–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–
Figure 1. Image Courtesy of ZoBell, Vanessa M., John A. Hildebrand, and Kaitlin E. Frasier. “Comparing pre-industrial and modern ocean noise levels in the Santa Barbara Channel.” Marine Pollution Bulletin 202 (2024): 116379.
Southern California waters are lit up with noise pollution (Figure 1). The Port of Los Angeles and the Port of Long Beach are the first and second busiest shipping ports in the western hemisphere, supporting transits from large container ships that radiated noise throughout the region. Underwater noise generated by these vessels dominate ocean soundscapes, negatively affecting marine organisms, like mammals, fish, and invertebrates, who rely on sound for daily life functions. In this project, we modeled what the ocean would sound like without human activity and compared it with what it sounds like in modern day. We found in this region, which encompasses the Channel Islands National Marine Sanctuary and feeding grounds of the endangered northeastern Pacific blue whale, modern ocean noise levels were up to 15 dB higher than pre-industrial levels. This would be like having a picnic in a meadow versus having a picnic on an airport tarmac.
Reducing ship noise in critical habitats has become an international priority for protecting marine organisms. A variety of noise reduction techniques have been discussed, with some already operationalized. To understand the effectiveness of these techniques, broad stakeholder engagement, robust funding, and advanced signal processing is required. We modeled a variety of noise reduction simulations and identified effective strategies to quiet whale habitats in the Santa Barbara Channel region. Simulating conservation scenarios will allow more techniques to be explored without having to be implemented, saving time, money, and resources in the pursuit of protecting the ocean.
Centre for Marine Science and Technology, Curtin University, Bentley, Western Australia, 6102, Australia
Benjamin Saunders
School of Molecular and Life Sciences
Curtin University
Bentley, Western Australia, Australia
Christine Erbe, Iain Parnum, Chong Wei, and Robert McCauley
Centre for Marine Science and Technology
Curtin University
Bentley, Western Australia, Australia
Popular version of 5aAB6 – The search to identify the fish species chorusing along the southern Australian continental shelf
Presented at the 185 ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0023649
Please keep in mind that the research described in this Lay Language Paper may not have yet been peer reviewed.
Unknown fish species are singing in large aggregations along almost the entire southern Australian continental shelf on a daily basis, yet we still have little idea of what species these fish are or what this means to them. These singing aggregations are known as fish choruses, they occur when many individuals call continuously for a prolonged period, producing a cacophony of sound that can be detected kilometres away. It is difficult to identify fish species that chorus in offshore marine environments. The current scientific understanding of the sound-producing abilities of all fish species is limited and offshore marine environments are challenging to access. This project aimed to undertake a pilot study which attempted to identify the source species of three fish chorus types (shown below) detected along the southern Australian continental shelf off Bremer Bay in Western Australia from previously collected acoustic recordings.
Each fish chorus type occurred over the hours of sunset, dominating the soundscape within unique frequency bands. Have a listen to the audio file below to get a feeling for how noisy the waters off Bremer Bay become as the sun goes down and the fish start singing. The activity of each fish chorus type changed over time, indicating seasonality in presence and intensity. Chorus I and II demonstrated a peak in calling presence and intensity over late winter to early summer, while Chorus III demonstrated peak calling over late winter to late spring. This informed the sampling methodology of the pilot study, and in December 2019, underwater acoustic recorders and unbaited video recorders were deployed simultaneously on the seafloor along the continental shelf off Bremer Bay to attempt to collect evidence of any large aggregations of fish species present during the production of the fish choruses. Chorus I and the start of Chorus II were detected on the acoustic recordings, corresponding with video recordings of large aggregations of Red Snapper (Centroberyx gerrardi) and Deep Sea Perch (Nemadactylus macropterus). A spectrogram of the acoustic recordings and snapshots from the corresponding underwater video recordings are shown below.
The presence of large aggregations of Red Snapper present while Chorus I was also present was of particular interest to the authors. Previous dissections of this species had revealed that Red Snapper possessed anatomical features that could support sound production through the vibration of their swimbladder using specialised muscles. To explore this further, computerized tomography (CT) scans of several Red Snapper specimens were undertaken. We are currently undertaking 3D modelling of the sound-producing mechanisms of this species to compute the resonance frequency of the fish to better understand if this species could be producing Chorus I.
