bluuebunny/crossref_metadata_2025 huggingface dataset:
Sample discrimination of frequency differences with irrelevant context–revisited
Authors: Neff Donna L. , Odgaard Eric C. , Jesteadt Walt
Published: October 2013

This experiment replicated earlier work to provide additional data for post hoc analyses of perceptual weights for conditions with large effects of context on performance. The non-adaptive, 2AFC task was sample discrimination of frequency differences (SD-F) in quiet and with added context stimuli. Listeners were to select the interval in which a pair of target tones was drawn from the higher of two Gaussian frequency distributions (means of 2000 and 2150 Hz). Pairs of context stimuli were added at frequency regions above and below the targets, at distances of 600, 1000 and 1400 Hz. Context stimuli were fixed-frequency tones, noise bands, or random-frequency tones. All stimuli were 100 ms with 5-ms ramps, presented simultaneously. Conditions were tested with and without Gaussian level jitter (standard deviation=3 dB). Mean levels of target and context stimuli were equated or systematically varied across conditions. The results confirm earlier work, with little effect of fixed-frequency tones or noise-band context at any distance from the targets. Random-frequency context tones produced large detrimental effects even at remote distances, due predominantly to effects of the lower-frequency context tone. Level variation had little effect. Different approaches to calculating perceptual weights influences data interpretation. [Work supported by NIDCD.]
Similar improvements in auditory discrimination produced by multiple-hour training with a labeling or discrimination procedure
Authors: Mossbridge Julia A. , Wright Beverly
Published: October 2013

Does the procedure used to train an auditory skill impact the characteristics of subsequent skill improvement? Here, the effects of multiple-hour training with either a labeling or discrimination procedure were compared by using a discrimination procedure to examine performance on six conditions. Listeners completed a pretest on the six conditions, trained on one condition for 720 trials/day for 8 days with either a labeling (n=6) or discrimination (n=6) procedure, then completed a post-test identical to the pretest. The trained condition for labeling-trained listeners was to determine, for each individual presentation, whether the onsets of two tones were synchronous or asynchronous. The trained condition for discrimination-trained listeners was to determine which of two presentations of these same tones had asynchronous onsets. All listeners showed significant improvements on the trained condition. Further, there were no significant differences between training groups in the pattern of improvement across the six conditions, both immediately and one month after training. Thus, multiple-hour labeling and discrimination training yielded similar learning, suggesting that, in this case, both procedures tapped the same neural substrate. These results inform our understanding of the mechanisms of learning and may guide clinical treatment for those with auditory perceptual disorders. [Work supported by NIDCD.]
Pyroshock data acquisition—recent developments using P/R and P/E accelerometers and isolators
Authors: Bateman Vesta I.
Published: October 2013

Mechanical isolators have been developed for piezoresistive and piezoelectric accelerometers to mitigate high frequency shocks before they reach the accelerometer because the high frequency pyroshocks may cause the accelerometer to resonate and/or break. Several commercial mechanically isolated accelerometers are available to the general public and their characteristics have been studied using Hopkinson bar test techniques. The in-axis response of these devices will be compared. Cross-axis response will be presented for one device. Additionally, pyroshock and ballistic shock measurements, performed by international organizations, will be presented for several isolators.
Pyroshock data analysis—The GCPP validation procedure
Authors: Piersol Allan G.
Published: October 2013

This procedure was developed for validating pyroshock data by Powers and the author, using techniques originated by Gaberson and Chalmers in validating naval shock data at lower frequencies and subsequently modified. It requires that the acceleration time history be single and double integrated to obtain a velocity and a displacement time history, which is to be examined. Valid data look like a low-pass filtered acceleration time history which is not integrated. The maximum resulting displacement should approximate the independently measured displacement (often near zero) or that previously computed analytically for the structure at the measured location. In addition, the positive and negative SRS are computed and compared. Valid data usually show similar spectral content.
Phonetic discrimination and non-native spoken-word recognition
Authors: Weber Andrea , Cutler Anne
Published: October 2013

When phoneme categories of a non-native language do not correspond to those of the native language, non-native categories may be inaccurately perceived. This may impair non-native spoken-word recognition. Weber and Cutler investigated the effect of phonetic discrimination difficulties on competitor activation in non-native listening. They tested whether Dutch listeners use English phonetic contrasts to resolve potential competition. Eye movements of Dutch participants were monitored as they followed spoken English instructions to click on pictures of objects. A target picture (e.g., picture of a paddle) was always presented along with distractor pictures. The name of a distractor picture either shared initial segments with the name of the target picture (e.g., target paddle, /paedl/ and competitor pedal, /pEdl/) or not (e.g., strawberry and duck). Half of the target-competitor pairs contained English vowels that are often confused by Dutch listeners (e.g., /ae/ and /E/ as in ‘‘paddle-pedal’’), half contained vowels that are unlikely to be confused (e.g., /ae/ and /aI/ as in ‘‘parrot-pirate’’). Dutch listeners fixated distractor pictures with confusable English vowels longer than distractor pictures with distinct vowels. The results demonstrate that the sensitivity of non-native listeners to phonetic contrasts can result in spurious competitors that should not be activated for native listeners.
Perception of English resyllabification by monolingual Japanese listeners
Authors: Nagao Kyoko , Lim Byung-jin , de Jong Kenneth
Published: October 2013

