bluuebunny/crossref_metadata_2025 huggingface dataset:
Quest for quiet floor and wall systems
Authors: Harris David A.
Published: October 2005

Lightweight floors over wood and metal joists are notoriously noisy. Both impact and airborne noise are intrusive. A unique technique has been developed that allows the use of hard surface materials such as vinyl, hardwood, or tile without compromising sound isolation attributes or economics. Recent subjective and objective testing of floor and wall systems that utilize constrained layer damping technology demonstrate significant promise. Lightweight wood wall and floor/ceiling assemblies utilizing these principles exhibit a perception of quiet solidarity typically found in expensive concrete systems. This paper presents a series of tests comparing conventional plywood and gypsumboard systems with similar assemblies containing constrained layer damped subfloor and wall materials.
Field impact noise test data on a concrete floor structure
Authors: Richards Roy L. , Park Ioana
Published: October 2005

A total of 83 field impact insulation tests were performed using a Bruel & Kjaer calibrated tapping machine. The tests generally followed ASTM procedures. All measurements were conducted in the same building, using two adjacent receiving rooms constructed for the purpose of the tests. The floor-ceiling constructions tested consisted of a 7-in. concrete base slab, over which were installed a variety of resilient underlayments and finished floors. Tests were conducted with and without a resiliently suspended gypsum board ceiling. Results were extended at low frequencies to the 50-Hz third-octave band. However, measurements in the 50 to 80-Hz frequency range were often limited by background noise. The field impact insulation class (FIIC) results showed one of the resilient underlayments to be clearly superior to others under a ceramic-tile surface, but not as clearly superior under wood surfaces. The resiliently suspended ceiling improved FIIC ratings by 6 to 15 points, depending on the materials laid on the concrete slab. No tests were conducted on carpeted surfaces.
Haptic speech perception: Are the possible pay-offs worth the effort?
Authors: Bernstein Lynne E.
Published: October 2005

Episodically throughout the 20th century, practical and scientific inquiries into speech perception by touch have been undertaken. While some extraordinary examples of communication by the natural (uninstrumented) method of Tadoma have suggested that touch has great potential for speech perception, artificial vibrotactile devices have produced relatively modest results. Why at this time, in the light of success (at times verging on spectacular) of auditory implants for people with profound hearing losses, should additional resources be invested in development and testing or sensory aids for speech perception via touch? In answer to this question, this presentation will summarize research on speech perception involving touch, outline important practical and clinical justifications for continued interest, and discuss some theoretical issues in speech perception to which studies involving touch can contribute. [Work supported by NIH DC00695 and DC01577.]
New discoveries in taction and their implications for tactile communication
Authors: Bolanowski Stanley J. , Verrillo Ronald T. , Gescheider George A. , Makous James C. , Pietras Bradley M. , Cohen Jason C. , Checkosky Christine M.
Published: October 2005

The implementation of tactile aids for the deaf and blind has progressed largely through the development of new technologies and strategies adapted to adequately and efficiently activate previously understood tactile mechanisms and processes. In the past decade, however, important new discoveries have been made relating to the basic mechanisms of taction such as the effects of aging and disease, submodality interactions, skin mechanics, and learning and cortical plasticity. These advances in our knowledge will impact heavily on future developments and applications of tactile aids. Several of these new discoveries will be described in the context of basic tactile mechanisms and in their implications for significant improvements in the effectiveness of aids for tactile communication. [Work supported by NIH.]
Fine surface-texture discrimination ability depends on the number of mechanoreceptors participating in the discrimination task
Authors: Miyaoka Tetsu , Ohka Masahiro , Kawamura Takuya , Mitsuya Yasunaga
Published: October 2005

The purpose of this study was to investigate the relation between fine surface-texture discrimination ability in tactile sensation and the number of mechanoreceptors participating in the discrimination task. Two experiments were performed. In experiment 1 the spatial-summation effect was measured at the fingertips using aluminum oxide abrasive papers as stimuli, with grit values between 600 and 8000. Difference thresholds could not be determined when the area of the papers was 25 mm2. Thresholds were between 11.3 and 13.5 μm at 100 mm2, and they were between 3.14 and 5.58 μm at 400 mm2. In experiment 2 the difference thresholds of the texture-discrimination tasks were measured at the fingertips and the thenar eminence using large-sized (2500 mm2) abrasive papers with grit values between 400 and 8000. The difference thresholds were smaller at the thenar eminence than at the fingertips because the stimulated area at the thenar eminence was eight times larger than the area at the fingertips. From the results of experiments 1 and 2, it was concluded that the larger the number of mechanoreceptors which participate in the discrimination tasks, the smaller the difference thresholds. [Work supported by the Ministry of Education, Science and Culture, No. 07610093 and Mikiya Science and Technology Foundation.]
The effect of frequency upon tactile apparent movement
Authors: Wake Tenji , Wake Hiromi
Published: October 2005

