Val Veirs

Speaking up: Killer whales (Orcinus orca) increase their call amplitude in response to vessel noise

This study investigated the effects of anthropogenic sound exposure on the vocal behavior of free-ranging killer whales. Endangered Southern Resident killer whales inhabit areas including the urban coastal waters of Puget Sound near Seattle, WA, where anthropogenic sounds are ubiquitous, particularly those from motorized vessels. A calibrated recording system was used to measure killer whale call source levels and background noise levels (1-40 kHz). Results show that whales increased their call amplitude by 1 dB for every 1 dB increase in background noise levels. Furthermore, nearby vessel counts were positively correlated with these observed background noise levels.

Ship noise extends to frequencies used for echolocation by endangered killer whales

Combining calibrated hydrophone measurements with vessel location data from the Automatic Identification System, we estimate underwater sound pressure levels for 1,582 unique ships that transited the core critical habitat of the endangered Southern Resident killer whales during 28 months between March, 2011, and October, 2013. Median received spectrum levels of noise from 2,809 isolated transits are elevated relative to median background levels not only at low frequencies (20–30 dB re 1 µPa2/Hz from 100 to 1,000 Hz), but also at high frequencies (5–13 dB from 10,000 to 96,000 Hz). Thus, noise received from ships at ranges less than 3 km extends to frequencies used by odontocetes. Broadband received levels (11.5–40,000 Hz) near the shoreline in Haro Strait (WA, USA) for the entire ship population were 110 ± 7 dB re 1 µPa on average. Assuming near-spherical spreading based on a transmission loss experiment we compute mean broadband source levels for the ship population of 173 ± 7 dB re 1 µPa 1 m without accounting for frequency-dependent absorption. Mean ship speed was 7.3 ± 2.0 m/s (14.1 ± 3.9 knots). Most ship classes show a linear relationship between source level and speed with a slope near +2 dB per m/s (+1 dB/knot). Spectrum, 1/12-octave, and 1/3-octave source levels for the whole population have median values that are comparable to previous measurements and models at most frequencies, but for select studies may be relatively low below 200 Hz and high above 20,000 Hz. Median source spectrum levels peak near 50 Hz for all 12 ship classes, have a maximum of 159 dB re 1 µPa2/Hz @ 1 m for container ships, and vary between classes. Below 200 Hz, the class-specific median spectrum levels bifurcate with large commercial ships grouping as higher power noise sources. Within all ship classes spectrum levels vary more at low frequencies than at high frequencies, and the degree of variability is almost halved for classes that have smaller speed standard deviations. This is the first study to present source spectra for populations of different ship classes operating in coastal habitats, including at higher frequencies used by killer whales for both communication and echolocation.

Vessel noise measurements underwater in the Haro Strait, WA

In the recent listing of southern resident orcas as endangered under the Endangered Species Act, disturbance by vessels is cited as a risk factor for the population and a factor in the designation of critical habitat. To help determine whether vessel noise underwater is disturbing orcas as they use sound to navigate, forage, or communicate, the source level of common large vessels transiting Haro Strait was measured. Since large vessels are the dominant source of underwater sound for the southern residents (based on water volume ensonified and duration of exposure at a given receive level), it is convenient that all commercial vessels longer than 65 ft are now required to broadcast their location, speed, and other data in real‐time. The automatic identification system (AIS) broadcasts data every 2 s via VHF that can be received and decoded with specialized radio receivers that are now coming on the market. AIS was used to log range, speed, and relative bearing while simultaneous recordings were made of th...

Source levels of free‐ranging killer whale (orcinus orca) social vocalizations

An array of four hydrophones spaced over 200 m near the shore of San Juan Island, WA, has been used to localize the underwater vocalizations of Southern Resident orca whales. The hydrophones (ITC) have home‐built pre‐amps and amplifiers and signals are digitized simultaneously by two computers. The system has been calibrated with an underwater speaker (J‐9). Automatic call detection is used to activate data logging on one computer and real‐time localization on a second that directs a video camera to record the water’s surface at the predicted source location. The system requires about 1 s to detect a call, locate it and redirect the video camera. This is the first report of source levels of social vocalizations of free‐ranging Southern Resident orcas. To date (July 2004), 160 orca calls have been localized within 200 m of the center of the array. The average acoustic intensity of these calls is 145 dB re 1 μPa@1 m. The range of intensities is from 137 to 157 dB re 1 μPa@1 m. Complete results including int...

Killer whale scouting: Listen live for troops J, K, and L.

The southern resident killer whales are highly vocal, sharing almost 40 distinct calls. The endangered population of about 87 orcas live in matriarchal groups (like troops) known as J, K, and L pods. Each pod has a favorite call that is used about half the time pod members vocalize. If you hear a favorite call you can guess (or infer) which pod is present. A new way to listen for orcas is with hydrophones (underwater microphones) that are connected to the internet. The Northeast Pacific Hydrophone Network—http://orcasound.net—includes five hydrophones located near Seattle, WA within the summertime range of the orcas. You can listen live through iTunes to discover which pods are calling or to monitor the environment for noise pollution that could be a problem for the whales. This hands‐on activity teaches you how to listen, identify the three pods based on their favorite calls, and share your observations with other listeners. High school students can use free software to record orca calls, whistles, and c...

