bluuebunny/crossref_metadata_2025 huggingface dataset:
Fred Fisher and research with acoustic vector sensors; Marine Physical Laboratory’s vertical array of directional acoustic receivers and ocean noise
Authors: D’Spain Gerald L. , Hodgkiss William S.
Published: October 2013

Fred Fisher had boundless enthusiasm for all topics acoustic. A chance encounter with him in the hallway usually led to a half-hour discussion of the latest research efforts at the lab and recent results he found exciting. In the 1980s, Fred became interested in the problem of identifying the physical phenomena forming the pedestal about the horizontal in vertical directionality measurements of the deep ocean’s low-frequency noise field. Two competing mechanisms had been proposed: downslope conversion of coastal shipping and noise from high latitude winds coupling into the deep sound channel due to the shoaling of the sound channel axis. The relative contributions of these two mechanisms possibly could be separated if the azimuthal ambiguity of a vertical line array of hydrophones somehow could be broken. Therefore, Fred proposed to build a vertical array of ‘‘DIFAR’’ sensors, which led to the design and construction of the Marine Physical Lab’s Vertical ‘‘DIFAR’’ Array. This talk will reminisce a bit about Fred as well as present some results from an ambient noise experiment conducted in 1992 on the continental shelf using the Vertical DIFAR Array co-deployed with MPL’s freely drifting vector sensors, the Swallow floats. [Work supported by ONR and ONT.]
Unifying approaches for modeling and predicting speech intelligibility
Authors: Bronkhorst Adelbert W. , van Wijngaarden Sander J.
Published: October 2013

Speech intelligibility is practically always affected by the acoustic environment (reverberation, interfering speech, noise). When speech is processed electronically, distortions introduced by the transmission chain can also deteriorate intelligibility. Furthermore, intelligibility can be strongly influenced by nonacoustic factors such as contextual information, non-nativeness, and hearing impairment. Various intelligibility prediction methods have been developed (including SII, STI, SRS, and PESQ), which cover almost all factors influencing intelligibility. However, each individual method has limited applicability and no attempts have been made to unify them. Recently, the application domains of two widely used methods, the SII and the STI, have been significantly extended. They now, for example, cover interference that fluctuates in level, live speech, and digital transmission channels. These methods are actually very similar in the way in which they treat frequency-domain effects. Because of this, it is not difficult to fuse the STI and SII into a single method with an unparalleled application domain. Still, important factors such as informational masking and context effects cannot be addressed and more effort should be invested in combining the SII/STI with other, less similar methods (such as the SRS) in order to develop a single, powerful, standard model for predicting speech intelligibility.
Development of word lists for word intelligibility tests in Japanese
Authors: Sakamoto Shuichi , Suzuki Yôiti , Amano Shigeaki , Kondo Tadahisa
Published: October 2013

Speech intelligibility tests are widely used to evaluate personal speech hearing ability accurately. Although various lists have been proposed for the tests, almost all lists in Japan do not properly consider word difficulty as an aspect of speech recognition. Consequently, even if these tests are performed under identical conditions, correct results cannot be obtained. We have been developing word lists for word intelligibility tests to cope with these problems. We control word familiarity, which strongly affects word recognition scores, to equalize difficulty in recognition between word lists. Words are divided into four word-familiarity ranks. Twenty lists of 50 words are constructed in each rank by considering phonetic balance. Moreover, to compensate slight differences in intelligibility scores among word lists within the same word-familiarity rank, the relationship between the difference of word familiarity and signal-to-noise ratio (SNR) is estimated. Then this relationship is used to compensate the difference of the intelligibility score. The other compensation method is based on speech recognition threshold (SRT). The intelligibility score of each word can be equalized by changing the SNR according to the difference of the SRT of the word. The effectiveness of these compensation methods is discussed.
Binaural and spatial factors affecting speech intelligibility in rooms
Authors: Colburn H. Steven , Carr Suzanne , Wan Rui
Published: October 2013

Prominent complaints of hearing-impaired listeners relate to the difficulties they experience in complex acoustic environments, particularly environments with multiple sources and reverberation. Available data and some theoretical ideas about the nature of the difficulties with speech intelligibility in these environments will be reviewed with impaired listeners in mind. The effects of the spatial characteristics of the sound sources and the room on the binaural signals and their processing is the primary focus of this presentation. Listeners with normal hearing as well as listeners with hearing impairments, with and without hearing aids, will be considered. Theoretical topics to be discussed include the effects of reverberation on interaural differences and on temporal modulation patterns, including the consequences for performance as predicted by standard models of binaural processing. [Work supported by NIH R01 DC00100.]
The effect of noise on novel word learning in sequential bilingual children
Authors: Kan Pui Fong , Kohnert Kathryn , Nelson Peggy
Published: October 2013

