bluuebunny/crossref_metadata_2025 huggingface dataset:
Finite element analysis of Langevin-type transducers for ultrasonic radiation
Authors: Yamabuchi T. , Kagawa Y.
Published: October 2005

Finite element technique is applied to develop a program for coupled electro-mechano-acoustic problems, which is capable of analyzing composite axisymmetric electrostrictive transducers for ultrasonic radiation. Two separate programs are so combined that pressure and particle velocity are compatible between the solid and liquid surfaces. Some calculations for Langevin-type transducers have water loading on one of their faces. The calculated results of the input impedances at the electrical terminals, which are now expressed as complex values due to the presence of radiation, are compared with the measured results. Good agreement is achieved. The effect of the water loading is small for the materials and the structures employed for the present analysis as the specific acoustic impedance of the water is much smaller than those of the transducers. The directional characteristics are also shown including for the cases of the higher modes and the nearfield sound pressure distribution in the vicinity of the radiators are also illustrated.
Application of a general purpose finite element program to damped composite structural systems
Authors: Lu Y. P. , Everstine G. C.
Published: October 2005

Finite element solutions using a general purpose computer program NASTRAN for damped structures are formulated and presented. Continuously and discontinuously constrained layer damped configurations are the two classes of structures considered. The former is the three-layered sandwich composite made up of two thin elastic layers with a viscoelastic damping core between them, while the latter is the damped composite made of a thin-walled elastic structure having a finite number of mass segments or elastic segments adhered to it by a viscoelastic material. The dependence on frequency and temperature of the dynamic properties of the viscoelastic materials is taken into consideration. Typical numerical solutions of transverse driving point mechanical impedances as well the transfer impedances of three-layered sandwich damped structural elements such as beam, ring, plate, and discontinuously constrained damped ring are presented and discussed. These solutions compare very well with experimental data and available theoretical results obtained by other analytical methods.
Planning, performing, and interpreting air base noise measurements
Authors: Rentz P. E.
Published: October 2005

Analytic estimates of aircraft-related day-night-level (DNL) contours around air bases frequently require experimental verification. For this purpose, a methodology for planning measurement programs was developed and is presented. The use of SEL, HNL, and DNL measurements to estimate average DNL are compared along with the concomitant aircraft operational data requirements. The results of a field test at Barksdale AFB are presented and analyzed with emphasis on field measurement techniques. Confidence intervals are established based on instrumentation accuracies and event variability. [Work supported by USAF.]
Long range acoustic tracking of low flying aircraft
Authors: Landers T. E. , Lacoss R. T.
Published: October 2005

Data from a 5-m array of microphones has been collected and analyzed in the band 20–200 Hz to find the accuracy to which the azimuth of low-flying subsonic aircraft can be tracked and to measure signal levels as a function of range. Flight paths were radar tracked and recorded on digital tape. Propagation characteristics were calculated from measured meteorological data and were used to help interpret observed signal level variations. The aircraft included helicopter, prop-driven and jet aircraft which flew 30 km reversed linear tracks at altitudes of 70 m, 300 m, and 1 km. Azimuth was measured by applying maximum-likelihood frequency-wavenumber analysis to the digitized data from the fractional wavelength array of microphones. Measured azimuths, after the appropriate moving source corrections, were found to be accurate to within a few degrees at ranges well beyond 5 km. Filtering and array gain allowed us to obtain good azimuth estimates for aircraft signals at least 10 dB below the background noise level. [Work supported by DARPA. The views and conclusions contained in this document are those of the contractor and should not be interpreted as necessarily representing the official policies, either expressed or implied of the United States Government.]
Role of scattering in the design of optimal duct treatments
Authors: Andersson A. O.
Published: October 2005

The effects of scattering at the beginning of a finite length, cylindrical duct wall treatment was studied. Single frequency attenuation and optimal impedance of a locally reacting lining was considered. The effect of backward scattering was found to be small, but that of forward scattering substantial. Optimal wall impedance is presented as a function of the ratio of treatment length to duct radius and the mode cutoff ratio, which has been introduced as a design criterion (E. J. Rice, NASA TMX-73411). Although the optimal impedance can be reasonably well described by the cutoff ratio, the attending attenuation cannot, but must be presented as a function of both azimuthal and radial mode indices.
Acoustic synthesis of a flowduct expansion discontinuity
Authors: Lambert R. F. , Steinbrueck E. A.
Published: October 2005

An experimental study of the acoustic pressure reflection coefficient at a sudden area expansion in a flowduct in regard to both magnitude and phase has been undertaken. The study was limited to low flow Mach numbers, frequencies supporting plane wave propagation, and an area aspect ratio of 0.25. The magnitude of the coefficient is flow dependent and relatively insensitive to frequency while the phase is frequency dependent and relatively independent of flow. A semi-empirical analytical model has been synthesized on the basis of available information that incorporates both frequency characteristics and flow effects through first order in the Mach number. The Karal discontinuity correction is important and appears to be a valid representation of the reactive acoustic fields at low Mach numbers, i.e., M ⩽ 0.20. The flow primarily influences the impedance level of the downstream duct and also produces nonreciprocity in the four-pole transmission matrix. Some effects of higher-order corrections in flow Mach number will be discussed briefly. [Work supported by a grant from the National Science Foundation.]
Measurement and spectral description of surface roughness
Authors: Franz G. J.
Published: October 2005

