bluuebunny/crossref_metadata_2025 huggingface dataset:
The Acoustical Society of America’s historical contributions to noise and its control
Authors: Beranek Leo L. , Lang William W.
Published: July 2012

The Society’s contributions to noise and its control, a subfield of the broad subject of acoustics, have been significant and constant over the years since the first noise paper was presented at the Society’s first meeting in 1929. The major contributions are considered in an historical context—during the period before World War II when the Society first produced national standards for instrumentation used for noise measurement, during the War and the Postwar Era when there was considerable government support for airborne acoustics research, during the 1950s when Noise Control magazine was published, followed by the 1960s and the later years of the 20th Century. Of the ASA members expressing interest in the 13 different subfields of acoustics, the number concerned with noise is near the top of the list. But ASA is no longer alone. Nearly a dozen other professional organizations in the U.S.A. have groups that are involved with noise and its control. Over the past three-quarters of a century, ASA has played a leadership role in developing the subfield of acoustics focused on noise control, and in producing a broad range of American National Standards on noise and vibration. In the future, ASA must take concrete, positive steps to retain its position of leadership.
Modulated otoacoustic emissions reveal features of the human cochlear impedance at low frequencies
Authors: Marquardt Torsten , Hensel Johannes , Scholz Guenther , Mrowinski Dieter
Published: July 2012

Basilar membrane (BM) displacement by loud low-frequency (LF) tones periodically alters the level of distortion-product otoacoustic emissions (DPOAEs) as a function of the phase of the modulating LF tone. For three human subjects the level of a modulating LF tone (15–320 Hz) was adjusted to maintain a constant DPOAE-modulation depth, indicating a constant periodic LF BM displacement. The resulting modulation LF-tone levels match the iso-loudness contours (ISO/R226) except for an antiresonance centered at about 55 Hz. Here, an increase in level of approximately 5 dB above the iso-loudness contour is required to maintain constant periodic LF BM displacement. The antiresonance separates two distinct regions of the cochlear impedance: a slope of 12 dB/octave at frequencies below 55 Hz suggests a mass-controlled impedance resulting from perilymph flow through the helicotrema; a slope of 6 dB/octave above 55 Hz suggests the existence of a traveling wave with resistive impedance. Psychophysical threshold experiments did not show the antiresonance. Antiresonances have been observed previously in animal experiments using cochlear microphonics or perilymph pressure measurements to estimate BM displacement. Modulated DPOAEs are a noninvasive method to investigate the BM movement at low frequencies.
Investigation of the influence of visual stimuli on the breakdown of the echo threshold
Authors: Djelani Thomas
Published: July 2012

Audiovisual interaction is already known from the ventriloquism effect [W. R. Thurlow and Ch. E. Jack, Percept. Mot. Skills 36, 1171–1174 (1973)]. Synchronously presented auditory and visual stimuli are perceptually grouped and localized as one object. The performed experiments aimed to explore a possible influence of visual stimuli on echo suppression. They focused on investigating whether visual stimuli can also cause a breakdown of the echo threshold. One hypothesis is that the breakdown of echo suppression is caused by violations of the listeners’ expectations concerning the presented scenario. The question is whether this implausibility can be attributed to acoustical reasons. Two different kinds of visual implausibilities were tested by measuring echo threshold with an adaptive paradigm. In the build-up phase of both experiments, visual and auditory parts of the stimuli have been presented from the same direction. In the test phase, the visual stimulus’ direction was altered. The main result of the investigations was that both experiments did not provide any evidence of a visually induced breakdown of the echo threshold. This holds true, even if the position of the auditory event corresponding to the direct sound was changed due to the ventriloquism effect by changing the corresponding visual stimulus’ direction of incidence.
Scattering from a partially filled elastic-shelled sphere
Authors: Fawcett John A.
Published: July 2012

Scattering from spherical scatterers can be analytically formulated in terms of a harmonic series solution. The case of a shelled sphere with an evacuated or filled interior has been particularly well studied. In this paper, the case of a partially filled sphere is considered. A solution for the scattered field is sought in terms of a harmonic Legendre function series. A standard series expansion is used for the shell and the exterior of the sphere. A modified expansion, which satisfies the interface condition within the interior, is used for the inner region. Unlike the standard spherical scattering problem, the system of equations for the various orders (for a fixed azimuthal order) of the Legendre functions are now coupled. Numerical computations are presented for a steel-shelled sphere with various levels of water-fill.
Focused arrivals in shallow water propagation
Authors: DeFerrari Harry A. , Williams Neil J. , Nguyen Hien B.
Published: July 2012