Tactile apparent movement was observed under the conditions of variation in stimulus duration, frequency, and separation between two stimuli. First, optimal stimulus onset asynchrony (SOA) was determined as a function of stimulus duration using stimuli with the same frequency. Second, optimal SOA was estimated as a function of frequency, by using two stimuli with different frequencies. The optimal SOA for tactile apparent movement increased with the increases of stimulus duration. When two vibrators activate with the same frequency, the optimal SOA depends on frequency. The optimal SOA of the low-frequency stimulus (10 Hz) is longer than that of the high-frequency stimulus (250 Hz). If the first stimulus is 10 Hz and the second stimulus is 200 Hz, the optimal SOA is shorter than two stimuli with same frequency (10 Hz). The first stimulus was kept constant at 10 Hz and the second stimulus was varied in frequency. As the frequency-difference increases, the optimal SOA is decreased, but at the second stimulus of 80 Hz, the optimal SOA is similar to that of two stimuli of 200 Hz. These findings suggest that there are interactions between two channels. [Work supported by the Ministry of Education, Science and Culture, No. 62810008.]
Is it possible to obtain the subjective-contour effect in touch?
Authors: Wake Hiromi , Wake Tenji
Published: October 2005

The so-called subjective-contour effect was examined in touch and compared with vision. The first experiment was designed to establish a criterion of the subjective pattern by modal completion. In experiment 2, free verbal reports were gathered from naive subjects. Verbal reports and rating scores for three characteristics, subjective pattern, depth displacement, and brightness transformation, were gathered from the well-trained subjects in experiment 3. Results were as follows. (1) The effect was strong in vision especially for the pattern. Subjective pattern was reported in touch, but, in most other cases, they understood the pattern to be just a triangle or square as a result of bridging, without perceiving the contiguous surface. (2) Subjective depth was not observed so much even in vision by the naive subjects, although it was clear to the well-trained subjects. When depth displacement was reported, the subjective surface was perceived as more concave than the surface of paper. In conclusion, although the subjective-contour effect was confirmed in touch, it might be somewhat different from that of vision. It is still not clear if the perceived effect in touch is the result of the modal completion as it is in vision. [Work supported by the Ministry of Education, Science and Culture, No. 0310063.]
A new method for measuring the bulk modulus of compliant acoustic materials
Authors: Guillot François M. , Jarzynski Jacek
Published: October 2005

In this method the sample is compressed, and a dual-beam laser Doppler vibrometer is used to measure the resulting strain. The sample is suspended in air by thin threads. A transient acoustic signal is used to compress the sample, where the wavelength of the acoustic signal in air is significantly greater than the sample dimensions. A rigid reflector is placed behind the sample to double the acoustic pressure. Data are presented for a rubber–air composite material. Extension of the above method to measurements as a function of temperature and pressure is described. The frequency range for this method is ∼100–3000 Hz.
Laryngeal gestures of traditional Japanese singing
Authors: Niimi Seiji
Published: October 2005

Needless to say, each nation has its own culture, including singing style. In Japan, various singing styles have been inherited over long periods of time. This study attempts to record the laryngeal gestures for performing traditional singing. Laryngeal gestures were monitored by fiberscope and recorded onto an ordinary video recorder with audio signals. Care was taken for singers to perform naturally. Since the singing method is so different from that of the Western operatic style, there have been discussions about vocal hygiene. Sometimes the singing voice used in traditional Japanese songs gives creaky, strained, or pressed acoustic impressions to the audience. Observing the laryngeal gestures during a performance, hyperadduction of the vocal fold, false vocal fold, or tight closure of the glottis, which are supposed to suggest hyperfunction of the larynx, was rarely observed. This observation suggests that the traditional Japanese singing style agrees with vocal hygiene; otherwise it could not be traditional. [Work supported by Grant-in-Aid for Scientific Research from Ministry of Education, Science and Culture No. 08457449.]
The removal of small particles using high-frequency ultrasonics
Authors: Busnaina Ahmed A.
Published: October 2005

High-frequency (near 1 MHz) liquid-based ultrasonic cleaning (known as megasonic cleaning) is widely used in industry for the removal of particulate contamination. Megasonic cleaning is an effective but poorly understood particle removal technology. It is found that acoustic streaming, microstreaming, and stable cavitation aid in particle removal. Results show that removal efficiencies near ten power is one of the most important parameters in megasonic cleaning. The megasonic input power has a greater effect on the removal efficiency than does temperature. An unexpected decrease in cleaning efficiency at high powers is reported, and attributed to energy attenuation due to increased bubble activity. This is consistent with previous results generated using different megasonic equipment. The results also show that when the optimum reported power is used, the removal efficiency will be high over a wide range of bath temperatures. [Work supported, in part, by the New York State Center for Advanced Materials Processing, Clarkson University.]
Piezoelectric copolymer array for nondestructive inspection
Authors: Yuasa Hajime , Masazumi Kuniyuki
Published: October 2005