Flow noise generated by boundary layers is critically related to surface roughness. In early flow noise experiments, roughness parameters were insufficiently controlled and documented. The present paper characterizes roughness shape, size, and height in terms of its inverse wavelength spectrum. The need for and usefulness of describing surface roughness and waviness more completely are reviewed. The energy spectra of simple geometric shapes are determined using Fourier transforms. The power spectra of various distributions of these shapes are then determined using a surface density of roughness elements. Specific examples are given of energy spectral density, power spectral density, rms height, and arithmetic average height for square and triangular elements. Comparison is made with measured spectra using a calibration block with two-dimensional triangular elements. Calibration problems are discussed. [Supported by DTNSRDC.]
Jet noise diagnostics: Spurious sound generated by hot wire-turbulence interaction
Authors: Richarz W. G.
Published: October 2005

Jet noise diagnostics via cross-correlation of the postulated source and radiated noise are most easily implemented when the source terms are proportional to certain readily measurable scalars. One such description is the Proudman form of Lighthill's theory. However, attempts to measure the source term by means of a cross-correlation technique have been only partially successful. The major difficulty is suspected to be spurious “probe noise” generated by turbulence/hot wire interaction. Theoretical considerations show that for low Mach numbers, at which the cross-correlation experiments are typically performed, the noise radiated by the probe is comparable with that part of the jet noise radiated from the correlation volume (eddy) surrounding the probe. This assertion is supported by comparison of jet noise-jet flow cross-correlations measured with a hot wire and with a nonintrusive device: a Laser Doppler Velocimeter (LDV). The hot wire is found to generate a spurious but well-correlated probe noise that leads to major error in the jet noise.
Probable correlations between morphology and tonotopic organization in frog amphibian papilla
Authors: Yano I. , Ooyama H. , Sugai T. , Sawada S.
Published: October 2005

Unit discharges were recorded from the nerve branch innervating amphibian papilla of bullfrog. Latencies for click stimulation are shorter for rarefaction than for compression, in fibers with CF lower than 300 Hz. The reverse is true in those with CF between 500 and 650 Hz. Fibers with CF higher than 650 Hz are indifferent to the phase of sound pressure. Mean minimum latencies of three CF groups mentioned above were 2.9, 2.1, and 2.4 ms, respectively. Morphological studies were carried out to elucidate the probable tonotopic organization of sensory macula underlying the above observations. Nerve fibers reaching the macula center are about 400 μm shorter than those reaching extremities. Tectorium is developed better toward the anterior macula than toward posterior. A sensing membrane is attached to the tectorium of middle portion. These results suggest that the anterior, middle, and posterior portions of the macula correspond to the high, medium, and low CF's, respectively. Ciliary orientation varies even between adjacent hair cells. CF-dependent, reciprocal responses to the phase of sound pressure still remain to be explained.
Species-specific coding strategies in bird song
Authors: Sinnott J. M.
Published: October 2005

Perceptual specializations exhibited by two species of North American blackbirds in the perception of their own species-specific songs are described. Redwing blackbirds (Agelaius phoeniceus) and brown-headed cowbirds (Molothrus ater) were trained to identify, using a go-right, go-left procedure, categories of complex song themes from their own, and from the other (control) species' repertoire. Themes were then broken up and birds were required to identify the constituent elements (“introductory notes” versus “trills” or “whistles”) of the themes. Results revealed that birds tend to process their own species-specific songs as total patterns, possibly making use of some sort of “template” matching. In contrast, songs of the control species seem to be processed by a serial examination of stimulus dimensions. Human perception of these stimuli is also discussed. [Supported by Grant No. NS12112 from NIH.]
Early development of sound localization by rats and gerbils
Authors: Potash Marc , Kelly Jack B.
Published: October 2005

Rats (13–20 days of age) and gerbils (16–23 days of age) were tested to determine their tendency to approach an auditory stimulus. Tests were conducted in a circular maze with a central start area and eight response areas around the periphery. Stimuli were played back over a loudspeaker placed behind one of the eight response areas. Signals included species calls and white noise at high and low intensities. Control conditions with blank tapes were also used. Both gerbils and rats showed a clear tendency to approach the low intensity playback of species calls. Additional experiments were conducted to investigate the importance of binaural cues for localization by infants. Subjects were tested with either one ear blocked, both ears blocked, or neither ear blocked. Animals with one ear blocked failed to show directional responses above a chance level, whereas other animals consistently made directional responses. The results indicate that localization is possible shortly after the onset of hearing in both rats and gerbils and that binaural cues are important. [Supported by National Research Council of Canada Grant A7654.]
Rabbit stapedial muscle reflex dynamics and vocal correlations
Authors: Lenhardt M. L.
Published: October 2005

