bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-cost demonstrations in acoustics for high school or liberal arts science courses
Authors: Spoor Philip S. , Hiller Robert A.
Published: July 2002

Finding effective demonstrations of physical principles that engage student interest, yet are cheap and easy to carry out, is a constant source of challenge to the high school or college science educator. The authors will share a number of such demonstrations which they have developed by drawing on their pooled knowledge of experimental acoustics. Included will be demonstrations developed for a musical acoustics class taught by one of the authors at Penn State University.
Noise labeling and the acoustical consultant—the importance of standardization
Authors: Brooks Bennett M.
Published: July 2002

The acoustical consultant’s interest in product noise mirrors that of the general public. He/she may be called upon to provide engineering guidance on product noise to a wide variety of interested parties. These may range from corporate manufacturers to individual users. The issues may range from an improved marketing image for a product to a claimed personal injury. The types of products can include consumer or industrial noise emitters, as well as architectural items such as moveable partitions or residential housing units. Standardized labeling within a general class of products is a useful tool to define the appropriate framework in which to assess the particular noise issues of a given project. Presently, this concept appears more developed in areas other than noise emission. For example, sound transmission class (STC) is an established and generally accepted ‘‘label’’ which precisely defines the acoustical performance of a wall partition. Similar labels for other classes of products would increase the awareness of all concerned of the noise issues involved. Clear communication, effective action, and satisfactory resolution could then be more easily achieved. Consensus standards on noise emission labeling would provide a fair yardstick for comparative product noise assessment.
Thirty years experience. . . and 100 million HVI certification labels
Authors: Wolbrink David W. , Craw Gary , Harper John , Schrank Tony
Published: July 2002

Measuring the sound level of products is fruitful when a practical system for applying sound certification labels to competing products meets with long-term success. A prime example of such success is the sound certification and labeling program of the Home Ventilating Institute (HVI). HVI is the trade association for manufacturers of residential exhaust fans and range hoods. HVI has successfully administered its sound certification program for 30 years, providing a simple, single number, linear rating that consumers can understand. The HVI sound certification and labeling program is today one of the most-used programs of its type (in excess of 100 million labels). Tight control over testing provides certified ratings which enable comparisons even though products are often quite similar. The HVI program measures sound pressure level in 24 one-third octave bands in a third-party semireverberant room and, through the substitution process, establishes sound power. The certified rating is in sones as described by the late Dr. S. S. Stevens of Harvard and published in the Journal of Acoustic Society of America.
Development of a speech-intelligibility-based method of hearing protector selection
Authors: Reeves Efrem R. , Michael Kevin
Published: July 2002

Commonly, attenuation and comfort are the major criteria used in selecting a hearing protective device (HPD) for a given noise environment. The objective of this study was to develop a method of HPD selection in which speech intelligibility is introduced as an additional selection parameter. Subjects with normal hearing, mild hearing loss due to noise exposure, and severe hearing loss due to noise exposure listened to speech presented in a background of noise. Both the speech and noise were filtered to emulate the transfer function of either an average plug type or an average muff type HPD, and the resulting signal was presented to the listener via headphones. Three noises with spectra of high-, middle-, and low-frequency energy concentration, respectively, were used, making for a total of six tested conditions. For each condition, six presentation levels were tested, simulating various degrees of HPD attenuation. A HPD selection criteria was developed based on the word recognition scores for each condition. This criteria was tested using actual haring protectors in a free-field environment, and a comparison with the results from the simulation was made.
Piezoelectric sensors
Authors: Lec Ryszard M.
Published: July 2002

A piezoelectric medium provides an attractive technology for realizing a variety of sensors that exhibit high sensitivity, small size and portability, fast responses, ruggedness and robustness, excellent aging characteristics, high accuracy, and the capability to measure multiple quantities in a single sensor package. Sensors based on this technology can be produced using standard photolithography and, hence, are inexpensive. Piezoelectric sensors are fabricated from materials in which the electromechanical transduction takes place within the material. This material-based transduction process very positively influences the performance of acoustic sensors in terms of their reliability, size, and cost. Piezoelectric sensors are versatile and can measure, in principle, any type of measurand. Usually, piezoelectric sensing is accompanied by both mechanical displacement and electrical field. Thus, both the electrical and mechanical properties of the environment can be monitored directly by piezoelectric sensors. One may increase the number of measurands detected by the acoustic sensor by attaching or connecting a specific sensing element to a piezoelectric transducer/substrate. In this paper, piezoelectric sensing mechanisms and a wide range of bulk piezoelectric waves used in the sensor development are described. Applications of piezoelectric sensors in the chemical, environmental, medical, automotive, and aeronautic industries are also provided.
Stabilization of a capillary bridge in air beyond the Rayleigh–Plateau limit in low gravity using acoustic radiation pressure
Authors: Marr-Lyon Mark J. , Thiessen David B. , Marston Philip L.
Published: July 2002

