bluuebunny/crossref_metadata_2025 huggingface dataset:
Motivations for using a pulsed full spectrum Doppler to measure bedload and near-bottom suspended sediment transport
Authors: Traykovski Peter , Irish James D. , Lynch James F.
Published: July 2002

Acoustic observations of bedform migration and suspended sediment transport at the New Jersey LEO-15 site revealed that bedload and near-bottom suspended load could be the dominant sediment transport mode over wave-formed ripples on a sandy bottom. Bedforms observed during storms using a rotary sidescan sonar were found to be wave orbital scale ripples which migrated in the onshore direction, forced by asymmetrical wave orbital velocities. Estimates of suspended sand transport were calculated from observations of acoustic backscattering and water velocity profiles. Suspended sand transport was also forced by asymmetrical wave velocities, and was found to occur primarily during the weaker offshore phase of wave motion. This net offshore suspended sediment transport was an order of magnitude less than the flux associated with onshore ripple migration. Thus it is hypothesized that ripple migration is most likely forced by unobserved bedload and near-bottom suspended transport. Spatially resolving bedload transport from the stationary bed is difficult since the motion occurs within a few grain diameters of the bed. Acoustic Doppler-based techniques, which are ideal for this type of measurement since the sediment velocity can be resolved from the stationary bed in the frequency domain, are being developed.
Acoustic propagation affected by internal solitons in a coastal area
Authors: Shang E. C. , Wang Y. Y. , Ostrovsky L.
Published: July 2002

The NOAA/Environmental Technology Laboratory (ETL) conducted the ‘‘Coastal Ocean Probe Experiment’’ (COPE) in the Oregon coastal area (with water depth of 150 m) in September, 1995. Strong internal soliton activities have been observed. The isotherm records measured by FLIP demonstrate that the maximum amplitude of isotherm depression can reach ∼30 m. Based on these internal soliton data, numerical simulation on acoustic propagation through solitons has been conducted. Some interesting features of the acoustic field are found: (1) The internal solitons can cause significant mode coupling, but there is no abnormal transmission loss (TL) appearing in the frequency range 50–1000 Hz. (2) Mode coupling strongly depends on frequency, mode number, and the direction of propagation. (3) The modal horizontal refraction (MHR) caused by the internal solitons is significant and offers additional useful information for acoustic monitoring of the internal soliton activities. [Work supported by NOAA.]
Transrectal high-intensity ultrasound therapy of localized prostate cancer
Authors: Chapelon Jean Y. , Gelet Albert , Blanc Emmanuel
Published: July 2002

Prostate cancer is the most common cancer in men. The Ablatherm project has been developed in order to achieve a minimally invasive treatment of localized prostate cancer using transrectal high-intensity focused ultrasound (HIFU). The method uses a sharply focused wideband transducer operating in the frequency range 2.25–3.0 MHz to induce a localized thermal necrosis with a shot of 4.5-s exposure. This therapy transducer focused at 40 mm is coupled to a retractable 7.5-MHz biplane imaging transducer. A computer-controlled positioning device moves the probe in the rectum to ablate the volume defined with the image by repeating the shots every 5 s. For patient safety, the system includes a power monitoring circuitry combined with a real time A-mode ultrasound detection of the rectal wall. Since 1993, 44 patients have been treated in Lyon: A complete response was obtained in 26 and only 18 numerous advantages: It is minimally invasive requiring only a short hospital stay; it is repeatable unlike radiotherapy and additional treatment centered on insufficiently treated area can be performed. [Work supported by Technomed and Rhone Alpes Futur.]
A method of interpolating the diffractive information of the sphere-baffled microphone in the sound field of the spherical wave
Authors: Fukudome Kimitoshi
Published: July 2002

The sphere-baffled microphone (SBM) has been used for estimating DOA of progressive plane waves and their extractions, but it is now planned to construct the diffractive information directory (DID) of the SBM with DOA entry and source—distance entry in the sound field of spherical wave. This paper deals with the interpolation methods of getting information associated with entries not appearing in DID. Numerical computation of the diffractive information is done for the 2-element SBM (right and left microphones at both ends of a diameter of 17.68 cm) at frequency points corresponding to the sampling frequency 22.05 kHz and 1024 point DFT. Two data sets of DOA interval of 6° [0,6,12,...] and [3,9,15,...] are used for interpolation and evaluation of errors. Interpolations and their error evaluations are done in the regions of both the log magnitude versus frequency and the group delay versus frequency. Both the bilinear interpolation and cubic interpolation method result in significant interpolation errors up to 10 dB and 0.14 ms for the shadow region. Finally, a new method is presented with high accuracy of interpolation based on the landmarks-loci of the diffractive information.
Target strength measurements of walleye pollock (Theragra chalcogramma)
Authors: Traynor Jimmie J.
Published: July 2002