One year of background underwater sound levels in Haro Strait, Puget Sound

Haro Strait, on the west side of San Juan Island, WA, is the home range of the Southern Resident orca whales, a major shipping lane to and from Canada, and a center of private and commercial boating, especially in the summer. Four ITC hydrophones in a near‐shore fixed array are used here to localize the underwater vocalizations of Southern Resident orca whales. The system operates 24 hours a day and has a frequency response of 100 Hz 10 kHz. Background sound levels are automatically characterized by half‐hour reports that include: statistics and graphics based on mean sound levels (2‐min running arithmetic mean pressure); a histogram of mean sound levels binned by frequency; and 2‐s sound samples from maximum background events. Sound levels range from ∼90 dB re 1 microPa (quiet conditions) to ∼130 dB re 1 microPa when loud commercial ships are passing in the nearby shipping lane or speedboats are passing close to the hydrophone array. Complete results for one year of continuous monitoring will be presente...

Approaches to reduce noise from ships operating in important killer whale habitats

Shipping is key to global trade, but is also a dominant source of anthropogenic noise in the ocean. Chronic noise from ships can affect acoustic quality of important whale habitats. Noise from ships has been identified as one of three main stressors-in addition to contaminants, and lack of Chinook salmon prey-in the recovery of the endangered southern resident killer whale (SRKW) population. Managers recognize existing noise levels as a threat to the acoustical integrity of SRKW critical habitat. There is an urgent need to identify practical ways to reduce ocean noise given projected increases in shipping in the SRKWs summertime critical habitat in the Salish Sea. We reviewed the literature to provide a qualitative description of mitigation approaches. We use an existing ship source level dataset to quantify how some mitigation approaches could readily reduce noise levels by 3-10 dB.

Orcasound lab: A soundscape analysis case study in killer whale habitat with implications for coastal ocean observatories

Orcasound lab is a cabled hydrophone array located near the shoreline of Haro Strait, the core summertime habitat of the endangered southern resident killer whales (SRKWs). In 2016–2017, we began to record data continuously on local hard drives and in 2018 are archiving both lossy and lossless data 24/7 in an AWS/S3 bucket. We discuss our statistical characterization of the soundscape from these continuous audio recordings, contextualized with the AIS data (to quantify sources of ship noise) and image data (to quantify sources of non-AIS boat noise). Of particular interest to ocean observatories are our methods of establishing non-anthropogenic acoustic baselines and then ranking noise pollution sources relative to these baselines. We explore the statistical consequences of selecting different averaging times (from seconds to years) and frequency band widths (spectrum to broadband levels) when computing baselines and pollution metrics, including “delta” metrics that may be most-relevant to SRKWs. Finally, we explain how soundscape analysis (with attention to tidal, diurnal, seasonal, or decadal time variations) could be implemented with cloud-based data in near-real-time and be enriched by citizen scientists interacting with a time-stamped live audio stream and other environmental data.Orcasound lab is a cabled hydrophone array located near the shoreline of Haro Strait, the core summertime habitat of the endangered southern resident killer whales (SRKWs). In 2016–2017, we began to record data continuously on local hard drives and in 2018 are archiving both lossy and lossless data 24/7 in an AWS/S3 bucket. We discuss our statistical characterization of the soundscape from these continuous audio recordings, contextualized with the AIS data (to quantify sources of ship noise) and image data (to quantify sources of non-AIS boat noise). Of particular interest to ocean observatories are our methods of establishing non-anthropogenic acoustic baselines and then ranking noise pollution sources relative to these baselines. We explore the statistical consequences of selecting different averaging times (from seconds to years) and frequency band widths (spectrum to broadband levels) when computing baselines and pollution metrics, including “delta” metrics that may be most-relevant to SRKWs. Finally,...

Shipping noise signatures.

Throughout 2010, underwater recordings have been made of each ship passing two separate Haro Strait nodes of the OrcaSound.net hydrophone network. About 20 ships pass each day. Each ship has been identified in real time [automatic identification system (AIS)]. Measurements of received underwater noise levels and AIS variables are recorded as each ship passes the listening stations. Individual ships are observed multiple times moving in either northerly or southerly directions at times separated by a day or two and also by intervals of months. A database has been developed that contains the spectrum level of each ship (bandwidth 96 kHz at one location and 22 kHz at the other) and the source level both in terms of intensity and angular distribution. Ship signatures in terms of frequency quantiles and angular distributions of emissions are quite reproducible. This database can be used to predict limitations on echolocating and vocalizing marine mammals’ active space due to specific ship noise emissions. In p...

Masking of southern resident killer whale signals by commercial ship noise.

The endangered southern resident killer whales (SRKWs) emit sound to communicate with each other and to hunt fish. Communication or fishing are possible only within a distance (R) at which a signal can be detected. We determine detection distance by comparing the power spectra of the ambient noise and the received signal, with attention to the auditory response curve of the receiver. In Haro Strait, the center of the SRKW critical habitat, about 21 commercial ships per day, increases the ambient noise level by about 20 dB. To assess how ship noise may affect the SRKW communication and hunting, we define the fractional reduction in the zone of audibility at any location and time as the ratio of the area where signal detection is expected to occur in the increased noise regime to the maximum detection area expected under ideal conditions R2/Rmax2. We map the decreased zones of audibility in Haro Strait during average and extreme ship noise by combining field measurements of spreading rates with source power...