound by eliminating destructive interference effects, (4) interference from two separated loud speaker sources measured vs microphone location, and transverse wave visualizations using a (5) torsion wave machine and (6) a small ripple tank. The traveling and standing wave patterns in (5) and the reflection, refraction, interference, and scattering effects in (6) are helpful wave visualizations and aid in the understanding of longitudinal sound wave effects.
Demonstration of an air column resonance with a corrugated tube.
Authors: Vigeant Michelle C.
Published: March 2010

Standing waves, or resonances, will occur in an open-ended tube when the air in the tube is excited at a particular frequency or its harmonics. The resonant frequencies are a function of the tube length. The first standing wave, fundamental mode or first harmonic, is set-up with antinodes at each end of the tube, as the air is free to move at the ends, with one node in the middle of the tube. Each successive standing wave has an additional anti-node and node, with the second harmonic containing three, antinodes and two nodes, the third containing four and three, respectively, and so on. This phenomenon of an air column resonance will be demonstrated using corrugated tubes. By spinning the tube overhead at a particular speed, the resonance frequencies will be excited. For slower speeds, lower frequencies will be heard, while the pitch will increase for faster speeds. Instrumental examples of open-ended tubes include the flute and organ pipes.
Amplification.
Authors: Sen Gupta Ananya
Published: March 2010

In this experiment the students will see a demonstration of how sound waves can be amplified. The setup of the experiment is simple: a tuning fork, a table, and a music box. First the tuning fork is struck by itself and the level of the sound emitted is noted. Then the tuning fork is struck again and held against a table. The amplification of the sound due to propagation of acoustic pressure waves through the larger surface area of the table is noted. The students are encouraged to participate and give their own reasoning for sound amplification. If time permits, students will experiment with the music box as well.
Ultrasonic levitation.
Authors: Pemberton Labuda Cecille
Published: March 2010

Ultrasonic standing waves are set up between a horn and a brass plate. Because the wavelength is short, several wavelengths fit in the space between the horn and the plate. There are locations in the standing wave pattern where the forces associated with the sound pressure and the motion of the air molecules are opposite in direction to the gravitational force. A light ball placed at any of these locations will levitate if the mass of the ball is such that the gravitational force on the ball is equal and opposite to the forces associated with the pressure and the motion of the air molecules.
Acoustic demonstrations for the iPod generation.
Authors: Johnson Shawn F. , Arvelo Juan I.
Published: March 2010

Today’s “iPod generation” can gain a unique and interactive exposure to physics by leveraging their musical interests, and their iPod, to explore the science of sound. Inside certain models reside a mini-computer and a suite of acoustic and vibration sensors, including loudspeakers, microphones, and accelerometers. Combined with free or inexpensive software applications or “apps,” these highly portable devices can offer a tangible means to help students understand many physics, audio, and acoustics concepts that they can explore both inside and outside the classroom. We will demonstrate several apps that are currently available, for example, a seismometer, signal generator, noise level meter, spectrum analyzer, oscilloscope, and various musical instruments. Demonstrations utilizing an iPod Touch are guaranteed to excite students of all ages.
Fourier synthesis.
Authors: Hanson Helen M.
Published: March 2010

Fourier synthesis is the act of building a complex waveform from simple sine waves. Fourier analysis, on the other hand, decomposes a complex waveform into simple sine waves. Both Fourier synthesis and analysis are powerful tools in many scientific and engineering fields, allowing one to understand waveforms of all types in terms of their frequency content. In this experiment, Fourier synthesis will be brought to life as an acoustic waveform is built by combining several harmonic waves. A keyboard will generate the waves, which will then be observed using a computer.
Ocean acoustic tomography: Live from the Philippine Sea.
Authors: Van Uffelen Lora J. , Wage Kathleen E.
Published: March 2010