The results of recent target strength measurements of walleye pollock from the North Pacific are presented. The measurements, made with a lowered transducer system are compared with historical results. The system allows the transducer to be moved closer to the target fish thus reducing the well-known bias of in situ target strength measurements due to range-dependent noise thresholds. Results using a conventional system with the transducer mounted on the research vessel and this system are discussed. The AFSC currently uses a target strength-to-length relationship [TS=20 log(L)−66.0, L, length in centimeters] to scale echo integration information to estimates of fish density. The appropriateness of this practice is discussed in light of the recent target strength measurements. Caveats regarding the limitations of in situ target strength measurement techniques are presented and suggestions for appropriate conditions for such measurements are provided.
Three-dimensional acoustic measurements of zooplankton swimming behavior in the Red Sea
Authors: McGehee Duncan E. , Genin Amatzia , Jaffe Jules S.
Published: July 2002

Three-dimensional swimming trajectories of several hundred thousand individual zooplankters were measured using the 445-kHz acoustical imaging system FishTV during a three night moored deployment in the Gulf of Eilat, Israel. The sonar examined a 5-m3 volume at 27 m depth, in water 300-m deep. The image rate was 4 images/s. Targets were tracked from image to image using an automatic three-dimensional tracking algorithm. Over 14 000 targets remained in view for over 5 s, and their trajectories were used in subsequent analysis. Data from net tows indicated that most targets were euphausiids. The horizontal speeds of targets −75 dB and below were highly correlated with flow measurements from an S4 current meter. These targets also exhibited strong vertical motions, apparently due to internal waves. Estimated mean flow was subtracted from each trajectory to compute the swimming speeds of the animals themselves. These were generally much lower than the mean flow. During the night, variance in the vertical component of the flow-removed tracks was much greater than variance in the horizontal. However, the variance became more isotropic as dawn approached. A hop-and-sink foraging behavior offers one possible explanation for this.
Harmonic imaging for microbubble contrast agent detection
Authors: Burns P. N. , Chin C. T. , Simpson D. Hope , Powers J.
Published: July 2002

The detection of microbubble contrast agents in the vessels of the microcirculation is currently limited by the relatively low concentrations attainable without causing acoustic attenuation, set against the high clutter signal imposed by surrounding soft tissue. By inducing nonlinear resonant oscillation in a population of microbubbles in transit in the circulation, echoes at the second harmonic can be detected preferentially, thus segmenting the blood signal from that due to tissue. Real-time harmonic imaging and Doppler have been implemented using a clinical array imaging system, and it is shown that with bubble agents it can detect flow in 40 μm vessels of the kidney. At higher incident peak pressures (above about 0.5 Mpa at about 3 MHz), some microbubble contrast agents are irreversibly disrupted by ultrasound. They then produce transient echoes which are high in amplitude and rich in harmonics. Furthermore, transient echoes can be obtained repeatedly over a period of milliseconds, allowing correlation imaging. Such ‘‘transient Doppler’’ imaging can demonstrate microcirculatory blood in the capillaries of the moving myocardium, a new development with significant clinical potential. [Work supported by Medical Research Council of Canada.]
Acoustical nonlinearity parameter of liquids with microbubbles
Authors: Gong X. F. , Ye S. G. , Zhang D. , Feng S. S. , Zhang R. Q. , Wang R. T. , Xu Z. Z. , Liu L. M. , Ha K. L.
Published: July 2002

The gas bubbles in liquid are the strong scatters of the sound propagation in such liquid. A liquid containing microbubbles is used as an effective ultrasound contrast agent in medical diagnosis to improve the contrast of the ultrasonic image. However, the existence of bubbles in liquid may enhance its nonlinearity parameter. In our previous paper, the preliminary results of some ultrasound contrast agents were reported and their large values of the nonlinearity parameter were obtained. This paper is devoted to an experimental demonstration of the influence of microbubbles on the nonlinearity parameter B/A values. These include measuring the dependence of B/A values of Echovist 300 on time. Results show that B/A values decrease with time (from 2678 to 16 over 45 min). B/A values of human blood with a different portion of Echovist were also studied. Larger B/A values are obtained with more Echovist. B/A values of a kind aqua, such as 76% Injectio Meglumini Diatrizoatis Composita (MDC), were studied before and after sonication with different bubble contents. Results indicate that the values of nonlinearity parameter depend on the presence of microbubbles obviously. Some explanation of this effect is discussed. [Work supported by NSF of China.]
Two-dimensional nonlinear propagation of pulsed ultrasound through a tissue-like material
Authors: Hallaj Ibrahim M. , Kargl Steven G. , Roy Ronald A. , Cleveland Robin O.
Published: July 2002

During a lithotripsy operation or ultrasound surgery, high-intensity acoustic waves propagate through tissue. Damage and thermal dose delivered to the target site and to tissue neighboring the target site is of significant interest in such operations. Results of a study of the propagation of intense ultrasonic pulses through a tissuelike material are presented. Two-dimensional simulations showing the effects of nonlinearity in inhomogeneous absorbing materials are used to calculate the acoustic pressure field, from which input is obtained for a bioheat equation calculation. Results show the mean and peak acoustic pressures within a target volume as a function of time, and the thermal dose delivered to a target volume due to a pulsed source in the range of frequencies used for ultrasound surgery. The degradation of the focusing ability of an ultrasonic array in nonlinear inhomogeneous media is illustrated, and conclusions regarding therapeutic ultrasound are made. [Work supported by ONR and DARPA.]
Area averaging sensors for vibro-acoustic control
Authors: Houston Brian H. , Corsaro Robert D.
Published: July 2002