In the absence of gravity, cylindrical capillary bridges consisting of liquid between two circular supports naturally become unstable and break when the length of the bridge exceeds its circumference. This limit is known as the Rayleigh–Plateau limit. The stability of liquid bridges is important to various technologies even in normal gravity. In experiments performed aboard NASA’s low gravity KC-135 aircraft, it was found that acoustic radiation pressure can be used to stabilize capillary bridges against breakup. Capillary bridges composed of a mixture of water and glycerol were deployed in a 21 kHz ultrasonic standing wave in air. The bridges were extended to a length about 11% beyond the natural limit, and the extended bridges broke immediately when the ultrasound was turned off. In contrast with previous work [M. J. Marr-Lyon et al., J. Fluid Mech. 351, 345–357 (1997)], this stabilization method does not use active feedback; the stabilization is a passive effect of the sound field. The acoustic wavelength is chosen such that the radiation pressure due to the sound field is a function of the local bridge radius, such that areas of larger radius are squeezed, and areas of smaller radius are expanded. [Work supported by NASA.]
High-frequency (8–20 kHz) reference thresholds for audiometry
Authors: Frank Tom , Bruno Erinn , Fowler Anthony , Uhring Elise
Published: July 2002

ANSI (S3.6-1996) and ISO (CD 389-5, 1996) have reported interim high-frequency (8–16 kHz) reference equivalent threshold sound pressure levels (RETSPLs). Since the interim RETSPLs were derived using very limited data, there is a need to increase the data base for specifying high-frequency RETSPLs. Thus, this study determined high-frequency (8–20 kHz) thresholds for 50 young adults having normal low-frequency (0.25–8 kHz) hearing across four test sessions, separated by at least one day, using Sennheiser HDA 200 and Koss HV/Pro earphones. The mean thresholds increased as frequency increased, especially at 16 kHz and above, and were similar to the ANSI and ISO interim RETSPLs. However, the standard deviations were very high and the range scores were very wide for each earphone at each frequency. This would indicate that specifying high-frequency RETSPLs may not be feasible due to very high intersubject threshold variability. On the other hand, the intrasubject threshold differences across each possible test session comparison were found to be very repeatable and within a clinically acceptable range. This would indicate the usefulness of high-frequency audiometry for monitoring patients having or suspected of having otopathology. [Work supported by the Pennsylvania Lions Hearing Research Foundation.]
Contributions of vocal tract shape to voice quality
Authors: Story Brad H. , Titze Ingo R. , Hoffman Eric A.
Published: July 2002

Three-dimensional vocal tract shapes and consequent area functions representing the vowels [i a u] have been acquired from one male and one female subject using MRI. The two subjects were highly trained professional singers, and both were adept at manipulation of vocal tract shape to alter voice quality. Each vowel was performed four times, each with one of the four voice qualities: typical speech, yawny, twangy, and high pitched classical singing. The purpose of the study was to determine how the vocal tract shape can be manipulated to alter vocal quality while retaining a desired phonetic quality. Relative to typical speech, the resulting area functions show, in general, that the lower pharynx is widened for both the yawny and classical singing productions and narrowed for the twangy voice type. Additionally, the yawny and classical singing qualities have widened oral cavities while the twangy quality shows decreased oral cavity area. This contrasts, however, with the lip opening where the twangy quality shows larger area than any of the other three qualities.
Benchmark models for propagation and scattering in Biot media
Authors: Stephen Ralph A.
Published: July 2002

Benchmark models have proved useful in comparing algorithms for studying acoustic wave propagation and scattering [for example, Jensen and Ferla, J. Acoust. Soc. Am. 97, 1499–1510 (1990); or Stephen, J. Acoust. Soc. Am. 100, 2070–2078 (1996)]. By addressing the same problem various investigators can focus on the strengths and weaknesses of various codes as objectively as possible. Ideally benchmark models should address a physically realistic experiment. Often the real experiment is so complex, however, that a sequence of models of increasing complexity is necessary to study the effects of one variable at a time. Some effort is required by the community to agree on a set of problems that is relevant but also amenable to solution by a number of methods. The necessity to accurately predict seafloor scattering strengths from high-porosity muds and sediments, often including gas bubbles in the subbottom, has prompted a renewed interest in Biot theory. For saturated, porous media there is some debate on the relevance of Biot theory to field observations which makes a series of benchmark problems even more important. Some candidate benchmark models for Biot media, for which reference solutions are available, are proposed. [Work funded by ONR.]
A hybrid ray and parabolic equation simulator
Authors: Kalantar Zadeh Kourosh , Shahsavari Payman , Amindehghan Khodabaksh
Published: July 2002