Ultrasonic sensors which use copolymer membranes, just like other single-crystal elements and ceramic elements, are able to transmit and receive with the same element. However, for meeting the required specifications to identify welding defects around 0.1 mm, there were many difficulties and problems in manufacturing an integrated type of sensor with functions for both transmitting and receiving, as well as from a costwise consideration. Consequently, to overcome these problems, the following new concepts were introduced for quick implementation. As far as the thin copolymer membrane is concerned, the reception part and the transmission part were not separated but integrated, and an independent electrode was installed for each function. The beam-receiving surface of the reception part of the membrane was made so as to form an overall earth electrode, while on the opposite surface, a number of comblike electrodes were installed in parallel. Furthermore, because the electrical impedance of the piezoelectric copolymer sensor is low, careful attention should be paid to matching between the cable and the electrical circuit. With this device, the installation of a preamplifier adjacent to the receiving element solved the problem. The developed ultrasonic sensor has a 1-channel transmitter with a frequency of 20 MHz and high-density receivers with 56 channels on a 20-mm-long membrane.
Numerical simulation of a combined acoustic preconditioning—Electrostatic precipitation (APEP) system and comparison with experimental data
Authors: Hoffmann T. L. , Riera-Franco de Sarabia E. , Gallego-Juárez J. A.
Published: October 2005

Based on a recently developed computer code (PAIS—particle agglomeration and interaction simulation), numerical simulations are presented which model the process of acoustic agglomeration using two different agglomeration kernels: the classical orthokinetic and the new acoustic drag interaction kernel. The results of the simulations are contrasted with experimental data. Acoustic particle agglomeration is an effect that occurs when an aerosol is sonified with high-intensity sound (140–165 dB). Experimental investigations show that acoustic agglomeration may increase the efficiency of conventional particle filtering devices (such as cyclone filters or electrostatic precipitators) by modifying the aerosol’s particle size distribution. However, existing models based on the classical orthokinetic kernel fail to predict certain important features of acoustic agglomeration. The new PAIS code overcomes this limitation by implementing acoustic drag interaction, a hydrodynamic effect that was only recently found to play an important role in the acoustic agglomeration process. As a result, new model predictions based on both kernels are compared with experimentally determined data. Important differences in the simulation with either kernel are pointed out. It is shown that the acoustic drag interaction kernel, in contrast to the classical model, accounts for the important agglomerations occurring between same and similarly sized particles.
Phase criterion in the feedback cycle of low-speed edgetones
Authors: Kwon Young-Pil
Published: October 2005

The phase criterion of the feedback cycle of low-speed edgetones has been obtained using the jet–edge interaction model in which the reaction of the wedge to the impinging jet is modeled by an array of dipoles. The edgetone is produced by the feedback loop between the downstream-convected unstable flow issued from the nozzle and the upstream-propagating sonic wave due to the wedge reaction. By estimating the phase difference between the downstream flow and the upstream wave, and by imposing the phase-locking condition at the nozzle lip, it is found that the phase factor should be p=−1/4 in the feedback relation h/Λ+h/λ=n+p, where h is the stand-off distance, Λ and λ are the wavelengths of downstream- and upstream-propagating disturbances, respectively, and n is a stage number for the ladder-like characteristics of frequency. The proposed criterion p=−1/4 is just the opposite, in phase, to p=1/4 that has been regarded as an established characteristic of edgetones. However, p=−1/4 is verified substantially in comparison with available experimental data and found to be effective up to a wedge angle of 90°. [Work supported by KOSEF.]
Computations of acoustic wave strength and vorticity in shear flow
Authors: Leep-Apolloni Laurine , Dowling David R.
Published: October 2005

While exact techniques are available for plane-wave propagation in uniform flow, acoustic propagation in nonuniform flow has proven much less tractable. A numerical technique has been developed to treat the simplest possible case: acoustic plane waves launched into a uniform shear. The computations are based on the Euler and continuity equations, using only the standard linearization for small acoustic amplitudes. When nondimensionalized, these equations produce a single governing parameter: m/f, where m is the flow’s shear rate, and f is the acoustic frequency. Numerical solution for acoustic fluctuation velocity and density at each grid point allows wavefront location and orientation as well as wave strength to be determined. The results for wavefront location and orientation from the current numerical method are compared to a WKB solution obtained from the simplest nonuniform flow approximation which uses a nonuniform speed of sound in lieu of a nonuniform background flow. Gradients of acoustic field variables along the wavefronts, which are not predicted by the standard approximation, are also presented. The acoustic vorticity field is examined to study the rotational nature of the plane waves after interaction with the shear.
Further work on numerical simulations of aerosound from jets using the Lighthill theory with the k-ε turbulence model and the large eddy simulation (LES) procedure
Authors: Meecham William C. , Lee Seungbae
Published: October 2005

Acoustic mechanical power from fluctuating fluid flows forms but a tiny part (about 10−5) of the power within the flow. The familiar, far-field solution to the Lighthill equation is used and is written as
The perception of rhythm in musical performance and poetry recital
Authors: Todd Neil
Published: October 2005