NRL has been conducting acoustic control research for underwater and in-air sound and vibration applications. In many of these studies, the success of the control system depends substantially on the ability of the sensors to measure the physical quantities of interest accurately while ignoring extraneous contributions. For example, the sensors developed for use in the Acoustic Boundary Control (ABC) research were required to monitor accurately the normal component of the average acoustic field on the tile surface, while being insensitive to transverse and high wave number components. The extremely low noise figures required in this study forced the development of special-purpose acoustic pressure and velocity sensors which now are finding use in other applications, including vibration isolation mounts.
Piezoelectric resonant sensor for sound velocity of liquids
Authors: Nowotny Helmut , Benes Ewald , Devcic-Kuhar Branka , Gröschl Martin , Harrer Dagmar , Thalhammer Rudolf , Trampler Felix
Published: July 2002

The sensor consists of two circular piezoelectric plates with the liquid in between. Each piezoelectric plate is a bulk resonator with two electrodes driven in thickness extensional modes. The two resonator plates are electrically connected in parallel and the total admittance is measured in the vicinity of two quasiharmonic series resonance frequencies by a PC-controlled electric admittance measurement system. The extensional thickness mode purity was checked directly by corresponding mode pattern measurements using a laser speckle vibration amplitude measurement system. The sensor element is mounted in a thermostated aluminum housing to avoid temperature effects and to obtain the sound velocity of the liquid at a defined temperature. Two quasiharmonic resonance frequencies are used to allow the elimination of the unknown density of the liquid. The sound velocity is calculated out of a rigorous one-dimensional theoretical model of the three-layer sensor arrangement. In addition to the determination of the sound velocity of the liquid, the mass density of the liquid can be obtained from the same primary measurements. However, at present the accuracy of the density value is one order of magnitude lower than that of the velocity (typically 0.1% for water, acetone, glycerin).
Effects of affective tone of voice on spoken word recognition
Authors: Nygaard Lynne C. , Queen Jennifer S. , Burt S. Alexandra
Published: July 2002

Traditionally, the study of emotional tone of voice has been considered separately from the study of formal linguistic aspects of spoken language. Research has typically focused either on how listeners detect emotion in an individual’s voice, or on how listeners extract abstract linguistic content. The present study was designed to investigate how these two sources of information interact. In two experiments, listeners were presented with homophones that had one affective (happy or sad) and one neutral meaning and with nonhomophones that had either a happy, sad, or neutral meaning. Within each experiment, words were spoken in a tone of voice that was either congruent, incongruent, or neutral with respect to affective meaning. In the first experiment, naming latencies were collected to determine if tone of voice affects the speed of lexical processing. In the second experiment, transcription accuracy was assessed to determine if tone of voice affects the selection of word meaning. The results suggest that emotional tone of voice was used to resolve lexical ambiguity, but did not appear to affect specifically the time course of lexical access. The implications of these results for current theories of spoken word recognition will be discussed. [Work supported by NIH.]
On the perception of qualitative and phonetic similarities among voices
Authors: Remez Robert E. , Van Dyk Jennifer L. , Fellowes Jennifer M. , Rubin Philip E.
Published: July 2002

A perceiver who learns to recognize an individual talker becomes familiar with attributes of the talker’s voice that are present in any utterance regardless of the linguistic message. Customary accounts of individual identification by ear presume that such durable personal aspects of an individual’s speech are graded qualities (e.g., vocal pitch and pitch range; melodious, breathy, or raspy timbre; etc.) independent of the acoustic properties that evoke segmental phonetic contrasts. Alternatively, some classic and recent studies alike suggest that familiarity includes attention to attributes of dialect and idiolect conveyed in the articulation of consonants and vowels. These linguistic phonetic properties of speech are effective for recognizing a talker when voice quality is eliminated as a source of information. The present investigation sought direct evidence of attention to qualitative and phonetic attributes of speech. Natural samples and sine wave replicas of sentences spoken by five male and five female talkers were used in a similarity tournament with adult listeners. The results establish the differential perceptual resolution of qualitative and phonetic attributes in the perception and recognition of talkers. [Work supported by NIDCD and NICHD.]
Experimental measurements of three-dimensional underwater sound propagation over a variable bathymetry
Authors: Glegg Stewart A. L. , Riley Joseph M. , LaVigne Antony
Published: July 2002