In this live interactive video session, scientists onboard the R/V Roger Revelle in the Philippine Sea off the coast of Taiwan describe the basic concept of sound propagation in the ocean in the context of an ongoing acoustic mooring deployment. Six acoustic source moorings and a distributed hydrophone array will be deployed during the course of the month-long cruise. The scientists will give an introduction to how research is carried out at sea and will describe basic concepts and advantages of using acoustics as a tool to learn about the ocean environment. They will show examples of oceanographic instrumentation, including conductivity-temperature-depth sensors, acoustic sources, and hydrophone receivers, and will describe the process of deploying acoustic moorings and acquiring oceanographic data. The girl scouts will learn how sound is used to map the 6-km deep ocean floor as well as how tomographic moorings can be used to sense the ocean interior. There will be the opportunity to interact with scientists on the research ship and ask questions about ocean acoustics or life at sea. [Field work supported by ONR.]
Standing waves on a spring.
Authors: Smith Holly A. , Tubbs Tara L.
Published: March 2010

This demonstration shows how standing waves on a spring can be generated by having two people simulate boundary conditions. If one person holds the end of the spring at rest while the other drives the opposite end in an up and down motion, the spring will begin to oscillate. By having the person driving the spring adjust her rate of motion, she will eventually find a rate of motion that produces a single standing wave on the spring. This rate is the fundamental frequency, and it is dependent upon the tension in the spring as well as the spring’s mass per unit length. The fundamental frequency can be measured by timing the up and down motion of the standing wave for 20 cycles and dividing 20 by the recorded time, giving you the fundamental frequency in cycles per second. Other harmonics of the spring can be produced by increasing the driving rate to integer multiples of the fundamental frequency.
Design of critical listening rooms: A historical perspective.
Authors: D’Antonio Peter
Published: March 2010

Critical listening room design has progressed to follow loudspeaker evolution from mono to two-channel to multi-channel, as well as the advances in loudspeaker quality. There are basically two fundamental approaches to two-channel room design. The non-environment room, in which the contribution of the room is minimized, and versions of live-end-dead-end, in which early reflections were minimized creating a spatio-temporal reflection free zone and diffuse reflections from the rear of the room are used to create passive surround sound. This presentation will focus on an immersive design for multi-channel loudspeaker formats, which utilizes broad bandwidth absorption and diffusion. Research with low-frequency plate resonators and a broad bandwidth diffusion chamber has contributed to the proposed design and results will be discussed. The proposed multi-channel critical listening room includes the use of low-frequency control down to 40 Hz provided by 4-in.-thick metal plate resonators on a portion of the front wall and in all corners, broad bandwidth diffusion on all wall and ceiling surfaces, and strategically placed multiple subwoofers. The intent is to minimize monophonic reflections and create lateral enveloping energy by uniformly scattering sound from all of the active sound sources in the room.
Work on the reproduction of sound at the Visualization Laboratories at the King Abdullah University of Science and Technology: A case study.
Authors: Ellison Steve , Otto Peter
Published: March 2010

Researchers at the newly opened King Abdullah University of Science and Technology are developing new ways to visualize and auralize complex data sets in immersive environments. These environments include the Interactive Media Room, a 100-seat multi-purpose facility, and Cornea, a 10 × 10 × 10 in.3 six-sided stereoscopic cave. Both facilities are equipped for multi-channel audio generation and playback in various standard and custom formats, as well as electronically variable acoustics utilizing electroacoustic architecture. Concurrent viewing and dialogue between participants in the two spaces is supported. Fully immersive environments present unique challenges due to physical properties of projection screens and the geometries that characterize these structures. Explorations of Cornea at KAUST and StarCave at UCSD are presented, along with strategies for reproducing sound and varying acoustics in these environments. Multi-use facilities such as the IMR also have conflicting acoustical goals. For instance, the optimal acoustic for multi-channel or cinematic reproduction is less reverberant than optimized classroom environments. The use of electroacoustic architecture to improve the listening and overall immersive experience at both Cornea and the Interactive Media Room is discussed. Examples are presented including an experimental VR emulation of the acoustics of the King Abdullah Grand Mosque on the KAUST campus.
Small music venues and amplified sound: High-sound pressure levels and architecture.
Authors: Woolworth David S.
Published: March 2010