Over the last 2 decades much work has been done on the nature of expression in musical performance. Expression, which takes the form of subtle transformations of timing, dynamics, pitch and timbre, etc., may be measured fairly accurately when a score-based representation is available. It is generally agreed that the major function of expression in these cases is the communication of the performer’s structural/motional interpretation of the piece being performed. Indeed, it is possible to demonstrate that the greater part of expressive variation may be accounted for by the two major components of rhythmic structure, namely, meter and grouping. However, little attention has been paid as to how the perception of rhythm may be influenced by expression. In this paper the perception of rhythm in expressive performance is reviewed from the point of view of a recent auditory-motor theory of rhythm perception [N. P. Todd and G. J. Brown, ‘‘Vizualization of rhythm, time and metre,’’ Artificial Intelligence Rev. (1996)]. The similarity between musical performance and the prosody of poetry recital is also discussed in light of a recent experiment to test the behavior of the model with speech. This is consistent with the view that rhythmic expression has a common origin in music and speech.
Acoustic correlates of emotionally expressive music
Authors: Gabrielsson Alf
Published: October 2005

Music is known for its ability to express as well as to evoke emotions. However, there is very little scientific research on what means musicians use in their performance to bring about different emotional expressions. In a series of ongoing experiments musicians are asked, using various instruments (violin, flute, electric guitar, synthesizer, singing voice), to perform short monophonic pieces of music to have them express ‘‘happiness,’’ ‘‘sadness,’’ ‘‘anger,’’ ‘‘fear,’’ ‘‘solemnity,’’ ‘‘tenderness,’’ and ‘‘no expression.’’ Listening experiments are conducted to confirm that listeners recognize the intended emotions. Approved performances are analyzed using sampling systems. The intended expressions affect practically all physical variables—tempo, timing of various units, articulation, sound level, amplitude envelopes, intonation, spectrum, onsets and decays, vibrato—in ways that differ among expressions and instruments used. There is considerable interindividual variation among performers in their ability to render the intended expressions as well as regarding the means that they use to achieve the expressions. On the other hand, listeners differ in their ability to recognize the intended expressions. Some emotions seem easier to express as well as to recognize than others.
The context effect on loudness in listening to music
Authors: Arakawa Keiko , Mizunami Tazu , Kuwano Sonoko , Namba Seiichiro , Kato Toru
Published: October 2005

As the first stage of the research into factors determining the optimum listening level of music performance, its methodology was examined. In experiment 1, a part of Symphony No. 6 in b-minor Op. 74, ‘‘Pathétique,’’ composed by Tchaikovsky, was used and the instantaneous impressions of loudness were judged using the method of continuous judgment by categories developed by Namba and Kuwano. A high correlation coefficient was found between LAeq, 100 ms, and instantaneous impression of loudness sampled every 100 ms, which confirms the applicability of the method to the loudness of music performance. In experiment 2, musically significant portions whose durations were 5 to 20 s, were selected from the stimulus used in experiment 1 and rearranged in descending series and ascending series according to their sound levels with about 5-s silent intervals. The instantaneous impression of their loudness was judged as in experiment 1. It was found that each block in the ascending series was judged louder than the corresponding block in the descending series. It was suggested that the loudness of musical performance is significantly affected by the context.
Interaction between auditory and visual processing in impressional evaluation of a piano performance
Authors: Shimosako Haruka , Ohgushi Kengo
Published: October 2005

To investigate the interaction between auditory and visual processing in impressional evaluation of a piano performance, a pianist was asked to play the same musical excerpt in three different expressive levels and these were recorded on a video. Three kinds of sounds and three kinds of body movements were combined and these nine performances were presented to musically trained students and less trained students. They rated the expressivity of each performance on a five-point scale in three modes: sound and vision together, sound alone, and vision alone. When sound and vision were presented, they also rated their subjective acceptability on a five-point scale. The result was that both musically trained students and less trained students could discern among the levels of a pianist’s expressive intent when sound alone or vision alone was presented. However, when sound and vision were presented, it was found that vision had a greater influence on the impressional evaluation. This tendency was more remarkable for less trained students than musically trained students. When sound and body movements were at different levels, performances were rated lower by musically trained students but not by less trained students.
Motion as music: Comparing final ritards with stopping runners
Authors: Friberg Anders , Sundberg Johan
Published: October 2005

Music and motion are generally assumed to be closely related. An attempt was made to analyze such relations with regard to the stopping of running and the termination of a piece of music. Velocity, step frequency, and step length of four professional dancers were measured while they were stopping from running. Six choreographers rated the esthetic quality of the decelerations from video recordings. The data curves from highly rated decelerations were more regular and smooth as compared to those decelerations rated lower. It was found that the average instant velocity of the runners corresponded well with the average of instant tempo in final ritards. A model of the ritard shape with varying curvature, including the observed deceleration shape, was applied to three music examples in a listening experiment. The observed deceleration shape was found to be within the range of the subjects’ preferences.
Measurement of performance response differences using aluminum and brass marimba resonators
Authors: Roberts Ronald A. , Larkin Barry J.
Published: October 2005