Observations of acoustic pulse transmissions for several sites in the Florida Straits consistently show that a single intense pulse dominates the arrival pattern. For these sound channels, the propagation is by refracted modes that interact with the bottom below the critical angle resulting in favorable low-loss transmission. The intense arrivals come about from focusing of the waveguide and are always observed for downward refracting sound speed profiles whenever the source and receiver are deep in the channel. The foci correspond to caustics of ray theory or to the phase-stationary summation of many modes. Such arrivals are often 20 dB higher than others and are of interest in that they will be the only detectable features at long ranges and have been shown to be stable and persistent enough for tomographic inversion. The coherence properties and fluctuation statistics of focused arrivals are presented and analyzed. Data from a 28-day propagation experiment are presented. The receptions of broadband pulse transmissions are compared for a 10-km propagation range for pulses with center frequencies from 100 to 3200 Hz. Simultaneous measures of the sound speed field are used as model inputs to predict and compare spatial and temporal features of the focused arrivals.
Community noise from theme parks
Authors: Carnes Ted N.
Published: July 2012

Theme and amusement parks are made to generate fun and excitement. As part of the guest experience a great amount of sound energy is often generated and it may be perceived as noise in the surrounding community. Defining outdoor noise criteria for the parks is often done for you by the local municipality zoning and building officials. Thus, one can use sound-modeling techniques to determine potential problems before the parks are built or expanded. While noise control of sound levels at the source is always desirable, there are many sources that defy their use. Thus, control of sound levels along the sound path is all that is often available. All of these concerns about theme parks will be addressed along with some suggestions on how to minimize community noise impacts. Some actual project examples will be discussed with the architectural acoustics aspects emphasized.
Reflector microphones for field recording of natural sounds
Authors: Swenson George W.
Published: July 2012

A directional microphone system for field recording of sounds in the air, for example, bird song or other animal activity, usually involves either a parabolic reflector to focus the sound waves on the microphone (transducer) element, or a linear array of transducers so phased as to respond preferentially to sounds from one directional sector. The latter system (the so-called ‘‘shotgun’’ microphone) can be analyzed in a fairly straightforward manner. The reflector system, however, involving as it does a structure comparable to a wavelength in linear dimension, is not susceptible to the conventional approximate methods of computation. Recently developed computational techniques now permit exact calculation of the directional responses of small reflectors. One result is a proposal for a very economical and effective system involving a plane reflector. No directional microphone can, in practice, reproduce sounds with fidelity to the sounds as emitted by the source.
Portable instrumentation for the recording, analysis, and playback of infrasonic animal vocalizations
Authors: von Muggenthaler Elizabeth
Published: July 2012

Several bioacoustic experiments required an affordable system capable of field recording, real-time analysis, signal editing, and real-time playback of infrasonic animal vocalizations. The synthesis of several types of recording devices and signal processing software has resulted in the capacity to record infrasound and perform analysis even during rain, heat, and high humidity. Small portable microphones and recorders can record in the field from 3 Hz to 22 kHz. On-site analysis including real-time FFT, color spectrographic function, filtering, cross-correlation, and other functions can be facilitated with the use of any portable computer with 92 Mbytes RAM. Signal editing, including frequency, amplitude, and cut/paste can be accomplished with readily available music signal processing software. Real-time field playback from 10 Hz to 45 kHz can be acheived by using portable car audio speakers. This system was used for the real-time analysis of elephant vocalizations, which were edited and played back immediately during recording sessions. It has also been used in field research involving tiger, binturong, rhinoceros, and giraffe. Tigers and elephants appear to respond behaviorally to real-time playback of original and edited vocalizations. [Work supported by National Instruments, Momentum Data Systems, and Sonic Foundry.]
The bioacoustic probe: A general-purpose acoustic recording tag
Authors: Burgess William C.
Published: July 2012

Recent research has demonstrated the utility of acoustic recording tags to assess the exposure and response of marine wildlife to sound [e.g., W. C. Burgess et al., Deep-Sea Res., Part II 45, 1327–1351 (1998)]. The experimental nature of these tags, however, has limited their adoption by the wider bioacoustical community. To enable broader use of acoustic recording tag technology, a new general-purpose tag is being developed. Miniaturization to a cylinder approximately 3 cm in diameter by 16 cm in length will allow application with a variety of species and attachment methods. Initial versions of the device will sample acoustics with 16-bit resolution at bandwidths up to 14 kHz, as well as temperature and depth with 12-bit resolution. Longevity will depend on the choice of sampling schedule; constant acoustic sampling at 2 kHz will fill the 288 MB solid-state flash disk in 21 h, but this lifetime can be extended by reducing resolution or by recording only during times of interest. Results from initial test deployments on free-ranging marine mammals are expected in late fall 2000. [Work supported by ONR.]
Echolocation signals of wild white beaked dolphins measured with a four-hydrophone short base line array in real-time
Authors: Au Whitlow W. L. , Rasmussen Marianne H. , Miller Lee
Published: July 2012