Preschool children must learn in noisy environments (Picard and Bradley, 2001), but young children are more negatively affected by background noise than are adults (Elliott, 1979). Young second-language learners are more negatively affected by noise than are monolingual children (Crandell et al., 1996; Nelson et al., 2005). Background noise may be still more detrimental in the case of preschool children who speak one language (L1) at home and who start to learn a second language (L2) in nursery school. In this present study we examine the effect of noise on fast-mapping skills in L1 (Hmong) and L2 (English). In the fast-mapping task each child was briefly presented with 5 novel wordscounterbalanced in Hmong and in English–in a quiet setting over two different sessions. Another 5 novel Hmong and English words were presented to each child in two sessions in the presence of babble background noise. During each session the children were tested immediately after their exposure to the novel words. The results confirmed (1) that the children demonstrated–in both L1 and L2–better skills in quiet than in noise and (2) that the childrens fast-mapping skills were positively correlated with their pre-existing L1 and L2 language skills.
Separating and understanding a talker from a mixture in reverberant spaces
Authors: Shinn-Cunningham Barbara G. , Shashanka Madhusudana , Bressler Scott
Published: October 2013

Many studies show that reverberant energy can interfere with the ability to understand a listener by smearing out the temporal modulations and distorting the spectral content that convey speech meaning. However, the amount of distortion caused by the reverberation in everyday settings often is not severe enough to degrade speech understanding when there is only one talker in a room. Despite this, even modest reverberation can have an enormous impact on the ability to understand the same talker when there is another sound source in the environment. One factor that likely contributes to the problem of understanding a talker in a mixture of sounds in reverberant spaces is that it is difficult to separate the target talker from the competing sounds. This talk will explore the ways in which reverberant energy degrades the ability to separate sounds in a mixture. The effects of reverberation on different cues for source segregation, including pitch and location, will be discussed. [Work supported by AFOSR and NIH.]
Reconstruction of bat sonar beams using a multichannel microphone array
Authors: Stilz Peter , Pflästerer Wiebke , Schnitzler Hans-Ulrich
Published: October 2013

We reconstruct the sonar beams emitted subsequently by flying bats from recordings of a two-dimensional microphone array. Based on the bats’ position in space, which can be accessed through a infrared 3D-video system, and the simultaneous recordings of 16 small microphones, the sonar beams emitted by the bats and the sonar footprints on arbitrary planes can be estimated. For the interpolation of a continuous sonar beam at different frequency bands, directional frequency responses, atmospheric and geometric attenuation, and different lag times are taken into account for each microphone. Mean and maximum call intensities can be analyzed and various analysis parameters can be adjusted, different visualizations are available, and numerical data are exported. The system provides access to estimations of the maximum intensity of each call in front of the bat, beam width, shape, and intensity for arbitrary frequency bands, the aiming of the beam, and the bat’s scanning behavior on its flight path.
A new low-power acoustic bat detector for long-duration observations
Authors: Heavner Matt
Published: October 2013

A new small, low-power, long-duration, field-deployable computer for the acoustic monitoring of bats in Southeast Alaska has been developed. Parker et al., (1997) report the northern geographic limit of four bat species to be Southeast Alaska. (A fifth species, E. fuscus, goes much farther north.) The relationship of the bats to forest management practices, the habitat usage of the bats, and population size and trends are all very poorly known for bats in Southeast Alaska. Long duration monitoring of several different types of area (such as old-growth versus recently logged forest) will provide knowledge to improve management practices in regards to bat ecology in Southeast Alaska. With the motivations just described, the hardware, development methods, and analysis software designed to develop an improved detector are presented. Tradeoffs between computation power, power consumption, cost, and other factors will be discussed. The project has benefitted in several direct ways from the system design requirement of modularity. [Work supported by Alaska epartment of Fish & Game.]
Can birds discriminate between simple sounds and natural vocalization with different degrees of reverberation
Authors: Blumenrath Sandra H. , Dooling Robert J.
Published: October 2013

Birds in natural habitats using long-range acoustic signals experience substantial acoustic alterations of their signals when transmitted from a sender to a receiver. The main degradation comes from reflections of the emitted sounds from surfaces in and around the transmission pathway. These reverberations cause tails of echoes and affect frequency and amplitude modulation within the sounds’ original time frame. Humans discriminate among reverberant and nonreverberant speech segments and use the nature of reverberation in determining the location of the sound source. Using operant conditioning and psychophysical methods, we investigated the ability of several species of small birds to discriminate between nondegraded sounds and sounds artificially reverberated to varying degrees, while holding other sound aspects constant. Birds were able to easily discriminate between nonreverberant sounds and sounds reverberated to various extents. By comparing the birds’ performance on stimuli varying along different dimensions of reverberation, we can make predictions as to the birds ability to use reverberations as acoustic cues in distance estimation and locating sound sources. [Work supported by NICD DC000198 (to R.J.D.) and DC004664.]
Underwater auditory localization by harbor seals (Phoca vitulina)
Authors: Bodson Anaïs , Miersch Lars , Dehnhardt Guido
Published: October 2013