There appear to be very few experimental measurements of the three-dimensional features of sound fields in the ocean, especially in shallow water where bottom interactions can have a dominant effect. One of the reasons for this lack of experimental data can be attributed to the difficulty in designing an experiment to identify three-dimensional propagation effects. Bathymetric refraction occurs, for the most part, on a very large scale and so to differentiate between local variability of the propagation and refraction by a bathymetric feature, measurements have to be carried out simultaneously over a large area. This is easier to achieve in the laboratory environment where repeatability of the experimental results is not an issue. This paper will describe a series of laboratory scale experiments which were carried out to identify the major features of underwater sound propagation over a realistic three-dimensional bathymetry. The model used is based on the bathymetry of the Santa Lucia Escarpment, but is not unlike bathymetry found in other coastal regions in different water depths if the correct scaling is used. A number of three-dimensional sound maps will be shown of the field from a point source. [Work supported by ONR.]
Three-dimensional sound propagation modeling of the Santa Lucia escarpment data
Authors: Porter Michael B.
Published: July 2002

The kraken normal-mode program includes options for both N×2-D and full 3-D modeling. The latter is implemented using Gaussian beams to treat the horizontal refraction of modes. Since the model allows for mixed acoustoelastic problems, 3-D sound propagation can be simulated over ocean bottoms supporting shear waves. To study its accuracy, the model is applied to several 3-D scenarios, including both a simple wedge and a topographically complicated case based on the Santa Lucia escarpment off the coast of California. The results are compared to the laboratory scale data presented by Glegg et al. in this session.
The late reverberation time as a new criteria for the evaluation of hall acoustics
Authors: Stauskis V. J.
Published: July 2002

Investigations show that the field decay after-35 dB has its reverberation values, which differ considerably from the values of the standard reverberation time. The experiment was carried out in a rectangular hall measuring 13.6×10.7×7.0 m. The sound absorption coefficients of all planes in the hall were small (0.02–0.05). One hundred seventy semi-upholstered chairs were used for the experiment. When the chairs were placed in the hall, the decrease in the field of a nonfiltered signal was sudden and pronounced, while in the interval from 1500–4000 ms it was slow. The experiments with the filtered signal showed that, at any frequencies, there existed both the initial sudden and the late slow decrease in the sound field energy. The higher the frequency, the longer the interval of the slow decrease in the sound field. When approximating the decrease from −35 to −40 dB, the reverberation time was 15 s at 250 Hz and 4000 Hz. When approximating the decrease from −45 to −50 dB, the reverberation time was as long as 20–21 s within the frequency range of 500 to −2000 Hz.
Effects of the spatial information of a sound field on listener envelopment
Authors: Hanyu Toshiki , Kimura Sho
Published: July 2002

The spatial information of sound fields in various kinds of concert halls as virtual sound-source distributions and short-term directional diffusion factors were measured. It is clear that the spatial information in a concert hall is characterized by how the reflections surround a listener. Accordingly, the relationship between the spatial information and listener envelopment was studied. First, subjective experiments were performed using a simulated sound field in an anechoic room in order to study the effects of lateral energy ratios on listener envelopment. As a result, the lateral energy ratios were not sufficient to evaluate listener envelopment. The research demonstrates that listener envelopment is not only related to late arriving reflections but also to early reflections. In addition, listener envelopment is related to the spatial distributions of the reflections that surround a listener. Furthermore, the implications for concert hall design were discussed.
An evaluation method of concert hall acoustics
Authors: Hirasawa Y. , Maekawa Z.
Published: July 2002

A lot of objective physical parameters for acoustic evaluation of a concert hall have been proposed. However, no one can believe that they provide a perfect method for designing a concert hall. There is a problem with the measuring method of physical parameters, i.e., almost all acoustical measurements in a hall use an omni-directional loudspeaker, which is not similar to most musical instruments. Also, no parameter specifies tone-color or sonority of music performance. These are important factors in evaluating concert hall acoustics. The remaining problems must be considered as follows: (1) The position of sources on a stage changes tone-color and generating sound power. (2) The directivity of sources gives different effects on room acoustics at the same position on the same stage. (3) Each musical instrument has its own important frequency range. What instrument shall be selected properly and what execution of the instrument shall be adopted for evaluation? (4) What is a suitable program of music for evaluation of hall acoustics? Some examples of the problems upon sources and its performance with using real musical instruments, and the remaining problems for evaluations of the concert hall will be presented.
Acoustical design of Sumida Triphony Hall
Authors: Fukuchi Toshiko , Nakamura Hideo
Published: July 2002

The Sumida Triphony Hall was opened near Kinshityo JR station, located in the eastern part of Tokyo, in October 1997. The building contains two concert halls, the Main Hall, with 1801 seats, as the home of the New Japan Philharmonic, and the Recital Hall, with 252 seats. The Main Hall has a rectangular shape with the sloped ceiling rising at 12.5 degrees toward the back of the hall in parallel to the main floor and with two balconies around the main audience area. The reflecting panels were hung over the stage to help the ensemble for players. The shape was basically checked with the technique of computer simulation and the detail of the ceiling and the wall was studied by use of a 1/10th-scale model. An organ with 66 stops was installed at the front of the hall. The Recital Hall is a typical ‘‘shoebox’’ hall. In order to attenuate the vibration caused by railroad tracks, the vibration isolating barriers were embedded around a part of the outer walls of the building, and also the vibration insulating structure was adopted at the Main Hall partly and the Recital Hall entirely. The outline of acoustical design will be reported.
Reverberation time in Serbian Orthodox worship spaces
Authors: Mijic Miomir
Published: July 2002

