This project will provide quantitative auditory masking data for individuals from three pinniped families: odobenid, otariid and phocid carnivores. It will include collecting direct critical bandwidth measurements and testing the effects of noise level on masking at a range of frequencies.

The goal of this project is to describe the behavioral response of cetaceans to anthropogenic impulsive noise sources and to verify the explosive propagation modeling for NAEMO.

This project will evaluate how the duration of individual sounds might influence how marine mammals perceive the sound’s loudness, which could affect the animal’s response.

This project is designed to test and quantify the behavioral responses of the Cuvier’s beaked whale (Ziphius cavirostris) to Navy mid-frequency active sonar activities employing continuous active sonar signals using controlled exposure experiments off Cape Hatteras, North Carolina.

This project is the fourth phase of the 3S (Sea mammals, Sonar, Safety) effort, part of an international research consortium that has been conducting behavioral response studies on different cetacean species in North Atlantic waters since 2006. During this phase, the project will continue studying behavioral responses to continuous active sonar versus pulsed active (intermittent) sonar and will investigate if responses from short duration experiments predict responses from longer duration exposures.

This project will provide auditory data for odobenid and otariid carnivores (Pacific walruses and California sea lions, respectively) needed to compare the acoustic sensitivity between these marine mammal taxa and support environmental compliance efforts.

This work, co-funded by the LMR program and the Naval Innovative Science and Engineering (NISE) program, is assessing conditioned hearing attenuation in bottlenose dolphins. The project will measure how quickly dolphins can learn to suppress (i.e., attenuate) their hearing in anticipation of an impending intense sound, determine how long they can maintain the attenuation and assess the role of outer hair cells in the conditioned hearing change.

The overall goal of this two-phase effort is to update previous studies done with LFA sources during the 1990s, based on lessons learned and best practices from controlled and observational behavioral response studies using other sonar sources conducted over the last 10 years. As part of the Phase I feasibility study, these projects are investigating the best approach to designing a scientific study to assess behavioral response to LFA sonar.

This project is measuring temporary threshold shift (TTS) in the bottlenose dolphin using auditory evoked potential (AEP) and behavioral threshold measurements for longer duration signal exposure with signal qualities simulating continuously active sonar (CAS). The focus is to determine if equal energy exposures result in equal TTS, independent of exposure duration.

This project is investigating perceived loudness in killer whales by determining the effect of signal duration on both response latency and detection thresholds, as well as determining the subjective loudness of short duration signals compared to long-duration signals.

By measuring behavioral and AEP hearing thresholds in the same individual bottlenose dolphins across the range of hearing, this project’s team will determine the frequency-dependent relationship between behavioral and AEP thresholds. The results of behaviorally equivalent AEP audiograms could substantially increase the data available for developing auditory weighting functions.

This project focuses on measuring TTS and hearing recovery in California sea lions (Zalophus californianus) for deriving auditory weighting functions.

This project is examining TTS in aquatic turtles and will potentially provide the initial sound exposure levels that induce these temporary threshold shifts. Resulting data could improve estimates of noise impacts to both freshwater and sea turtles and guide the development of a TTS study with sea turtles.

Researchers are working with a specially trained adult male Hawaiian monk seal to obtain reliable measures of underwater auditory sensitivity thresholds across the full frequency range of hearing. The resulting data will be used to generate an underwater audiogram that will help to support impact assessments of the Hawaiian monk seal’s sensitivity to sound.

To assess the effect of sonar source sources and distance (range), researchers are conducting controlled exposure experiments (CEE) with sonar from two different platforms. Each will be deployed at multiple, pre-defined distances from tagged animals to collect data on responses.

The results from this project will help to predict potential effects to fish that may occur during Navy explosives training activities.

The effort will generate significantly larger samples of high-resolution behavioral data, particularly for beaked whales, to support development of risk functions.

This project is measuring the hearing of up to three Auk species to provide key hearing data needed to define acoustic criteria for the marbled murrelet.