The stapedus muscle is known to contract during adequate auditory stimulation, prior to vocalization and spontaneously. The rabbit's stapedial muscle, as well as its neural connections, has been studied in detail. Furthermore, the rabbit model is frequently used as an analog for human pathology. The rabbit differs from man acoustically by being primarily vocally silent. The adult rabbit does have at least two distinct call types, the aggressive growl and a high frequency distress call. The latter in young rabbits has a spectrum peaking in the frequency bands that correspond to areas of greatest sensitivity of the stapedial reflex. (Lorente de No and Harris, 1933; Price, 1963, and Borg, 1974). Behavioral techniques of all call elicitations and spectrums will be discussed. The calls also served as stimuli in evoking reflexes in twenty animals. Thresholds and reflex dynamics will be presented. Essentially the thresholds were 15 dB lower in rabbits than man. Distress cries were better stimuli for eliciting the reflex than growls and young cries were better than those of adults. Comments on the choice of this animal as a “representative” mammal for clinical related studies will be made.
Underwater audiogram of the northern fur seal (Callorhinus ursinus)
Authors: Schusterman R. J. , Moore P. W. B.
Published: October 2005

In order to compare the underwater hearing of otariid and phocid pinnipeds, two feral, yearling females were tested in a “go/no-go” response procedure. Using a tracking procedure, 20 runs was the minimum number of runs for each threshold estimate. Audiograms for both seals were similar in shape and absolute threshold values. The range of maximal sensitivity for Callorhinus is between 2 and 28 kHz. Between 28 and 42 kHz there is a hearing loss of about 120 dB/octave, setting the high-frequency cutoff for this species at 40 kHz. These results are consistent with the idea that the major difference between the underwater bearing of the otariid and phocid pinnipeds is the high-frequency cutoff.
Discrimination of solid cylinders and cubes by a blindfolded echolating bottlenose dolphin (Tursiops truncatus)
Authors: Nachrigall Paul E. , Murchison A. Earl , Au Whitlow W. L.
Published: October 2005

An Atlantic bottlenose dolphin was trained to discriminate between cylinders and cubes of syntactic foam covered with epoxy resin. Performance was maintained with targets presented 2 m away within a highly reverberant environment. Choice of the cylinder was maintained as target aspect was changed, except when the flat top of the cylinder was positioned toward the animal. The targets were acoustically examined using dolphinlike echolocation signals to determine the features of the targets which enabled the animals to perform the discrimination task. The acoustic data indicated that target strength variations as a function of aspect and multiple echoes from surfaces meeting at an edge can provide the animal with important clues.
The just-noticeable movement speed of obstacles perceived by echolocating bats
Authors: Jen Philip H.-S. , Lee Yung H.
Published: October 2005

The ability of Myotis lucifugus to avoid obstacles was measured by making them fly through an array of vertically strung monofilament nylon threads, 1.0 mm in diameter. The numbers of misses and hits were recorded relative to the threads that were stationary or moving horizontally at an average speed of 12.4 or 23.5 cm/s. The results showed that bats could fly successfully between threads with a significantly higher score of misses when the obstacles were moving than when they were stationary. Assuming a bat could code the movement of obstacles by changing its score of misses, we studied the sensitivity of its coding process by calculating its just-noticeable movement speed (jnms). The smallest jnms at a 75% correct level was 1.2 cm/s. The average for five bats was 4.2 ± 2.7 cm/s. These data suggest that the auditory system of a bat may contain neurons which are highly sensitive to moving objects. [Work supported by NSF.]
Psychophysical tuning curves in vibrotaction
Authors: Fay R. , Gescheider G. , Labs S.
Published: October 2005

The frequency response characteristics of channels used in human vibrotaction were studied using the psychophysical tuning curve (PTC) paradigm derived from auditory research. Sinusoidal 200 ms vibratory bursts delivered to the thenar eminence of the hand were detected in the presence of sinusoidal maskers delivered to the same skin area either continuously or pulsed in forward masking using a two-interval tracking method. Under simultaneous masking, PTC's determined with signals at 15 and 25 Hz are similar to neural tuning curves for quickly adapting, non-Pacinian cutaneous afferents of the monkey, while the PTC's determined for 250 and 400 Hz signals are quite similar to the neural curves for Pacininian afferents. PTC's for 100 Hz signals suggest that both channel types are stimulated, and that detection decisions are made using information from the channel with the largest S/N. The low frequency, but not the high frequency channels are subject to greater interference under forward than under simultaneous masking. These data support the notion that at least two independent channels operate in human vibrotaction, and show no evidence for frequency selective mechanisms other than those determined peripherally. [This work supported in part by an N.S.F. grant to R. Fay, and by Hamilton College.]
A method for measuring electrostrictive properties of ultrasonic transducer material under high hydrostatic pressure
Authors: Takahashi S. , Sato K.
Published: October 2005

