John E. Joseph

First direct measurements of behavioural responses by Cuvier's beaked whales to mid-frequency active sonar.

Most marine mammal strandings coincident with naval sonar exercises have involved Cuviers beaked whales (Ziphius cavirostris). We recorded animal movement and acoustic data on two tagged Ziphius and obtained the first direct measurements of behavioural responses of this species to mid-frequency active (MFA) sonar signals. Each recording included a 30-min playback (one 1.6-s simulated MFA sonar signal repeated every 25 s); one whale was also incidentally exposed to MFA sonar from distant naval exercises. Whales responded strongly to playbacks at low received levels (RLs; 89–127 dB re 1 µPa): after ceasing normal fluking and echolocation, they swam rapidly, silently away, extending both dive duration and subsequent non-foraging interval. Distant sonar exercises (78–106 dB re 1 µPa) did not elicit such responses, suggesting that context may moderate reactions. The observed responses to playback occurred at RLs well below current regulatory thresholds; equivalent responses to operational sonars could elevate stranding risk and reduce foraging efficiency.

Baleen whale calling behavior and response to anthropogenic sound

Without a means of studying large whales in a controlled experimental environment, less is understood about their sound production mechanisms than is understood about those of smaller odontocetes. To describe call production behavior in fin whales, we used a recent technique that correlates fast-sampling accelerometer signals from tags with concurrently recorded acoustic signals to identify calls produced by the tagged animal. We tagged 18 fin whales as part of the Southern California Behavioral Response Study (SOCAL BRS), of which four were confirmed to be calling. We were then able to describe their kinematic and social behavior in relation to call production. Behaviors associated with elevated call rates included shallow maximum dive depths, little body movement, and negative pitch in body orientation, similar to some other calling baleen whale species. These are the first descriptions of body orientation and dive depths at which fin whales are most likely to call. We also describe calling responses (o...

Monterey Bay ambient noise profiles using underwater gliders

In 2012, during two separate week-long deployments, underwater gliders outfitted with external hydrophones profiled the upper 100 m of Monterey Bay. The environment contains various noises made by marine mammals, ships, winds, and earthquakes. Unlike hydrophone receivers moored to a fixed location, moving gliders measure noise variability across a wide terrain. However, underwater mobile systems have limitations such as instrument and flow noise, that are undesired. In order to estimate the system noise level, the hydrophones on the gliders had different gain settings on each deployment. The first deployment used a 0 dB gain during which the ambient noise recordings were dominated by the glider. The second used two hydrophones, one with a 0 dB gain and the other with 20 dB. Apart from system sounds, the higher-gain hydrophone also recorded far-away sources such as whales and ships. The noise recordings are used to estimate the spectrograms across depth and record time. The spectrograms are integrated with...

Acoustic propagation at low-to-mid-frequencies in the Connecticut River

An estuary is a constrained environment which often hosts a salt wedge during flood and a fresh water plume on ebb, the structures of which are complex functions of the tide’s range and speed of advance, river discharge volumetric flow rate and river mouth morphology. A field experiment was carried out in the Connecticut River in June 2017, one goal of which was to investigate the low-to-mid-frequency acoustic propagation characteristics of the riverine salt wedge as well as the plume outside the river mouth. Linear frequency-modulated (LFM) acoustic signals in the 500-2000 Hz band were collected during several tidal cycles. Data analyses demonstrate the degree to which these features in this highly energetic environment impact acoustic propagation; dominant mechanisms are boundary interactions, salt wedge sound speed gradients and bubble clouds at the ebb plume front.An estuary is a constrained environment which often hosts a salt wedge during flood and a fresh water plume on ebb, the structures of which are complex functions of the tide’s range and speed of advance, river discharge volumetric flow rate and river mouth morphology. A field experiment was carried out in the Connecticut River in June 2017, one goal of which was to investigate the low-to-mid-frequency acoustic propagation characteristics of the riverine salt wedge as well as the plume outside the river mouth. Linear frequency-modulated (LFM) acoustic signals in the 500-2000 Hz band were collected during several tidal cycles. Data analyses demonstrate the degree to which these features in this highly energetic environment impact acoustic propagation; dominant mechanisms are boundary interactions, salt wedge sound speed gradients and bubble clouds at the ebb plume front.

Temporal variations in humpback whale (Megaptera novaeangliae) song in Monterey Bay National Marine Sanctuary, northeast Pacific

Using two years of nearly continuous recordings from Monterey Bay National Marine Sanctuary, August 2015 through July 2017, variations in humpback whale song are examined on diel, seasonal, and interannual time scales. The cabled hydrophone is in humpback feeding and migratory habitat at 36.7128°N, 122.186°W. Diel analyses show 69% of song during night, 23% during day, and 8% during dusk or dawn. Seasonal analyses show song absence during summer (June–August), emergence during fall (September–October), peak during late fall/winter (November–January), and highly variable detection during spring (February–May). During both years >80% of song occurred during the November–January peak. Song detection within a month reached a maximum of 58% of the time during November 2016. Song length increased (p < 0.01) month-to-month from the start in fall through the end of the peak in January. The months of maximum song occurrence coincide with declining visual sighting of humpbacks within Monterey Bay, consistent with s...