Previous results (Nagao et al., 2001) show that non-native listeners exhibit remarkably similar patterns of perceptual resyllabification with English listeners, suggesting that perceptual resyllabification is not a language specific phenomenon. The same listeners tended to identify voiced English tokens as voiceless, in keeping with Japanese voicing categories. In order to determine the degree to which the non-native perceptual resyllabification was due to extensive exposure to English, monolingual Japanese listeners, 8 from an older and 12 from a younger generation, participated in the same experiment. Monolinguals showed perceptual resyllabification of the same tokens as do English listeners’, consistent with the previous results. Also consistent with previous results, especially older listeners’ responses were more affected by Japanese voicing categories. In addition, older listeners were more likely than English listeners to identify tokens as CV’s, while younger listeners were less likely to. The results for older listeners are what is expected of biases toward native categories. The results for the younger listeners, however, seem to indicate a developmental process involving the construction of new prosodic categories. [Work supported by NIDCD and NSF.]
On the role of phonetic inventory in the perception of foreign-accented speech
Authors: Sereno Joan , McCall Joyce , Jongman Allard , Dijkstra Ton , van Heuven Walter
Published: October 2013

The current study investigates the effect of phonetic inventory on perception of foreign-accented speech. The perception of native English speech was compared to the perception of foreign-accented English (Dutch-accented English), with selection of stimuli determined on the basis of phonetic inventory. Half of the stimuli contained phonemes that are unique to English and do not occur in Dutch (e.g., [θ] and [æ]), and the other half contained only phonemes that are similar in both English and Dutch (e.g., [s], [i]). Both word and nonword stimuli were included to investigate the role of lexical status. A native speaker of English and a native speaker of Dutch recorded all stimuli. Stimuli were then presented to 40 American listeners using a randomized blocked design in a lexical decision experiment. Results reveal an interaction between speaker (native English versus native Dutch) and phonetic inventory (unique versus common phonemes). Specifically, Dutch-accented stimuli with common phonemes were recognized faster and more accurately than Dutch-accented stimuli with unique phonemes. Results will be discussed in terms of the influence of foreign accent on word recognition processes.
Language-specific effects in speaker and rate normalization
Authors: Jongman Allard , Lai Yuwen , Moore Corinne
Published: October 2013

This study concerns the effects of context on the perception of Mandarin tones. Mandarin tones are primarily distinguished in terms of F0 range and temporal location of inflection point. The most relevant context effects therefore involve changes in speaker and speaking rate. In this study, we compared speaker and rate normalization of Mandarin tones 2 (mid–rising) and 3 (low–falling–rising) by Mandarin and English listeners. Synthetic tone 2–tone 3 continua varying in turning point (TP, the inflection point of the tone), ΔF0 (the difference in F0 between onset and turning point), or both were appended to natural precursor phrases representing high- and low-pitched speakers, as well as fast and slow speaking rates. Results of the rate experiments with Mandarin listeners confirmed that normalization occurs only when precursors and stimuli vary along the same acoustic dimension, a finding previously observed for speaker normalization [C. B. Moore and A. Jongman, J. Acoust. Soc. Am. 102, 1864–1877 (1997)]. English speakers showed speaker and rate normalization effects as well, but only for the continuum in which TP and ΔF0 varied simultaneously. We propose that limitations on perceptual resources allow English listeners to attend to extrinsic information only when intrinsic acoustic differences become more perceptually salient.
An acoustic study of hiatus resolution in two Romance languages
Authors: Chitoran Ioana , Hualde Jose Ignacio
Published: October 2013

Spanish and Romanian contrast vowel sequences [CiV] in hiatus and corresponding diphthongs [CjV], with some interspeaker variation. Both languages contain surface diphthongs derived historically by gliding, /CiV/ > [CjV]. They both show a strong tendency for blocking gliding word-initially, supported by native speaker judgments: Sp. [miope], Rom. [miopu] short-sighted; Sp. [italjana], Rom. [italjana] Italianf. Data from six speakers of each language confirmed this variation. The duration and F2 transition rate of the vocalic sequence were compared, in words containing [i.a] and [ja]. [ia] was significantly longer in hiatus, and had a significantly slower transition rate than in [ja]. However, the ranges of the hiatus and [ja] sets showed some overlap, suggesting that hiatus resolution is not a categorical phonological process. Instead, lexical items fall on a hiatus-to-[ja] continuum. Further comparison of ranges and standard deviations confirmed the correlation between this variation and word position. In both languages more word-initial sequences resist gliding. Significantly less variation was found in the range for hiatus word-initially than for [ja] word-medially. This suggests that the combination of lingual gestures between high and nonhigh vowels is more tightly controlled word-initially than word-medially, a result previously reported for stop sequences [Byrd (1996); Chitoran, Goldstein, and Byrd (unpublished)].
Acoustic and perceptual evidence of complete neutralization of word-final tonal specification in Japanese
Authors: Maniwa Kazumi
Published: October 2013