The model used here is a hybrid model. It consists of two basic parts. Standard ray theory method [A. Zielinski and X. Gen, IEEE Oceans’94, III, 184–189] used in high frequencies and finite difference parabolic equations [D. Huang, J. Acoust. Soc. Am. 84, 1405–1413 (1988)] used in lower frequencies for the shallow water cases. In both high frequency and low frequency cases the acoustic wave propagation simulator can be used for range-dependent environments. The simulator is highly user friendly. Thus a nonprofessional user is able to work with it easily. For the user, inputs are speed and bottom profiles, source level, beam pattern, and depth and environmental data. Outputs are pressure phase and amplitude in each point of underwater and bottom media. For checking correctness of the results, they were compared with various available benchmarks and they seemed to be quite acceptable. The implementation is to run on PCs under DOS operating systems.
Modeling of surface wave and bubble effects on sonic boom underwater penetration
Authors: Tracey Brian H.
Published: July 2002

Standard theories of sonic boom penetration into the ocean assume the ocean is a homogeneous halfspace. Recently, efforts have been made to allow for a more realistic model of the ocean, including the effects of surface waves and near-surface bubble plumes. Studies of these effects have been carried out using BEM techniques [Rochat and Sparrow, J. Acoust. Soc. Am. 102, 3159(A) (1997)]. As an alternative approach, scattering and propagation codes developed for underwater acoustics problems can be adapted to calculate boom penetration. Both rough surface and volume scattering theories have previously been integrated into ocean acoustics propagation codes. These implementations can be used to study propagation of scattered sound in the ocean, and have given results which compare favorably with data. The applicability of existing underwater acoustics approaches to sonic boom penetration is discussed. Several adaptations of these approaches are identified which could lead to more efficient calculation of sonic boom penetration.
Dispersion relations for waves on doubly periodic beams
Authors: Gueorguiev Dimitar P. , McDaniel J. Gregory , Dupont Pierre E.
Published: July 2002

Waves in periodic structures are highly dispersive, experiencing either small or large spatial decays depending on whether the frequency lies in a pass or stop band. For ribbed plates, these dispersion relations have been analytically derived by Rumerman [M. L. Rumerman, J. Acoust. Soc. Am. 57, 370–373 (1975)]. This presentation concerns the dispersion of waves in doubly periodic structures, which have received considerably less attention in the literature. The problem analyzed here consists of an infinitely long beam or plate which is attached to two types of substructures. Each type of substructure is characterized in the frequency domain by a complex impedance and is attached to the beam at evenly spaced positions. The presentation will describe the extent to which singly periodic physics prevail and the possibility of creating very wide stop or pass bands by adjusting the parameters of the doubly periodic structure. Ultimately, this work is intended to aid in the design of structures which either confine or release energy near drive-points over very wide frequency bands. [Work supported by NSF.]
Effects of speaking fundamental frequency on the normalization of Cantonese level tones
Authors: Wong Patrick C. M. , Diehl Randy L.
Published: July 2002

Four experiments were designed to look at how Cantonese level tones are perceived. In all the experiments, subjects were asked to identify the Cantonese syllable /si/, which could be perceived as three different words depending on the associated tone. The first two experiments, in which tokens were either mixed or blocked by speakers, showed that Cantonese tones are difficult to identify in isolation. Performance was greatly improved when a phonetic context was provided in the third experiment. In this experiment, Cantonese speakers were asked to produce a semantically neutral Cantonese sentence ending with the target syllable /si3/ (/si/ with Tone 3, the mid-level tone). The fundamental frequency (F0) of the context (i.e., the nontarget portion of the sentence) was raised or lowered via resynthesis. When the F0 of the context was raised (lowered), subjects perceived the target syllable as a lower (higher) tone. In the fourth experiment, an English context was used instead. The results did not differ significantly from the third experiment, which may suggest that, in judging tonal value, Cantonese listeners rely on speaking F0 of the context. [Work supported by NIDCD.]
The “inverse problem” solved for a three-dimensional model of the cochlea. III. Brushing-up the solution method
Authors: de Boer Egbert , Nuttall Alfred L.
Published: July 2002

In two earlier papers [de Boer, J. Acoust. Soc. Am. 98, 896–903 and 904–910 (1995)] the inherent problems of the inverse-solution method in cochlear mechanics were described. The present paper shows results obtained with a more universal solution method. With the new method it is possible to construct a three-dimensional model of the cochlea producing a response that accurately simulates a measured mechanical basilar-membrane response. With earlier methods this could not be done. The inverse solution invariably yields that, with low stimulus levels, the model simulating a viable cochlea must be locally active. For the response of a dead animal a passive model is sufficient. Once more the inherent intricacies and problems of the inverse-solution method are discussed. Conservation of fluid volume leads to the concept of the “virtual stapes velocity.” For best results, the input signal to the inverse-solution procedure should be acquired in the form of a “composite cross-correlation spectrum.” Inverse analysis can, under certain circumstances, produce aberrant results. In this paper it is shown why the resulting impedance function is the most accurate in the region of the response peak. Therefore, it is unlikely that a passive model would exist of which the response simulates the data obtained from a healthy animal.
A new method for nonlinear nondestructive testing of developing defects inside inhomogeneous solids
Authors: Robsman Vadim A. , Rudenko Oleg V.
Published: July 2002