The echolocation signals of Lagenorhynchus albirostris were measured in the waters off Keflavik, Icelend during 22–26 August 1998. A four-hydrophone array was used with each hydrophone located at the tip of an equilateral triangle and one located at the center of the triangle. Each of the outer three hydrophones was spaced 0.61 m from the center hydrophone and the separation angle between outer hydrophones was 120 deg. An underwater video camera was attached 10 cm from the center hydrophone. The array was mounted on a long pole that was lowered to a depth of about 2 m from the side of a 10-m diesel driven boat. The hydrophones were connected to two GAGA-1210 data acquisition boards operating at a 500-kHz sample rate. The computer clock was synchronized with the clock on portable video recorder. Two-hundred pretrigger and 200 posttrigger points per channel with four channels of data were acquired simultaneously and stored in the memory of a transportable computer. The results indicate that the white beaked dolphins emitted high-frequency clicks with peak frequencies close to 120 kHz. The maximum source level of the echolocation signals was 219 dB and the source levels increased with range from the array.
Application of space-based synthetic aperture radar imagery for estimating underwater ambient noise
Authors: Hutt Daniel L.
Published: July 2012

Synthetic aperture radar (SAR) imagery of the ocean surface provided by the Radarsat satellite can provide estimates of surface waves, winds, and shipping density. These are the parameters which are mainly responsible for underwater acoustical ambient noise. The remotely sensed surface conditions can be combined with knowledge of the acoustical propagation environment and geoacoustic properties of the bottom to estimate the ambient noise field. Although difficulties exist with SAR-derived wind fields and ship detection, these are balanced by the wide area coverage and high spatial resolution of the SAR sensor. We review space-based SAR capabilities relevant to ambient noise estimation and compare Radarsat-derived wind fields to in situ measurements for two Radarsat passes over the Atlantic Ocean. Ambient noise levels measured during the overpasses compare favorably with those estimated using the Radarsat wind data.
Computation of free-jet turbulence and exhaust-mixing noise from a turbofan engine
Authors: Schein David B. , Meecham William C.
Published: July 2012

A model presented previously [D. B. Schein, paper 3pEA3, 136th Meeting of ASA (1998)] has been extended and applied to prediction of exhaust noise from a high Reynolds number, hot exhaust flow. Simulations for a Williams Research WR19-4 turbofan engine exhaust have been performed and results compared with far-field acoustic data measured during static test runs of the engine at exhaust Mach numbers up to 0.8. The hybrid CFD/CAA approach employs a deductive subgrid scale model for small-scale compressible turbulence combined with the time-derivative form of Lighthill’s source-integral acoustic analogy, containing the fluctuations represented by the time-varying stress tensor. Overall sound pressure level directivity and representative spectra are presented. Analytical results indicate generally good agreement with measured data and popular semiempirical prediction methods. Spectral analysis indicates that significantly larger computational domains and simulation times will be required to obtain low-frequency energy content radiated from aircraft engine exhausts.
Noise and vibration control for the Alameda Corridor project
Authors: Vazquez Joel
Published: July 2012

The Alameda Corridor project is a 20-mile railroad cargo expressline that will connect the ports of Los Angeles and Long Beach to the transcontinental rail network east of Los Angeles. Once completed, the corridor will create a fast and efficient way to move cargo through United States and overseas world markets. The midcorridor section of the project consists of a 10-mile long, 33-ft descent into a by-railway Trench. Although this Trench will be the featured portion of the midcorridor project, the construction of a by-pass track will facilitate cargo-laden freight passage while the Trench is constructed as well as provide access for local businesses after completed. On its path from the ports to downtown Los Angeles this massive construction project will traverse potential noise and vibration-sensitive areas that house single and multi-family residences, motels, schools, daycare centers, parks, and churches. One of the greatest challenges encountered with projects of this magnitude is the successful control of construction and operational noise and vibration. The presentation will focus on various noise and vibration control methods that have been implemented as part of an abatement program. The scope of this successful program includes monitoring, equipment noise certification, and impact studies.
Laryngeal configuration and acoustical properties during flute vibrato
Authors: Hwang Joon-Hee Beth , Thorpe C. William
Published: July 2012

This study reports on simultaneous measurements of glottal aperture and spectral analysis of flute vibrato for a group of six expert flute players. The glottal aperture was recorded using a nasendoscope and the sound was recorded using a portable DAT recorder. Video images were selected from stable portions and digitized, and measurements of the vocal fold opening were made from the display. The sound recording was also digitized and was analyzed using matlab. The results showed an oscillatory pattern on the glottal opening together with the vibrato oscillations in the acoustic signal. The change in glottal opening between maximum and minimum adduction during this oscillation was an average of 7.42 mm for loud playing and 1.73 mm for soft playing. The spectral analysis also showed that the amplitude modulation occurs mostly in the higher partials of the tone. These results strongly suggest that the larynx plays an important role in developing vibrato in the flute tone. It appears that the larynx modulates the airflow, thus producing pressure fluctuations in the mouth that generate the oscillatory ‘‘vibration’’ of the acoustic tone as observed in previous studies [N. H. Fletcher, J. Acoust. Soc. Am. 57, 233–237 (1975)].
Effective lengths of trombone bells with mutes
Authors: Lodin Michael S. , Ayers R. Dean , Eliason Lowell J.
Published: July 2012

