Installation protocol: sound recorder

The point of a protocol is comparability. Two recorders installed the same way in two places hear the same fraction of what is there. Deviations are fine; write them in the device notes.

Placement

• Height 1.5 to 2 m on a post, fence pole or small tree (Kit A and B). Bats (Kit C): 3 to 4 m, microphone pointing into the open, 1.5 m clear of foliage.
• Microphone horizontal, facing the open habitat, never into a trunk or wall. Detection ranges are up to 52% larger in open land than in forest and fall by up to 15 dB at 40 kHz when the microphone faces the wrong way.
• Not within 30 m of a road, pump or building unless that noise is what you want to measure (it is counted as Autonomy signal either way, but it masks birds).
• Spacing 250 to 300 m between recorders in open land (one per 6 to 9 ha). One recorder at the edge covers a 3 to 5 ha meadow. For bats, 150 to 200 m along hedgerows, tree lines and water.
• Record the position with your phone's GPS and put it in the device registration (lat, lon, heightM).

Schedule (Kit A, offline)

• Birds: 1 h before sunrise to 3 h after, plus 1 h around sunset, at 48 kHz.
• Summer addition for crickets and frogs: 22:00 to 02:00.
• Bats: sunset −30 min to sunrise +30 min, trigger-based, 256 to 384 kHz.
• The AudioMoth configuration app computes battery life for the schedule. A dawn/dusk schedule runs 6 to 8 weeks on three lithium AA cells.

Kit B (connected) runs continuously.

Weatherproofing

• Kit A: the IPX7 case with a Porelle membrane vent; a silica sachet inside; lid seal checked at every swap.
• Kit B: PUC in the shade of its panel, panel facing south at 30 to 45 degrees, router in a barn with an external antenna if the field is more than 30 m away.
• Cable lock through the case loop. Recorders do get stolen; a €10 lock halves it.

Maintenance

What to write in the device notes

Mount type, direction the microphone faces (compass), habitat within 50 m (hedge, ditch, crop), nearest noise source and distance, schedule used. These are read by verifiers and by anyone comparing places.