Seven years ago, at the ASA Meeting in November 1990, this author presented some preliminary results of acoustical research realized in the Serbian Orthodox worship spaces. At that time the results for only seven churches were included in the paper. This research has been continued until now and nearly 60 churches were analyzed, different in volume, age, and the architectural style. Such a large number of measurements allow some more general conclusions about acoustical characteristics of orthodox worship spaces. Reverberation times obtained in realized measurements show the important influence of several specific factors such as strong orthodox rules in church interior design and volume shapes. These factors are influenced by traditional architectural styles accepted as unalterable even in the contemporary architectural design. Some differences in the frequency characteristic of the reverberation time according to different historical periods were also discovered.
Individual differences of subjective preference for sound fields with a different preferred delay time of reflection
Authors: Kuroki Souichiro , Yamamoto Ippei , Sakai Hiroyuki , Ando Yoichi
Published: July 2002

The purpose of this study is to clarify the relationship between the individual preferred delay time of reflection and the effective duration of the autocorrelation function (ACF) of sound source. Subjective preference tests were conducted by varying the delay time of reflection (Δt1) which is one of the four objective parameters related to subjective preference of sound fields. In this paper, five dry sources of instrumental music with different effective duration are used. In addition to the global preference with a number of subjects, individual-preference-scale values also were obtained by the method of paired-comparison tests. An attempt is made here whether or not individual differences in subjective preference may be explained by the categorical classification of musical experience, sex, and age of subjects.
Calculation of speech intelligibility using four orthogonal factors involved in autocorrelation functions
Authors: Shoda Tetsuichi , Ando Yoichi
Published: July 2002

In this paper, a method of calculating speech intelligibility for the sound field with the direct sound and the first reflection is proposed. This method is based on the model of an auditory-brain system consisting of the autocorrelation mechanisms which is equivalent to the power spectrum. The autocorrelation function (ACF) may play an important role on the speech information processing. Four factors may be extracted from ACF, such that (1) τe: the effective duration of ACF (the ten percentile delay) meaning the repetitive feature of signals; (2) τ1 : the delay time of the first peak of ACF signifying the pitch of signals; (3) φ1 : the amplitude of the first peak indicating the strength of the pitch; and (4) Φ(0) : the power of the signal frame. The distance between the syllable in sound fields and the syllable of the direct sound were calculated by the use of these four factors. Using these distances and its linear combination, speech intelligibility of the syllables in the sound fields may be calculated. Results of speech intelligibility tests as a function of the delay time of the reflection are in good agreement with the calculated values.
Acoustic estimates of zooplankton and micronekton biomass using an ADCP
Authors: Ressler Patrick H. , Biggs Douglas C. , Wormuth John H.
Published: July 2002

A calibrated 153-kHz narrow-band ADCP (Acoustic Doppler Current Profiler) has been used to collect acoustic backscatter intensity (Sv) data during several cruises in the Gulf of Mexico. Data have been gathered both while on station and while underway along transects through different hydrographic regimes, enabling an examination of both temporal and spatial trends in backscatter. In addition, zooplankton and micronekton stocks were intensively sampled with a 1 m2̂ MOCNESS (Multiple Opening-Closing Net Environmental Sensing System). Empirical correlations between spatial and temporal variations in Sv and in standing stocks of zooplankton/micronekton will be presented. Sv measured with an ADCP may be useful as an index of zooplankton and micronekton biomass. The location and abundance of these food stocks are hypothesized to be important in determining the distribution and abundance of marine cetaceans in the Gulf of Mexico. In addition, Sv-derived estimates of such stocks may allow inferences about secondary biological productivity in the Gulf, and the role that mesoscale circulation features might play in driving large-scale patterns. [This ongoing research is supported by the USGS Biological Resources Division and the US Minerals Management Service under USGS BRD Contract No. 1445-C109-96-004. For more information, see http://www.tamug.tamu.edu/gulfcet.]
Monitoring the growth and mortality rates of pelagic fish with absorption spectroscopy measurements
Authors: Diachok Orest , Smith Paul
Published: July 2002

