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 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 provided 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.

This work, co-funded by the LMR program and the Naval Innovative Science and Engineering (NISE) program, assessed conditioned hearing attenuation in bottlenose dolphins. The project measured how quickly dolphins can learn to suppress (i.e., attenuate) their hearing in anticipation of an impending intense sound, determined how long they can maintain the attenuation and assessed 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 investigated the best approach to designing a scientific study to assess behavioral response to LFA sonar.

This project measured 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). 

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 determined the frequency-dependent relationship between behavioral and AEP thresholds. The results of behaviorally equivalent AEP audiograms are being used to 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 examined TTS in aquatic turtles and provided the initial sound exposure levels that induce these temporary threshold shifts. Resulting data was used to revise estimates of noise impacts to both freshwater and sea turtles and guide the development of a TTS study with sea turtles.

This project developed tools needed to advance AEP measurements below 1 kHz by examining the potential for frequency-modulated, upward sweeping “chirp” stimuli to enhance marine mammal auditory brainstem response (ABR) amplitudes across a broad range of frequencies, including frequencies below 1 kHz.

This project used behavioral response experiments as a proxy for audiometric measurements to estimate hearing sensitivity in humpback whales. A range of tones were played to migrating humpback whales at frequencies across their expected hearing range and the team observed their behavioral response to develop an audiogram.

This project collected auditory evoked potential (AEP) hearing thresholds for one mysticete species, the minke whale (Balaenoptera acutorostrata). This method involves measuring small voltages that the brain and auditory nervous system generate in response to sound. The minke AEP hearing thresholds provided the first direct measurement of hearing in a mysticete, which will contribute to the development of a mysticete audiogram.

This project measured TTS and hearing recovery in harbor seals for deriving auditory weighting functions for seals.

A specially trained adult male Hawaiian monk seal will participate in a study 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), the team conducted coordinated exposure experiments with sonar from two different platforms. Each was deployed at multiple, pre-defined distances from tagged animals to collect data on responses.

The 3S (Sea mammals, Sonar, Safety) project, evaluated whether exposure to continuously active sonar leads to different types or severity of behavioral responses than exposure to pulsed active (also called intermittent) sonar signals. In addition, the project evaluated how the distance to the source affects behavioral responses.

This project measured potential physical effects to fish that may occur during Navy explosives training activities.

This effort published the first behavioral risk function for the Blainville’s beaked whale at the Pacific Missile Range Facility.

This effort defined weighting functions and Temporary Threshold Shift/Permanent Threshold Shift values for mid-frequency cetaceans.

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

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

This project established a behavioral dose–response relationship for sonar signals around 3 kHz in harbor porpoises.

The study provided the first demographic hearing data from killer whales by measuring behavioral audiograms for animals of multiple ages.

This project predicted a range of best hearing for the humpback whale based on a finite element model (FEM) of the middle ear.

This project investigated potential reasons why hearing data obtained by measuring auditory evoked potentials (AEPs) were not reliable for use in determining marine mammal weighting functions. Low frequency stimuli produced both low and high frequency AEPs, and therefore the AEP measurements were not reliable at predicting perceived loudness in marine mammals at low frequencies.

This project increased our understanding of marine mammal reactions to sound and provided a robust scientific basis for estimating the effect of Navy mid-frequency active sonar (MFAS) on marine mammal behavior.

This project finalized hardware/infrastructure for the Marine Mammal Monitoring on Ranges (M3R) system which automated passive acoustic marine mammal detection, localization, classification, and display tools using the Navy’s existing undersea hydrophone ranges. The M3R system aids visual and tagging methods, and enables comprehensive marine mammal monitoring to investigate long-term abundance and behavioral changes in the presence of sonar.