The underwater sound localization acuity of a swimming harbor seal was measured in the horizontal plane. The stimulus was either a double sound (two 6-kHz pure tones lasting 0.5 s separated by an interval of 0.2 s) or a single continuous sound of 1.2 s. Testing was conducted in a 10-m-diameter underwater half-circle with hidden loudspeakers. The animal was trained to swim along the diameter of the half-circle and to change its course towards the sound source right after the signal was given. The seal indicated the sound source by touching its assumed position at the half-circle. The deviation of the seal’s choice from the actual sound source was measured by means of video analysis. In trials with the double sound the seal localized the sound sources with a mean deviation of 2.8° and in trials with the single sound with a mean deviation of 4.5°. In a second experiment minimum audible angles of the animal were determined as a function of frequency (2, 4, 6, 8, and 16 kHz resulting in MAAs of 9.4°, 9.6°, 9.8°, 13.0°, and 13.5°, respectively). Intraspecific differences of the MAA will be presented for five additional harbor seals.
Reaction of plaice (Pleuronectes platessa) and cod (Gadus morhua) to low-frequency sound in an experimental tank
Authors: Mueller-Blenkle Christina , Luedemann Karin
Published: October 2013

Anthropogenic sound in the sea is an increasing problem and more knowledge on the influence of sound on fish needs to be collected. For this reason experiments are carried out in an experimental tank 10 m in diameter to examine the reaction of juvenile and adult cod and plaice to sound. Pure tones from the frequency range of offshore wind turbines are artificially emitted in typical wind turbine sound levels of 130 and 140 dB re 1 Pa. A sound gradient in the tank enables the fish to avoid highest sound levels. The number of fish in the vicinity of the sound source is determined in regular time intervals before, during, and after the 24-h period of sound exposure. Changes in numbers of fish can be seen in the periods with and without sound in many experiments. Reactions of plaice are ambiguous, pointing to both avoidance of or attraction to the sound. In the majority of the experiments carried out on cod, avoidance behavior to the sound can be seen with strongest reactions at 25, 60, and 90 Hz. The results indicate potential avoidance behavior of cod to the operational noise of offshore wind farms.
High-frequency response of polymer shell contrast agents
Authors: Ketterling Jeffrey A. , Mamou Jonathan , Allen John S. , Aristizábal Orlando , Williamson Rene G. , Turnbull Daniel H.
Published: October 2013

Ultrasound contrast agents were originally designed for use at low MHz frequencies; however, recent experimental evidence suggests that many of these agents may also be useful for contrast imaging at frequencies above 20 MHz. Three polymer shelled agents (mean diameters of 0.56, 1.1, and 3.4 μm) from POINT Biomedical were investigated to determine their optimal high-frequency responses. A flow phantom was constructed to restrict the flow of a dilute contrast agent solution to a small volume. The focus of a 40-MHz single-element transducer from a Visual Sonics V770 was positioned within the flow phantom. Radio-frequency backscatter data from individual contrast agents were digitized under a variety of pulse durations (1–15 cycles) and pressure levels (1.4–7.6 MPa). Echo signals from individual bubbles were windowed, and spectra were calculated. Each of the POINT agents reflected energy at the 40-MHz fundamental; however, only the 1.1-μm-diameter agent displayed characteristics of a harmonic response under longer excitations (15 cycle) and medium pressure settings (2.5 to 5 MPa). Experimental results were compared to theoretical calculations for the case of the polymer shell remaining intact during excitation and for free gas nuclei that result from a ruptured shell.
Optical observations of the collapsing behavior of polymer micro-capsule irradiated in the ultrasonic sound field
Authors: Yamato Tetsuo , Yoshida Kenji , Kiyan Wataru , Watanabe Yoshiaki
Published: October 2013

For the medical use, it is important to understand the micro-capsule behavior during collapsing under the ultrasonic sound field. In this report, the behavior of micro-capsule collapse was observed using the high-speed video camera system (HPV-1, SHIMADZU: maximum recording rate; 1000000 frames/second). By using this system, the detail phenomena can be observed. The micro-capsule leaked the internal gases through a small pin hole on the surface of the micro-capsule while repeating asymmetrical vibration. The internal gases were emitted during the positive period of driving sound pressure and returned again in the micro-capsule during the negative period. By repeating the outflow and inflow of internal gases, the stress was cumulated on the shell. Therefore, the small pin hole developed into the big one, then, the micro-capsule emitted a large amount of internal gases and the capsule was collapsed. After the collapsing, only the shell was remained. From the results, it was found for the effect of the shell, that is, the micro-capsule radius shrunk in positive pressure phase, however it hardly expanded in negative pressure phase. These phenomena were numerically simulated by the vibration model, which the effect of the shell was removed only when shrinking. This simulation results qualitatively agreed with observation results.
Engineering the acoustic response of lipid-based microbubbles: Simulations and high speed optical imaging results
Authors: Stride Eleanor , Eckersley Rob , Chetty Kevin , Sennoga Charles , Hajnal Jo
Published: October 2013