This paper is a survey of typical popular live music venue sound pressure levels observed in Oxford, MS. An attempt is made to measure clarity and articulation in the venues with increasing sound pressure, and the results are correlated with previous observations of Knudsen and others. Additional analysis of challenges to sound operators and programs to control high-stage volumes are discussed.
Evaluation of a boss model and subtraction technique for predicting wideband scattering phenomena in room acoustics.
Authors: Natsiopoulos Georgios
Published: March 2010

Scattering from a hard hemisphere on an infinite plane is studied experimentally and theoretically in a laboratory environment using a subtraction technique. With this technique, the scattered field is determined by subtracting the transient responses from the plane with and without the boss present. Scattering for different combinations of transducer and hemisphere positions are then classified into a number of cases, denoted in-plane/off-plane and back-/forward/mixed scattering. Theoretical and experimental results are compared and evaluated from an auralization point of view using a one-third octave band smoothing of the contribution from the hemisphere. With the smoothing used, average intensity level discrepancies typically less than 3 dB are obtained for a six octave wide ka-interval, where a equals the hemisphere radius.
Overcoming the idiosyncrasies of spectrogram correlation detection.
Authors: Fristrup Kurt M.
Published: March 2010

Spectrogram correlation has been widely used to detect animal sounds. Effective application of this method to identify Black-capped Vireo (Vireo atricapillus) sounds in 22 000 h of environmental recordings required the use of multiple spectrogram templates for each general type of sound to ensure that substantial subsets of these sounds were not missed by the detector. Over 5 million candidate sounds were identified, but the majority of these were not confirmed by expert review. Accordingly, acoustical features were extracted from a stratified random sample of 8284 candidate sounds that were identified by experts, and a random forest classifier was developed to winnow out the false alarms. The estimated classification error varied by site from 0.5% to 6%. When this classifier was applied to the entire data set, approximately 740 000 vireo sounds were identified. This project illustrates both the feasibility of monitoring birds over large spatial and temporal scales and the challenge of adequately sampling the range of variation in a very restricted class of biological signals.
Wavelets: A comparison with the spectrogram and other methods for time-frequency analysis.
Authors: Loughlin Patrick , Cohen Leon
Published: March 2010

Many natural signals exhibit spectral content that changes over time. Methods for time-varying spectral analysis first emerged in the 1940s with the development of the “sound spectrograph” at AT&T Bell Laboratories. Since then, the spectrogram has become the primary method for time-frequency analysis. Originally implemented as a bank of band-pass filters, today the spectrogram is typically computed digitally via the short-time Fourier transform. Recently, wavelets have been proposed as a superior method for time-frequency analysis. The usual argument is that the spectrogram uses a fixed window length, whereas the wavelet approach uses windows that are longer for lower frequencies and shorter for higher frequencies. While the benefits of this approach are usually taken as self-evident, we explore in critical detail the aims of time-frequency analysis, and the benefits afforded by wavelets versus the spectrogram and modern methods such as the Choi–Williams distribution. In particular, since a primary aim of time-frequency analysis is to study the local spectral and temporal characteristics of signals, we examine the local moments of the various methods. Local moments are related to important signal features such as the instantaneous frequency and bandwidth. We show the effect of fixed windowing versus variable wavelet windowing on these features.
Studies on the effect of shear on compressional wave attenuation.
Authors: Potty Gopu R. , Miller James H.
Published: March 2010

