Volume 109, Issue 1, January 2001
Index of content:
- BIOACOUSTICS 
109(2001); http://dx.doi.org/10.1121/1.1333419View Description Hide Description
By considering the blood as a mixture of ultrafiltrate and protein concentrate, the additive nature of compressibility and density from the components is utilized to deduce a linear relation between the compressibility and density for blood. This deduction also indicates that the intercept and slope of the linear relation are independent of the hematocrit, plasma protein concentration, and hemoglobin concentration of red blood cells. To verify experimentally this linear relation, saline and plasma dilutions on porcine or canine blood flowing in an extracorporeal circuit were carried out. The hematocrit of the experiments ranges from 0% to 55% and the plasma protein concentration ranges from 10 to 90 g/l. A resonance device in the circuit measured the density of blood at 37 °C and an ultrasound system measured the soundvelocity The range of density is from 1010 to 1060 g/l and that of soundvelocity is from 1530 to 1580 m/s. The linear relation that best fits the data of compressibility [computed as ] and density has a correlation coefficient of 0.9978. The linear relation is found to fit well the dependence of compressibility on density derived from the soundvelocity data of human, horse, and porcine blood in the literature.
109(2001); http://dx.doi.org/10.1121/1.1329619View Description Hide Description
A linear error propagation analysis was applied to a hydrophone array used to locate sperm whales [see Møhl et al., J. Acoust. Soc. Am. 107, 638–648 (2000)]. The accuracy of two-dimensional (2D) and three-dimensional (3D) array configurations was investigated. The precision in source location was estimated as a function of inaccuracies in measurements of sound velocity, time-of-arrival differences (TOADs), and receiver positions. The magnitude of additional errors caused by geometric simplification was also assessed. The receiver position uncertainty had the largest impact on the precision of source location. A supplementary vertical linear array consisting of three receivers gave information on the vertical bearing and distance to the sound sources. The TOAD data from an additional receiver as well as from surface reflections were used to form an overdetermined location system. This system rendered positions within two standard deviations of the estimated errors from the original 3D array.
109(2001); http://dx.doi.org/10.1121/1.1326082View Description Hide Description
Whistles were recorded and analyzed from free-ranging single or mixed species groups of boto and tucuxi in the Peruvian Amazon, with sonograms presented. Analysis revealed whistles recorded falling into two discrete groups: a low-frequency group with maximum frequency below 5 kHz, and a high-frequency group with maximum frequencies above 8 kHz and usually above 10 kHz. Whistles in the two groups differed significantly in all five measured variables (beginning frequency, end frequency, minimum frequency, maximum frequency, and duration). Comparisons with published details of whistles by other platanistoid river dolphins and by oceanic dolphins suggest that the low-frequency whistles were produced by boto, the high-frequency whistles by tucuxi. Tape recordings obtained on three occasions when only one species was present tentatively support this conclusion, but it is emphasized that this is based on few data.
Sound localization in a new-world frugivorous bat, Artibeus jamaicensis: Acuity, use of binaural cues, and relationship to vision109(2001); http://dx.doi.org/10.1121/1.1329620View Description Hide Description
Passive sound-localizationacuity and its relationship to vision were determined for the echolocating Jamaican fruit bat (Artibeus jamaicensis). A conditioned avoidance procedure was used in which the animals drank fruit juice from a spout in the presence of sounds from their right, but suppressed their behavior, breaking contact with the spout, whenever a sound came from their left, thereby avoiding a mild shock. The mean minimum audible angle for three bats for a 100-ms noise burst was 10°—marginally superior to the 11.6° threshold for Egyptian fruit bats and the 14° threshold for big brown bats. Jamaican fruit bats were also able to localize both low- and high-frequency pure tones, indicating that they can use both binaural phase- and intensity-difference cues to locus. Indeed, their ability to use the binaural phase cue extends up to 6.3 kHz, the highest frequency so far for a mammal. The width of their field of best vision, defined anatomically as the width of the retinal area containing ganglion-cell densities at least 75% of maximum, is 34°. This value is consistent with the previously established relationship between vision and hearing indicating that, even in echolocating bats, the primary function of passive sound localization is to direct the eyes to sound sources.