Nonlinear acoustic interactions in defect solids subjected to the growing force load are studied both experimentally and theoretically. Three types of nonlinear processes are considered, which can be named as ‘‘wave–defect’’ interaction, ‘‘defect–defect’’ interaction (through the acoustic radiation), and the ‘‘defect–secondary radiation’’ one. Acoustic signals passed through the different building materials and constructions being under a load were recorded, as well as pulses radiated by growing defects at the increase in load. The nonlinear parameter of defect solid containing cracks was evaluated from the measured data. A new mathematical model describing the kinetics of statistical ensemble of cracks and based on nonlinear integrodifferential equation was developed. At an increase in force applied to the solid (including extremely high load up to a destructive one) new phenomena were observed, namely, jumps from one statistical distribution to another, radically different stages of nonlinear transformations in frequency spectra, and transitions from dynamic to stochastic behavior. Such processes can serve as new highly sensitive indicators of the defect solid structure and as a forerunner of catastrophic destruction.
Target strength spectra of swim-bladdered fish
Authors: Foote Kenneth G. , Francis David T. I.
Published: July 2002

Swim-bladdered fish are modeled by the actual shape of the swimbladder as determined from microtomed sections. Target strength spectra are computed for specimens of pollack (Pollachius pollachius) and saithe (Pollachius virens). Results obtained with both the Kirchhoff approximation and boundary-element method at each of four ultrasonic frequencies are compared with each other and with measurements of target strength of the same specimens before swim bladder morphometry. [Partial support of the EU through RTD Contract No. MAS3-CT95-0031 is acknowledged.]
The lower limit of melodic pitch with filtered harmonic complexes
Authors: Pressnitzer Daniel , Patterson Roy D. , Krumbholz Katrin
Published: July 2002

Sounds with temporal regularities can evoke a variety of percepts: pitch, roughness, flutter, or rhythm, according to the frequency range of the regularity. However, only pitch supports the perception of melodies. In an effort to determine the lower limit of pitch, as opposed to flutter, etc., an experiment has been performed to study melody perception with very low notes, as a function of frequency region and phase. These bandpass-filtered harmonic complexes had cosine, alternating, or positive-Schroeder phase. Listeners had to detect differences between two successive four-note melodies that where built around a base pitch. The lowest base pitch at which listeners could perform the task depended on both frequency region and phase. When the combination tone region was masked by low-pass noise, the phase dependence was strongly reduced. The lower limit of pitch increased markedly with frequency region when the masking noise was present. The results are discussed with regard to time-domain models of pitch involving autocorrelograms or auditory images. These models suggest the presence of precise pitch cues in high-frequency regions which appear to be contradicted by the current data. [Work supported by the Fyssen Foundation and the UK MRC (G9703469).]
A reciprocal method to evaluate low, close to track noise barriers
Authors: van Tol P. F. , Holties H. A.
Published: July 2002

In the framework of the Dutch program Quiet Train Traffic (Stiller Trein Verkeer) low, close to track barriers and absorptive layers on a slab track have been investigated. Following numerical calculations on low, close to track barriers and absorptive layers an experimental study has been made in order to evaluate the different solutions. A special test site has been constructed, which acoustically resembles a slab track. It enables a quick mounting and dismounting of different low, close to track barriers and absorptive layers on the slab. Using a reciprocal measurement method the acoustical performance (insertion loss) of different solutions has been determined. One of the advantages of a reciprocal method is that the noise reduction for different noise sources on a freight train, such as wheels, rails, and wagon superstructure, due to absorptive layers and low, close to track barriers is easily identified. Note that this stationary method is very efficient since no train passby is necessary. It is explained that a real train passby may be simulated by combining the measurements over multiple angles. Finally, a comparison will be made between the experimental and the numerical results.
Insights into the acoustic behavior of sperm whales
Authors: Pavan Gianni
Published: July 2002

Sperm whales are still mysterious creatures. Other than to communicate, it is very likely they use sounds to navigate, to orientate, to avoid obstacles, and to find food in obscure ocean depths. Their regular clicking may serve for both communication and long-range echolocation, while codas and other patterned click sequences may serve mostly for social communication. It is known that sperm whales dive deep to search for food, probably squid and giant squid. However, to date nobody has been able to see a sperm whale detecting and capturing prey. Recordings made with towed arrays while pursuing underwater animals at close range have revealed sounds possibly used for echolocation. Accelerated click series may serve for detection and interception of prey. The patterning of clicks closely resembles the echolocation trains of dolphins, and it is very likely that sperm whales search for food in a very similar way. Bioacoustics and new technologies, such as time-depth recorders, ‘‘crittercams,’’ and satellite-based telemetry devices may offer new and valuable insights in understanding their behavior, their survival strategies, and their relationships in the food chain. Understanding these aspects is required to define and to tune conservation strategies to offer them a chance to survive.
Acoustic inversion for Biot parameters in water-saturated sand
Authors: Chotiros Nicholas P.
Published: July 2002