Listening to fish choruses can tell us about where these fish live, what habitats they use, their spawning behaviour, their feeding behaviour, can indicate their biodiversity, and in certain circumstances, can determine the local abundance of a fish population. For this information to be applied to marine spatial planning and fish species management, it is necessary to identify which fish species are producing these choruses. This pilot study was the first step in an attempt to develop an effective methodology that could be used to address the challenging task of identifying the source species of fish choruses present in offshore environments. We recommend that future studies take an integrated approach to species identification, including the use of arrays of hydrophones paired with underwater video recorders.
NUWC Division Newport, NAVSEA, Newport, RI, 02841, United States
Dr. Lauren A. Freeman, Dr. Daniel Duane, Dr. Ian Rooney from NUWC Division Newport and
Dr. Simon E. Freeman from ARPA-E
Popular version of 1aAB1 – Passive Acoustic Monitoring of Biological Soundscapes in a Changing Climate
Presented at the 184 ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0018023
Climate change is impacting our oceans and marine ecosystems across the globe. Passive acoustic monitoring of marine ecosystems has been shown to provide a window into the heartbeat of an ecosystem, its relative health, and even information such as how many whales or fish are present in a given day or month. By studying marine soundscapes, we collate all of the ambient noise at an underwater location and attribute parts of the soundscape to wind and waves, to boats, and to different types of biology. Long term biological soundscape studies allow us to track changes in ecosystems with a single, small, instrument called a hydrophone. I’ve been studying coral reef soundscapes for nearly a decade now, and am starting to have time series long enough to begin to see how climate change affects soundscapes. Some of the most immediate and pronounced impacts of climate change on shallow ocean soundscapes are evident in varying levels of ambient biological sound. We found a ubiquitous trend at research sites in both the tropical Pacific (Hawaii) and sub-tropical Atlantic (Bermuda) that warmer water tends to be associated with higher ambient noise levels. Different frequency bands provide information about different ecological processes (such as fish calls, invertebrate activity, and algal photosynthesis). The response of each of these processes to temperature changes is not uniform, however each type of ambient noise increases in warmer water. At some point, ocean warming and acidification will fundamentally change the ecological structure of a shallow water environment. This would also be reflected in a fundamentally different soundscape, as described by peak frequencies and sound intensity. While I have not monitored the phase shift of an ecosystem at a single site, I have documented and shown that healthy coral reefs with high levels of parrotfish and reef fish have fundamentally different soundscapes, as reflected in their acoustic signature at different frequency bands, than coral reefs that are degraded and overgrown with fleshy macroalgae. This suggests that long term soundscape monitoring could also track these ecological phase shifts under climate stress and other impacts to marine ecosystems such as overfishing.
A healthy coral reef research site in Hawaii with vibrant corals, many reef fish, and copious nooks and crannies for marine invertebrates to make their homes.
Soundscape segmented into three frequency bands capturing fish vocalizations (blue), parrotfish scrapes (red), and invertebrate clicks along with algal photosynthesis bubbles (yellow). All features show an increase in ambient noise level (PSD, y-axis) with increasing ocean temperature at each site studied in Hawaii.
Popular version of 5aUW-Underwater soundscapes at critical habitats of the endangered Hawaiian monk seal, presented at the 183rd ASA Meeting.
The ocean is a noisy place. From chatty marine mammals to territorial fish and hungry shrimp, marine animals use sound to communicate, navigate, defend territories, and find food, mates, and safe spaces to settle down. However, human activities are negatively impacting the abilities of marine animals to effectively use sound for critical life functions. For the endangered Hawaiian monk seal with a population size of approximately 1,570 seals, we’re finding that vocal communication (Audio File 1) may play an important role for reproduction, yet we lack a foundational knowledge of the seals’ acoustic environment, better known as a soundscape. In this study, we found that biological sounds produced by snapping shrimp, fish, and seals dominate and shape the underwater soundscapes at critical habitats of the Hawaiian monk seal, with little input from man-made sources (Figure 1).
Figure 1 | A) Spectrogram of a 24-hour period on 11 May 2021 at Lehua Rock. A spectrogram is a visual representation of a sound where the x-axis is time, the y-axis is frequency (or pitch), and the color represents the amplitude of the sound (how loud or soft the sound is). The black icons indicate the source of the sound: snapping shrimp, boat, scuba divers, humpback whale song, Hawaiian monk seal vocalizations, and the vertical migration of the deep scattering layer. B) Spectrogram showing overlapping Hawaiian monk seal vocalizations from 0-1 kHz and humpback whale song from 0.5-5 kHz (listen to this in Audio File 1).