A brass player employs mutes in performance to modify spectral characteristics of the sound output for musical effect. An undesirable side effect is a modification in pitch center, which is easily compensated for in the trombone by a small adjustment in playing slide position. The effects of various mutes upon the sounding frequencies of the trombone are studied by determining the change each mute produces in the effective length of an equivalent, closed-end air column. For both the open-bell case as well as with various mutes inserted, an impulse-response technique is used to determine the phase shift of each frequency component induced at the bell end, leading to a calculation of a frequency-dependent effective length for each configuration [R. W. Pyle, Jr., J. Acoust. Soc. Am. 57, 1309–1317 (1975); R. D. Ayers, ibid. 98, 81–87 (1995)]. The various lengths are compared with each other, as well as with the practical experience of brass players in using them during performance. [Work supported in part by the Scholarly and Creative Activities Committee at CSULB.]
Nonlinear effects in an asymmetrical vibrating wire
Authors: Hanson Roger J. , Macomber H. Kent , Morrison Andrew
Published: July 2012

The asymmetries of a vibrating harpsichord wire which yield different free vibrational frequencies along two characteristic orthogonal transverse axes were described previously [Hanson et al., J. Acoust Soc. Am. 106, 2141 (1999)]. This splitting of the fundamental vibrational frequency is of the order of 0.3%. Its value depends upon the particular wire sample and the tension, with lower tensions yielding larger absolute splittings. For the 2nd, 3rd and 4th vibrational modes, splittings differ greatly from integral multiples of the splitting of the fundamental. If the wire is driven sinusoidally there can be large nonlinear generation of motion in a direction (P) perpendicular to the driving direction (D) and of higher harmonics of the driving frequency. These nonlinear effects are, however, very sensitive to the frequency splitting and the relation of the driving direction to the characteristic axes. Theory indicates that P/D∼1, independent of the vibrational amplitude. However, with a small splitting of 0.11 Hz out of 77 Hz, it was found that to obtain P/D∼1 an amplitude at the antinode of about 0.15% of the wire length was necessary. The driving frequency region for generation of higher harmonics is sharply dependent on the higher free-vibration mode frequencies.
Study on double decay of individual partials of piano sound—Preliminary results on the ‘‘unison quality.’’
Authors: Causse Rene , Felix Simon
Published: July 2012

A characteristic of piano tones is their double decay (the initial sound followed by the ‘‘aftersound’’). The difference in mistuning between the three strings of a unison group, and also the adjustment of the regularity of the action of the hammer in the case of important irregularities in hammer striking, are parameters used by the tuner to adjust the temporal evolution of the sound. This study is a part of a more general study to explore what tuners call ‘‘unison quality,’’ which means finding objective and qualitative criteria to decide that the temporal evolution is well adjusted. The results of experiments are reported where the decay of the first 12 partials of real sounds recorded under different conditions is analyzed and then modified by signal processing. The results of informal listening tests indicate that experts (tuner, professional pianists, and composers) are sensitive to these modifications (removal of very brief amplitude falls observed for the different partials). The decay of the different partials seems to be more complex than the double decay observed for the global sound and for the fundamental frequency. Sound illustrations will be presented.
Infinite impulse response-based simulation of room acoustics
Authors: Amin Parita , Tsui Jing , Thompson Charles
Published: July 2012

In this work, the problem of filter construction for the point-to-point impulse response in a room is examined. Our particular interest is infinite impulse response (IIR) filters. It will be shown that such filters can be constructed from image-based models. The use of subband IIR filter models is investigated. Our model provides perfect reconstruction of early arrivals. The late arrivals in the impulse response are in agreement only in the least-squared sense. Experimental results will be given for the room impulse response.
On the estimations of sound field by source-distributed methods
Authors: Too Gee-Pinn James
Published: July 2012

Source-distributed methods were developed earlier by Stepanishen et al. and many others to study the radiation sound field. There are several articles discussing the properties of these methods, although there are alternative names for the source-distributed methods. In the present study, the properties of these methods are summarized. The applications of source-distributed methods for radiation and scattering sound fields are demonstrated. It is interesting to show that the errors in the near-field measurement might be canceled out in the estimation in the far field. In the application for estimation of interior sound field, the source-distributed methods also give good results compared with the results of the Helmholtz integral formulation. In addition, it is pointed out that there are some restrictions in the methods. [Work supported by NSC of ROC.]
Application of random walk methods to wave propagation
Authors: Budaev Bair , Bogy David
Published: July 2012