Historically, percussionists have maintained that a perceptible difference exists in the responses of aluminum and brass marimba resonators. Brass resonators are thought to produce a fuller and richer sound, whereas aluminum resonators are considered to yield an inferior, thinner sound. Marimba performers will seek out and pay a premium price for instruments equipped with brass resonators, while lower cost aluminum resonators are found primarily on student model instruments. Experiments are being performed to determine if any such difference can be detected in laboratory measurements. This paper will outline experimental techniques used in recording airborne responses generated by repeatable, mechanized mallet strokes. Data analysis will be summarized, and results will be presented showing the nature of measured differences in both overtone structure and response evolution.
Basic study of acoustic display of John Milton’s Paradise Lost
Authors: Moritani Mineo
Published: October 2005

Knowing how emotions change with sound pressure is the present concern with a synthesized acoustical display of this poem. Emotional changes in the poem are felt like the music of Beethoven. The sound pressure alone cannot express the delicate nuances of the emotion; other elements are needed for the whole emotional expression. But the sound pressure is the basic medium by which emotion is communicated; when one is emotionally excited, one often raises his voice. So, in the epic, strong sound pressure is assumed to be an expression of strong emotion. Hence, it occurred to the author to represent the emotional changes in terms of those of sound pressure. It is clear that each book has its idiosyncratic pattern of change of sound pressure; hence, emotion is inseparably related to the contents. Most interestingly, the fall of Eve and Adam appears in Book IX with two changes of abnormally high increase of sound pressure to about 80 dB against the average 73 dB. The change of emotion can be heard with a sine-wave generator using techniques developed by the author.
On the duration of pre-Helmholtz triggering in bowed violin attacks
Authors: Guettler Knut , Askenfelt Anders
Published: October 2005

The attacks of most bowed notes on a violin show a nonperiodic initial part before Helmholtz triggering occurs. Depending on the particular combination of bowing parameters, this state is characterized either by periods which are prolonged, or by a division of the nominal period into two or several parts, multiple flyback. A ‘‘perfect’’ onset with only one slip per period from the very start is also possible. The present study includes: (a) computer simulations of a violin G-string and characterization of the attack quality as function of bowing parameters; (b) evaluation of acceptability of a series of (machine-bowed) violin attacks with respect to duration of the pre-Helmholtz triggering; the evaluation took place in a listening test that involved music students and professionals; (c) analyses of 1694 attacks in different musical contexts as performed by two professional violinists. The limits for acceptability established by the listening test were about 50 and 90 ms of prolonged and multiple-slip periods, respectively, for an open G-string (196 Hz). These demands were confirmed by the playing test, even for other strings and a larger group of bowing styles. [Work supported by The Nordic Research Council.]
The configuration of an adaptive prediction-type active noise control system
Authors: Honda Shinichi , Hamada Hareo
Published: October 2005

In this paper, a new active noise control system is proposed using an adaptive prediction algorithm. The adaptive prediction-type active noise control system has many attractive advantages; for example, no prior knowledge of primary noise fields will be needed. However, difficulty in the control of broadband noise was encountered. For example, a new system configuration with an auxiliary sensing microphone is proposed. The computer simulation revealed that an auxiliary sensing microphone can improve the noise reduction remarkably in a wide frequency range if the effective sensing of primary noise is not expected by a single microphone. It is also demonstrated that the improvement of noise reduction is considerable depending on the arrangement of sensing microphones.
Passive–active broadband sound absorption
Authors: Smith Jerome P. , Burdisso Ricardo A.
Published: October 2005

Researchers have proposed hybrid systems to achieve high sound absorption over a wide frequency range. The passive component of the system is comprised of a layer of sound absorbing material positioned at a distance from a movable wall, leaving an air space. The wall is the active component and is used to increase the absorption of the system at frequencies where the passive system is not effective. The control input that drives the active wall is determined in order to achieve a desired boundary condition at the back of the absorbing layer. Both pressure-release (i.e., minimizing the pressure at the back surface of the layer) and impedance-matching (i.e., minimizing the reflected wave in the cavity) conditions have been proposed to increase the absorption of the system. The performance of the hybrid system for these two boundary conditions is compared for broadband disturbances over a frequency range of 0–1000 Hz. The passive system showed absorption coefficients greater than 0.7 only above 500 Hz. The impedance-matching condition yielded absorption coefficients of 0.8–1.0 over the 100- to 1000-Hz range, which was significantly better than the absorption achieved with the pressure-release condition. Sensitivities of these two control approaches to system parameters are also investigated.
An adaptive algorithm with error path estimation for active control of periodic noise
Authors: Seguchi Nobuyuki , Shimada Yasuyuki , Nishimura Yoshitaka , Usagawa Tsuyoshi , Ebata Masanao
Published: October 2005

