What are we hearing?

There are 3 types of sounds that we monitor in our estuaries including biological, physical, and anthropogenic noise. Biological sound in the estuary comes mainly from snapping shrimp, fish, and dolphins. More cryptic animals include right whales, manatees, and alligators. Physical sounds include waves, water flow, wind, and rain. Lastly, anthropogenic noise includes all sounds that are man-made including vessel noise from boats, ships, or ferries and also from construction such as pile driving.

Refer to the acoustic catalog for different sounds and noise.

What are we measuring?

For each sound (i.e. wav) file collected, we identify biological sounds and noise.

For snapping shrimp, we use a MATLAB script to count the number of individual snaps.

For each fish species, we determine calling intensity (0 = no calls, 1 = one call, 2 = multiple calls, or 3 = chorus).

For bottlenose dolphins, we identify and count the number of echolocation bouts, burst pulse sounds, and whistles.

All cryptic species (e.g. alligators, manatees, right whales, various fish species, unknown sounds) are marked as either present or absent.

We determine if recreational boats or ships are present in each wav file.

We then use MATLAB to determine the sound pressure levels (perceived loudness) of each wav file over various bandwidths.

We also measure water depth and temperature continuously for each acoustic recorder, as well as salinity, pH, dissolved oxygen, and temperature at each station every month.

How far can we hear?

We are working on acquiring this information. Due to the complexity of how sound travels in water (sound propagation) – particularly within the complex topography of tidal rivers and estuaries – the true detection ranges of acoustic signals detected by our recorders are currently unknown. Each range is obviously a function of how loud each sound is at the source. The range can be estimated using cylindrical spreading loss models or through empirical measurements via playback experiments (e.g., Jensen et al., 2012; Simard et al., 2015). One study conducted in the West Florida Shelf that used DSG Ocean recorders (with similar hydrophone sensitivity of −186 dBV/μPa) found that the detection range of bottlenose dolphin whistles using a cylindrical spreading model was approximately 200 – 300 m (Simard et al., 2015).