I would like to get the ambient noise levels of a habitat that I have been monitoring for some time (monitoring birds, 0-16 kHz). For this, I want to calibrate my recorders and get their sensitivity and frequency response and then use my calibrations on the recordings to get to the noise levels.
However, I still didn't manage to come up with a workflow that would enable me to reproduce the sensitivity measurements very well. Does someone have an idea/solution to help me with :
- making sure that the recorders are all exactly at the same spot every time and facing the same direction (until now, attaching them to a tripod always gave rise to some variation in the direction the microphone was facing, even with a lot of care)
- reduce as much as possible the reflections from tripods around the microphone: what would be an appropriate distance between the loudspeaker and the microphone for audible sound?
- analysis: what would be an acceptable measurement error? let's say that I have a 3dB difference between two sensitivity measurements of the same microphone two weeks apart, is it fine? or should I aim for smaller differences?
Finally, is my workflow OK? or are long-term recordings too variable (due to e.g. temperature variation, battery level, etc.) to extract anything reliable?
Any experience/tips and tricks to do good and reliable microphone calibration are welcome!