This study investigated the extent to which the Japanese lexical pitch-accent distinction is neutralized in word-final position. Native speakers of Tokyo Japanese produced minimal word pairs differing in final accent status. Words were produced both in isolation and in a sentential context, where neutralization would not be expected due to following tonal specification. Examination of pitch patterns on relevant moras revealed a clear distinction between accent-opposed pairs produced in context but no such difference between items produced in isolation. Both the words produced in isolation and the words excised from sentential contexts were then presented to Japanese listeners in a lexical identification task. Participants could clearly distinguish items extracted from sentences but identified words uttered in isolation at chance level. These results suggest that phonological neutralization of final pitch accent is complete, showing no effects of underlying specification in either production or perception.
Tone classification of syllable-segmented Thai speech based on multilayer perception
Authors: Satravaha Nuttavudh , Klinkhachorn Powsiri , Lass Norman
Published: October 2013

Thai is a monosyllabic tonal language that uses tone to convey lexical information about the meaning of a syllable. Thus to completely recognize a spoken Thai syllable, a speech recognition system not only has to recognize a base syllable but also must correctly identify a tone. Hence, tone classification of Thai speech is an essential part of a Thai speech recognition system. Thai has five distinctive tones (‘‘mid,’’ ‘‘low,’’ ‘‘falling,’’ ‘‘high,’’ and ‘‘rising’’) and each tone is represented by a single fundamental frequency (F0) pattern. However, several factors, including tonal coarticulation, stress, intonation, and speaker variability, affect the F0 pattern of a syllable in continuous Thai speech. In this study, an efficient method for tone classification of syllable-segmented Thai speech, which incorporates the effects of tonal coarticulation, stress, and intonation, as well as a method to perform automatic syllable segmentation, were developed. Acoustic parameters were used as the main discriminating parameters. The F0 contour of a segmented syllable was normalized by using a z-score transformation before being presented to a tone classifier. The proposed system was evaluated on 920 test utterances spoken by 8 speakers. A recognition rate of 91.36% was achieved by the proposed system.
Japanese adult’s and children’s production and perception of English fricatives: A longitudinal study
Authors: Aoyama Katsura , Guion Susan , Yamada Tsuneo , Akahane-Yamada Reiko
Published: October 2013

This study examined the production and perception of English fricatives by native Japanese (NJ) adults and children (16 per group, mean age=40 and 10 years), and age-matched native English (NE) adults and children (16 per group). The subjects were tested two times (T1, T2) 1 year apart. (At T1, the NJ subjects’ mean length of residence in the U.S. was 0.5 year.) A picture-naming task was used to elicit the production of English words beginning with /s/ and /θ/, and intelligibility scores were obtained for both. The intelligibility scores of the NJ children but not adults improved significantly from T1 to T2. The NJ children obtained significantly lower scores than the NJ adults did at T1, but at T2 the adult–child difference was nonsignificant. The perception of /s/ and /θ/ was tested by a categorial discrimination task. Although the NJ adult’s and children’s scores improved from T1 to T2, the T1–T2 differences were nonsignificant. Thus, the results showed that the NJ children’s production scores improved significantly from T1 to T2, while there was no significant change for the perception scores on the discrimination of /s/–/θ/. The relationship between production and perception in L2 speech learning will be discussed. [Work supported by NIH.]
Temporal features of Spanish-accented English
Authors: Shah Amee , Strange Winifred
Published: October 2013

In this study we attempt to identify the acoustic parameters of Spanish accented English that give it the perception of being accented. Recordings of eight multisyllabic (3, 4, and 5 syllables) words spoken in sentences by 22 Spanish speakers of English and five native speakers of American English (AE) were analyzed for temporal acoustic differences. Segmental durations of Spanish productions, including differences of stressed–unstressed (s/u) vowel duration ratios, Voice Onset Time (VOT) and flap/stop duration, differed from native productions. The sentences and the excised target words were given to native (AE) listeners (N=10) who judged the degree of accentedness on a 9-point scale. The degree of accentedness on target words correlated with perceived ratings on the eight sentences (i.e., global accentedness), rho=+0.82. Spearman rank-order correlations between s/u vowel duration ratios and native listener ratings of accentedness on target words varied from +0.04 to 0.68. The VOT duration of initial voiceless stops correlated positively with accentedness ratings for three of the four words (+0.26 to +0.35). Overall, results suggest that Spanish-accented English is characterized by significant temporal differences from native American English, and that these temporal differences contribute to the perception of accentedness as judged by native American English listeners.
A cross-language study of vowel sounds produced with and without emphasis: Testing the theory of adaptive dispersion
Authors: Hay Jessica F. , Sato Momoko , Coren Amy E. , Diehl Randy L.
Published: October 2013