The motional impedance or admittance method cannot be applied to a test transducer contained in a small non-sound-absorbing pressure tank, because admittance or impedance loop does not make a circle due to sound reflection at the tank wall. The method we used is to excite a bar-shaped test transducer in a pressure tank into longitudinal vibration by the use of a mechanical driving system, and to observe short-circuit current or open-circuit voltage of the test transducer. A transducer material for high power use was taken as a sample. Electrostrictive stress constants e31, h31 and dielectric constant ε31 were measured at hydrostatic pressures from 1 to 600 atm. Vibrational velocity dependence of e31 and h31 was also measured, varying driving velocity level at the test transducer end as high as 80 cm/s. The results are that e31 and h31 become slightly large as hydrostatic pressure increases but show no appreciable velocity level dependence.
An automated coupler calibration system for laboratory standard condenser microphones
Authors: Fujimori. T. , Takahashi T. , Sato S. , Miura H.
Published: October 2005

An automated coupler calibration system for laboratory standard condenser microphones is manufactured for trial use. Active couplers whose cylindrical wall vibrates as a sound source are designed. These couplers are used so as to get pressure response levels of microphones in a short time and to reduce manual transaction. A microcomputer controls the system, processes measured values, examines them, and stores final results in a diskette. In addition, many digital techniques are adopted for noise reduction and for the convenience of calibration. Accuracies were tested for 1-in. condenser microphones, such as MR103, using a coupler which has the same dimensions as the 20-cm3 a coupler. Pressure response levels calibrated by the system agree well with those calibrated by the ordinary precise coupler calibration system within 0.2 dB at the frequencies 100–10 000 Hz.
Real-time pitch detection by two mini-computers
Authors: Gohbara M. , Suminaga Y. , Miyaguchi H. , Ozawa S.
Published: October 2005

Many algorithms that detect pitch frequencies for voiced segments have been presented. But few of them can perform in real time. This paper presents an algorithm that can detect time-varying pitch frequencies in real time using two mini-computers in parallel. The amplitude of the speech waveform is sampled every 100 μs by one of the computers, and the energy of each zero-crossing interval is calculated and tabulated. The pitch frequency candidate is determined by the other computer from the envelope curve of the tabulated energy values, based on the assumption that the time distance between a zero-crossing interval with large energy and the next similar one is a pitch period. A reasonable pitch frequency is obtained from the candidates, eliminating double pitch and half pitch errors. The program operates in real time by mini-computers having a cycle time of 1.4 μs. With a minimum 8 kW memory for the program and data, the pitch can be detected continuously.
Temporal and spectral changes with restricted jaw movement
Authors: Tobey E. A. , Harris K. S. , Finger I. M.
Published: October 2005

A central question in speech-production theory is how speakers adapt to restricted movement of an articulator (for example, the jaw). Productions of five subjects in normal speaking conditions were compared with utterances produced when wearing an occlusal appliance which maintained jaw opening at 1 cm. Targets consisted of monosyllabic CVC's with initial consonants [d, t, r, s, tr, str], syllable nuclei [æ, i, u], and terminal consonant [p] in a carrier phrase. Results show a general increase in duration of initial consonant and syllable nuclei segments. An increase in F0 and a decrease in F2 values occur for all vowels. F1 increases for [i] and [u]; F1 shifts for [æ] are context dependent. Overall, data indicate instantaneous adaptation to restricted jaw movement does not necessarily occur when stimuli are in contexual frame. [Supported by NIH grants NS-11647 to Kresge Hearing Research Laboratory and NS-13617 to Haskins Laboratories.]
Airway area by acoustic reflectometry in man
Authors: Fredberg J. J. , Wohl M. E. , Dorkin H. L. , Sidell R. S.
Published: October 2005

The geometry of the upper airway of the respiratory system in normal adults has been inferred noninvasively by an acoustic reflectometry technique. Short duration pressure transients launched into the respiratory system at the mouth give rise to echoes reflecting from the inhomogeneous airway structure. This data is transformed into an inference of the cross-sectional area of the airway as a function of distance from the lips. The results indicate a local area maximum in the vicinity of the uvula (velum closed), a local minimum in the oropharynx near the top of the epiglottis, and another local maximum in the vicinity of the hypopharynx. The area contracts passing through the thyroid and cricoid cartilages, and expands to a plateau in the extra-thoracic and intra-thoracic trachea. At fixed lung volume the areas of the larynx and extra-thoracic trachea are sensitive to transrespiratory system pressure while the area in the vicinity of the thyroid and cricoid cartilages and intrathoracic trachea are not. Radiographic determinations indicate that this method tends to systematically overestimate the anatomic area in the subglottic region as a result of nonrigidity of the airway walls. [Supported by NHLBI contract N01-HR-6-2901.]
Acoustic and aerodynamic correlates of Hindi stops
Authors: Ohala Manjari , Ohala John J.
Published: October 2005