We sought to describe the underwater soundscape, or the acoustic environment, at locations that Hawaiian monk seals utilize for foraging, breeding, communication, and other critical life functions. We wanted to know 1) how loud are ambient (background) sound levels, 2) are sound sources biological, geophysical, or manmade, 3) how do sound sources and levels change throughout the day, and 4) how does the soundscape compare between the more-densely human-populated main Hawaiian Islands and the remote Northwestern Hawaiian Islands. To do this, we deployed passive acoustic recorders, known as SoundTraps, at four critical habitats of the Hawaiian monk seal: Rabbit Island, Oahu; Lehua Rock, Niʻihau; French Frigate Shoals; and Pearl and Hermes Reef. The SoundTraps recorded sounds from 20 Hz up to 24 kHz – this includes low-frequency sounds like earthquakes to high-frequency sounds like dolphin echolocation.
Our results indicate that sound levels are generally loud at these nearshore reef environments thanks to the persistent crackling sounds of snapping shrimp, low-frequency vocalizations of monk seals, and a variety of fish sounds. With little input from manmade sound sources, except at the popular scuba diving site Lehua Rock, we suspect that the elevated sound levels are indicative of healthy reef environments. This is good news for Hawaiian monk seals – less manmade noise means less acoustic masking making it easier to hear and “speak” to each other under water. We also opportunistically recorded sounds from Hurricane Douglas (Category 4) and a 6.2 magnitude earthquake around the time Kilauea began erupting. Overall, this study provides the first description of underwater soundscapes at Hawaiian monk seal critical habitats. These measurements can serve as a baseline for future studies to understand the impact of human activity on underwater soundscapes.
Ross Chapman – chapman@uvic.ca University of Victoria 3800 Finnerty Road Victoria, BC V8P 5C2 Canada
Popular version of 2pUW2- Pacific Echo: A deep ocean collaborative experiment Presented Tuesday afternoon, May 24, 2022 182nd ASA Meeting Click here to read the abstract
The ocean bottom in large regions of the Pacific Ocean consists of a thin layer of deep ocean sediment on top of oceanic crust (Figure 1). Crustal rock created at deep ocean fractures at spreading zones moves slowly away outward over millions of years, generating a rugged crustal layer of increasing geological age with increasing distance from the spreading zone. The presence of solid basalt crustal rock close to the sea floor creates a strikingly different ocean bottom environment compared to most other ocean regions.
Figure 1. The ocean bathymetry in a region of the older Pacific Echo crust sites. Ocean depth is ~5400 m.
In the latter stages of the Cold War, researchers in navy laboratories carried out a series of experiments at sea to study the impact of this solid rock ocean bottom on sound propagation and underwater target detection. The experimental programme, Pacific Echo, was a collaboration between researchers at the US Naval Research Laboratory in Washington and the Canadian Defence Research Establishment Pacific in Victoria. Four sea trials were carried out between 1986 and 1992 at various deep water Pacific sites. The research objective was to understand the physics of sound interaction with the solid rock ocean bottom, where the dominant reflection of sound was from an interface beneath the sea floor. Interaction of sound with the rock generates an additional energy loss due to shear waves that propagate in the rock. This type of energy loss is not significant in other ocean bottom environments that consist of layers of unconsolidated sediment where shear waves in the sediment material are very weak.
Figure 2. Deploying the hydrophone line array from the stern of CFAV Endeavour at sea.
The experimental plan in Pacific Echo involved measurements of the ocean bottom reflection coefficient using a towed horizontal hydrophone line array (Figure 2). A new technique, the broadside reflectivity measurement (BRM), was developed for efficient acquisition of high quality data. The BRM method involved two ships, USNS DeSteiguer deployed sound sources while CFAV Endeavour towed the hydrophone array along headings shown in Figure 3. The array acts as a directional receiver to enable separation of the specular or mirror-like reflection from unwanted contributions arising from basalt outcrop features.
Figure 3. Schematic diagram of ship tracks during the BRM measurement.
The measured reflection coefficients, as in the example shown in Figure 4, revealed large energy loss at low grazing angles less than ~55°. This loss, due to shear waves generated in the rock, confirmed the hypothesis of reflectivity dominated by the oceanic crust.
Figure 4. Reflection coefficient measured at one of the older sites in Pacific Echo.
The Pacific Echo data also provided new information about an underlying research question in marine geophysics related to the aging process in oceanic crust. Estimates of sound speed in basalt derived from the Pacific Echo data revealed sound speeds as low as ~2500 m/s in very young basalt (0-3 million years old), increasing to ~3600 m/s at the oldest sites (~70 million years old). These results gave support to the research hypothesis that sound speed in oceanic crust increased with the age of the basalt.