Using an inversion of Biot’s theory, based on the formulation by Stoll, operative values of grain bulk modulus and the frame bulk and shear moduli of water-saturated sand may be extracted from measurements of compressional and shear wave speeds and reflection loss. The inversion process is nonlinear, but in practice it is well behaved and converges quite rapidly to unique values. The term grain bulk modulus, as defined in the formulation by Stoll, is not necessarily identical to the bulk modulus of the grain material, as is often assumed. Examples of the inversion will be given, and the significance of the operative values of the grain bulk modulus will be discussed. [Work supported by Office of Naval Research: Ocean Acoustics.]
Investigation of dissipative effects in a poroelastic layer coated plate
Authors: Rigobert Stephane , Sgard Franck , Atalla Noureddine
Published: July 2002

Nowadays, porous media are widely used in multilayered structures for noise control applications in such fields as aeronautics, automobiles, building acoustics, and environmental acoustics. Recently, a finite-element model based on pressure-deplacement formulation of Biot’s poroelasticity theory has been extensively used to predict the acoustical and structural reponse of a multilayer structure. For practical applications, such models may lead to large frequency-dependent matrices and thus require huge computational ressources. The goal of this work is to solve the problem in the particular case of a poroelastic layer attached to an elastic plate. The idea is to develop a plate finite element which acounts for the behavior of the elastic plate and the porous solid phase. The fluid phase of the porous medium will be taken into account using equivalent fluid finite elements. In this paper, the assumptions and numerical results justifying the proposed simplifications will be discussed. In particular, the relative importance of the different dissipation mechanisms in the plate-porous system will be numerically assessed. These results constitute guidelines for considering the relevant dissipation phenomena in the simplified finite-element model of the system.
Spatial sound reproduction with wave field synthesis
Authors: Boone Marinus M. , Vries Diemer de
Published: July 2002

Wave field synthesis is a reproduction technique developed at TU Delft, that enables the generation of high-quality three-dimensional spatial sound fields. The benefit of the method is that spatial impressions are highly independent of the position of the listeners within a large listening area. In short, the method uses a limited number of audio channels that are reproduced by generating plane and spherical wave fields with arrays of loudspeakers that surround the listening place. Applications include spatial sound reproduction in the home and in cinemas, sound reinforcement in theaters, teleconferencing with large video screens, and variable acoustics.
Acoustics education in France: Past, present and future
Authors: Hamonic B.
Published: July 2002

Acoustics is the science of sound. The interdisciplinary nature of acoustics implies the broad scope of acoustics education and the necessity to teach it at various levels of the student education, from high school to Ph.D. In the 1960s acoustics was not an important part of the French education system. Progressively teaching acoustics at a higher education level became natural and, in the 1990s, France was the only country to give a diploma between six and eight years after the secondary studies leaving certificate (Bac in french). The quality of this diploma was directly related to the emergence in France of research teams specialized in acoustics. Teaching acoustics at a secondary level came into effect only in 1994 for senior high school students. This presentation will first summarize the current acoustics education system in France with its characteristic in secondary education (senior high school) and higher education, univerities (first, second, and third cycle), engineering schools (French typcial system), etc. The future of acoustic education seems directly related to computer-based courses, the emergence of videotapes and videodiscs demonstration experiments, internet communication, etc. Reflection toward teaching acoustics in France in the future will then be addressed.
Survey of the university institutions teaching acoustics in Poland
Authors: Hojan Edward
Published: July 2002

Higher education in Poland is either state owned or private. The total number of students in the institutions of higher education at the university level amounts to 630000, which makes 15 students per 1000 citizens. As a rule, the education provided by state-owned schools is free. Among the state-owned educational institutions, presently in Poland, there are 13 universities, 18 technical universities, 8 musical academies, and 12 medical academies in which acoustics (or only psychoacoustics) is learned at selected branches of the studies The subject of acoustics is not provided in private schools. In this survey a directory of schools will be given with the details of studies where acoustics is available, including the numbers of students, hours, and the topics taught in the lectures and tutorials.
Acoustics education in the Low Countries
Authors: Houtsma Adrianus J. M.
Published: July 2002

This presentation is an overview of acoustics education programs found at universities and professional colleges in the Netherlands and Flanders. As has happened in many other academic areas, the traditional organization of educational programs along disciplinary lines has to a large extent made a place for an organization based on application areas. In university programs on acoustics, one finds clusters of specialized subjects that seem to be typical for schools or departments, such as audiology, audiometry, and speech therapy in medical schools, phonetics, music, and speech in humanities departments, and architectural acoustics, noise control, imaging, and fundamentals in applied sciences or engineering departments. Several professional colleges offer courses that are focused on measurement techniques, insulation properties of materials, and noise control in buildings and structures. A fundamental and broad treatment of acoustics, followed by a treatment of specialized applications in the areas of noise control engineering, architectural acoustics, or electroacoustics as elective options, is found in the Advanced Acoustics Course, organized by the Dutch and the Belgian acoustical societies and taught annually in Antwerp.
UK education in acoustics
Authors: Rice C. G.
Published: July 2002

