TiTLEY Scientific CHORUS, User Manual

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What is the difference between full spectrum and zero crossing?
There are two main recording formats for ultrasonic files, zero crossing analysis (.zc) and full
spectrum (.wav). Acoustic files are only available as full spectrum. Full spectrum records the
full spectral information within a sound file, just like a music file. Whereas zero crossing
analysis renders the spectral information down into a series of time vs. frequency dots.
Full Spectrum Zero Crossing
The advantages of full spectrum include the ability to see intensity, harmonics, multiple bat s
calling at the same time, and faint bat pulses during high ambient noise. The disadvantages
of full spectrum are that they are much larger files (typically 6 times the size of a zero crossing
file), they require more processing power to record, and are slower to render on a computer
for post-recording analysis. The advantage of zero crossing analysis is the small file size, so
memory space is not an issue, and many published guides to bat calls are based on zero
crossing analysis. The disadvantages of zero crossing are that spectral information is lost
(which may be helpful to species identification), and that in cases of high frequency ambient
noise (e.g. insects), bat calls may not be recorded fully.
It is important to note that full spectrum files can b e converted to zero crossing post-
recording, but zero crossing files cannot be converted to full spectrum. Deciding which
recording format is best will depend on the aims of your survey and the recording
environment.
How far away can a bat be detected usi ng the Chorus?
Detection distances will vary with frequency and loudness (amplitude) of the bat calls,
atmospheric attenuation, and the directional characteristics and sensitivity of the bat
recorder. It will also be affected by the amount of structural c lutter (obstacles such as
vegetation) which can block the path of the signal.