When active noise control (ANC) systems are actually implemented, it is necessary to take account of the modeling error of an error path. The modeling error limits the performance of ANC and it makes the system unstable at worst. The characteristics of the error path cannot be assumed to be stable, so that on-line estimation is preferred for actual applications such as an active control system of the exhaust noise of an engine. An adaptive algorithm called the delayed-X harmonics synthesizer (DXHS) algorithm for periodic noise has been proposed. This algorithm controls amplitude and phase parameters for each harmonic component. The original algorithm controls parameters represented in polar coordinates with constant delay parameters. This paper presents an extended algorithm to estimate delay parameters of the error path on-line. Delay parameters, which are important for the stability, are introduced as a phase, while other parameters are represented in orthogonal coordinates. The performance of the algorithm is evaluated by computer simulations. When SNR at the control point is 0 dB, the estimate delay is nearly the same value as the actual delay, and the system converges very stably.
Sound diffraction effects by screens in a room
Authors: Habault Dominique M. , Kristiansen Ulf R.
Published: October 2005

Several numerical methods are used to describe the effects of diffraction by two kinds of screens in a room: a perfectly rigid screen and a vibrating screen. This study has two main applications in acoustics: In room acoustics, the aim is to describe the influence of a vibrating screen on the acoustical characteristics of a room in which screens made of light materials are suspended from the ceiling; in structural acoustics, it is to describe the effect of a vibrating structure in a cavity. An application in active noise control is also presented. First, the sound pressure in the room is computed by using a boundary element method. Then, a perturbation method is used in the case of the vibrating screen. Comparisons are made between the two methods and a finite-element method for two typical geometries. The numerical examples presented correspond to a 2-D problem and a rectangular room. From the acoustics point of view, it is shown that the effect of a vibrating screen compared with a rigid screen is bigger at low frequencies and for light materials. This difference also depends on the acoustical properties of the room (i.e., the reflection coefficients on the walls).
Multivariable structural acoustic control with static compensation
Authors: Clark Robert L. , Cox David E.
Published: October 2005

The active control of turbulent boundary layer noise in commercial aircraft has gained significant interest in recent years, and, due to the stochastic nature of the disturbance, feedback control strategies are required. Linear quadratic Gaussian control has been proposed in the past [Baumann et al., J. Acoust. Soc. Am. (1991)], but compensators resulting from such control approaches are typically quite involved. The thrust of the current effort is to demonstrate that acceptable performance in structural acoustic control can be achieved with static compensation implemented through a multiple input, multiple output (MIMO) array of colocated transducers. Since static compensation requires a matrix of constant gains, it is easily realized in analog or digital hardware. By augmenting the system dynamics to include radiation filters, the dual Levine–Athans algorithm was implemented to design the appropriate static compensator. Results for various MIMO control cases are presented.
Multivariable active structural acoustic feedback control using piezoelectric sensoriactuators
Authors: Vipperman Jeffrey S. , Clark Robert L.
Published: October 2005

Analytical and experimental results from the implementation of a feedback, active structural acoustic control (ASAC) system are presented. The test bed is a rectangular, simply supported steel plate inserted in a semi-infinite baffle inside an anechoic chamber. Piezoceramic patches are wired as bending transducers and implemented as adaptive piezoelectric sensoriactuators or self-sensing actuators. The transfer function across a sensoriactuator is minimum-phase, thereby enhancing stability for feedback control applications. Radiation filters are implemented to design the performance cost used in the control synthesis. Several design parameters are examined for different square (equal number of inputs and outputs) control configurations. Both single- and multichannel control system implementations are considered. Sensor and actuator optimization is performed using nonlinear optimization techniques, and both dynamic and static compensation are compared.
Control of sound radiation from panels using multiple globally detuned vibration absorbers
Authors: Fuller C. R. , Charette F. , Carneal J. P.
Published: October 2005

In this paper, the results of an investigation on using multiple globally detuned vibration absorbers to minimize sound radiation from vibrating elastic panels will be presented. The vibration absorbers consist of lumped mass–spring systems whose characteristics (i.e., resonance frequency) can be electronically varied. A fully coupled multiple-channel control algorithm, implemented on a DSP, is used to adapt the characteristics of the multiple absorbers so as to minimize the radiated sound at selected positions in the far field. Both theoretical and experimental results are presented and are compared to those obtained using tuned (i.e., to the disturbance frequency) vibration absorbers. Improved sound attenuation is shown to be obtained using the globally detuned vibration absorbers. The results are very similar in characteristics to those obtained previously using active structural acoustic control implemented with electrodynamic shakers or piezoelectric actuators. The results thus suggest a combined active–passive method to minimize structural sound radiation which requires lighter, smaller actuators and much lower control electrical power. [Work supported by ONR and NASA LaRC.]
Active control of vibration intensity flow in a beam in the far field
Authors: Iwaya Yukio , Sakata Masato , Suzuki Yoiti , Sone Toshio
Published: October 2005