The experimental geometry for absorption spectroscopy measurements, which was employed during Modal Lion, can be adapted for monitoring the growth and mortality rate of pelagic fish. During the juvenile stage, in which sardines grow from 3.5 to 13.5 cm over a period of about 1 year and mortality rates are relatively high, absorption spectroscopy measurements (together with complimentary biological and oceanographic measurements) conducted for a few days approximately once per month would permit investigation of the environmental determinants of these parameters. Measurement sites would have to follow the migration route of juvenile sardines over a period of about 1 year. To minimize cost and simplify logistics, a broadband omnidirectional source (instead of a parametric source) would be suspended from a moored ship or buoy. A relatively low source level (∼170 dB) would be adequate. Simulations will be presented of the temporal evolution of the resonance frequency, absorption coefficient, and transmission loss due to sardines between 0.6 and 6.0 kHz. Simulations will illustrate the sensitivity of transmission loss to source and receiver depth, and the average depth and thickness of absorbing layers. In addition, calculations that illustrate the potential of estimating the depth and thickness of absorbing layers by varying the depth of an omnidirectional source will be presented. [This work was supported in part by the Office of Naval Research.]
Improved TV/radio listening for hearing impaired
Authors: van Zutphen J. G. H. , Druyvesteyn W. F. , Slump C. H.
Published: July 2002

In case different persons, having different preferences for the loudness level, want to listen to one sound program in one room, problems arise concerning the loudness of the reproduced program. An example: person A has a normal hearing threshold, while person B is hearing impaired. A sound reproduction system, consisting of a small array of loudspeakers at the TV/radio can solve this problem with digital signal processing; the directivity pattern of the array is manipulated such that the main lobe is directed to person B. The investigation and the presentation at the conference contains two parts: (1) physical acoustics: design and testing of the loudspeaker array including digital processing, and (2) subjective evaluation with normal-hearing subjects and hearing impaired subjects. The subjects listen (and view) a TV program consisting of a selection from 120 short spoken sentences. The normal-hearing subjects adjust the loudness level at their listening position. The hearing-impaired subjects test the effect of the array. These listening tests show a clear improvement in the speech intelligibility for the hearing-impaired subjects as expressed in the number of correct understood sentences and in subjective terms as ‘‘easier to understand‘‘ or ‘‘less tiring to listen to.’’
High degree of freedom muffler optimization using genetic algorithms: Experimental verification
Authors: Pottie Siska , Botteldooren Dick
Published: July 2002

This paper reports on an experimental verification of a nonconventional muffler design. The optimal design is searched using a genetic algorithm (GA). GAs are a powerful optimization technique that are well suited to handle multiparameter optimization problems. The degrees of freedom used to describe the structure is far beyond the usual set. The muffler has a fixed length and width and is described by a set of design rules defining the use of the available space. Different coding alternatives for the GA were analyzed. Best results are obtained with a coding that describes the position and size of the design rules. The performance of the mufflers is characterized by the theoretically achieved sound reduction and by the ease of construction of the optimized muffler. The theoretically achieved sound reduction is calculated using a time domain simulation. In order to verify the promising theoretical performance of the optimized mufflers, a good performing design is built and tested in the laboratory. General agreement between the theoretical and experimental results is found. Since no conventional muffler design rules are imposed, the optimization is completely open for new approaches which can led to new insights for conventional muffler design.
Observations of characteristic transmission and reflection coefficients of a splitter duct attenuator
Authors: Terao M. , Sekine H.
Published: July 2002

The characteristic transmission coefficients (including the reflection coefficients) of a splitter duct attenuator with two air channels containing higher-order wave modes were investigated. These were evaluated at interfaces taken in the straight duct sections in both sides of the attenuator and were determined experimentally and numerically (by BEM). The determination method introduced here requires the solution of two sets of the simultaneous equations given by the superposition principle of traveling waves. One is that the sound pressure at a point is the sum of the pressures of all the traveling waves that could possibly exist there, and it was applied to decompose the incoming and outgoing waves of all modes at each interface. The other is that each outgoing wave pressure of each mode at each interface equals the sum of the products of the incoming wave pressures of all modes at all interfaces and the corresponding transmission factors. It was applied to determine, without using an echoic termination, each characteristic transmission coefficient by which each incoming wave contributes to each outgoing wave pressure. The transmission coefficients of the attenuator were obtained for the fundamental and the first-order modes. Agreement of those by experiment and numerical results is substantially good.
Directional microphone array for measurement in an anechoic wind tunnel
Authors: Alfredson Robin J. , Wilson Alison K.
Published: July 2002

An anechoic wind tunnel in which full-scale acoustic measurements may be conducted on automobiles at speeds up to 200 km/h has been constructed. The wind tunnel uses an open jet which is collected and returned in the closed-loop wind tunnel. This design allows for microphones to be positioned outside of the air flow typically some 4 to 5 m from the vehicle. Thus problems associated with extraneous wind noise on the microphones are largely eliminated but this has resulted in the need to develop microphone arrays which have directional characteristics in order to identify noise sources on the vehicle. A wide range of microphone configurations was examined recognizing the various constraints imposed by cost, data collection facilities, frequency range, and the geometry of the wind tunnel and vehicle. The design that produced an optimum solution was based on an arced array of 10 microphones. The output from each was summed having first been weighted. The array could be moved along the vehicle. Data will be presented indicating the characteristics of this and other arrays as well as the cost of construction.
Theoretical and experimental study of surface waves on solid–fluid interfaces when the fluid sound velocity is larger than the shear wave velocity in the solid
Authors: Padilla F. , de Billy M. , Quentin G.
Published: July 2002