To definitively report on the status of acoustics education in the UK must be regarded as a challenging task. The areas of interest are even wider than the normally accepted classification of acoustic subjects (e.g., PACS), and the variety of situations to which such knowledge can be applied in practice is daunting. However, whatever the level of expertise required of practitioners in acoustics, everyone ought to be educated within a framework of life-long learning and continuing professional development. In the UK such formal educational and training requirements needed to practice the profession of acoustics have been specified, and it is in this context that UK education in acoustics will be reviewed. Formal educational requirements leading to chartered engineer status for individuals (e.g., CEng and FEANI EurIng) have been laid down by the UK Engineering Council in their ‘‘Standards and Routes to Registration (SARTOR)’’ document. These procedures were compiled by members from the professional engineering institutions and include guidelines for the accreditation of university degree courses. The Institute of Acoustics plays an important role in the implementation of such procedures. Information relating to the wider role of the importance of acoustics education in nonengineering disciplines will also be presented.
Measurement of loudspeaker parameters by inverse nonlinear control
Authors: Klippel W.
Published: July 2002

Nonlinear loudspeaker models have been developed to predict and explain the generation of nonlinear distortions in the reproduced sound at large amplitudes. These models require additional nonlinear parameters such as the force factor, stiffness of the mechanical suspension, and voice-coil inductance depending on the instantaneous excursion of the voice-coil. These parameters have to be measured dynamically since static approaches have shown to produce inaccuracies in describing the dynamic behavior of the loudspeaker due to hystereses and creep effects. The identification of the optimal model parameters can be accomplished by using an adaptive nonlinear system provided with the known input signal and an output signal measured on the speaker. An inverse nonlinear identification by using a nonlinear controller connected to the loudspeaker input has advantages over direct loudspeaker modeling in respect to robustness, convergence speed, and stability. Results of practical loudspeaker measurement are presented and discussed in respect to quality assessment of loudspeakers in the large-signal domain.
Beams of sound: A low-distortion airborne parametric array
Authors: Pompei F. Joseph
Published: July 2002

An improved airborne parametric array, which uses audio preprocessing and wideband transducers to significantly reduce distortion, is described and demonstrated. The airborne parametric array has been previously shown [Yoneyama et al., J. Acoust. Soc. Am. 73, 1532–1536 (1983)] to produce highly directional audible sound from the nonlinear self-demodulation of a modulated ultrasonic beam. The resulting audible sound contained a high degree of distortion (up to 50% THD), which is a result of using pure AM modulation and narrow-band transducers. By preprocessing the audio signal and employing wideband transducers, the distortion is shown to be reduced to only 5%, while still maintaining a 3° beamwidth.
Turbulent acoustic streaming excited by resonant gas oscillation with periodic shock waves in a closed tube
Authors: Yano Takeru
Published: July 2002

Resonant gas oscillations with periodic shock waves in a closed tube are studied by executing large-scale computations of the compressible 2-D Navier–Stokes equations with a finite-difference method. In a quasisteady state of oscillation, acoustic streaming (mean mass flow) of large Rs is excited, where Rs is the streaming Reynolds number based on a characteristic streaming velocity, the tube length, and the kinematic viscosity. When Rs=560, relatively strong vortices are localized near the tube wall. The resulting streaming pattern is almost stationary but quite different from that of the Rayleigh streaming. The streaming of Rs=6200 involves unsteady vortices in a region near the center of the tube. Turbulent streaming appears in the result of Rs=56000, where vortices of various scales are irregularly generated throughout the tube.
Verification of the HIC algorithm
Authors: Dunlop John I.
Published: July 2002

Computation of the Head Injury Criterion (HIC), specified in test standards for impact attenuation, involves an integrand maximization formula which should be verified in any system calibration. Two types of wave form—the translated triangle and half sine wave—are suggested as suitable for verifying the calibration of the test system and the validity of the computation algorithm.
A curved piezo-structure model: Implications on active structural acoustic control
Authors: Henry James K. , Clark Robert L.
Published: July 2002

Current research in Active Structural Acoustic Control (ASAC) relies heavily upon accurately capturing the application physics associated with the structure being controlled. The application of ASAC to aircraft interior noise requires a greater understanding of the dynamics of the curved panels which compose the skin of an aircraft fuselage. This paper presents a model of a simply supported curved panel with attached piezoelectric transducers. The model is validated by comparison to previous work. Further, experimental results for a simply supported curved panel test structure are presented in support of the model. The curvature is shown to affect substantially the dynamics of the panel, the integration of transducers, and the bandwidth required for structural acoustic control.
Lung response to low-frequency underwater sound
Authors: Dalecki Diane , Raeman Carol H. , Child Sally Z. , McAleavey Stephen A. , Carstensen Edwin L.
Published: July 2002