From the point of view of physical impedance, vibration intensity carried by a bending wave propagating along a beam can be decomposed into two components: One is the component owing to a mechanical impedance Z, and the other is owing to a bending moment impedance Mz. To control intensity, both components must be taken into consideration, though it causes some difficulties in execution, such as a complex cost function, many sensors, etc. However, a one-dimensional bending wave consists of four waves. Two of them are decaying waves and these can be negligible in the far field, which means far from the edge of the beam. In the far field, Z becomes the reciprocal of Mz. Using this relationship, three simple ways were found to control intensity as follows: (1) control amplitude at one point; (2) control of amplitude gradient, and (3) direct intensity control in the frequency domain. Computer simulations have been performed in these cases. The results were that case (3) showed the slowest convergence of parameters, and cases (1) and (2) could give equally good results. Furthermore, two shakers have been mounted on a beam and an experiment of control with a DSP has been accomplished for case (2).
Thermal phonon resonance in a cylindrical cavity
Authors: Hattori Koichiro , Sakai Keiji , Takagi Kenshiro
Published: October 2005

Resonance phenomena were observed of a thermally excited phonon confined in a very small space. The power spectrum changes due to the boundary condition of the cavity shape. A cylindrical cavity which has a 1450-μm inner diameter containing water was prepared as a sample. The resonance frequency in the cylindrical cavity is given by a solution of Bessel’s function. An optical beating system is used which has a hyperfrequency resolution to detect this fine structure of the resonance spectrum. The spatial decay of phonons is very large in the liquid sample. The low-frequency measurement is required to observe the resonance phenomena, because the phonon can reflect many times in the cavity. Generally though, a broadening of the wave vector due to angular divergence of the laser light is very large in a small-angle light-scattering measurement, since the wave vectors of the resonance peaks are determined only by a boundary of the cavity. Several resonance peaks can be observed around the 8 MHz measurement and a typical peak width is 50 kHz. The strong peaks are observed at every 500 kHz. These peaks are the symmetric and lowest asymmetric tangential modes.
Acoustic pre-condensation of deuterium
Authors: Hoffer James K. , Asaki Thomas J. , Sheliak John D.
Published: October 2005

Millimeter to centimeter size light-metallic shells are of interest as investigative tools in the inertial-confinement-fusion community. Such shells are typically filled at room temperature with pure or mixed hydrogen isotopes at high pressure. At low temperatures, the hydrogens condense forming a solid or liquid in equilibrium with the vapor. The sound speed of gaseous deuterium (1% He-3) in a closed aluminum shell has been investigated using a cavity/shell resonance method. An anomalous decrease in the measured sound speed is observed as the saturation pressure Ps (about 15 atm at 38 K) is approached during a nearly constant-volume reduction in temperature. This effect is explained qualitatively in terms of a reduced acoustic admittance at the shell wall due to a precondensed liquid layer at pressures below Ps [J. B. Mehl and M. R. Moldover, J. Acoust. Soc. Am. 77, 455–465 (1982)]. Comparison is made with precondensation phenomena observed by various authors for single-component gases in experiments performed at constant temperature.
Relation for calculating the heat capacity at constant volume for multicomponent systems by using the values of sound velocity for the pure components and binary systems
Authors: Denisov Dmitrii A.
Published: October 2005

It is known that heat capacities at constant volume CV can be calculated by using the relation connecting CV with values of sound velocity for these substances [A. J. Matheson, Molecular Acoustics (Wiley, London, 1971)]. The relation for calculating CV for mixtures following the lattice model of regular mixtures in the zero quasichemical approximation [I. Prigogine, The Molecular Theoryof Solutions (North Holland, Amsterdam, Interscience, New York, 1957)] on the basis of some data including sound velocity referring to the pure components has been derived. The analogous problem for mixed solutions, namely for the solutions containing several solutes, has been solved. The relation for calculating CV for a mixed solution consisting of the solvent and one of the solutes and having the same solvent chemical potential value (which the considered mixed solution has), follows the same conditions.
Observation of phase transition and critical behavior in Langmuir films by a ripplon light scattering technique
Authors: Sakamoto Naoto , Sakai Keiji , Takagi Kenshiro
Published: October 2005

The light-scattering study of ripplon (thermally excited surface tension waves) was used to measure the surface elasticity of a myristic acid monomolecular film spread on a water surface in its coexisting state of two-dimensional liquid and vapor phases. The temperature dependence of the surface elasticity of both phases suggested that the critical behavior analogous to that of the usual three-dimensional fluids occurred in this two-dimensional system. The surface elasticity of the liquid phase decreased monotonously with temperature from 1.2×10−2 N m−1 at 20 °C to 2×10−3 N m−1 at 60 °C, while that of the vapor phase showed no appreciable difference from the value on a clean water surface. The Van der Waals equation of state specially reduced for the two-dimensional fluid was used to explain the result, and the Π-A isotherms were theoretically calculated so that the surface elasticity predicted from these curves agrees well with the observed values. The two parameters characterizing the equation were determined, a=6.5×10−39 N m3 and b=3.9×10−19 m2, which are associated with effects of the attractive force and the excluded area, respectively. These values gave the critical temperature TC=85 °C.
Brillouin scattering in the isotropic phase of liquid crystals
Authors: Ueno Taketo , Sakai Keiji , Takagi Kenshiro
Published: October 2005