Gas microbubbles coated with a surfactant or polymer shell have become well established as contrast agents for ultrasound imaging and are under investigation for therapeutic applications such as targeted drug delivery. The purpose of this study was to examine the effect of modifying the microbubbles’ coating composition upon their response to ultrasound excitation. Using a high speed camera operating at 3 MHz, the radial oscillations from the commercial contrast agent SonoVueTM and four in-house microbubble preparations were measured under controlled insonation conditions (four-cycle Gaussian pulse; center frequency 0.5 MHz; peak negative pressure 30–70 kPa). The results indicate that microbubble response varies as the lipid structure and functional components in the coating change. These findings have been compared with simulation results using the generalized model for microbubble dynamics developed by the authors, in order to quantify the observed effects of changing the shell composition upon the microbubbles viscoelastic and diffusion characteristics. Both microbubble shrinkage and variable shell viscoelasticity can have significant implications for the acoustic response. This in turn can affect contrast specific imaging methods, especially those involving multipulse sequences such as pulse inversion. Similarly, these phenomena may affect the microbubble destruction threshold and hence the efficiency of drug delivery procedures.
Wideband piezoelectric rectangular loudspeaker using a tuck-shaped polyvinylide-fluoride bimorph
Authors: Itoh Taira , Ohga Juro , Takei Toshitaka , Moriyama Nobuhiro
Published: October 2013

A bimorph sheet of polyvinylide-fluoride (PVDF) film was applied to a flat rectangular loudspeaker as a folded zigzag-tack shape diaphragm whose size is, e.g., 260–144 mm with various depths. These loudspeakers, which we call bimorph tuck loudspeakers, are characterized by their moderate size, wide frequency range, light weight, and lack of magnetic flux radiation. This study examines the electro-acoustic transducer characteristics of these loudspeakers. Their sensitivity and resonance frequency were measured using a flat-panel baffle. Their electrical properties and sound field characteristics were also examined. A speaker’s resonance frequency was estimated theoretically as a function of tuck depth. The measured resonance frequencies were, for example, 200, 160, 90, and 60 Hz. These low resonance frequencies are satisfactory for full-range loudspeaker use. Frequency characteristics of output sound pressure were also measured. They still include some irregularities that are attributable to a local bending resonance of the diaphragm. This paper examines the control methods for those irregularities.
Digital measurement method for dynamic distortion of loudspeakers
Authors: Imaoka Keiichi , Ohga Juro
Published: October 2013

Though many sorts of measuring methods using digital signal processing techniques have been developed, most of them are only for measurements in a linear range. There is still no suitable digital measuring method for nonlinear distortion of acoustical devices. An accurate and convenient nonlinear distortion measurement system should be developed for evaluation of electroacoustical transducers. A new digital distortion measuring method for acoustical devices is presented briefly. This method applies a Pink-TSP signal (time stretched pulse, i.e., quickly swept sinusoidal signal), whose frequency band is partially eliminated, to an acoustical system to be measured. The detected component produced in the rejected band is picked up by a bandpass filter and measured as a distortion. First, two kinds of small size electrodynamic loudspeaker units were measured by using the dynamic distortion measurement system mentioned above. Next, distortion characteristics of mechanical single resonant system models whose component shows amplitude-dependent nature were examined. This paper describes the relationship between distortion characteristics and quality factor, input signal level, and nonlinear parameters. The difference in distortion of two kinds of loudspeakers is detected by this measurement. It is seen that the resonant phenomenon has an influence on distortion characteristics.
Effect of acoustical load parameters for frequency response of headphones
Authors: Kobayashi Megumi , Ohga Juro , Onoda Wataru , Oohira Ikuo
Published: October 2013

This report describes experimental and theoretical analyses for characteristics of headphones to examine the effect of significant parameters for design. Though various types of headphones are being used, the standard design procedure is still not established, because physical relationship between headphone construction and the human ear is not understood satisfactorily. The authors measured frequency response of various headphones by using IEC 60318 artificial ear and IEC 60959 head and torso simulator (HATS), and also measured the response by human ears by inserting a miniature microphone for comparison. By these examinations, a few mechanoacoustical parameters important for design were picked out. Especially, the effect of acoustical leakage shall be noted. Design parameters for supra-aural and intraconcha headphones will be reported.
A two-dimensional mechanical resonator array filter with reduced sensitivity to disorder
Authors: Judge John A. , Vignola Joseph F. , Mathews Scott A.
Published: October 2013