According to Lindbloms Theory of Adaptive Dispersion (TAD), the aim of talkers is to make phonological contrasts sufficiently distinctive to promote linguistic comprehension by the listener while minimizing the articulatory effort needed to achieve this degree of distinctiveness. When part of an utterance carries new—rather than given—information, it tends to be spoken with greater emphasis and clarity. In this study, several possible acoustic correlates of vowels in emphasized words were examined in American English, French, and Japanese in comparable phonetic and sentence contexts. These possible correlates include an expanded vowel space, greater vowel inherent spectral change, and a greater systematic variation in vowel length. Preliminary analyses suggest that the contrast-enhancing properties of emphasized vowels vary considerably across languages. [Work supported by NIDCD.]
Buried target detection using time reversal in inhomogeneous sediment
Authors: Pierson David , Drake Thomas
Published: October 2013

Time reversal has been demonstrated to refocus acoustic waves in homogeneous media with multiple scatters. It has also been shown to work through a liquid–solid interface when both media are homogeneous. We will show that time reversal can also work to detect objects in inhomogeneous solids. By modeling a single transducer in water located 10 m above the water–solid interface we will show the location of the object can be isolated using an iterative time reversal method. Simulations are performed with the solid medium having a mean density of quartz sand varying spatially with horizontal correlation length 0.5 m and vertical correlation length 0.02 m. A sphere is buried in the sand having a density of iron in one test and a density closer to quartz sand in another. The sphere diameter was changed in each simulation ranging from 9 cm to 19 cm. The initial pulses were sinusoidal with frequencies of 10 kHz, 100 kHz, and 500 kHz. Results show improved localization of the sphere. It will also be shown that the iterative time reversal method goes to a response that is independent of initial pulse frequency as predicted by previous theories. [Research supported by ONR.]
Computer modeling/auralization: Can these computer aids assist architects and owners in making proper project decisions?
Authors: Coffeen Robert C.
Published: October 2013

Computer modeling of architectural spaces and subsequent auralization provides the acoustical consultant with information which is not easily obtained by other techniques and methods, and which leads to better acoustical designs. But, what information does modeling/auralization produce which will help the architect and facility owner make proper decisions relating to room acoustics and electro-acoustics when such decisions have economic and architectural implications? This paper will present several examples of how modeling/auralization will assist in this quest for acoustical understanding and suitable project decisions.
Utilizing computer models for optimizing classroom acoustics
Authors: Hinckley Jennifer M. , Rosenberg Carl J.
Published: October 2013

The acoustical conditions in a classroom play an integral role in establishing an ideal learning environment. Speech intelligibility is dependent on many factors, including speech loudness, room finishes, and background noise levels. The goal of this investigation was to use computer modeling techniques to study the effect of acoustical conditions on speech intelligibility in a classroom. This study focused on a simulated classroom which was generated using the catt-acoustic computer modeling program. The computer was utilized as an analytical tool in an effort to optimize speech intelligibility in a typical classroom environment. The factors that were focused on were reverberation time, location of absorptive materials, and background noise levels. Speech intelligibility was measured with the Rapid Speech Transmission Index (RASTI) method.
A case-study comparison of computer modeling and scale modeling in acoustics consulting
Authors: Calamia Paul T.
Published: October 2013

As an alternate or compliment to computer models, acoustics consultants often make use of scale models to evaluate the efficacy of architectural designs. The intention of this paper is to compare the two modeling approaches, using one or more case studies, to explore the pros and cons of each. Topics of comparison will include cost, geometric representations, effective bandwidths, propagation phenomena (e.g., diffraction), simulation of material properties, and auralization. Where possible, measured data from existing spaces will be presented to provide a reference for the modeled data.
Whale contribution to long time series of low-frequency oceanic ambient sound
Authors: Andrew Rex K. , Howe Bruce M. , Mercer James A.
Published: October 2013

It has long been known that baleen (mainly blue and fin) whale vocalizations are a component of oceanic ambient sound. Urick reports that the famous ‘‘20-cycle pulses’’ were observed even from the first Navy hydrophone installations in the early 1950’s. As part of the Acoustic Thermometry Ocean Climate (ATOC) and the North Pacific Acoustic Laboratory (NPAL) programs, more than 6 years of nearly continuous ambient sound data have been collected from Sound Surveillance System (SOSUS) sites in the northeast Pacific. These records now show that the average level of the ambient sound has risen by as much as 10 dB since the 1960’s. Although much of this increase is probably attributable to manmade sources, the whale call component is still prominent. The data also show that the whale signal is clearly seasonal: in coherent averages of year-long records, the whale call signal is the only feature that stands out, making strong and repeatable patterns as the whale population migrates past the hydrophone systems. This prominent and sometimes dominant component of ambient sound has perhaps not been fully appreciated in current ambient noise models. [Work supported by ONR.]
Revisiting Buldyrev’s theory of the ‘‘axial wave’’ after 30 years
Authors: Palmer David R. , Grigorieva Natalie S. , Fridman Gregory M.
Published: October 2013

