Yes, a microphone attached to a tree can act as a vibration sensor, but with significant limitations.
- Contact Pickup of Vibrations – If firmly attached (e.g., with a solid mechanical coupling like a clamp), the microphone diaphragm can pick up vibrations transmitted through the tree rather than the air.
- Low-Frequency Sensitivity – Some microphones, particularly condenser or piezoelectric types, can detect low-frequency vibrations, which trees can conduct well.
- Reduced Airborne Noise – If you effectively muffle air-transmitted sound (e.g., using acoustic insulation or placing the mic inside an enclosure), then tree vibrations may dominate the signal.
- Designed for Air, Not Solids – Typical microphones are engineered for air-transmitted sound, so their response to solid vibrations is unpredictable and inefficient.
- Poor Mechanical Coupling – Even if attached, the microphone’s diaphragm isn’t optimised for solid conduction; it’s too small and too loosely coupled to the tree’s surface.
- Environmental Noise – Wind, rain, and other disturbances can introduce unwanted noise, making it hard to isolate meaningful signals.
- Limited Frequency Range – Vibrations in trees often include subsonic (below 20 Hz) signals, which most microphones aren’t designed to capture effectively.
- Contact microphones (piezoelectric transducers) – Specifically designed to pick up vibrations in solids.
- Geophones – If you’re interested in seismic-like vibrations.
- Accelerometers – If you need precise vibration measurements.
Verdict: It can work in a crude way, but it’s far from ideal. If you need serious vibration sensing, use a sensor designed for the job.