The structural acoustics of perfectly periodic arrays of coupled mechanical resonators are characterized by frequency passbands, outside of which waves do not propagate across the array, but in which wave propagation is attenuated only by dissipation. Arrays of high-Q micromechanical resonators, with sufficiently high resonant frequencies, can thus be used as filters for rf band electrical signals. However, small deviations from periodicity, such as the disorder induced by finite fabrication tolerances, are known to have significant consequences for energy propagation across such arrays. This is particularly true in narrow passband applications, in which resonators are weakly coupled, and the passband energy transmission can be significantly degraded. In this work, a two-dimensional array of resonators is demonstrated that is less sensitive to disorder than equivalent one-dimensional arrays, improving filter performance without the need for improved manufacturing tolerances. The concept is explained in terms of a simple model, and the design of a prototype array is described, including a statistical investigation of disorder effects using finite-element analysis. Experimental measurements are reported demonstrating improved performance of the two-dimensional array (relative to one-dimensional arrays), by comparing laser Doppler vibrometry measurements of equivalent 2-D and 1-D arrays created in silicon wafers using laser microfabrication.
Throat-contact microphone with an elastomer-supported piezoelectric diaphragm
Authors: Yoshioka Daisuke , Okano Hiroaki , Ohga Juro , Oohira Ikuo , Miyoshi Masato
Published: October 2013

Throat-contact microphones are free from environmental acoustical noise because they pick up only local vibration of the throat. This paper proposes a new piezoelectric throat-contact microphone using an elastomer-supported diaphragm. It is smaller and lighter than conventional electromagnetic throat-contact microphones, which have a magnet and coil. Transducer characteristic and parameters are examined in this paper to establish design procedures for such microphones. Frequency characteristics of output signals and electrical impedance for the microphones and their transducing components are presented. The piezoelectric diaphragm is supported by a few elastomer boundaries.
Acoustic communication system using bone conduction elements
Authors: Muto Kenji , Chen Guoyue , Takano Kunihiko , Asai Kikuo , Kondo Kimio
Published: October 2013

This study examines an acoustic communication system constructed using a bone conduction speaker and a bone conduction microphone. This system is a headset that places a bone conduction speaker to the user’s cheek, and a bone conduction microphone to the other cheek. A user can thereby hear a voice through the bone conduction speaker while hearing a voice of a loudspeaker and surrounding noise when using it for teleconferencing. It can transmit the voice of the remote loudspeaker using the external ear, but the user can hear the translated voice through bone conduction. However, the sound of the bone conduction speaker and the surrounding sound are mixed with the speaker’s voice using the bone conduction microphone. The vibration level of the bone conduction microphone from the bone conduction speaker was about 0 dB, although it was the same level as the level of the speaker’s voice. The vibration level from surrounding sound was about −3 dB, although it was a smaller level than the level of the speaker’s voice. This device removed mixed sounds using the echo canceller [K. Muto et al., Proc. Inter-noise (2004), p. 248]. The echo elimination level was about 12 dB. [This work was supported by JSPS KAKENHI 17300283.]
Observing the effects of waveguide model elements in acoustic tube measurements
Authors: Smyth Tamara , Abel Jonathan
Published: October 2013

The theory of digital waveguide synthesis and its use in modeling virtual musical instruments, and in particular for cylindrical and conical bores, is well documented. Current models rely on certain approximations, however, particularly in cases where the theory provides no exact closed form solution, such as the reflection and transmission occurring at the bore’s open end. In this research, we observe, from a time domain, waveguide model perspective, how the theory corresponds to actual acoustic measurements. We consider four simple acoustic tube structures, incorporating both open and closed boundary conditions for both a simple cylinder and a cylinder with a conical flare, allowing us to isolate, and observe, the filtering effects of each model component.
Input impedance measurements of alto saxophones with a calibration error analysis
Authors: Lefebvre Antoine , Scavone Gary
Published: October 2013

Recent investigations are presented for the measurement of acoustic input impedance of wind music instruments. Initial efforts have focused on measurements of alto saxophones using a two-microphone, three-calibration tube procedure. We first present the design of the impedance probe, as well as the data sampling and analysis procedures. We then discuss the relationship between errors in the calculated calibration parameters and the resulting measured transfer functions. Finally, we compare the input impedances of Yamaha Z and Selmer Series II alto saxophones for several low register fingerings. We note several instances where the Yamaha saxophone possesses significantly stronger fundamental resonances than the Selmer saxophone.
Interactive program for computer-aided design of woodwind musical instruments
Authors: Cordourier-Maruri Héctor Alfonso , Orduña-Bustamante Felipe
Published: October 2013

Current scientific knowledge on the acoustics of woodwind instruments allows accurate physical modeling of the sound generation mechanisms, and the acoustic interaction with the air column. These physical models can be incorporated into computer software, in order to evaluate not only the tuning, voicing, and other tonal characteristics of existing instrument designs, but also to estimate the potential effects of proposed modifications, and to anticipate the characteristics of new designs. This presentation describes the development of an interactive computer program for the acoustic design, evaluation, and auralization of woodwind musical instruments. The program displays a graphical user interface that allows convenient entry of air column data, including constant and variable cross-section segments, open and closed fingerholes, and air column terminations. It also implements different types of sound excitation mechanisms, which include jet-driven (flutelike) and single reed (clarinetlike) models. The program can produce input impedance and reflection function data for further acoustic analysis, and synthetic sounds that approximate the musical tones that can be expected form the actual instrument. The software has been validated by comparative analysis of calculated versus measured air columns, and simulated versus actual (recorded) flute tones.
Virtual wind instruments based on pulse forming synthesis
Authors: Oehler Michael , Reuter Christoph
Published: October 2013