We review and summarize some of the more interesting aspects of Buldyrev’s theory of the axial wave as it relates to long-range propagation. Just as with the experimental observations, the theory describes the near-axial acoustic signal in terms of early, geometrical-like arrivals followed by an incoherent arrival that cannot be described using geometrical acoustics. This incoherent arrival, or axial wave, results from a large number of waves which interfere with one another because of the presence of caustic structures along the waveguide axis. It is this interference which prevents the waves from being described in terms of geometrical acoustics. As the propagation range increases, the nature of the axial wave changes because the number of caustics increases and the region of interference associated with each one also increases. For a normal waveguide (axial energy arrives last) the axial wave ‘‘eats’’ a geometrical arrival as each new caustic is encountered along the propagation path. A range is ultimately reached beyond which no geometric arrivals are present in the signal. In underwater acoustics this maximum range is probably unphysically large. For an abnormal waveguide (axial energy arrives first), the axial wave ‘‘spits’’ out geometrical arrivals as the range increases.
The sound production characteristics of high-frequency impinging jet tones
Authors: Henderson Brenda S. , Bridges James , Wernet Mark P.
Published: October 2013

An experimental investigation into the production of high-frequency tones by a supersonic impinging jet using phase-locked shadowgraph photography and high-resolution digital particle image velocimetry (DPIV) is presented. High-frequency tones are often produced for nozzle-to-plate spacings less than two nozzle exit diameters and for nozzle pressure ratios (NPR) less than approximately 3.4, where NPR is equal to the stagnation pressure divided by the pressure at the nozzle lip. The high-frequency tones have lower amplitudes and less impulsive wavefronts than the more dominant low-frequency impinging tones and are presumably produced by a significantly different sound production mechanism. Periodic motion of the jet appears to be confined to the peripheral regions of the jet with no significant motion of the flow in the central regions of the jet behind the standoff shock wave. Unlike the jet motion associated with low-frequency impinging jet tones, recirculating regions are not formed and swept downstream behind the standoff shock wave and stationary stagnation regions are also not observed.
Shallow cavity flow tone experiments: Onset of locked-on states
Authors: Rockwell D. , Lin J.-C. , Oshkai P. , Reiss M. , Pollack M. L.
Published: October 2013

Fully turbulent inflow past a shallow cavity is investigated for the configuration of an axisymmetric cavity mounted in a pipe. Emphasis is on conditions giving rise to coherent oscillations, which can lead to locked-on states of flow tones in the pipe–cavity system. Evaluation of pressure gradients on plan views of three-dimensional representations allows extraction of the frequencies of the instability (Strouhal) modes of the cavity oscillation. These frequency components are correlated with traditional models originally formulated for cavities in a free stream. In addition, they are normalized using two length scales; inflow boundary-layer thickness and pipe diameter. These scales are consistent with those employed for the hydrodynamic instability of the separated shear layer, and are linked to the large-scale mode of the shear layer oscillation, which occurs at relatively long cavity length. The foregoing considerations provide evidence that pronounced flow tones can be generated from a fully turbulent inflow at very low Mach number. These tones can arise even for the extreme case of a cavity having a length over an order of magnitude longer than its depth. Suppression of tones is generally achieved if the cavity is sufficiently shallow.
Wind tunnel measurements of windscreen performance
Authors: Maniet Edward R.
Published: October 2013

Microphone windscreens are routinely used in outdoor acoustic measurements to reduce wind noise pickup. Characterization of windscreen performance outdoors with real wind has several drawbacks notably that the test conditions cannot be controlled. Test methodology has been developed that provides controlled, repeatable measurements of microphone windscreen performance in a laboratory setting. Wind noise measurements are performed using a high-speed/laminar-flow, low-noise wind tunnel that incorporates a large anechoic chamber. The wind tunnel is modified to produce a turbulent flow into which the microphone and windscreen under evaluation are placed. The turbulent velocity spectrum is measured using multi-axis hot-wire anemometers and compared to outdoor data to locate the best position in the turbulent flow to place the test article. Comparative performance measurements of several windscreen designs are presented.
A parametric study of location effects on the sidebands of Helmholtz resonators using boundary element analysis
Authors: Shaw Christopher E. , Moenssen David J. , Kostun John D.
Published: October 2013

