Filtering in Bioacoustics
Pp. 302-335 (34)
Philip K. Stoddard and Michael J. Owren
Working in bioacoustics requires knowledge of filtering, which is the
application of frequency-dependent energy attenuation. General filter types include
low-pass, high-pass, band-pass, and band-stop versions, each of which involves
selecting a target frequency range, corresponding corner frequencies, and an optimized
combination of attenuation slope and pass-band ripple. Filters can be constructed in
either analog (hardware) or digital (software) forms, the former being necessary when
converting signals between these two kinds of representations. However, the latter are
more flexible, less expensive, and the more common when working with digital
signals. Readily available programs allow even novice users to easily design and use
digital filters. Filtering applications include removing various kinds of noise,
simulating environmental degradation effects, and searching for signals embedded in
noise. While easily performed, each of these applications requires some background
knowledge. There is also good reason to avoid unnecessary use of filtering, as it is easy
to create unintended effects. This chapter discusses these and other issues in the context
of the everyday work of bioacoustics.
Analog filter, Artifact, Attenuation slope, Digital filter, Digital
sampling, Gain function, Pass-band ripple.
Florida International University, Miami, FL 33199, United States.