A new synthesis method for wind instruments is presented, the digital pulse forming. The core of that principle is that every wind instrument sound can basically be put down to its excitation impulses, which independently of the fundamental always behave according to the same principles. By controlling the pulse width and shape it is possible to generate all sound nuances that can be produced on a real wind instrument. Based on the 1975 found principles of generating wind-instrument-like spectra with typical stable formant areas and spectral gaps evoked by the excitation pulses of double-reeds or lips [J. P. Fricke, Fortsch. Akust. 4(DAGA75), 407–411 (1975)], a virtual wind instrument, the Digital Variophon, is developed. The resulting software-based version of the original Variophon, the first analog wind synthesizer using the pulse forming principles, is a further step towards the intended scientific experiment system for analyzing and synthesizing (wind) instrument sounds. Trumpet, bassoon, and oboe modules are already digitally implemented in a flexible, realtime sound generating and analyzing framework. Acoustic analyses and hearing experiments show extensive concordance between the original instruments and the Digital Variophon. [Work supported by DFG.]
Flow regimes at the output of oboe double-reeds
Authors: Vergez Christophe , Caussé Reneé
Published: October 2013

Measurements of the quasistatic nonlinear characteristic curve for double reeds show systematic deviations from an elementary model of a reed instrument based on a spring model associated to a Bernoulli flow input into the reed. These deviations were previously explained by the pressure recovered by the flow as it expands in the conically divergent output duct of the reed. We will show measurements of the pressure recovery inside the reed as well as detailed flow profiles that can explain the different regimes observed for the pressure recovery (laminar and turbulent). An extension of these measurements to oscillating regimes allows us to observe some qualitative differences in the flow, suggesting an important influence of the dynamic terms in the Navier-Stokes equation in these kinds of regimes.
Wolf notes in brass wind instruments
Authors: Moore Thomas R. , Codrey Isaac E. W.
Published: October 2013

It has been recently reported that experiments using artificial lips have shown that damping the bell vibrations of a trumpet can result in changes in the sound spectrum. New data now suggest that these effects are enhanced when the fundamental frequency of the note is near a resonance frequency of the bell vibration. This effect results in a situation that is analogous to the wolf note commonly found on stringed instruments. Although the physics of the process is still poorly understood, the effect appears not to be related to a change in impedance of the air column.
Sound field modeling in a street canyon with a diffusion equation
Authors: Picaut Judicaël , Colle Stéphane , Bérengier Michel
Published: October 2013

The transport theory of sound particles is applied to the sound field modeling in an empty street canyon with partially diffusely reflecting facades. A diffusion equation is then derived to predict the sound field distribution and the sound decay in the street. The main parameter, namely the diffusion coefficient, is a function of the street width and the acoustic reflection laws of both building facades. For a single rectangular street, analytical solutions can be found. For more complex urban spaces, a finite-element based approach is proposed. Several numerical examples are given, like the sound propagation in a street with a nonuniform cros section, and in street intersections, for point and line sources. In comparison with ray-tracing-based models, the diffusion model requires less computation time and could be applied to the calculation of a sound map for large urban areas. However, at the present time, the diffusion coefficient can be calculated only for simple building reflection laws, like the Lambert’s one.
Prediction of road traffic noise using two-dimensional numerical analysis
Authors: Sakamoto Shinichi , Fukushima Akinori , Okubo Tomonao , Yamamoto Kohei
Published: October 2013

For acoustically complicated road structures such as semi-underground roads and special areas in which a viaduct road and a flat road with noise barriers exist together, prediction of road traffic noise is complicated because of multiple reflections and diffractions that occur inside the road structures. For such road structures, an energy-based engineering model cannot be applied and noise propagation should be addressed through introduction of wave theory. When the road structures have almost identical cross-sectional shape along the road, two-dimensional (2-D) wave-based numerical analyses are applicable. In the prediction model of road traffic noise, the ASJ-RTN Model 2003, published by the Acoustical Society of Japan (ASJ), the application of 2D wave-based numerical analysis was introduced as a prediction method for such complicated road structures. Comparisons between calculations by BEM and FDM and field measurements and experiments for three actual road structures were conducted. Consequently, calculation results agreed well with measured ones. Therefore, the validity of the calculation methods was confirmed. This research was discussed in the Research Committee of Road Traffic Noise in ASJ. Measurement data were provided by Nippon Expressway Company and the Nagoya Expressway Public Corporation.
Modeling outdoor sound propagation in mountainous areas
Authors: Botteldooren Dick , Van Renterghem Timothy , de Greve Bram
Published: October 2013