Two surface waves can propagate on a solid–fluid interface: the Rayleigh and the Stoneley waves. The problem is well known when the fluid sound velocity cF is lower than the velocities in the solid (cS and cL). The Scholte–Stoneley dispersion equation has been studied when cF is greater than the shear wave velocity cS. The numerical results obtained for PVC–water and PlexiglasR–water show that there might exist two surface waves whose velocities are lower than cS. The two corresponding roots of the dispersion equation tend to the Rayleigh root of the solid–vacuum interface as the density of the fluid tends to zero. The structure of the two waves has been studied using the formalism of the evanescent plane waves. They are theoretically propagating without attenuation along the interface and exponentially decaying along the direction normal to the interface inside both media. These two waves have been experimentally observed. They exponentially decay along the direction normal to the interface inside both media. The experimental arrival times are in very good agreement with the theoretical ones.
Development of active and passive processes in gerbil cochlea
Authors: Mills David M. , Rubel Edwin W.
Published: July 2002

Distortion product otoacoustic emissions were monitored in neonatal gerbils during furosemide intoxication, to examine the ontogeny of different mechanisms underlying cochlear responses to acoustic stimuli. Results indicate: (1) Above 2 kHz, active processes were functional at adult levels at all ages. (2) In the youngest animals (14 days) the maximum frequency seen for the active response was 16 kHz, while in adults it was 40 kHz. This limitation on the active frequency response is believed to be due to the underlying passive cochlear mechanical response, and is consistent with the known place code shift. (3) The length of the active amplification zone at the extreme base decreased from 1.2 mm at 15–19 days to 0.6 mm at maturity. (4) At midfrequencies, there was an increase in net active gain from 15 to 19 days, then a subsequent decrease to reach a uniform 25-dB gain across frequency by maturity. Overall, these results are consistent with an increase in the rate of gain (dB/mm) from 15 to 19 days as the endocochlear potential increases to mature levels, followed by a decrease in the length of the active amplification zone throughout the cochlea with maturity. [Work supported by NIH DC00395.]
Excessive auditory backward masking and its potential remediation in children with specific language impairment
Authors: Wright Beverly A.
Published: July 2002

Approximately 5% of children who are otherwise unimpaired have marked difficulties perceiving and producing spoken language. This disorder is typically labeled specific language impairment. Recent psychoacoustic tests indicate that children with specific language impairment have excessive auditory backward masking, as demonstrated by their extreme difficulties detecting brief tonal signals followed by longer noise maskers. These results are consistent with the hypothesis that specific language impairment results from an auditory perceptual deficit that makes difficult the discrimination of brief, rapidly presented sounds, including phonemes in speech. Subsequent studies using adults with normal hearing and language skills indicate that the interference from a backward masker can be reduced with practice. This learning generalizes from trained to untrained backward-masking conditions and appears to result from improvements in temporal rather than spectral processing. Taken together, these data imply that training in auditory backward-masking conditions may be a useful intervention for children with specific language impairment. [Work supported by the McDonnell-Pew Program in Cognitive Neuroscience, NIDCD, the Charles A. Dana Foundation, and March of Dimes.]
The multipole method: Contributions of Manfred Heckl and new developments for high-frequency acoustic scattering
Authors: Ochmann Martin
Published: July 2002

In 1988, Cremer and Wang suggested spherical field synthesis (one-point multipole method) for calculating sound radiation from nonspherical bodies. Then, Heckl derived a close connection between Cremer’s method and the Helmholtz integral equation. Also, he recommended the use of several multipole locations for applying the method to nonconvex radiators (multipoint multipole method). From these ideas, the multipole method has since been extended in several directions. Recent research results were obtained by investigating the high-frequency scattering from a nonconvex structure. This structure consists of a sphere where the positive octant is cut out. The region of the missing octant is called a ‘‘cat’s-eye,’’ since it acts like a three-dimensional reflector. Hence, depending on the angles of incidence, multiple reflections can occur. The surface may be rigid or characterized by a local absorbing surface impedance. A boundary element model of this structure consists of nearly 8000 elements for accurate consideration of large values of ka. The results of the multipole method are compared with a newly developed iterative solver of the Helmholtz integral equation for high-frequency scattering. Both methods agree well. However, it is shown that commonly used approximations at high frequencies fail, e.g., the plane wave approximation, if multiple scattering occurs.
The effect of stress on duration in Aleut
Authors: Rozelle Lorna
Published: July 2002