The response of the lung to exposure to low-frequency underwater sound was investigated for frequencies of 100–500 Hz. Several different experimental and theoretical approaches demonstrated that the lung responds to low-frequency underwater sound as a resonant structure. Measurements of acoustic scattering near murine and rat lung indicated that the response of the lung to low-frequency acoustic fields can be described well by the theory of linear oscillations of a bubble in water. The measured mean resonance frequency was 325 Hz for adult mice (30 g), 420 Hz for young mice (10 g), and 175 Hz for rats (320 g). Noninvasive measurements of the displacement amplitude of the lung using an ultrasonic pulse-echo ranging technique confirmed that the lung oscillates in response to exposure near the resonance frequency. At the resonance frequency the response of the lung is maximized and the thresholds for damage to the lung and surrounding tissues (such as liver) were lowest. For exposure of adult mice at the resonance frequency, the threshold for lung hemorrhage and for liver hemorrhage was ∼184 dB re: 1 μPa (i.e., 1.6 kPa).
Active control of fan tones radiated from turbofan engines. II. In-duct error sensors
Authors: Joseph P. , Nelson P. A. , Fisher M. J.
Published: July 2002

This paper continues an earlier companion paper in which the results of active control computer simulations aimed at assessing the potential for reducing the fan tones radiated from the inlet of turbofan engines were presented. The earlier study found that good levels of reductions in the sound power transmitted and sound pressure radiated towards the sidelines could be obtained by using error sensors located in the radiated far field. The present paper is also concerned with these control objectives, but with the important difference that the error sensors are located on the duct wall. The error sensor array described in this paper is comprised of a number of axial line array of discrete sensors uniformly distributed around the duct wall. By applying the appropriate phase delay between the sensor signals in a single axial array and summing, an estimate of the mode amplitudes versus axial propagation angle can be obtained. This in-duct pressure measurement can be related to the far-field radiation pattern. Practical issues are also addressed such as the influence on the array’s performance of the in-duct boundary layer and interference from cut-off modes. The basis for the technique is the close relationship between the in-duct ray–mode angles and those of the far-field peak pressure lobe of the radiated field.
Response to “Comments on ‘A field survey on the annoyance caused by sounds from large firearms and road traffic’ ” [J. Acoust. Soc. Am. 106, 1594–1597 (1999)]
Authors: Buchta Edmund , Vos Joos
Published: July 2002

Percentages of “highly annoyed” respondents were determined by utilizing the more commonly adopted cutoff point at 72% instead of at 63% of the rating scales. The results showed that (1) the community response to the road-traffic sounds was not different from that obtained in many other field surveys, and (2) the overall adjustment to the C-weighted day–night level of the artillery sounds was equal to the previously derived adjustment. The estimated optimal parameter values in Schomer’s new rating procedure for high-energy impulsive sounds were hardly different from the previously obtained values. It was shown that analyses in which (inaudible or faintly audible) single events with relatively low CSEL values were excluded yielded essentially the same results as reported earlier.
Intonation and speech timing: Association or dissociation?
Authors: Seddoh Samuel A.
Published: July 2002

A number of prosodic studies on brain damaged patients [e.g., Gandour et al., Brain & Lang. 43, 275–307 (1992)] have concluded that the production of fundamental frequency (F0) is tied to temporal control, and that abnormalities in F0 associated with intonation exhibited by aphasic patients is due to underlying disturbance in speech timing. The present study examined F0 and durational measures in syntactically simple English statements and interrogatives produced by fluent and nonfluent aphasic patients as well as a group of normal subjects. Measures conducted included initial F0 peak (P1), the initial frequency at the terminal region of the F0 contour (TIF), amount of terminal F0 fall/rise, utterance length, duration of terminal F0 fall/rise, and distance between P1 and TIF. Results showed that the nonfluent aphasic patients performed at comparable levels with the normal subjects on all F0 measures, but they were severely impaired across the board on temporal measures. The fluent aphasic patients’ performance on both sets of measures were generally comparable to normal performance, although in absolute terms their durations were also longer than normal. These findings contradict the view that F0 production depends on speech timing. Rather they suggest that the two parameters may be dissociated.
Holographic interferometric visualization of weak shock waves in castor oil packed with equal-diameter gelatine spheres
Authors: Hosseini S. Hamid R. , Moosavi Nejad S. , Nahaboo Tasneem B. F. R. , Takayama Kazuyoshi
Published: July 2002