An important noise source used to tune automotive interior sound levels and quality is the sound which radiates from the open end of the engine induction system—induction noise. Understanding this source and its tuning can be vital to produce the customer-desired sound inside the vehicle. The most traditional method to attenuate (or tune) induction noise is through the addition of passive devices, the most common of which is the Helmholtz resonator. An unfortunate side effect to such a device is that narrow bands of frequencies higher and lower than the bandwidth of the resonator, called sidebands, tend to be amplified by the device. The subject of this study is to qualify the effect of changing resonator location on these sidebands. This is studied by determining the system frequency response to a white noise input by performing boundary element analysis on a simplified air induction system. The location of the device is varied, and the magnitude and frequency shift of the sidebands are studied. Experimental validation is also provided for select models.
Resonant acoustic measurement of vapor phase transport phenomenon in porous media
Authors: Schuhmann Richard , Garrett Steven
Published: October 2013

Diffusion of gases through porous media is commonly described using Fick’s law and is characterized by a gas diffusion coefficient modified by a media-specific tortuosity parameter. A phase-locked-loop resonance frequency tracker [J. Acoust. Soc. Am. 108, 2520 (2000)] has been upgraded with an insulated copper resonator and a bellows-sealed piston instrumented with an accelerometer. Average system stability (temperature divided by frequency squared) is about 180 ppm. Glass-bead-filled cores of different lengths are fitted into an o-ring sealed opening at the top of the resonator. The rate at which the tracer gas is replaced by air within the resonator is controlled by the core’s diffusion constant. Mean molecular weight of the gas mixture in the resonator is determined in real time from the ratio of the absolute temperature to the square of the fundamental acoustic resonance frequency. Molecular weight of the gas mixture is determined approximately six times per minute. Changes in the gas mixture concentration are exponential in time (within 0.1%) over nearly two decades in concentration. We will report diffusion constants for two different sizes of glass beads, in samples of five different lengths, using two different tracer gases, to establish the validity of this approach. [Work supported by ONR.]
From Kratzenstein to Wheatstone: Episodes in the early history of free reed acoustics
Authors: Cottingham James P.
Published: October 2013

In 1780 C. G. Kratzenstein published a paper in St. Petersburg describing a machine which produced vowel sounds using free reeds with resonators of various shapes. This marks a convenient, if arbitrary, starting point for the history of the free reed musical instruments of European origin. These instruments developed rapidly, and by 1850 the accordion, concertina, harmonica, reed organ, and harmonium all had been invented and developed into more or less final form. A key figure in this period is Charles Wheatstone, who not only published papers on acoustical research but was also an inventor and commercially successful manufacturer of musical instruments, most notably the Wheatstone English concertina. Much of Wheatstone’s research in acoustics and almost all of his work as an inventor of musical instruments involved free reeds. This paper presents some episodes in the development of the free reed instruments and some examples of acoustical research involving free reeds during the 18th and 19th centuries.
Laboratory measurements on free reeds from the reed organ, accordion, and khaen
Authors: Busha Michael , Cottingham James P. , Koopman Philip D.
Published: October 2013

Several series of experimental measurements have been made on the motion of air-driven free reeds. These include individual reed organ reeds mounted on a laboratory wind chamber, accordion reeds mounted on the accordion reed block, and khaen reeds in individual bamboo pipes, in which the symmetric free reed is coupled to the pipe resonator. Measurements of reed displacement and velocity as a function of time have been made using a variable impedance transducer and a laser vibrometer system. Additional measurements made for each type of reed include sound pressure and air flow waveforms, as well as variation of sounding frequency and amplitude of vibration with blowing pressure. In comparing the sound pressure and air flow waveforms among the various types of reeds or for the same reed at different blowing pressures, differences can be understood in terms of the configuration of the reed and reed frame system and the amplitude of reed vibration. Some of the results can be interpreted in terms of simple theoretical models.
Scattering of acoustic evanescent waves by circular cylinders: Partial wave series solution
Authors: Marston Philip L.
Published: October 2013

Evanescent acoustical waves occur in a variety of situations such as when sound is incident on a fluid interface beyond the critical angle and when flexural waves on a plate are subsonic with respect to the surrounding fluid. The scattering by circular cylinders at normal incidence was calculated to give insight into the consequences on the scattering of the evanescence of the incident wave. To analyze the scattering, it is necessary to express the incident wave using a modified expansion involving cylindrical functions. For plane evanescent waves, the expansion becomes a double summation with products of modified and ordinary Bessel functions. The resulting modified series is found for the scattering by a fluid cylinder in an unbounded medium. The perfectly soft and rigid cases are also examined. Unlike the case of an ordinary incident wave, the counterpropagating partial waves of the same angular order have unequal magnitudes when the incident wave is evanescent. This is a consequence of the exponential dependence of the incident wave amplitude on the transverse coordinate. The associated exponential dependence of the scattering on the location of a scatterer was previously demonstrated [T. J. Matula and P. L. Marston, J. Acoust. Soc. Am. 93, 1192–1195 (1993)].
Performance of acoustic sensor arrays operating in atmospheric turbulence: Geometric acoustics regime
Authors: Collier Sandra L. , Wilson D. Keith
Published: October 2013