In order to find out how the four Hindi stop types, p, ph, b, bh, are produced, we obtained the following data from native speakers: averaged fundamental frequency (FO) contours (on either side of the stops), oral air flow, and lung volume (via a plethysmograph) during the production of the stops in a sentence frame. The results include the following: (1) although the breathy-voiced stops lower FO a great deal on the vowels following them, there is no consistent effect on FO by the other stop types, assuming the comparison of the various FO contours is done with respect to consonant onset, (2) the plethysmographic data reveal that short-term variations in lung volume are purely a passive reaction to the rate of air flow out of the lungs—in other words, in contrast to previous claims, there is no active participation of the pulmonic system in the production of aspirated stops. [Supported by NSF.]
Glottalized stops in K'ekchi (Maya)
Authors: Pinkerton S.
Published: October 2005

Stop duration (VOT and closure) and intraoral air pressure were measured for comparison of the production of glottalized stops with that of nonglottalized stops. The pitch and duration of the preceding and following vowels were also measured. Subjects read natural language minimal pairs in which glottalized and nonglottalized stops contrasted in word initial, medial, and final positions. The results establish preliminary acoustic and physiological variables by which glottalized stops in K'ekchi may be characterized and distinguished from such stops in other languages. These glottalized stops had a significantly greater VOT than their nonglottalized counterparts. However, /b′/ had two productions in free variation: (l) a voicing lead and (2) a zero VOT. Glottalized /t′/, /k′/, and /q′/ exhibited a greater positive air pressure than their nonglottalized counterparts. /b′/ exhibited a zero air pressure, thus demonstrating that the inventory of glottalized stops in K'ekchi consists of one bilabial implosive and three ejectives. The pitch of a vowel following a glottalized stop began at a lower frequency than that of a vowel following a nonglottalized stop except when the vowel was found before /q′/ and /q/. The pitch in these latter cases was the same.
Timbre of Kiais: Analysis and synthesis
Authors: Lassez J.-L.
Published: October 2005

Kiai is a name given to sudden and violent vocalizations practised by Martial Artists. An investigation to determine formant frequencies, bandwidths and source-spectrum giope was performed on vocalizations made by five high ranking Karateka. Spectral classifications were made using adaptations of those used for infant cries [H. M. Truby and J. Lind Act, Paed. Scand. 163, 11 (1965)]. All cepstra show strong peaks regularly spaced at pitch-period intervals. This phenomenon is usually linked with irregularities in the pitch-pulse timing [A.M. Noll, J. Acoust. Soc. Am. 41, 293–309 (1967)]. However digital simulations using a Terminal Analog Synthesizer indicate that it is likely that these peaks are due to an opening quotient of the vocal cords which is less than 10%. This leads to a nearly flat source spectrum. The fundamental frequency range was found to be in the order of 450–500 Hz and high amplitude resonances were found up to 6000 Hz for all vocalizations studied. Physiological considerations concerning the production and perception of these screams will be discussed and shown to be consistent with claims that Kiais have a characteristic timbre, which this analysis supports. [Work supported by U. M. E. R. G.]
An analysis of errors in the performance of the Japanese language
Authors: Hiki S.
Published: October 2005

Errors in the performance of the Japanese language made by adults having normal competence were investigated. The data were about 1500 samples of errors, in total, for six kinds of performance: listening, silent reading, speaking, reading aloud, writing, and copying. These errors were made by more than 400 different persons, and they were recorded by four observers, including the present author, during the period from September 1975 to May 1978. The nature of these errors were analyzed in terms of the linguistic units in which they occurred, the linguistic levels in which they could be explained, and their causes. The linguistic units considered here were the phone, phoneme, Japanese mora, syllable, word, phrase, and sentence, as well as individual Japanese kana and kanji. Among the types of errors considered were: (1) the duplication, deletion and and insertion of various units, (2) confusions of conjugation, voice, and respect expressions, and (3) misunderstandings regarding synonyms, antonyms, homonyms, homographs, etc. Many of the errors that could be explained on the syntactic, semantic and orthographic levels were found to be also related to the phonetic. level. [Work supported by Minisity of Education, Japan.]
Speech production processes in the mina
Authors: Yoshimoto C. , Hirahara T. , Ifukube T.
Published: October 2005

One might ask whether the formants of a vowel are essential to characterize its pattern of perception. This question has occupied us since we began to develop our monosyllabic voice typewriter. If the formants are not essential, there might be some other possible ways to realize better discrimination of vowels for the development of the automatic recognition of speech and speech synthesis. To find a possible answer to this problem, we recorded the imitation of human speech by a mina and the speech of the person who taught the mina. Comparing the formants of each Japanese vowel in the mina and in the man, it was found that the first format was not an essential factor to characterize the perception and the pronunciation of vowels. In addition, the number of zero crossings was also different in the mina and in the man. Hence, a vocal tract model was not concluded to be essential for speech analysis. By eliminating the different speech production factors in the man and in the mina, we tried to find a new concept of cues.
Volume scattering strengths and plankton distribution at acoustic frequencies between 0.5 and 3 MHz
Authors: Holliday D. V. , Pieper R. E.
Published: October 2005

