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Journal of the Acoustical Society of America

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Jun 2001

Volume 109, Issue 6, pp. 2537-3083

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In situ source level and source position estimates of biological transient signals produced by snapping shrimp in an underwater environment

Brian G. Ferguson and Jane L. Cleary

J. Acoust. Soc. Am. Volume 109, Issue 6, pp. 3031-3037 (2001); (7 pages) | Cited 3 times

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Biological transient signals produced by snapping shrimp are sensed underwater by a wide aperture array. The instantaneous range and bearing of the source position of each snap is estimated along with a source level equal to the peak-to-peak amplitude of the pressure impulse generated by the snap at a standard distance of 1 m from its point of origin. For a sample of 1000 snaps recorded in Sydney Harbour, the distribution of peak-to-peak sound pressure levels has a mean value of 187 dB (re 1 μPa) and an interquartile range of 185–189 dB (re 1 μPa). Plotting the Cartesian coordinates of the source positions of the biological transient signals over a period of time maps the two-dimensional spatial distribution of the local snapping shrimp population. The principal habitat is found to be geocoincident with a 120-m-long wharf, the closest point of which is 60 m from the middle of the receiving array. The passive ranging performance of the wide aperture array is evaluated by generating mechanical transient signals at selected positions along the wharf. Precise estimates of the relative times-of-arrival of the acoustic wavefronts lead to source range and bearing estimates with standard deviations of only 0.1 m and 0.005 degrees (respectively), in agreement with theoretical predictions. © 2001 Acoustical Society of America.
Show PACS
43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
43.60.Gk Space-time signal processing, other than matched field processing

Localization and visual verification of a complex minke whale vocalization

Jason Gedamke, Daniel P. Costa, and Andy Dunstan

J. Acoust. Soc. Am. Volume 109, Issue 6, pp. 3038-3047 (2001); (10 pages) | Cited 10 times

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A recently described population of minke whales (Balaenoptera acutorostrata) offered a unique opportunity to study its acoustic behavior. The often-inquisitive dwarf minke whale is seen on the Great Barrier Reef nearly coincident with its suspected calving and breeding seasons. During drifting encounters with whales, a towed hydrophone array was used to record sounds for subsequent localization of sound sources. Shipboard and in-water observers linked these sounds to the closely circling minke whale. A complex and stereotyped sound sequence, the “star-wars” (SW) vocalization, was recorded during a series of visual and acoustic observations. The SW vocalization spanned a wide frequency range (50 Hz–9.4 kHz) and was composed of distinct and stereotypically repeated units with both amplitude and frequency-modulated components. Broadband source levels between 150 and 165 dB re 1 μPa at 1 m were calculated. Passive acoustic studies can utilize this distinct vocalization to help determine the behavior, distribution, and movements of this animal. While the SW vocalization’s function remains unknown, the regularly repeated and complex sound sequence was common in low latitude, winter month aggregations of minke whales. At this early stage, the SW vocalization appears similar to the songs of other whale species and has characteristics consistent with those of reproductive advertisement displays. © 2001 Acoustical Society of America.
Show PACS
43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
43.30.Sf Acoustical detection of marine life; passive and active

Ultrasound detection by clupeiform fishes

David A. Mann, Dennis M. Higgs, William N. Tavolga, Marcy J. Souza, and Arthur N. Popper

J. Acoust. Soc. Am. Volume 109, Issue 6, pp. 3048-3054 (2001); (7 pages) | Cited 8 times

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It has previously been shown that at least one species of fish (the American shad) in the order clupeiforms (herrings, shads, and relatives) is able to detect sounds up to 180 kHz. However, it has not been clear whether other members of this order are also able to detect ultrasound. It is now demonstrated, using auditory brainstem response (ABR), that at least one additional species, the gulf menhaden (Brevoortia patronus), is able to detect ultrasound, while several other species including the bay anchovy (Anchoa mitchilli), scaled sardine (Harengula jaguana), and Spanish sardine (Sardinella aurita) only detect sounds to about 4 kHz. ABR is used to confirm ultrasonic hearing in the American shad. The results suggest that ultrasound detection may be limited to one subfamily of clupeiforms, the Alosinae. It is suggested that ultrasound detection involves the utricle of the inner ear and speculate as to why, despite having similar ear structures, only one group may detect ultrasound. © 2001 Acoustical Society of America.
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43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.66.Cb Loudness, absolute threshold

Ultrasound phased arrays for prostate treatment

Joseph S. Tan, Leon A. Frizzell, Narendra Sanghvi, Shih-jeh Wu, Ralf Seip, and Jeffrey T. Kouzmanoff

J. Acoust. Soc. Am. Volume 109, Issue 6, pp. 3055-3064 (2001); (10 pages) | Cited 1 time

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The effect of array geometry on the steering performance of ultrasound phased arrays is examined theoretically, in order to maximize array performance under the given anatomical constraints. This paper evaluates the performance of arrays with spherical and cylindrical geometry, determined by using computer simulations of the pressure fields produced at various extremes of steering. The spherical segment arrays were truncated for insertion into the rectum, and contained either annular or linear elements. The cylindrical arrays were either flat or had a variable curvature applied along their length. Fields were computed by dividing the array elements into many point sources. The effectiveness of an array configuration when steered to a particular focal location was assessed by defining a parameter, G, as the ratio of the intensity at the desired focus to the maximum intensity of any unwanted lobes. The performance of truncated spherical arrays with annular elements was evaluated for focal steering along the array axis (in depth, in the z direction). When steered 15 mm toward the source, these truncated spherical annular arrays exhibited excellent performance, with G>5.7 for arrays containing more than 10 elements. Similarly, the spherical arrays with linear elements performed well when steered along the array axis to the same degree, with G>7 (for element widths up to 3 λ), though many more array elements were required. However, when these arrays were steered 15 mm laterally, along the length of the prostate (the y direction), the value for G fell below 1 for element widths greater than about 1.6 λ. It was found that the cylindrical arrays performed much better for y-direction steering (G>4, for 60 mm arrays with an element width of 1.75 λ), but their performance was poorer when steered in the z direction (G ≅ 4 for an element width of 1.5 λ). In order to find a compromise between these extremes, a curved cylindrical array was examined, which was a cylindrical array with additional curvature along its length. These curved cylindrical arrays yielded performance between that of spherical linear arrays and cylindrical arrays, with better steering along the y direction than the spherical arrays and better z-direction steering than the cylindrical arrays. © 2001 Acoustical Society of America.
Show PACS
43.80.Sh Medical use of ultrasonics for tissue modification (permanent and temporary)
43.80.Vj Acoustical medical instrumentation and measurement techniques
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