I Yun Su – r07525010@ntu.edu.tw Wen-Yang Liu – r06525035@ntu.edu.tw Chi-Fang Chen – chifang@ntu.edu.tw Engineering Science and Ocean Engineering, National Taiwan University, No. 1 Roosevelt Road Sec.#4 Taipei City, Taiwan
Popular version of paper 2pUWb2 Presented Tuesday afternoon, December 8, 2020 179th ASA Meeting, Acoustics Virtually Everywhere
A flight recorder is installed in every aircraft to record the flight status. When the aviation accident occurs, this recorder can help clarify the cause of the incident. Furthermore, if the plane crashes into the ocean, the underwater locater beacon (ULB) inside the flight recorder will be triggered which would make a sound that could be located by the rescue team.
In 2009, there was a serious accident involving the Air French flight 447. According to the final report, French Civil Aviation Safety Investigation Authority suggested that the ULB should acquire extended transmission time up to 90 days and increased transmission range. In Taiwan, the flight recorder has already been installed with a 37.5 kHz ULB inside the tail section of every vehicle, and now Taiwan Transportation Safety Board considered to put in an additional 8.8 kHz ULB in the flight belly. (Picture 1)
Picture 1: The positions of the 37.5 kHz and 8.8 kHz ULB on the plane.
The main propose of this study is to understand the performance of the newly bought 8.8 kHz ULB – DUKANE SEACOM DK180. Firsts off, I did the simulation on both ULB to compare the detection ranges (DR), and according to the beacon specifications, the source level (SL) of the both is 160 dB re 1μPa.
For the DR to be simulated, the transmission loss (TL) which is affected by a lot of different environmental parameters must be determined first. This study is based on the Taiwan database, and using the Gaussian beam propagation to calculate the TL. After the TL is acquired, the noise level (NL) which also has certain impact on the DR has to be determined. Generally, the lower the frequency, the longer the DR. DR can be determined by passive sonar equation, and can be derive the FOM = SL – NL – DT. The DT is Detection Threshold and the FOM is Figure of Merit, which is the maximum TL that can detect. The intersection of the TL and FOM is DR. In the study, the DT is set to be zero. At the Point A, the NL of the 8.8 kHz is 78 dB re 1μPa and for 37.5 kHz is 65 dB re 1μPa, so the FOM of the 8.8 kHz is 82 dB re 1μPa and for 37.5 kHz is 95 dB re 1μPa. The DR in 8.8 kHz ULB is about twice than 37.5 kHz ULB at Point A. (Picture 2)
Picture 2: Detection Ranges of 8.8 kHz ULB and 37.5 kHz ULB in the Point A.
In the study, I have also done the experiment in Taiwan Miaoli offshore. The results also show that the newly bought 8.8 kHz ULB would have a smaller TL and longer DR. In summary, with an additional 8.8 ULB, the more precise prediction of the beacon location could be obtained.
Figure 1. Image Courtesy of ZoBell, Vanessa M., John A. Hildebrand, and Kaitlin E. Frasier. “Comparing pre-industrial and modern ocean noise levels in the Santa Barbara Channel.” Marine Pollution Bulletin 202 (2024): 116379.
Each fish chorus type occurred over the hours of sunset, dominating the soundscape within unique frequency bands. Have a listen to the audio file below to get a feeling for how noisy the waters off Bremer Bay become as the sun goes down and the fish start singing. The activity of each fish chorus type changed over time, indicating seasonality in presence and intensity. Chorus I and II demonstrated a peak in calling presence and intensity over late winter to early summer, while Chorus III demonstrated peak calling over late winter to late spring. This informed the sampling methodology of the pilot study, and in December 2019, underwater acoustic recorders and unbaited video recorders were deployed simultaneously on the seafloor along the continental shelf off Bremer Bay to attempt to collect evidence of any large aggregations of fish species present during the production of the fish choruses. Chorus I and the start of Chorus II were detected on the acoustic recordings, corresponding with video recordings of large aggregations of Red Snapper (Centroberyx gerrardi) and Deep Sea Perch (Nemadactylus macropterus). A spectrogram of the acoustic recordings and snapshots from the corresponding underwater video recordings are shown below.
A healthy coral reef research site in Hawaii with vibrant corals, many reef fish, and copious nooks and crannies for marine invertebrates to make their homes.
Soundscape segmented into three frequency bands capturing fish vocalizations (blue), parrotfish scrapes (red), and invertebrate clicks along with algal photosynthesis bubbles (yellow). All features show an increase in ambient noise level (PSD, y-axis) with increasing ocean temperature at each site studied in Hawaii.