Characteristics of the Arctic environment in the southern Beaufort Sea from Ice Exercise data

In early March of 2016 and 2018, the Naval Postgraduate School participated in the biennial naval Ice Exercise (ICEX) conducted in the southern Beaufort Sea. Oceanographic and acoustic data sets collected near the ice camps during both events are compared. While the drift track of the ice camp during ICEX-18 was approximately one-degree south of the track in ICEX-16, there are important similarities in the oceanographic structure shown in both datasets. These characteristics have significant impacts on sound propagation in the region and may affect the performance of acoustic systems such as naval sonar and UUV navigation. Of particular interest are properties at the interface between the cold, fresh surface layer and the contrasting warm, saline Pacific Summer Water (PSW) that lays immediately below it. Sensors indicate turbulent mixing of high-spice and low-spice water occurs at this interface. PSW also sets up a stable subsurface sound channel with Pacific Winter Water and Atlantic Water layers below it. Strength of the sound channel varies from year to year; however, historical data from this region indicates an increasing trend. Other oceanographic features found in the upper 200 m of the under-ice water column in our 120-kHz echosounder dataset are discussed.In early March of 2016 and 2018, the Naval Postgraduate School participated in the biennial naval Ice Exercise (ICEX) conducted in the southern Beaufort Sea. Oceanographic and acoustic data sets collected near the ice camps during both events are compared. While the drift track of the ice camp during ICEX-18 was approximately one-degree south of the track in ICEX-16, there are important similarities in the oceanographic structure shown in both datasets. These characteristics have significant impacts on sound propagation in the region and may affect the performance of acoustic systems such as naval sonar and UUV navigation. Of particular interest are properties at the interface between the cold, fresh surface layer and the contrasting warm, saline Pacific Summer Water (PSW) that lays immediately below it. Sensors indicate turbulent mixing of high-spice and low-spice water occurs at this interface. PSW also sets up a stable subsurface sound channel with Pacific Winter Water and Atlantic Water layers below i...

Characteristics of the under-ice soundscape in the southern Beaufort Sea during Ice Exercise 2016

Ice Camp SARGO was the remote hub of operations for the multi-national naval operation Ice Exercise 2016 (ICEX-16), held in March of that year. Over a three-day period in early March, continuous recordings of the under-ice soundscape were collected with receivers deployed at various depths through first-year ice in the vicinity of the ice camp as it drifted westward across the Beaufort Sea approximately 175 nm north of Prudhoe Bay, Alaska. A significant reduction in the strength of easterly winds resulted in deceleration of the ice sheet during the period of observation, inducing notable ice cracking and ridging events near the camp. Ice sheet movement slowed from about 0.5 knots early in the test to virtually coming to a halt near the end of the recording period. Sounds from naturally occurring and anthropogenic sources in the 10-Hz to 10-kHz band detected in the recordings were analyzed in connection to the origins of the sound and correlated to varying environment conditions including wind speed and ic...

Acoustic propagation in the Connecticut River at low-to-mid frequencies

An estuary is a constrained environment which often hosts a salt wedge, the stratification of which is a function of the tides range and speed of advance, river discharge volumetric flow rate and river mouth morphology. A field experiment was carried out in the Connecticut River in June 2017, one goal of which was to investigate the low-to-mid-frequency acoustic propagation characteristics of the riverine salt wedge as well as the plume outside the river mouth. Linear frequency-modulated (LFM) acoustic signals in the 500–2000 Hz band were collected during several tidal cycles. Data-model comparisons demonstrate the degree to which this highly energetic environment impacts acoustic propagation; dominant mechanisms are sound speed stratification, boundary interaction, flow noise, and background noise.An estuary is a constrained environment which often hosts a salt wedge, the stratification of which is a function of the tides range and speed of advance, river discharge volumetric flow rate and river mouth morphology. A field experiment was carried out in the Connecticut River in June 2017, one goal of which was to investigate the low-to-mid-frequency acoustic propagation characteristics of the riverine salt wedge as well as the plume outside the river mouth. Linear frequency-modulated (LFM) acoustic signals in the 500–2000 Hz band were collected during several tidal cycles. Data-model comparisons demonstrate the degree to which this highly energetic environment impacts acoustic propagation; dominant mechanisms are sound speed stratification, boundary interaction, flow noise, and background noise.

Acoustic characterization of the new Arctic using mobile acoustic sources

The Naval Postgraduate School (NPS) participated in Ice Exercise 2016 (ICEX-16), a multi-national naval exercise conducted in the Beaufort Sea during March 2016. Operating at the remote Ice Camp SARGO, NPS deployed several conductivity, temperature and depth (CTD) sensors to capture oceanographic variability to 500 m depth while performing a series of propagation tests. Four mobile mid-frequency sources transmitted signals for approximately 10 hours each to a pair of vertical line array receivers positioned in the field to investigate depth, range, angular and specular characteristics of acoustic propagation and their correlation to variability in oceanographic structure and under-ice conditions. CTD data indicated significant variability in sound speed at 50 m depth where cold, fresh mixed-layer water interfaces with contrasting warm, saline Pacific Summer Water (PSW) that lays immediately below it. The data also show a persistent and stable subsurface sound channel existed as a result of the PSW with pe...

Sensitivity of acoustic propagation modeling to variations in ocean environmental conditions

A parabolic equation acoustic model has been used to estimate transmission loss for a mid-frequency sound source to assist in marine mammal behavioral response studies. The sound propagation is modeled for a range-dependent environment using the Navy Digital Bathymetric Data Base and Bottom Sediment Type database, NOAA Global Ocean Sediment Thickness Dataset, and the High-Resolution Global Sea Surface Wind Speed monthly climatology. The sound speed along the propagation path is modeled using two ocean temperature/salinity fields of different spatial and temporal resolution: monthly 0.25 deg outputs of the Generalized Digital Environmental Model (GDEM), and the daily 1/12 deg outputs of the regional Hybrid Coordinate Ocean Model (HYCOM). The modeling was done for two operational areas with strikingly different ocean environments, the Southern California Bight and the Gulf Stream region off Cape Hatteras. The latter represents a much more dynamic ocean environment with profound temperature fronts, highly va...