Detailed modeling of outdoor sound propagation in mountainous area imposes special requirements. The strong gradients in ground surface create propagation conditions that may lead to noise levels much higher than expected at some distance from the source partly due to a focusing effect. Meteorological conditions are particular: main winds following the valley, strong temperature gradients often including stable inversion, slope winds, etc. Because of these particular conditions, efficient modeling of outdoor sound propagation in mountainous area requires adaptations to be made to general purpose models. In this paper we will present possibilities for making time-domain models terrain following and consider options to decrease the memory requirements. For the higher frequency range and distances one is generally interested in, these adaptations are insufficient. Hence, a Green’s function parabolic equation model is added to the toolbox. To tackle the problem in three dimensions, a number of two-dimensional slices connecting the receiver point to all (segments of) sources considered is made. Propagation results for each slice are added. Numerical simulations are compared to field measurements made close to an Alpine highway.
Measurements of acoustic impedance and their application to sound propagation calculations and audible simulations
Authors: Iwase Teruo , Murotuka Yu , Yoshihisa Koichi
Published: October 2013

Acoustic impedance is an important value that determines the boundary condition of each sound field, but collections of actual values are not sufficient for evaluation of many sound fields. First, measurements using a particle velocity sensor for acoustic impedance were tested on various fields. Such measurement results were applied to calculations of sound propagation. Frequency characteristics of sound propagation were obtained along such surfaces as fields of lawns and snow, and areas paved by porous asphalt for drainage. Those characteristics showed fair correspondence with inspected field measurement results. Then, fine calculations in the frequency domain were converted to the impulse response for each sound field model. Convolution operations based on the impulse response and on voice, music, and some noise sources readily produced an ideal sound field to the audible sound file. Furthermore, simulations of the noise, including noise reduction effects from a car running through a drainage pavement area, were executed as advanced applications. Our measurement method of acoustic impedance is inferred to be useful. Calculated sound propagation characteristics based on the measured acoustic impedance correspond to actual propagation characteristics. Audible simulation will be effective as a future means of sound-field evaluation. [Research supported by KAKENHI.]
Influence of short-term variations of meteorological parameters on sound propagation outdoors
Authors: Blanc-Benon Philippe , Cotte Benjamin , Gauvreau Benoit , Berengier Michel
Published: October 2013

Predicting long-range sound propagation over a nonurban site with complex propagation media requires the knowledge of micrometeorological fields in the lower part of the atmospheric boundary layer. In the framework of road traffic noise characterization there is a need for reliable sound pressure level predictions for specific propagation conditions that must be representative of time and space (small scale and site effects) characteristics of the acoustic situation. Outdoor measurements involving roughly 100 meteorological and acoustic sensors have been carried out during 3 months in 2005 in the southwest of France. This large database enables us to study the variability of meteorological parameters (wind speed, temperature, etc.) on different time scales. Scaling parameters in the atmospheric surface layer (such as the friction velocity and the Monin-Obukhov length) are estimated every 15 min, which allows looking at relatively short-term variations. Some longer-term effects, from days to months, are studied too. These include occurrences of meteorological configurations and variation of ground parameters. The effect of meteorological variability on sound propagation is studied using parabolic equation simulations. Comparisons between numerical predictions and experimental data will be discussed.
Effect of parameters on modeling low-frequency propagation of petrochemical plant noise over water
Authors: Brittain Frank , Di Xiao
Published: October 2013

Modeling noise is vital to designing petrochemical plants to meet community noise limits. Models are used to specify equipment noise, choose add-on controls, and confirm limits will be met. For propagation over land, there are substantial variations of actual levels from the long-term average computed using ISO 9613-2. Commercial modeling software based on ISO 9613-2 excludes propagation over water, where levels are often higher and more variable than at the same distance over land. Over water, higher levels and variability arise primarily from wind, thermal inversions, and lack of attenuations from ground clutter. Often a petrochemical plant and receivers are separated by a large body of water, which reduces modeling accuracy. To better understand propagation over water, full-wave Green’s Function-Parabolic Equation (gf−pe) software was used to predict levels between 50 m and 10 km for various lapse rates (temperature increase with elevation) as well as inversion, source, and receiver heights. Plots of attenuation with distance and contours in a vertical plane are presented for 63 Hz. Rates of attenuation considerably less than −6 dB per distance doubling for spherical spreading were found; these and implications for design are discussed. The potential application of gf−pe to verify algorithms for outdoor propagation is indicated.
A review on barrier diffraction theories and related insertion loss comparisons in highway noise models
Authors: Shu Ning , Cohn Louis F. , Harris Roswell A. , Kim Teak K.
Published: October 2013