Measurements of acoustic volume scattering strengths were made at four frequencies between 0.5 and 3 MHz in continuous profiles to depths over 100 m. Concurrent data on the thermal structure of the water column is also presented. Water samples were obtained from discrete depths using a pump with a nominal 0.5 m3/min capacity. The water samples were analyzed for chlorophyll and for zooplankton. Additional sampling included oblique meter net tows and tows with an opening/closing net. Measurements include quantitative data on vertical distribution and horizontal patchiness, both in the presence and absence of temperature variations >0.1°C. The shape and level of the acoustic scattering profiles are discussed in relation to the observed distribution of zooplankton of sizes greater than about 0.4 mm. [Work supported by NSF and ONR.]
Quantitative acoustic estimation of zooplankton distribution
Authors: Greenlaw C.
Published: October 2005

The target strengths of individual zooplankters are known to depend upon frequency and the size of the organism. Scattering models are known for certain species. The existence of a scattering model allows prediction of volume scattering strengths (Sv) at given frequencies from known distributions of size and abundance and suggests that the inverse problem—estimating population distributions from measurements of Sv at certain frequencies—can be solved in some cases. Plausible estimates of abundances and size distributions of a scattering layer composed principally of euphausiids have been obtained from measurements of Sv at three frequencies, using a least squares estimation technique [R. K. Johnson, J. Acoust. Soc. Am. 61, 1636–1639 (1977)] and a scattering model for euphausiids. Practical methods using measurements at only one or two frequencies have been developed for estimating abundances at sea.
Hydroacoustic system for fish counting
Authors: Maniwa Y. , Furusawa M.
Published: October 2005

The hydroacoustic system to count the numbers of sea fish with precision have been studied. Experiments have been performed on fish cultivated in culturing nets, numbers of which have been counted manually. In this system, the volume of fish school and their distribution density are separately measured by applying the principles of the fish finder and then the number of fish are determined by multiplying one by another. The approximate volume is determined by the shape of section of fish school which is displayed by using the principle of PPI sonar. The ultrasonic waves reflected from fish in the effective volume are compounded. Accordingly, the number of fish in the effective volume is obtained from the intensities of the reflected waves. The distribution density is calculated by dividing the number by the effective volume. In the case of good distribution of fish, the error is within ±5%. It is expected that such a system will be extended to the measurement of fish stocks.
In situ target strength measurement for acoustic fish stock assessment
Authors: Traynor J. J. , Ehrenberg J. E.
Published: October 2005

In an acoustic fisheries assessment survey, the target strength distribution of the fish being surveyed is an important parameter, primarily as a factor to scale the output of an echo integration system to fish density; however, good techniques to evaluate target strength of the surveyed fish are not readily available. Results of target strength measurements using tethered or caged fish are available but, because little is known about the orientation and aspect of the surveyed fish population, the scaling of echo integration to fish density using these results is questionable. In situ estimation techniques are the most promising alternative. Indirect in situ methods which statistically convert echo strength distributions to target strength distributions are available but often provide poor results. A dual beam method (J. E. Ehrenberg, Proc. 1974 IEEE Conf. Engr. Ocean Environ. 1, 152–155) utilizes a dual beam transducer system and corrects echo strength to target strength for each detected single fish target. Unlike the indirect techniques, the dual beam method allows the effect of an inherent bias caused by a system noise induced threshold to be reduced. Field results using a standard target (ping-pong ball) and fish targets are reported and comparisons with theoretical predictions are made.
Seasonal changes in fish size distributions as detected by acoustic resonance survey and by conventional sampling
Authors: Holliday D. V. , Smith P. E.
Published: October 2005

The larvae, juveniles, and adults of the northern anchovy inhabiting the Southern California Bight were monitored by conventional direct sampling, by the commercial fishery, by trawl sampling, and by plankton net sampling during 1977. Broadband acoustic techniques were used to further characterize sonar targets in terms of the presence or absence of gas-filled swimbladders. For targets whose spectra exhibited resonance structure, distributions of swimbladder sizes were calculated for individual schools, school groups, and for ensembles of school groups. Observed seasonal changes in swimbladder size distributions implicate fish growth, mortality, and behavior as parameters impacting the frequency dependence of the acoustic backscattering from schools. A comprehensive list of species known to frequent this ocean area will be discussed in this context. An overview of the distribution and biophysical characteristics of the common pelagic nekton which inhabit the Southern California Bight will provide the background for a description of the distribution of schools and aggregations as determined acoustically in March, May, and September of 1977. [Work supported by NOAA/NMFS.]
Investigations into the accuracy and precision of hydroacoustic techniques for fishery resource assessment
Authors: Thorne Richard E.
Published: October 2005