We present an approach to problems of diffraction that has its roots in a number of well-established theories such as the geometric theory of diffraction, the methods of Feynman’s path integrals and Wiener’s functional integrals, and the theory of stochastic processes. We start our analysis of the Helmholtz equation by closely following the scheme of the ray method, but instead of approximating the resulting second-order auxiliary equation by a first-order transport equation, we study the original auxiliary equation and obtain its exact solution as the mathematical expectation of a specified functional in the space of Brownian trajectories with the Wiener probabilistic measure. The obtained solution appears to be a direct improvement of the ray method approximation to the exact solution of the Helmholtz equation, and it is shown to admit efficient numerical evaluation. [Work supported by NSF Grant 9730779.]
Analysis of fields and forces on particles in an open-sided acoustic resonator using FEM with a perfect matched layer
Authors: Zheng Yibing , Apfel Robert E.
Published: July 2012

The standing acoustic field in an axisymmetric open-sided resonator with a curved reflector is studied using the finite element method (FEM) with an anisotropic perfectly matched layer (PML) boundary condition. This kind of open-sided resonator is widely used in acoustic and acousto-electric levitators, where the acoustic field is not considered as one-dimensional due to the shape of the reflector. The method has been successfully employed to calculate the acoustic field profiles, the resonance frequencies, and the quality factors of the resonant modes. The numerical results of resonators with a concave or convex reflector are compared with those of the analytical asymptotic method. In the resonator of a real acoustic levitator, this method can calculate the acoustic fields driven by the surface vibration of the transducer, with and without particles levitated. The acoustic radiation forces on levitated particles are analyzed in such acoustic standing fields. The authors are trying to extend this study to characterize the levitation of a three-dimensional drop array in an acousto-electric levitator. [Work supported by NASA (NAG3-2147) and by NSF (CTS-9870015).]
The effect of time-dependent void fractions in the oscillations of wet foam drops
Authors: Akhatov Iskander , McDaniel J. Gregory , Holt R. Glynn
Published: July 2012

We develop a model for the nonlinear oscillations of spherical drops composed of aqueous foam. Beginning with a simple mixture law, and utilizing a mass-conserving bubble-in-cell scheme and a uniform pressure approximation, we obtain a Rayleigh–Plesset-type equation for the dynamics of bubbles in a foam mixture. The dispersion relation for sound waves in a bubbly liquid is then coupled with a normal-modes expansion to derive expressions for the frequencies of modal oscillations. These modal (breathing plus higher-order shape modes) frequencies are elicited as a function of the void fraction of the foam. A Mathieu-type equation is obtained for the dynamics of the higher-order shape modes and their parametric coupling to the breathing mode. Numerical results are presented. [Work supported by NASA.]
A study of knock and adiabatic process in multi-fuel engines
Authors: Cerdá Salvador , Romero José , Navasquillo Joaquín , Zurita Grover
Published: July 2012

For both engine designers and control purposes, a better understanding of the knocking that occurs during combustion in engines can lead to optimal decisions which will make engines operate more efficiently. The rapid rise in diesel engines is recognized as an audible impulse noise, which is known as ‘‘knock.’’ The knock is caused by the spontaneous combustion of a significant volume of fuel/air mixture. The knock produces shock waves within the combustion chamber and results in a great number of combustion chamber resonance frequencies. The engine used in the experiments was a six-cylinder modified diesel engine running in ethanol conditions. The main purpose of this research is to determine the knock phenomena and the adiabatic process. To perform the data analysis a time-frequency spectral approach was used. The results revealed both radial and circumferential resonances. The most important adiabatic coefficients were carried out and used to calculate the heat release rate.
A study of simulation methods of limited diffraction beams
Authors: Peng Hu , Zhang Zuosheng , Lu Jian-yu
Published: July 2012

Limited diffraction beams such as Bessel beams and X waves have been studied extensively because of their potential applications in many areas such as medical imaging and optical communications. Computer simulations have been powerful tools for understanding the fundamentals of these beams. In this study, limited diffraction beams, specifically, Bessel beams and X waves, were simulated. The simulations were based on the frequency-domain method (Rayleigh–Sommerfeld diffraction formula), time-domain method, and finite-element or finite-difference method. For Bessel beams, a circular transducer divided into multiple rings was assumed. For pressure distributions on axial axis, the simulations were simplified due to the symmetry. In the case of X waves, the differential property of acoustic waves was used. The results of the simulation methods were compared with each other. Advantages and disadvantages of these methods will be reported. In all cases, the results are very close to those predicted by theory. [This work was supported in part by Grant HL 60301 from the National Institute of Health of the U.S.A.]
Temporal weights for loudness comparisons
Authors: Ellermeier Wolfgang , Schrödl Sabine
Published: July 2012