The performance of acoustic sensor arrays operating in atmospheric turbulence with fluctuations described by a von Kármán spectrum has been investigated for strong diffraction in the presence of strong or weak scattering [Collier and Wilson, ASA June 2001 Meeting, ASA Dec. 2001 Meeting, J. Acoust. Soc. Am. (in submission)]. Here the previous analysis is extended to the geometric acoustics regime, i.e., to the weak diffraction and weak scattering limit. A model for the probability likelihood function is developed and the coherence function calculated. The Cramer–Rao lower bounds of the wavefront angles of arrival are investigated for geometric acoustics and are shown to reduce to the expected expression for the angle-of-arrival variance in the limit of zero noise.
An empirical model for the frequency spectrum of surface pressure fluctuations
Authors: Goody Michael
Published: October 2013

An empirical model is presented for the surface pressure fluctuations beneath a two-dimensional, zero-pressure-gradient, turbulent boundary layer. The model is based on the form of Chase’s model [J. Sound Vib. 70 (1), 29–67 (1980)] given by Howe (Acoustics of Fluid-Structure Interactions (Cambridge U.P., Cambridge, 1998), p. 208]. The model of Chase is adjusted to better agree with several well-respected experimental data sets that cover the momentum Reynolds number range, 1400<Reθ<23400. The new model requires knowledge a priori of the free-stream velocity, friction velocity, displacement thickness, and kinematic viscosity. The new model also incorporates the observed scaling behavior of the pressure spectrum. The size of the midfrequency overlap region of the model spectrum is Reynolds-number dependent. Additionally, the model spectrum beneath flows with different Reynolds numbers collapse to a single curve that decays as ω−5 at high frequencies when normalized using viscous scales. By collapsing at high frequencies when normalized on viscous scales, the model offers a high degree of confidence when extrapolated to flows with a higher Reynolds number (Reθ>23400). Examples are given using analytically calculated flows that extend to Reθ=2.45×106. Integration of the model equation recovers the measured p′/τW to within 8%.
A scheme for noise suppression and spectral enhancement of speech to alleviate speech reception problems from loss of frequency selectivity
Authors: Lyzenga Johannes , Festen Joost M. , Houtgast Tammo
Published: October 2013

Even after sufficient amplification, hearing-impaired listeners often experience problems in understanding speech under noisy conditions. This may be caused by suprathreshold deficits such as loss of compression and reduced frequency selectivity. In this project we investigate a scheme in which speech and noise are processed before presentation to try and alleviate intelligibility problems caused by reduced frequency selectivity. The scheme contains three strategies, one in which the peak-to-valley ratios of selected modulations in the speech spectrum are enlarged, a second in which the overall speech spectrum is modified, and a third in which noise is suppressed before the two enhancement steps. An overlap-and-add (OLA) algorithm is used in the implementation. The effect of the speech processing is evaluated by measuring speech-reception thresholds (SRT) for sentences in speech noise, estimating the signal-to-noise ratio at which listeners can correctly reproduce 50% of presented sentences. Hearing-impaired and normal-hearing listeners were used. To simulate the hearing impairment resulting from a loss of frequency selectivity, we spectrally smeared the stimuli presented to the normal-hearing listeners. We found that the preprocessing scheme achieved a modest improvement of nearly 2 dB in the SRT for normal-hearing listeners. Data for hearing-impaired listeners are presently being collected.
Directional hearing aid using hybrid adaptive beamformer (HAB) and binaural ITE array
Authors: Shaw Scott T. , LaRow Andy J. , Gibian Gary L. , Sherlock LaGuinn P. , Schulein Robert
Published: October 2013

A directional hearing aid algorithm called the Hybrid Adaptive Beamformer (HAB), developed for NIH/NIA, can be applied to many different microphone array configurations. In this project the HAB algorithm was applied to a new array employing in-the-ear microphones at each ear (HAB-ITE), to see if previous HAB performance could be achieved with a more cosmetically acceptable package. With diotic output, the average benefit in threshold SNR was 10.9 dB for three HoH and 11.7 dB for five normal-hearing subjects. These results are slightly better than previous results of equivalent tests with a 3-in. array. With an innovative binaural fitting, a small benefit beyond that provided by diotic adaptive beamforming was observed: 12.5 dB for HoH and 13.3 dB for normal-hearing subjects, a 1.6 dB improvement over the diotic presentation. Subjectively, the binaural fitting preserved binaural hearing abilities, giving the user a sense of space, and providing left–right localization. Thus the goal of creating an adaptive beamformer that simultaneously provides excellent noise reduction and binaural hearing was achieved. Further work remains before the HAB-ITE can be incorporated into a real product, optimizing binaural adaptive beamforming, and integrating the concept with other technologies to produce a viable product prototype. [Work supported by NIH/NIDCD.]
Physical modeling of the feedback path in hearing aids with application to adaptive feedback cancellation
Authors: Hayes Joanna L , Rafaely Boaz
Published: October 2013