An optical beating technique was applied to the study of thermal fluctuations in isotropic phases of nematogens (those liquids changing into nematic liquid crystals in cooling) by Brillouin scattering. Wide-range and high-resolution spectroscopy was made. With this method, the power spectra of the light scattered in 6 CB (p-n-hexyl p′-Cyanobiphenil) was observed over the temperature range from 28.8 to 65.0 °C. Not only the fluctuation of density, which causes the Brillouin triplet, but also the fluctuation of orientation, a kind of the local order, appears in these liquids. The light-scattering spectrum reflects the reorientational relaxation. The model suggested by de Gennes theoretically predicts the spectra of both polarized (VV) and depolarized (VH) scattering. By fitting these equations to the experimental results, characteristic values were obtained which describe the dynamics of nematogens: Γ, the relaxation frequency of the orientational fluctuation, and C, the coupling constant between the orientational fluctuation and the local shear flow. The physical meanings of these parameters are discussed in the framework of critical phenomena.
Acoustic coherent backscattering in inhomogeneous media
Authors: Sakai K. , Yamamoto K. , Takagi K.
Published: October 2005

Observed for the first time was strange behavior of an ultrasonic wave called ‘‘coherent backscattering’’ from inhomogeneous media. This effect is theoretically expected to occur as a result of a weak localization of waves propagating in a medium with many scatterers. It is a general nature of all kind of waves and has actually been confirmed for the optical waves. The ultrasonic wave incident to the dispersion system of small particles is scattered by the difference in the mechanical impedance in the system, whose intensity profile has a peak in the backscattering direction with respect to the incident wave. The peak height is expected to be twice as intensive as that of the diffuse scattering. The stroboscopic Schlieren image of the ultrasonic propagation scattered by the dispersion of polystyrene particles 100 μm in diameter was obtained and an intensive component going back the same way as the incident light was found. The quantitative measurement of the scattering profile was also carried out by a laser diffraction method and the result obtained shows good agreement with the theoretical prediction, giving a peak factor of 2. This phenomenon would be important when treating ultrasonic waves in inhomogeneous systems such as human organs.
Wave propagation at a water–chiral boundary
Authors: Yang Shiuh-Kuang , Hsia Shao-Yi
Published: October 2005

To model the dynamic response of a particles-mixture composite, the plane-wave propagation in an elastic matrix containing the structural chiral microstructures had been asymptotically investigated. In this so-called effective chiral (isotropic, noncentrosymmetric) composite, six independent wave numbers can be found from the dispersion equations. Two of the wave numbers represent the nondispersive longitudinal waves while the remaining four represent the dispersive circularly polarized shear waves. According to the dispersion equations, two cutoff frequencies divide the frequency response of the transverse wave numbers into three different groups and the four transverse modes can only be distinguished in a specified frequency range. In this study, the reflected and transmitted characteristics at a water–chiral interface are solved. To further illustrate the effects of the chirality, the reflected and transmitted fields at the water–isotropic and the water–micropolar interfaces are also solved. It is observed that, due to the mode conversion of the chirality and scattering resonances in the chiral medium, the chiral material should instigate a reducible reflected plane wave, and may be used as an anechoic coating to ‘‘absorb’’ sound underwater.
Theoretical and experimental investigation for LFB acoustic microscopy characterization of proton-exchanged LiTaO3
optical waveguides
Authors: Miyashita Masahito , Kushibiki Jun-ichi
Published: October 2005

Line-focus-beam (LFB) acoustic microscopy has been recognized as a new analytical technique of quantitative material characterization, by measuring the phase velocities of leaky surface acoustic waves (LSAWs) excited on the water-loaded specimen surface. Recently, application of this ultrasonic technique has been demonstrated successfully for characterization of proton-exchanged layers for LiNbO3 and LiTaO3 optical waveguides and for evaluation of the device fabrication processes. It is necessary and important to calculate LSAW propagation characteristics, viz., velocity and attenuation, for interpretation of experimental results and for evaluation of physical properties, such as optical and elastic properties, in proton-exchanged layers. In this paper, LSAW propagation characteristics for the structural model of water/piezoelectric layer/piezoelectric substrate are analyzed. The propagation characteristics are interpreted with calculations of spatial distributions of mechanical displacements and electric potential. Specimens of Z-cut LiTaO3 substrates, with a layer thickness of 0.5 μm, were prepared. Experimental data of LSAW propagation characteristics, measured in the frequency range 100 to 300 MHz, are discussed in detail comparing with the calculated results.