The attenuation of shock waves in castor oil in which equal-diameter gelatine spheres were packed was measured with hydrophones at various stand-off distances. The motion of shock waves was quantitatively visualized by using double exposure holographic interferometry. Diameters of gelatine spheres under study were 3.0 mm ±1%, 4.5 mm ±1%, and 6.0 mm ±1%. Shock waves were produced at the center of a chamber in which gelatine spheres of total 4 L in volume were densely immersed in castor oil. In order to generate shock waves, irradiation of a pulsed YAG laser beam on silver azide pellets were used. The weight of silver azide pellets ranged from 3 μg to 10 mg, with their corresponding energy of 4.5 mJ to 15 J. The effect of the nonuniformity on the shock-wave attenuation created due to the multiple interaction of shock waves with the gelatine spheres was experimentally clarified. The result will be useful to establish a model of human tissue in numerically simulating the complex interaction of underwater shock waves with human tissue which takes place in shock-wave therapies.
Acoustics on the planet Mars: A preview
Authors: Sparrow Victor W.
Published: July 2002

Assuming no operational difficulties, NASA’s Mars Polar Lander will settle on the Martian surface in December 1999 and will transmit back to Earth sound samples from an audio frequency microphone designed and built by the University of California Space Sciences Laboratory and funded by The Planetary Society. Information on this MARS MICROPHONE is available on the World Wide Web at plasma2.ssl.berkeley.edu/marsmic/ and planetary.org. It is hoped that the microphone will detect natural environmental sounds on Mars as well as monitor operational noises made by the lander itself. This talk presents what little is known about the acoustic environment of Mars. Using available knowledge of the Martian surface atmosphere, the acoustics between Earth and Mars can be easily compared. Although the sound speeds on Earth (343 m/s) and Mars (228 m/s) are comparable, Mars’ ambient density is only 1.4% of that on Earth. The resulting difference in characteristic impedances implies that a machine vibrating on Mars will radiate sound at a level approximately 20 dB lower than on Earth. Additional comparisons will be presented. [The helpfulness of Dr. Janet Luhmann and Dr. Greg Delory of the Berkeley SSL is appreciated.]
Development of an on-line diagnosis system for rotor vibration via model-based intelligent inference
Authors: Bai Mingsian R. , Hsiao Ilong , Tsai Hsuming , Lin Chinteng
Published: July 2002

An on-line fault detection and isolation technique is proposed for the diagnosis of rotating machinery. The architecture of the system consists of a feature generation module and a fault inference module. Lateral vibration data are used for calculating the system features. Both continuous-time and discrete-time parameter estimation algorithms are employed for generating the features. A neural fuzzy network is exploited for intelligent inference of faults based on the extracted features. The proposed method is implemented on a digital signal processor. Experiments carried out for a rotor kit and a centrifugal fan indicate the potential of the proposed techniques in predictive maintenance.
Inverse problem solution techniques as applied to indirect in situ estimation of fish target strength
Authors: Stepnowski Andrzej , Moszyński Marek
Published: July 2002

In situ indirect methods of fish target strength (TS) estimation are analyzed in terms of the inverse techniques recently applied to the problem in question. The solution of this problem requires finding the unknown probability density function (pdf) of fish target strength from acoustic echoes, which can be estimated by solving the integral equation, relating pdf’s of echo variable, target strength, and beam pattern of the echosounder transducer. In the first part of the paper the review of existing indirect in situ TS-estimation methods is presented. The second part introduces the novel TS-estimation methods, viz.: Expectation, Maximization, and Smoothing (EMS), Windowed Singular Value Decomposition (WSVD), Regularization and Wavelet Decomposition, which are compared using simulations as well as actual data from acoustic surveys. The survey data, acquired by the dual-beam digital echosounder, were thoroughly analyzed by numerical algorithms and the target strength and acoustical backscattering length pdf’s estimates were calculated from fish echoes received in the narrow beam channel of the echosounder. Simultaneously, the estimates obtained directly from the dual-beam system were used as a reference for comparison of the estimates calculated by the newly introduced inverse techniques. The TS estimates analyzed in the paper are superior to those obtained from deconvolution or other conventional techniques, as the newly introduced methods partly avoid the problem of ill-conditioned equations and matrix inversion.
Some numerical result properties of nonlinear and dispersive equations
Authors: Hadouaj Hichem
Published: July 2002

It is known that the envelope-solitary shear horizontally surface waves at the top of an elastic film superimposed on a nonlinear elastic substrate are goverened by a nonlinear Schrödinger equation at the interface. And also, the cubic Schrödinger equation using the complex amplitude is the model equation which describes the envelope optical solitons propagation in fibers. The generalized Zakharov system has found a number of applications in various physical problems, such as interaction of intramolecular vibrations giving rise to Davidov solitons with acoustic disturbances, interaction of high-frquency and low-frequency gravity disturbances in an atmosphere, and so on. Some numerical simulations of soliton propagation and soliton–soliton collisions in a generalized Zakharov system are presented. It envisages soliton–soliton interactions in the damped ac-driven nonlinear Schrödinger equation, which is the simplest model of charge-density wave conductor or of a cold plasma driven by an external ac electric field. Numerical simulations on collision of two solitons with zero initial velocity at infinity are given, and it is confirmed that after the collision the soliton separates at a finite velocity, i.e., a two-soliton breather does not exist in this model.