Hearing aid system modeling based on two-port network theory has been used previously to study the forward gain and the feedback path in hearing aids. The two-port modeling approach is employed in this work to develop an analytic model of the feedback path by reducing the model matrices to simplified analytic expressions. Such an analytic model can simulate the frequency response of the feedback path given the values of relatively few physical parameters such as vent dimensions. The model was extended to include variability in the feedback path due to slit leaks, for example. The analytic model was then incorporated in an adaptive feedback cancellation system, where the physical parameters of the model were adapted to match the actual feedback path and cancel the feedback signal. In the initial stage of this study, the ability of the model to match the frequency response of various measured feedback paths was studied using numerical optimization. Then, an adaptive filtering configuration based on the physical model was developed and studied using computer simulations. Results show that this new approach to adaptive feedback cancellation has the potential to improve both adaptation speed and performance robustness.
Pyroshock testing—shock simulation facilities
Authors: Bateman Vesta I.
Published: October 2013

A variety of shock simulation facilities are available to simulate pyroshock events. These facilities range from bounded impact shock machines and electrodynamic shakers to resonant fixture techniques. This presentation will focus on the use of general purpose and tuned resonant fixture techniques including a unique tunable beam apparatus developed at SNL. Examples of application of the resonant fixture technique for both component and full-scale structure pyroshock simulations will be presented. Advantages and disadvantages of each technique will be discussed along with the usable frequency content and bandwidth.
Neuroimaging studies of phonetic category learning
Authors: Fiez Julie
Published: October 2013

The Japanese perception of /r/ vs /l/ is being used as a model system to explore a Hebbian-based model of adaptive plasticity. Prior behavioral work has demonstrated the effectiveness of an adaptive training regime and the utility of response feedback on the acquisition of the ability to discriminate a minimal speech pair (e.g., ‘‘rock’’ vs ‘‘lock’’). Imaging, using fMRI methods, is now being used to explore the neural substrates that underlie changes in categorical perception. Two questions are being addressed: (1) in which brain areas can a differential response to /r/ vs /l/ be identified, and is activity in these regions influenced by training? and (2) can the effectiveness of feedback as a part of the training regime be explained by the recruitment of reward-related brain regions that support learning?
Perceptual interference effects on phonetic categorization by second-language learners and cochlear implant patients
Authors: Iverson Paul
Published: October 2013

This talk will outline a new theory that describes how distortions in auditory processing, due to language experience or to hearing impairment, can interfere with phonetic categorization processes. Experimental data will be presented on the perception of American English /r/ and /l/ by American and Japanese listeners. Native-language tests of adult cochlear implant patients, for the /t/–/d/ contrast, will also be presented. The results suggest that the formation and adaptability of phonetic categories are impaired when the auditory processing of speech stimuli increases the salience of within-category acoustic variation.
Formation of categories for complex novel auditory stimuli
Authors: Mirman Daniel , Holt Lori L. , McClelland James L.
Published: October 2013

Categorization of complex sounds with multiple, imperfectly valid cues is fundamental to phonetic perception. To study the general perceptual and cognitive processes that support complex sound categories, a novel stimulus set was created that allows tight control of category structure and input distributions. Stimuli were created from 300-ms noise bursts by applying bandstop filters at varying center frequencies and manipulating rise/fall time of stimulus onset and offset. Stimuli were assigned to one of two categories and presented to participants in a category identification and an AX discrimination task. Feedback was provided during identification trials, but not during discrimination tasks. Participants quickly learned to apply the category labels with high accuracy. Identification reaction times followed a pattern typical of speech stimuli with an apex in reaction time at category boundary. These results are consistent with formation of new auditory categories. Preliminary results indicate that discrimination performance is not tightly coupled with development of sharp identification functions and response-time peaks at category boundaries. Implications for mechanisms of speech categorization and category formation will be discussed. [Work supported by CNBC, NIH, and NSF.]
Forward-scattered acoustic intensity from prolate spheroids
Authors: Rapids Brian R. , Lauchle Gerald C.
Published: October 2013

In bistatic scattering geometries, the detection of a forward-scattered signal is particularly difficult because the incident and scattered waves combine into a simultaneous mixture. The result is that the amplitude of the scattered wave becomes masked by that of the incident wave. During detection of the scattered signal, conventional space-time processing techniques regard the source signal as interference and attempt to suppress it. While vector sensors alone possess an inherent directivity due to their fundamental nature, intensity vector sensors coherently measure the acoustic pressure and particle velocity components (or related quantity such as acceleration, displacement, or pressure gradient). The coherent measurement of both acoustic field parameters may provide unconventional information regarding the presence of an object because of their known relationship. It is hypothesized that techniques based upon these coherent measurements will be able to process the total acoustic field rather than filter the scattered signal from the incident signal during detection. Theoretical and available experimental results will be presented to describe these hypothesized capabilities. [Work supported by ONR, Code 321SS under Grant No. N00014-01-1-0108, Dr. James F. McEachern, project monitor.]