Results of a modeling study to examine the effect of shear on compressional wave attenuation are presented. This study also investigates a shear inversion algorithm based on interface waves using synthetic data. Recent studies suggest that inclusion of shear speed is necessary to explain the correct frequency dependence of attenuation. Synthetic data will be generated for elastic bottom, with different shear speeds, and these data will be inverted for compressional wave attenuation. This could provide insight into the effect of shear speed on the attenuation coefficient obtained from inversion at various frequencies. In addition to investigating this effect, we also develop inversion algorithms for shear speed. One of the most promising approaches is to invert the relation between seismo-acoustic interface waves (Scholte waves) that travel along boundaries between media and shear wave speed. The propagation speed and attenuation of the Scholte wave are closely related to shear-wave speed and attenuation over a depth of 1–2 wavelengths into the seabed. The dispersion characteristics of the Scholte wave has been successfully used for inversion of sediment shear properties. Synthetic data will be used in our study to develop an inversion scheme. [Work supported by Office of Naval Research.]
Toward passive acoustic remote sensing of ocean-bottom gas seeps.
Authors: Greene Chad A. , Wilson Preston S.
Published: March 2010

Cold seeps are gas vents that are found in the ocean, often along continental shelves near sediment-borne methane hydrates. Methane hydrates and methane gas seeps are of particular interest both for their potential use as an energy source and for their possible contribution to global climate change. This work is an initial step toward passively locating cold seeps and quantifying their gas flow rates using acoustic remote sensing techniques. Results are presented from laboratory experiments in which gas fluxes were determined from the radiated acoustic signature of a model seep. The physical principle that supports the technique and its accuracy will be discussed. [Work supported by ONR.]
Numerical experiments on weak shock propagation in marine sediments.
Authors: McDonald B. Edward
Published: March 2010

NRL is planning a set of laboratory and field experiments to investigate weak shock propagation in saturated marine sediments. Questions to be addressed are as follows: (1) How much does the granular content of the sediment increase the effective nonlinearity coefficient? (2) Does the 3/2 order Hertzian nonlinearity inherent to grain contacts play a significant role? Numerical and analytic solutions involving the Hertzian nonlinearity reveal maximum nonlinearity coefficient near zero stress, whereas in a fluid, nonlinearity increases with stress. Numerical experiments are presented using the NPE model [McDonald and Kuperman, J. Acoust. Soc. Am. 81, 1406 (1987)] to determine whether shocks resulting from Hertzian nonlinearity can be observed in the presence of nominal values of frequency-linear attenuation common to granular media. [Work supported by the Office of Naval Research.]
Study of sonoporation at the single cell level and cellular bioeffects associated with sonoporation facilitated by microbubbles.
Authors: Deng Cheri X.
Published: March 2010

The interaction of ultrasound-driven microbubbles with cells results in multifaceted cellular bioeffects including physical disruption of cell plasma membrane and subsequent downstream effects. Microbubble facilitated sonoporation, the ultrasound-induced disruption of plasma membrane, enhances the transport of ions, other intracellular contents, and external agents through the membrane into the cytoplasm via diffusion, thereby making it useful for intracellular drug and gene delivery. Transport of these entities, which depends on the dynamic process of pore formation and resealing, plays important roles in many downstream cellular effects of sonoporation beyond the initial pore formation and subsequent diffusion-related transport. For example, extracellular calcium ions diffused into the cytoplasm initiate the process of membrane resealing. In addition, intracellular calcium transients are generated which may be related to many cellular processes triggered by the important second messenger molecule. Recent results of sonoporation at the single cell level and related bioeffects will be discussed. Electrophysiological techniques reveal the dynamic process of sonoporation. Real-time fluorescence imaging measurements of intracellular calcium concentration in mammalian cells subjected to sonoporation demonstrate the spatiotemporal evolution of sonoporation related calcium transients including the large influx of calcium in sonoporated cells and the complex dynamic calcium oscillations and waves. [Work supported by NIH.]
Ultrasound standing wave fields induce endothelial cell sprouting within three-dimensional engineered tissue.
Authors: Garvin Kelley A. , Hocking Denise C. , Dalecki Diane
Published: March 2010