Although duration is often one of the physical correlates of stress, it has been claimed [A. Berinstein, UCLAWPP 47 (1979)] that languages with contrastive vowel length do not use duration as a correlate of stress. This study addresses three questions about the phonetic correlates of stress in Aleut, a language with contrastive vowel length. Is duration a correlate of stress in Aleut? If so, does the change in duration caused by stress neutralize the phonemic contrast between short and long vowels? Finally, does stress assignment precede or follow the optional deletion of the final syllable? Data from four native speakers of Pribilof Aleut were analyzed. Vowel duration was measured from the spectrographs produced by a Kay CSL 4300B speech analysis system. Vowels were categorized as stressed or unstressed according to the Aleut stress rule [A. Taff, MA thesis, University of Washington, 1992] and as long or short according to the words dictionary entry. Statistical analysis shows that duration is a correlate of stress, counter to Berinstein’s claim. However, despite the change in duration wrought by stress, contrastive ratios between short and long vowels are maintained. In addition, stress is assigned before final syllable deletion.
Influence of functional and acoustic parameters of intonation contours on prosody lateralization
Authors: Pell Marc D.
Published: July 2002

The perception of prosody by adults with unilateral right- (RHD) and left-hemisphere (LHD) damage and subjects without brain injury was assessed through six tasks that varied functional (i.e., linguistic/emotional) and acoustic attributes of a common set of stimuli. Three tasks measured the ability to detect prominence cues in short utterances (focus perception) and three tasks examined the perception of emotional-prosodic features by the same listeners (emotion perception). Within each condition, an initial task tested recognition of each ‘‘type’’ of prosody when all naturally occurring acoustic features (but no semantic features) signalled the target response (baseline). Two additional tasks assessed how changes in (a) duration and (b) fundamental frequency parameters of the stimuli influenced performance on the baseline task within each condition. Results indicated that, irrespective of the availability of specific acoustic parameters, recognition of prosody by both RHD and LHD patients was highly influenced by functional attributes of the stimuli (i.e., LHD patients were selectively impaired in detecting linguistic prominence whereas both groups were impaired in deriving the emotional tone). Brain-damaged patients also displayed irregularities when individual acoustic properties of the stimuli were manipulated, indicating that both functional and acoustic attributes of prosody may be determinants of prosody lateralization.
The effects of discourse focus and lexical accent on the prosodic phrasing in Japanese
Authors: Choi Young-Sook , Sato Shigeru , Yoshimoto Kei
Published: July 2002

Measurement of F0 was made of utterances of Japanese sentences to observe behavior of intonation contours with varied focus assignment and lexical accent specifications. Materials were 80 sentences of right-branching structures of the type NP1-NP2(-NP3)-VP, where 16 have two three-mora NP’s and 64 three NP’s, including all the permutations of NP’s, each with one of the four lexical accent types. The utterances were generated in question–answer discourse contexts so that in a sentence, one NP was always focused. The results are: (1) focus assignment has no significant effect on NP1, (2) NP2 and NP3 are significantly higher when focused than when not focused, and (3) focused/unfocused NP2 preceded by unaccented NP1 is significantly higher than those preceded by accented NP1, and so is NP3 preceded by NP2 with the same conditions. These suggest that focus assignment on NP2/NP3 requires rephrasing there, that a lexical accent of an NP narrows the pitch range of the following phrase, and that the prosodic status of focus assignment is lower than that of the lexical accent.
Speaking rate-induced acoustic variability in Parkinson’s disease
Authors: Tjaden Kris
Published: July 2002

The idea that speech consists of overlapping gestures that slide with respect to one another suggests that measurable kinematic, and hence, acoustic differences should characterize utterances produced with varying degrees of gesture overlap. [Saltzman and Munhall, Ecolog. Psych. 1, 333–382 (1989)]. Further research suggests that a simple acoustic model of overlapping gestures [Weismer et al., J. Phon. 23, 149–164 (1995)] accounts for some of the spectral and temporal variability in speech produced by individuals with apraxia of speech. One implication is that articulatory deficits associated with motor speech disorders can be modeled, in part, as disruptions in gesture overlap. The extent to which a model of overlapping gestures accounts for acoustic variability in other motor speech disorders is largely unknown. The present study explored the extent to which a simple acoustic model of overlapping gestures accounted for speaking-rate induced variability in F2 trajectories produced in target words by individuals with Parkinson’s disease (PD), young adults, and older adults. F2 onset frequency was used as an acoustic measure of overlapping consonantal and vocalic gestures; F2 onset frequency also was used to predict across-repetition temporal variability in F2 trajectories.
Speaker identification using noncontemporary speech samples
Authors: Hollien Harry , Schwartz Reva
Published: July 2002

There are two noncontemporary elements important to speaker identification. In one, listeners are asked to make identifications at various latencies after hearing the speaker (time of identification is noncontemporary) or, in the second, samples of the speaker’s voice are obtained at markedly different times (noncontemporary samples). It has been found that memory for voice decays over time in the first case; hence it has been assumed that the noncontemporary samples pose just as difficult a challenge. AN aural–perceptual speaker identification project was carried out to test this second relationship. Noncontemporary samples, with latencies of 4, 8, and 32 weeks, and then 6 and 20 years, were studied. It was found that mean correct identification was initially reduced by 15% and this level was sustained for up to 6 years. It was only after 20 years that levels dropped significantly (to 33%). It is concluded that listener’s efficiency in identifying noncontemporary speech will show only modest decay over time and, hence, its use ordinarily should have only a minimal effect on the speaker identification process.