Song Meter SM4M User Guide Supplement
3 SM4M Specific User Guide Notes
Wildlife Acoustics, Inc.
page
19
3
SM4M Specific User Guide Notes
This chapter contains specific notes relating specifically to settings or functions
that differ from those as described in the SM4 or SM4BAT User Guides.
3.1
Setting Gain
Acoustic Gain (in Audio Settings section of SM4 User Guide)
The SM4 module has a gain range for the Left and Right channels of 0 dB to
59.5 dB in 0.5 dB steps. 12 dB is a good starting point for recording marine
mammals or quantifying lower noise levels with the
Acoustic Hydrophone
. If
the unit is near louder animals or anthropogenic noise sources, 0dB might be
more suitable to avoid clipping. Test recordings are encouraged to select the
optimal gain.
For the High-SPL Hydrophone Option when combined with the standard
hydrophone, 0dB gain on both channels will assure that sounds can be recorded
from about 78dB SPL all the way up to 240dB SPL. There is no reason to use
additional gain as both hydrophones are fully covering the available dynamic
range. Further gain will not allow recording quieter sounds due to the self-noise
of the standard hydrophone.
Preamplifier Gain (in Audio Settings section of SM4 User Guide)
This gain only affects the built-in microphones of the SM4 unit and it will have
no effect on the SM4M.
Ultrasonic Gain (in Audio Settings section of SM4 User Guide)
The SM4BAT module has two gain settings only, 0 dB or 12 dB. A good starting
point for the Ultrasonic hydrophone is 12 dB. This will be optimal for recording
distant marine mammal echolocations. If the unit is very near the marine
mammals, the lower gain setting might be better. Test recordings are
encouraged to select the optimal gain.
3.2
Deactivating Scrubber on Ultrasonic Models
The SM4M includes a file scrubber, carried over from the SM4BAT terrestrial bat
recorder, which tries to determine if a triggered recording contains bat
echolocations and deletes the file automatically if it does not. Since this is not
well tested on dolphin echolocations, you should turn the scrubber off if you are