Hydroacoustic techniques are becoming widely used in fishery resource assessment. There are many sources of variability and uncertainty in these techniques, and their accuracy and precision has been questioned. Studies at the University of Washington have evaluated the performance of hydroacoustic techniques in a variety of applications where substantial ground truth data were available. These studies have documented the magnitude of several variance components and shown that many of the larger sources of variability are biological rather than physical. [Work supported by Sea Grant.]
Comparison of target strengths of marine organisms
Authors: Penrose J. D. , Kaye G. T.
Published: October 2005

An empirical relationship which links fish length, target aspect, and target strength for geometric region scattering has been developed [R. H. Love, J. Acoust. Soc. Am. 62, 1397–1403 (1978)]. When peak target strengths of squid, crabs, and penaeid prawns at dorsal aspect are compared with this relationship, it can be noted that the target strengths for nonfish lie within 6 dB below Love's prediction for fish of similar size. Some zooplankton values are within similar limits if the insonifying frequencies are sufficiently high to ensure that geometric region interactions occur. The target strength data reviewed show little overall frequency dependence, in contrast to what would be expected if the scatterers were modeled as finite cylinders. [Work supported by the Fishing Industry Research Committee of the Australian Department of Agriculture and the Naval Ocean Research and Development Activity.]
Fish school target strength measurements off southern California
Authors: Vent R. J.
Published: October 2005

Measurements of target strength were made of pelagic fish schools in the Los Angeles Bight where the dominant schooling species is the northern anchovy, Engraulis mordax. Data were collected using a hull-mounted, side-looking 30-kHz sonar system. Among the parameters studied were peak target strength, integrated target strength, target extent, and variation of peak target strength with aspect. Three schools were interrogated, while the vessel was hove to, with varying pulse durations: 2, 10, 50, and 170 ms. Results indicate that peak target strength varies directly with the pulse duration when the pulse length is less than the target extent, whereas integrated target strength appears to be independent of pulse duration. School peak target strength and target extent, for 10-ms pulse duration, were measured while the vessel circled a school through 360°. Variations in target strength of 20 dB and in target extent of 30 m were observed. The minimum target strength corresponded with the maximum target extent, which may possibly be explained by the school's geometry and variations of individual fish target strength with yaw aspect.
Euphausiid distribution and biomass determined acoustically at 102 kHz
Authors: Pieper R. E.
Published: October 2005

102 kHz scattering was recorded at depths varying from 130 to 280 m in the San Pedro and Santa Catalina basins off southern California. The scattering from these layers was quantified and volume scattering coefficients per m3 were determined. These acoustic measurements are correlated with the biomass and distribution of euphausiids (primarily Euphausia pacifica) which were collected concurrently. Qualitative and quantitative variations in scattering values are related to the patchiness of the euphausiids. [Work supported by ONR.]
Backscattering models for zooplankton
Authors: Johnson R. K.
Published: October 2005

Various homogeneous and layered models for the backscattering from spherical targets are compared with measured backscattering from zooplankton. The models include liquid and elastic targets with and without viscous effects. Several of the models appear to be of value, but evaluation of them is limited by ignorance of several of the physical/acoustical properties of the zooplankton. [Work supported by ONR.]
Measurement of zooplankton patchiness with a 87.5 kHz sonar system
Authors: Greenblatt Paul , Pinkel Robert
Published: October 2005

A narrow beam 87.5-kHz sonar is being used to quantitatively estimate scattering strength as a function of range and time in the upper ocean. The sonar is aimed horizontally from the bottom of FLIP. Backscattered intensity will be used to estimate horizontal zooplankton patchiness on a scale of 10's–100's of meters. During a fall 1978 cruise, the sonar system and a multiple opening-closing plankton net, towed from a second ship, will simultaneously measure zooplankton patchiness. The objectives of this effort are to determine whether the sonar provides a consistent picture of plankton patchiness, whether there is significant change in the scales of patchiness from night to day, and whether a specific category of organisms can be identified as being primarily responsible for the scattering.
High frequency, dual beam transducer array developed to look at zooplankton patchiness
Authors: Mullin M. M. , Richter K. E.
Published: October 2005

A 1.1-MHz acoustic array is part of a multi-instrument experiment designed to look at the scales and causes of the patchy distribution of nearshore marine zooplankton. The transducers have narrow, dual beam patterns (0.3 and 1 from axis to −3 dB point) and will be fired with 0.1-ms pulses. They are to be used to determine absolute target strengths and distributions of discrete copepod-size and larger targets. Acoustic returns will also be integrated over variable ranges. The three element array is to be placed on the bottom in 70 m of water next to thermistor, current meter, and continuous fluorometer strings. Simultaneous sampling with a large volume pump will be used to identify scatterers. Patch dimensions from 10's cm to 10's km should be observable. Current and near future work consists of calibrating the transducers and determining target strength distributions of live, local plankters and plankton assemblages in the laboratory.
Relation between the maximum value of volume backscatter strength and layer column strength for the near-surface biological scattering layer at Ocean Acre
Authors: Saenger R. Alfred
Published: October 2005