The field of tissue engineering is working to develop fully functional replacement tissues and organs. To achieve this goal, methodologies aimed at controlling the growth of new vascular systems in three-dimensional (3-D) engineered tissues are needed. We hypothesized that organizing endothelial cells into multicellular, planar bands of cells within 3-D collagen gels using the radiation forces developed in an ultrasound standing wave field (USWF) would promote an angiogenic endothelial cell phenotype. Human umbilical vein endothelial cells were suspended in an unpolymerized type-I collagen solution and were exposed to continuous wave USWFs. The collagen solution was allowed to polymerize during the 15 min USWF treatment to maintain the USWF-induced banded pattern of cells within a 3-D collagen gel. Following a 24 h incubation period, endothelial cell sprouts were observed emerging from USWF-induced endothelial cell bands. The average length of these sprouts was ∼100 μm. Sprouting was absent in sham samples where a rounded cell morphology was observed. The influence of acoustic exposure parameters on endothelial cell sprouting was investigated. These studies indicate that USWF technologies promote formation of capillary precursors in 3-D engineered tissue and thus, this technology has the potential to advance the field of tissue engineering.
Histological evaluation of continuous and pulsed high-intensity focused ultrasound induced vascular bioeffects in the presence or absence of contrast agents.
Authors: Tokarczyk Anna , Rivens Ian , ter Haar Gail
Published: March 2010

A novel experimental model which uses an isolated, cannulated rat mesenteric artery (∼ 400 μm diameter) has been used for the visualization of vessel behavior and damage during therapeutic ultrasound (US) exposures in the presence of contrast agents. The experimental setup includes a fluorescence microscope, ultrasound transducer, and a chamber in which the vessel, attached to micropipettes, can be perfused with a feeding buffer ± contrast agents and fluorescent dyes. A range of continuous and pulsed 1.7 MHz high intensity focused ultrasound (HIFU) exposures have been used at therapeutic and sub-therapeutic intensities (pressures). Vessel wall damage and leakage of intravascular buffer have been observed, predominantly in the presence of contrast agents. The observed lack of vascular constriction and expansion in response to phenylephrine and acetylcholine indicates smooth muscle and endothelial cell damage. This has been confirmed by histology (haematoxylin and eosin staining) and immunohistochemistry. Factor VIII and alpha-actin antibodies (which have receptors localised on endothelial, and smooth muscle cells respectively) have been used for accurate localisation of HIFU affected areas. This model will be also used to investigate the bio-effects induced by the exposure of vessels to diagnostic US exposures in the presence of contrast agents.
Ultrasound induced mechanical induction of mesenchymal stem cells.
Authors: Ruan Jia-Ling , Wang Yak-Nam , Mitchell Stuart B.
Published: March 2010

Low-intensity pulsed ultrasound (LIPUS) has been used to accelerate fracture healing and tissue regeneration but the biological mechanism of these responses is not completely understood. Stem cell activity can be induced through biochemical and mechanical mechanisms. Despite the common use of LIPUS in fracture healing and tissue regeneration, there are only a few studies that examine the mechanical induction of stem cells with ultrasound. The purpose of this study is to determine the effects of ultrasound-generated mechanical stimulus on the behavior of human mesenchymal stem cells (hMSCs) in vitro. In our preliminary studies low-intensity pulsed ultrasound was used to induce mechanical strains on hMSCs in vitro. Amplitudes, pulse durations, and pulse repetition frequencies were varied such that different radiation pressures were generated on hMSCs in culture. Results indicated a significant increase in cell proliferation after 4 consecutive days of treatment as well as a significant difference in the cellular response between treatment parameters. Results suggest that LIPUS can be used to influence mechanical mediated stem cell behavior; however, more research is needed to fully elucidate the relationship between ultrasound and hMSC response.