Bioacoustics - lots of Bands, no Trombone.

Meatloaf references mean I'm both old AND nerdy.

When you study acoustics and sound, you'll often hear the word "band" used in various ways.  Bandwidth, narrowband, broadband.  It may sound like we're talking about the size of a musical band (this is acoustics, after all).  However, in this case band refers to sound frequencies, not the waist-size of the lead singer.  Meatloaf has nothing to do with it (although, compared to modern fitness standards, 1980s Meatloaf is looking pretty svelte to me these days).

In Acoustics terms, "band" refers to a span of frequencies.

Sound frequency is a measurement of how often the soundwave repeats itself, like so:

 

Each of these waves represents one sound frequency, like one key being played on a piano. If we were to play multiple notes on a piano at the same time, the bandwidth is measured as the difference between the highest key/frequency and the lowest key/frequency.  Here are some extreme examples from hydrophone recordings:

Broadband.  This is a spectrogram of a hydrophone hitting the side of a boat as it comes out of the water.  Frequency is on the y axis, time is on the x axis, and the more "hot" the color is, the louder the sound.  These sounds are considered broadband because they contain a large range of frequencies. On a spectrogram, the broadest band is a vertical line across the entire screen. The width of the vertical line will vary depending on the length of the sound.

Narrowband: This is the spectrogram of a dolphin whistle. Axes the same as before.  As you can see here, the whistle only uses a few frequencies at a time, so it looks like a narrow, almost horizontal or diagonal line.

What about this killer whale call, with a bunch of harmonics? On one hand, it's made up of a bunch of narrowband signals, but on the other hand, it covers a wide range of frequencies.  It's a hard call, and probably depends on the context and the scientist.

So now when you hear someone use the word "band" in acoustics, you'll know that they are referring to a range of frequencies.  For example:

Bandpass filter - Allows a specific range of frequencies pass though a sound filter

1/3 Octave Band: A range of frequencies that is defined as 1/3 of an octave

One Man Band: What a grad student in acoustics looks like when they are trying to learn programming, engineering, and statistics all at the same time.

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