The volume backscatter strength S(z;F) of a scattering layer at frequency F depends on the product of the number of scatterers n(z) per unit volume and the average backscatter cross-section σ(z;F) of the scatterers at depth z. In the isolume modes [J. Acoust. Soc. Am. 62, S1(A) (1977), CC10], a functional form for n(z) is derived assuming the scatterers track preferred values of light intensity I which are normally distributed about some characteristic population value, while σ(z;F) is assumed to be a constant, σ̄(F), independent of z. Here we deduce from the model that the difference between Smax and layer column strength is a constant and show that this relation is satisfied by the 3.85–15.5 kHz near surface scattering layer observed during midnight periods at Ocean Acre. According to the model, the constant depends on the relative species composition of the layer and is independent of the standing crop. The insensitivity of the constant to frequency can be explained by a physical analysis of the model. [Work supported by Naval Material Command.]
Physical analysis of the isolume model for volume backscatter strength
Authors: Saenger R. Alfred
Published: October 2005

The purpose of this paper is to present a fundamental bioacoustic interpretation of the isolume model [J. Acoust. Soc. Am. 62, S1(A) (1977) CC10] which clarifies the physical significance of model parameters and defines the bioacoustic conditions under which the model can provide an effective analytical representation of the scattering strength profile S(z;F) of a light-sensitive biological scattering layer. The physical basis for the interpretation is the discovery that nightcatch density profiles nb(z) of air-bladdered fish measured at Ocean Acre can be described by the theoretical profile functions n(z) of the model. Analysis shows that a model profile derived from an experimental sample average profile will provide a representative analytical descriptor so long as there are no unusually large variations in the average backscatter cross-section σb(z;F) over space scales comparable with layer thickness. At frequencies F where such variations are small, the constant σ̄(F) in the model may be identified with the average of σb(z;F) over the layer, and model “population parameters” defining n(z) with those characterizing the biological distribution nb(z). [Work supported by Naval Material Command.]
Room acoustic design of multipurpose auditoria in Japan
Authors: Yamamoto T.
Published: October 2005

Japan is divided into 47 administrative districts, i.e., prefectures (including the Tokyo Metropolitan Area), containing a total of about 670 cities. Most of the prefectures and over half the cities have public halls, which are playing an important role as community cultural centers, and about 20 new halls are being constructed annually on an average. Most of these halls are designed as multipurpose auditoria, from the viewpoint of greatest efficiency and versatility of use. Most are 8000–15 000 m3 a in size with a seating capacity of 800–2000. As to the architectural and acoustical conditions of these halls, many objective and subjective studies have been carried out by research groups, with our laboratories playing a central role. The reverberation times of many good halls have been found to lie close to or slightly below the Knudsen and Harris's optimum value. The new halls have been designed in accordance with these results. A distinctive architectural feature of these halls is their wide variety of facilities, including movable stage sound reflectors for concerts, settings for stage performances, etc. Recently, a considerable number of halls have been designed to be adapted for different types of presentation by adopting variable reverberation units, a movable proscenium, variable room volume facilities, and movable partition walls.
Experiments in acoustic imaging with an isochronal convergence imaging method
Authors: Katakura K. , Kuroda M. , Takabayashi Y.
Published: October 2005

The method used in this study employs a multielement transducer. Each transducer element transmits successive cylindrical sound waves at a predetermined interval. During the transmission intervals, all elements receive echos from targets. A digital processor then distributes the amplitude data of these echos on elliptic addresses located in a digital memory system. The relation between sound propagation time and element location determines these elliptic addresses. The resolution power is estimated to be the same as that of a cylindrical transducer measured at the focal point for pulse echo mode operation. The results of numerical analyses agree well with the estimated values and indicate a high resolution power within the entire imaging plane. A prototype system utilizing this method, containing a 32-element transducer and a minicomputer, is used to complete some experimental imaging of stationary targets, and the obtained images are discussed.
An electrostatic transducer for absolute measurement of ultrasonic wave displacement amplitude in liquids
Authors: Cantrell John H. , Heyman Joseph S.
Published: October 2005

A broadband capacitive electrostatic acoustic transducer (ESAT) has been developed for use in a liquid environment at megahertz frequencies. The ESAT basically consists of a thin conductive membrane stretched over a metallic housing which is sealed for immersion in a liquid environment. The membrane functions as the ground plate of a parallel-plate capacitor, the other plate being a dc biased electrode recessed approximately 10 μm from the electrically grounded membrane. An ultrasonic wave incident on the membrane vibrates the membrane-electrode gap spacing and generates an electrical signal proportional to the wave amplitude. Calibration of the ESAT with incident ultrasonic waves of constant displacement amplitude from 1 to 12 MHz reveals a decrease in signal response with increasing frequency independent of membrane tension. A theoretical analysis shows that the coupling between the membrane and the contacting liquid is responsible for this frequency rolloff and that the absolute measurement of the ultrasonic wave displacement amplitude is possible with the ESAT when the correction for the rolloff is applied.