Temporal integration of the loudness of level-fluctuating sounds was investigated using the trial-by-trial analysis developed by Berg [J. Acoust. Soc. Am. 86, 1743–1746 (1989)]. In a two-interval, forced-choice procedure, two noise samples of 1-s duration were presented on each trial. Their levels were randomly varied every 100 ms by repeatedly, and independently, drawing from normal distributions having expected values of 60 or 61 dB SPL, respectively. The subject’s task was to decide which of the two noise samples sounded louder. Based on a few thousand judgments, conditional psychometric (COSS) functions were estimated in order to determine to what extent each temporal segment contributed to the judgment. Data collected on six subjects showed considerable individual differences in the weighting functions, but—in contrast to averaging techniques widely used in sound evaluation—exhibited a statistically significant trend to accentuate the onset of the noise. These results were compared to the outcome of a second experiment, in which the total duration of the noise samples was shortened to 200 ms to address a different stage of echoic memory. Conclusions regarding the sensory and cognitive mechanisms involved in short-term loudness integration will be presented.
Effect of frequency region and noise bandwidth on the AMFR
Authors: Bhagat Shaum P. , Champlin Craig A.
Published: July 2012

This study investigated the effect of varying stimulus frequency region and noise bandwidth on the amplitude modulation following response (AMFR). The stimulus for the AMFR was an amplitude-modulated burst of bandlimited white noise. Two carrier frequency regions (1 and 4 kHz) and two noise bandwidths (100 Hz and 1 kHz) were employed. Three women and three men with normal hearing participated in the study. Low carrier-frequency regions produced significantly larger AMFRs than high carrier-frequency regions. Wide-noise bandwidths generated significantly larger AMFRs than narrow-noise bandwidths. The noise bandwidth effect was dependent on the rate of amplitude modulation. Modulation transfer functions were derived by plotting the AMFR amplitude as a function of modulation rate. At the greatest modulation depths, the transfer function resembled a bandpass filter. For lower modulation depths, the transfer function resembled a low-pass filter. The results of the study are in general agreement with previous research that investigated the AMFR with tone and wideband noise carrier signals.
Computational modeling and analysis of SAW devices
Authors: Xu Guanshui
Published: July 2012

Direct full-scale computational simulation of electronic acoustic wave devices is among the most challenging problems for designing high performance devices. The problem also becomes urgent as the conventional methods fail to characterize the behavior of miniaturized devices that operate at high frequency for demanding applications. The effective computational methodology has not yet been developed for the full-scale simulation of multi-physical phenomena in many micro-electromechanical devices of complex geometric structure on the nano- and micro-scale. Here a direct finite element model for the full-scale analysis of the frequency response of surface acoustic wave (SAW) devices is presented. The ability of the method to quantitatively evaluate the influence of the bulk waves at the high-frequency end of the filter passband and the influence of the number of electrodes on insertion loss is noteworthy. Some practical computational challenges of finite element modeling of SAW devices are also discussed parenthetically.
Auditory temporal resolution and speech performance in cochlear implant users
Authors: Fu Qian-Jie
Published: July 2012

It has been widely assumed that speech recognition depends, among other factors, on the auditory temporal resolution function. The present study was conducted to investigate the relationship between auditory temporal resolution and speech performance in nine Nucleus-22 cochlear implant (CI) listeners fitting with the SPEAK strategy. A modulation detection threshold task was used to evaluate auditory temporal resolution. Modulation detection thresholds were measured as a function of current levels. Results showed some marked difference in the temporal modulation function across CI users. Some patients showed increased modulation thresholds across the entire dynamic range while others showed thresholds asymptoted as low as 30% of the dynamic range. There is a strong correlation between consonant recognition scores and the mean modulation detection thresholds (across the entire dynamic range) among CI users. The correlation between the mean modulation detection thresholds and vowel recognition scores was relatively weak but was still significant. The results suggest that phoneme recognition, especially consonant recognition, depends highly on the patients’ capability to detect temporal modulation. One implication from the present results is that the high variability of speech performance is at least partly due to the differences in the temporal resolution of CI users. [Work supported by NIDCD.]
Speech perception, production, and intelligibility improvements in vowel-pair contrasts among adults who receive cochlear implants
Authors: Vick Jennell , Lane Harlan , Perkell Joseph , Matthies Melanie , Gould John , Zandipour Majid
Published: July 2012

This study investigates relations among speech perception, speech production, and intelligibility in postlingually deaf adults who receive cochlear implants (CI). Measures were made for seven vowel pairs that neighbor in acoustic space from eight postlingually deafened adults, pre- and postimplant. Improvements in a speaker’s production, perception, and intelligibility of a given vowel contrast tended to occur together. Subjects who produced vowel pairs with reduced contrast in the preimplant condition (measured by separation in the acoustic vowel space) and who showed improvement in their perception of these contrasts postimplant (measured with a phoneme identification test) were found to have improved production contrasts post-CI. These enhanced production contrasts were associated with enhanced intelligibility, as measured from responses of a group of normal-hearing listeners. The results support the hypothesis that the implant user’s improving speech perception contributes, at least in part, to that speaker’s improving speech production. [Work supported by the NIDCD, NIH.]
Effect of masking of spectrally reduced speech with modulated noise
Authors: Grosgeorges Angélique , Berthommier Frédéric , Lorenzi Christian
Published: July 2012