This paper presents a review on diffraction theories for highway noise barriers. Insertion loss based on different diffraction theories was investigated with two highway noise models, STAMINA and TNM 2.5. STAMINA implements the Kurze and Anderson empirical diffraction formula while TNM 2.5 deploys a simplified MacDonald analytical model. Quantitative analysis indicates that from the perspective of diffraction theory, the average difference of insertion loss between TNM and STAMINA for a point source is about 3 dB(A). To improve the prediction accuracy of TNM, it is recommended that the MacDonald solution, but with real and image sources, should be deployed.
Amplification of acoustic intensity of a pulse wave propagating through a tube having a temperature gradient
Authors: Biwa Tetsushi , Tashiro Yusuke , Shinmei Masatoshi , Yazaki Taichi
Published: October 2013

Ceperley has theoretically pointed out that when acoustic traveling waves pass through a long duct with a positive temperature gradient, the acoustic intensity is amplified as a result of the thermodynamic cycles that the gas undergoes. Even though he only observed damping of the acoustic intensity in the experiment, his idea serves as a starting point of new acoustic devices known as thermoacoustic Stirling heat engines. For a further progress of the thermoacoustic technology, experimental verification of his idea is of great importance. In this paper, we report on the thermoacoustic amplification of acoustic intensity using pulse waves traveling in a long tube equipped with a differentially heated regenerator. A reservoir filled with pressurized air and a solenoid valve were used to generate the acoustic pulse running in one direction in the tube with length 60 m. A series of pressure transducers was used to determine the axial distribution of the acoustic intensity. Use of a pulse wave enabled us to see the frequency dependence of the amplification rate of acoustic intensity very easily. We found that the amplification rate was essentially determined by the ratio of thermal boundary layer thickness to the pore radius of the regenerator.
Anharmonic acoustic resonators in miniature thermoacoustic cooler
Authors: El-Gendy H. , Lyard L. , Symko O. G.
Published: October 2013

In optimizing miniature thermoacoustic coolers for high cooling power density, the acoustic resonator has to be able to sustain very high amplitude acoustic oscillation at the resonant frequency of the driver in order to pump heat up a temperature gradient. Nonlinear effects in cylindrical-shaped resonators lead to acoustic saturation; acoustic energy is dissipated in higher harmonics, thus limiting the intensity of the fundamental mode. To overcome this limitation, noncylindrical resonators were studied here. Conical, exponential, and halfcosine shapes were used. They produce high-amplitude sound waves with essentially no shock waves. Such resonators were chosen here to operate at around 4 kHz, the resonant frequency of the piezoelectric driver. They are easily adapted to the miniature refrigerator. Moreover, they provide an impedance match, which is shape dependent, between the driver and the resonator. Tests at sound intensity levels up to 170 dB show essentially no distortion of the acoustic waveform. Results of their performance will be discussed. [Work supported by ONR and the State of Utah.]
Marginal instability of thermoacoustic oscillations of a gas in a tube
Authors: Sugimoto Nobumasa , Yoshida Masatomi
Published: October 2013

This paper examines a marginal condition of instability of thermoacoustic oscillations of a gas in a tube with one end open and the other closed by a flat wall, subjected to a smooth temperature distribution axially. Assuming a boundary layer is thin compared with the tube radius, the linear theory is developed in the framework of the first-order theory in its thickness. An idea of the method of renormalization enables us to obtain analytical solutions and to derive the marginal condition when the temperature distribution is parabolic. Solving the condition numerically, the marginal curve for the temperature ratio is displayed graphically against the tube radius relative to the boundary-layer thickness. It is found that the temperature ratio has a minimum and that the curve has two branches with respect to the minimum. While the left branch for viscous mode extends to infinity, the right branch, close to the curve for neutral oscillations, asymptotes a certain temperature ratio as the tube radius increases. Such results should be compared with the ones obtained by Rott in the case of a step distribution. Spatial mode of oscillations is also displayed in the marginal state and some discussions on the energy balance are included.
Direct observation of thermoacoustic energy conversion
Authors: Tashiro Yusuke , Biwa Tetsushi , Yazaki Taichi
Published: October 2013

A gas column starts to oscillate when the externally imposed temperature gradient exceeds a critical value. Also, when an acoustic wave propagates through a differentially heated regenerator, the acoustic intensity is thermally amplified. Such thermoacoustic phenomena attract considerable interest not only because it becomes possible to develop pistonless Stirling heat engines, but because an alternative approach to understand a heat engine has been proposed based on energy flows. In this work, we report the direct observation of the thermoacoustic energy conversion in a tube filled with atmospheric air to test the validity of the proposal. A gas column was partly heated by an electrical heater and driven by an oscillating piston at 1.00 Hz to assure good thermal contact with the surrounding tube wall. We simultaneously measured pressure and velocity oscillations to determine the acoustic intensity. As a result, we found the amplification of acoustic intensity in the region with a positive temperature gradient. This supports the proposed approach. Further test was made by comparing the acoustic power produced per unit length and the thermodynamic cycles of the gas, the latter of which was also experimentally determined from measurements of temperature and pressure.