The generation of acoustic waves by a modulated thermal source is examined for anisotropic materials. A wave equation is developed to include the effect of a thermoacoustic source for the anisotropic case. The dependence of the thermoacoustic source term upon the material elastic constants is identified for a thermal source varying in one dimension. This dependence is examined for several classes of crystalline anisotropy and it is found that thermoacoustic generation varies with crystallographic orientation. The directions of maximum and minimum thermoacoustic generation are not consistent for a given crystal class and are dependent upon the specific values of the elastic constants for the material.

Killer whales produce pulsed calls, which are used for communication. Calls are highly stereotyped and repertoires are unique to individual pods. Discrimination amongst these calls and comparison of call repertoires between pods can help determine population structure in killer whales and can be used to track pod movements. Calls were detected in underwater acoustic recordings in August and September 2017 in the Arctic waters of Eclipse Sound, in Nunavut, Canada. We present a repertoire of killer whale calls recorded. Eleven stereotypic call types, three biphonic and eight monophonic, were identified using manual call organization and manual whistle contour extraction. A higher diversity of calls was detected in the hydrophone located in the known narwhal aggregation site in Milne Inlet, than at the second hydrophone deployed at the mouth of Eclipse Sound which is the proposed entrance and exit point for the killer whales. The potential for increased killer whale presence and magnitude of predation on narwhals is a source of concern for management of the population and by Inuit subsistence hunters who rely on narwhals for food and economic benefit. Describing the acoustic repertoire of killer whales seasonally present in the Canadian Arctic may help understand their behavior and seasonal movements. The results presented may provide a basis for future acoustic comparisons across the North Atlantic and aid in characterizing killer whale ecotypes making seasonal incursions into Arctic waters.

Acoustict ravelt ime measurementwse reu sedt o navigatet he elementso f a large-aperture(9 00 m) acoustica rray. Array navigations ystemp erformancew ase valuatedd uring a vertical deploymenitn the northeasPt acificf rom the ResearchP latformF LIP. A networko f bottommooreda coustictr ansponderws erei nterrogatedfr om FLIP and their 12-kHz repliesw ere detectedb y receiversa t 75-m intervalsa longt he array. A nonlinearl east-squareasl gorithm wasu sedt o estimateF LIP and array elementp ositionsfr om the travelt ime measurements. The FLIP positionsd erivedf rom this procedurea greedw ith positionso btainedf rom global positionings ystem( GPS) satelliten avigationt o within a 10-mr mse rror. Navigatedp ositions for FLIP were internallyc onsistenwt ith a 0.5-m meanr ms error and standardd eviationo f 1.1 m, and, for an array element,w ere consistentw ith a 2.8-m mean rms error and standard deviationo f 0.8 m. The resultingti mes erieso f arraya nd FLIP motionsw erea nalyzedw ith respecto wind, tidal, and internalw avef orcingf unctionsW. ind and tidal forcingh ad the greatesti nfluenceo n FLIP motion,w hereasa rray motionw asg overnedb y FLIP movement, tides,a nd higherf requencys ourcesL. ow-frequencya rray motion,w ith periodso n the ordero f hours,w asa resulto f FLIP towingt he array overa horizontalr angeo f 300 m in responsteo the wind and the semidiurnalt idal oscillationst;h e array remainedw ithin a 30-m horizontal range of FLIP's position. Higher frequency array motion had apparent internal wave and surface-couplecdo mponentsT. he array shapew asp rimarily straighta nd nearly vertical,t o within approximatelya 2ø t ilt, respondinga sa simplep endulumw ith smalld isplacements.

Mysticetes (baleen whales) often make long, annual migrations from high latitude summer feeding areas to low latitude wintering areas. Eastern North Pacific gray whales (Eschrichtius robustus) migrate within a few kilometers from shore for most of their route from summer feeding areas in the Bering, Chukchi, and Beaufort Seas to wintering areas in the lagoons along the south-western coast of the Baja California Peninsula in Mexico. This dissertation combines passive acoustic recordings, infrared camera video, and visual sightings to investigate gray whale behavior and how it changes across different timescales. I use a four-element hydrophone array in central California to present the first published full-season acoustic monitoring and tracking of migrating gray whales. I describe the characteristics of calls produced by migrating gray whales and analyze how these characteristics change due to propagation. I show that gray whale behavior changes on diel and seasonal timescales. Notably, gray whales increase their vocalizations at night but their mean swimming behavior does not change, contrary to previous assumptions used in population size estimates. Over seasonal timescales, vocalizing gray whale swimming behavior aligns with previous observations. I explore how passive acoustic and infrared camera monitoring can help quantify whales by calculating cue rates or call and blow rates for migrating gray whales. Acoustic calling rates indicate that the gray whale population size is greater than estimated using visual sightings alone and that calling rate increases over the southbound migration. Infrared camera blow rates are less affected by whale behavior and are useful for daytime and nighttime monitoring, but are limited by visibility and distance. To understand gray whale behavior over seven migration seasons, I use visual daily counts at two sites and single-hydrophone call detections which indicate that migratory behavior seems to be driven more by intrinsic than the tested environmental factors. I find that the proportion of the population using a coastal route through the Southern California Bight, especially past Los Angeles, increased over these years. Understanding the behavior of migrating gray whales will help improve abundance estimates and determine how these whales may be impacted by nearshore anthropogenic activities and climate change.

Advancements in low-power and high-data-capacity consumer computer technology during the past decade have been adapted to autonomously record sounds from marine mammals over long periods. Acoustic monitoring has advantages over traditional visual surveys including greater detection ranges, continuous long-term monitoring in remote locations under various weather conditions and independent of daylight, and lower cost. However, until recently, the technology required to autonomously record whale sounds over long durations has been limited to low-frequency (< 1000 Hz) baleen whales. The need for a broader-band, higher-data capacity system capable of autonomously recording toothed whales and other marine mammals for long periods has prompted the development of a High-frequency Acoustic Recording Package (HARP) capable of sample rates up to 200 kHz. Currently, HARPs accumulate data at a rate of almost 2 TB per instrument deployment which creates challenges for processing these large data sets. One method we employ to address some of these challenges is a spectral averaging algorithm in which the data are compressed and viewed as long duration spectrograms. These spectrograms provide the ability to view large amounts of data quickly for events of interest, and they provide a link for quickly accessing the short time-scale data for more detailed analysis. HARPs are currently in use worldwide to acoustically monitor marine mammals for behavioral and ecological long-term studies. The HARP design is described and data analysis strategies along with software tools are discussed using examples of broad-band recorded data.