Accurate recognition performance can be obtained with spectrally degraded speech [R. V. Shannon et al., Science 270, 303–304 (1995)]. Part of this experiment was initially reproduced for 16 VCVCV stimuli (a/C/a/C/a) spectrally degraded and presented in quiet. Then, the contribution of low- and high-frequency amplitude modulations (AM) of speech and noise masker presented at 6-dB SNR was investigated, using a 2 factors/2 levels experimental design: The speech envelope was low-pass filtered at 10 or 500 Hz; the masker was a white noise with low-frequency AM components (<8 Hz), which was sinusoidally amplitude modulated at 100 Hz or not. In addition, the low-frequency AM components of the masker were co-modulated across the four frequency bands or not. Compared to the scores obtained in quiet, a decrease of about 50%–75% in the transmitted information for place and voicing cues was observed in all conditions, and transmission of manner was dramatically suppressed. As expected, recognition of spectrally degraded speech was strongly affected by temporal masking, but the detrimental effects of noise were not uniform for all speech features, giving some insight about their respective temporal encoding. [Work supported by RESPITE.]
Speaking clearly for learning-disabled children: Sentence perception in noise
Authors: Bradlow Ann R. , Kraus Nina , Hayes Erin
Published: July 2012

This study sought to establish connections between two findings regarding speech perception in special populations. First, children with learning problems often have difficulty perceiving speech in noise. Second, naturally produced clear speech is more intelligible for adult hearing-impaired listeners. Given recent interest in the use of digital enhancement techniques in speech and language training procedures for learning-disabled children, we wanted to investigate whether naturally produced clear speech yields perception benefits for this population. We presented children with learning problems (n=46) and normal children (n=17) with sentences embedded in noise. Factors that varied were speaking style (plain versus clear) and signal-to-noise ratio (high versus low). Results indicated that: (1) children with learning problems had poorer sentence-in-noise perception than normal children; (2) both groups had poorer perception with increasing noise levels; and (3) both groups benefited from naturally produced clear speech. There were no significant two- or three-way interactions between listener group, noise level, and speaking style. In combination with acoustic analyses of the plain and clear sentences, these findings have broad implications for our understanding of the speech perception deficits in this population, and the design of appropriate training procedures. [Work supported by NIH-NIDCD Grants DC 03762 and DC 01510.]
Co-modulation masking release (CMR) in consonant recognition
Authors: Kwon Bom Jun
Published: July 2012

In the psychoacoustic phenomenon of co-modulation masking release (CMR), detection of a target in a narrow-band noise is improved in the presence of a co-modulated flanking noise band. The present study investigates whether CMR could improve speech perception. Consonant recognition scores of bandlimited speech, 1200–2200 Hz, were measured under a modulated noise of the same bandwidth, and a second band of noise (5000–7000 Hz), which was either co-modulated or non-co-modulated with the first band. With a hypothesis that CMR improves discrimination of phonemes that are characterized by temporal cues, i.e., amplitude envelope, rather than spectral cues, two groups of consonants were selected for testing: stop consonants (similar temporal envelopes, but different spectra) and alveolar–dental consonants (similar spectra, but different temporal envelopes). Results agreed with the hypothesis: significantly higher recognition scores were obtained with the co-modulated noise band for alveolar–dental consonants, while the difference was marginal for stop consonants. This indicates that CMR can improve speech perception as well as psychophysical thresholds. Co-modulation in the flanking band seems to enable listeners to better ‘‘hear out’’ subtle temporal speech cues in noise, leading to better recognition. [Work supported by Quota scholarship and NIDCD.]
Discriminant analysis of acoustic cues to three Green Mong tones
Authors: Andruski Jean E.
Published: July 2012

Green Mong is a tone language with an inventory of seven contrastive tones. The tonal system of Green Mong incorporates both pitch and phonation-type distinctions, and appears to make use of many of the acoustic parameters which have been shown to correlate with phonation-type cross-linguistically. This study looks at three Green Mong tones that have similar pitch contours, but are distinguished by the distinctive use of breathy, creaky, and modal phonation. Acoustically, the three tones are distinguished to some degree on the basis of pitch, relative amplitude of lower and higher harmonics (H1–H2), duration, vowel quality, and voice onset time. Discriminant analysis is used to estimate the value of these different cues for classifying tokens into tone categories based on observed characteristics in tone production. Discriminant functions were generated using measurements from 270 CV words produced by six speakers, for which every combination of three vowels (/i/, /u/, /a/) five consonants, and three tones (breathy, creaky, modal) was attested. Results of the analyses will be presented, as well as results for classification of a separate, test set of 102 CV tokens produced by the same six speakers.
Analysis-by-synthesis and acoustic landmarks
Authors: McGowan Richard S.
Published: July 2012

