Index of content:
Volume 130, Issue 1, July 2011
- BIOACOUSTICS 
Classification of behavior using vocalizations of Pacific white-sided dolphins (Lagenorhynchus obliquidens)a)130(2011); http://dx.doi.org/10.1121/1.3592213View Description Hide Description
Surface behavior and concurrent underwater vocalizations were recorded for Pacific white-sided dolphins in the Southern California Bight (SCB) over multiple field seasons spanning 3 years. Clicks, click trains, and pulsed calls were counted and classified based on acoustic measurements, leading to the identification of 19 key call features used for analysis. Kruskal-Wallis tests indicated that call features differ significantly across behavioral categories. Previous work had discovered two distinctive click Types (A and B), which may correspond to known subpopulations of Pacific white-side dolphins in the Southern California Bight; this study revealed that animals producing these different click types also differ in both their behavior and vocalizationpatterns. Click Type A groups were predominantly observed slow traveling and milling, with little daytime foraging, while click Type B groups were observed traveling and foraging. These behavioral differences may be characteristic of niche partitioning by overlapping populations; coupled with differences in vocalizationpatterns, they may signify that these subpopulations are cryptic species. Finally, random forest decision trees were used to classify behavior based on vocalization data, with rates of correct classification up to 86%, demonstrating the potential for the use of vocalizationpatterns to predict behavior.
Measuring body length of male sperm whales from their clicks: The relationship between inter-pulse intervals and photogrammetrically measured lengths130(2011); http://dx.doi.org/10.1121/1.3578455View Description Hide Description
Sperm whales (Physeter macrocephalus) emit short, broadband clicks which often include multiple pulses. The time interval between these pulses [inter-pulse interval (IPI)] represents the two-way time for a pulse to travel between the air sacs located at either end of the sperm whale’s head. The IPI therefore, is a proxy of head length which, using an allometric relationship, can be used to estimate total body length. Previous studies relating IPI to an independent measure of length have relied on very small sample sizes and manual techniques for measuring IPI. Sound recordings and digital stereo photogrammetric measurements of 21 individuals were made off Kaikoura, New Zealand, and, in addition, archived recordings of whales measured with a previous photogrammetric system were reanalyzed to obtain a total sample size of 33 individuals. IPIs were measured automatically via cepstral analysis implemented via a software plug-in for pamguard, an open-source software package for passive acoustic monitoring. IPI measurements were highly consistent within individuals (mean CV = 0.63%). The new regression relationship relating IPI (I) and total length (T) was found to be T = 1.258I + 5.736 (r2 = 0.77, p < 0.001). This new regression provides a better fit than previous studies of large (> 11 m) sperm whales.
Noise-induced temporary threshold shift and recovery in Yangtze finless porpoises Neophocaena phocaenoides asiaeorientalis130(2011); http://dx.doi.org/10.1121/1.3596470View Description Hide Description
In Yangtze finless porpoises Neophocaena phocaenoides asiaeorientalis, the effects of fatiguing noise on hearing thresholds at frequencies of 32, 45, 64, and 128 kHz were investigated. The noise parameters were: 0.5-oct bandwidth, −1 to +0.5 oct relative to the test frequency, 150 dB re 1 μPa (140–160 dB re 1 μPa in one measurement series), with 1–30 min exposure time. Thresholds were evaluated using the evoked-potential technique allowing the tracing of threshold variations with a temporal resolution better than 1 min. The most effective fatiguing noise was centered at 0.5 octave below the test frequency. The temporary threshold shift (TTS) depended on the frequencies of the fatiguing noise and test signal: The lower the frequencies, the bigger the noiseeffect. The time-to-level trade of the noiseeffect was incomplete: the change of noise level by 20 dB resulted in a change of TTS level by nearly 20 dB, whereas the tenfold change of noise duration resulted in a TTS increase by 3.8–5.8 dB.
130(2011); http://dx.doi.org/10.1121/1.3596472View Description Hide Description
The crawling wave experiment was developed to capture a shear wave induced moving interference pattern that is created by two harmonic vibration sources oscillating at different but almost the same frequencies. Using the vibration sonoelastography technique, the spectral variance image reveals a moving interference pattern. It has been shown that the speed of the moving interference pattern, i.e., the crawling wave speed, is proportional to the shear wave speed with a nonlinear factor. This factor can generate high-speed artifacts in the crawling wave speed images that do not actually correspond to increased stiffness. In this paper, an inverse algorithm is developed to reconstruct both the crawling wave speed and the shear wave speed using the phases of the crawling wave and the shear wave. The feature for the data is the application to in vitro prostate data, while the features for the algorithm include the following: (1) A directional filter is implemented to obtain a wave moving in only one direction; and (2) an L 1 minimization technique with physics inspired constraints is employed to calculate the phase of the crawling wave and to eliminate jump discontinuities from the phase of the shear wave. The algorithm is tested on in vitro prostate data measured at the Rochester Center for Biomedical Ultrasound and University of Rochester. Each aspect of the algorithm is shown to yield image improvement. The results demonstrate that the shear wave speed images can have less artifacts than the crawling waveimages. Examples are presented where the shear wave speed recoveries have excellent agreement with histology results on the size, shape, and location of cancerous tissues in the glands.
130(2011); http://dx.doi.org/10.1121/1.3598464View Description Hide Description
Hyperthermic temperatures, with potential applications in drug/gene delivery and chemo/radio sensitization, may be generated in biological tissues by applying focused ultrasound (FUS) in pulsed mode. Here, a strategy for optimizing FUS exposures for hyperthermia applications is proposed based on theoretical simulations and in vitro experiments. Initial simulations were carried out for tissue-mimicking phantoms, and subsequent thermocouplemeasurements allowed for validation of the simulation results. Advanced simulations were then conducted for an ectopic, murine xenograft tumor model. The ultrasound exposure parameters investigated in this study included acoustic power (3–5 W), duty cycle (DC) (10%–50%), and pulse repetition frequency (PRF) (1–5 Hz), as well as effects of tissue perfusion. The thermocouplemeasurements agreed well with simulation outcomes, where differences between the two never exceeded 1.9%. Based on a desired temperature range of 39–44 °C, optimal tumor coverage (40.8% of the total tumor volume) by a single FUS exposure at 1 MHz was achieved with 4 W acoustic power, 50% DC, and 5 Hz PRF. Results of this study demonstrate the utility of a proposed strategy for optimizing pulsed-FUS induced hyperthermia. These strategies can help reduce the requirement for empirical animal experimentation, and facilitate the translation of pulsed-FUS applications to the clinic.