manatee vocalization

Living in a Noisy World

So how do scientists study sound and determine what is noise and what is an animal?

First, scientists use microphones or hydrophones (which is just an underwater microphone) to record vocalizations of their chosen species. Below is an image of a hydrophone setup used to record sound underwater.

hydrophone
Hydrophone setup

One of the ways scientists look at what they recorded is to use a spectrogram. A spectrogram provides a graphic image of sound. An example can be seen in the image below. The horizontal axis is time and the vertical axis is frequency.

manatee vocalizations
Spectrogram of manatee vocalizations

This image is an excellent example of what we scientists call a high signal to noise ratio.  What this means is we can see the image rather well and there is not a lot of noise in the signal.  Here is an example of a sound that would have a low signal to noise ratio.

noise
Noisy spectrogram

The animal vocalization is outlined in red but is buried in all that noise (in this case ,its boat noise). Scientists can measure this noise, determine how loud it is and what potential effects it could have on animals.

We study manatee vocalizations and sometimes record sounds that are not manatees. This can be biological or ambient noise and are sounds that are made by other animals and the environment. In the following video, we show you vocalizations of manatees and other sounds we recorded with their respective spectrograms.

Studying the sounds animals produce and the noisy environments in which they reside can be interesting as well as challenging. Next time you are out and about, listen to your environment and determine what is noise and what sounds are important to you.