In the 1950s and 1960s Ken Stevens and Morris Halle proposed a model for human speech recognition that incorporated analysis-by-synthesis. In the more recent past the notion of acoustic landmarks has arisen from the speech group at MIT as part of a model for human lexical access from features by human listeners. Here, it is proposed that these ideas are fruitful ones for incorporation into a method (constraint and refinement) for training a machine with its own vocal tract to imitate human speech, while learning the relation between articulation and acoustic output. The machine would be trained in stages starting with the attempts to imitate the sequence of relatively open articulations and closed articulations. Landmarks, based on acoustic criteria, would be placed near the peaks in the amplitude envelope, allowing the machine to constrain the type of articulatory activations. This constraining step would involve, initially, an overly restrictive set of phonotatic rules, such as all sequences are obstruent-vowel sequences. The refining step would be the analysis-by-synthesis with the machine’s vocal tract. As the stages progress, the machine would attend to more acoustic properties of the speech signal with different kinds of landmarks and increase the generality of the phonotatic rules.
Forward-scatter barrier with a time-reversal mirror
Authors: Kuperman W. A. , Akal T. , Hodgkiss W. S. , Kim S. , Edelmann G. , Song H. C.
Published: July 2012

The classic difficulty in constructing an acoustic trip line barrier is that the forward-scattered field from the target must be extracted from the (usually) much more intense direct blasting arriving beam, i.e., ‘‘looking into the sunlight effect.’’ During the time-reversal experiment conducted in May 2000, we investigated the forward-scatter barrier concept using a six-element transponder at 65-m depth drifting along with a ship, which traversed the trip line between two moored vertical arrays separated by 5 km in 110-m water depth. A 10-ms cw pulse from a probe source (PS) located at the bottom of the vertical receive array (VRA) is received and time-reversed at the source/receive array (SRA). The transmitted time-reversed signal is then refocused at the PS location of the VRA. This time-reversed signal is also captured by the transponder simulating the forward-scatter target and is retransmitted to the VRA with various amplitudes simulating different forward-scatter target strengths. With an appropriate time delay, the main blast and the transponder signal arrived at the VRA simultaneously. For comparison, one-way broadside transmissions were also made.
Impact sound rating of floor toppings
Authors: Warnock Alf
Published: July 2012

Resilient materials either alone or under a slab of material are commonly placed on top of a hard floor surface to reduce impact sound transmission to rooms below. It is often impossible to select among such floor toppings when they have been tested on different base floor assemblies and only composite impact sound insulation ratings are available. ISO 140-8 measures the improvement due to a floor topping when placed on a concrete slab. The improvement may then be used to estimate the impact sound insulation of floors incorporating concrete slabs. In the project to be described, reductions in impact sound level were measured for a variety of toppings on several different floor types. The measurements confirmed that the ISO procedure works well and that relatively small specimen areas can be used without serious error for evaluation of floor toppings. The measurements showed that these improvements may not be applied to joist floors with lightweight subfloors such as plywood, but are useful for joist floors with thin concrete toppings. ASTM is adopting this test protocol for concrete slabs and is working on a modification that will provide data useful for toppings on joist floors with only light wood subfloors.
Polish standardization of acoustic parameters of buildings in connection with ISO standards
Authors: Zuchowicz-Wodnikowska Iwonna , Izewska Anna
Published: July 2012

One of the foundations of Polish standardization in building acoustics for many years has been to establish the Polish Norms, as EN ISO Standards translated into the Polish language. In recent time, following establishment of ISO 717, it became necessary to amend the Polish Standard (PN-B-02151-3:1999) in which the required acoustic insulation were defined. The new quantities of air-borne noise insulation are adapted to two model types of noise spectrum: pink noise characteristic, e.g., for residential noise, and road traffic noise with a considerable content of acoustic pressure levels in low- and medium-frequency ranges. The standard provides the following basic rules to determine the apparent indices of acoustic insulation (depending on the model spectrum): R′A1 = R′W + C or R′A2 = R′W + Ctr. The standard also includes an informative supplement describing the simplified computing method of the flanking transmission. The key advantage of this standard lies in its obligatory character, i.e., it must be adhered to in both the design as well as execution of buildings, and it ensures the basic standard of acoustic performance. To cater to the needs of the designers, the Acoustic Division of ITB prepared a classification of building products comprising the indicated standard for measurement or computation and the class symbol and the range of the single-number quantity.
Seasonal contribution of mysticete vocalization to ambient noise in southern California waters
Authors: Helweg David A.
Published: July 2012

Many species of baleen whales reside or migrate annually through California waters. During these times some species of vocalizing whales can be detected, identified, and tracked with SOSUS arrays. Historical research by W. Cummings documented strong seasonal changes in narrow-band ambient sound associated with then unidentified sounds. Contemporary research shows these sounds to be blue and fin whale vocalizations. The current study compares historical and contemporary narrow-band ambient measurements with respect to mysticete residency and movement through southern California waters. Seasonal peaks in ambient noise agree with earlier reports, but increased anthropogenic sound reduced the magnitude of the effect. Potential sources of changes in ambient noise and their effects on the whales are discussed. [Research supported by the Strategic Environmental Research and Development Program, Project CS-1082.]