I build a simple measurement-mic with a Panasonic WM-61A (or copy ?) from ebay.
It works, but I have no way of knowing whether it has a flat freq-response.
So, airflow/wind is white noise and if averaged over (long enough time) it should measure flat right?
Maybe a low-noise 12V fan and some ducting could provide a wind-source?
Sounds too simple, but whats the flaw?
Kind regards TroelsM
It works, but I have no way of knowing whether it has a flat freq-response.
So, airflow/wind is white noise and if averaged over (long enough time) it should measure flat right?
Maybe a low-noise 12V fan and some ducting could provide a wind-source?
Sounds too simple, but whats the flaw?
Kind regards TroelsM
Check out my response here: https://www.diyaudio.com/community/...n-ideas-with-no-reference.385568/post-7008126 The B&K instrument response is shown and its not flat. It is pretty good however. Various aspects will alter the response that relate to turbulence and fan blade shape. You may also have resonances to deal with.
TroelsM, one option is to borrow or buy 2nd hand at least one calibrated mic and do some comparison spectrum sweeps. That obviously would need some test setup effort, but that is the path you appear to may have take anyway. Comparison testing of uncalibrated devices also relies on periodic testing (ie. set up at least two WM-61A measurement mics, and keep one in controlled storage to act as a future comparison) - although there will always be some risk of devices deviating in a like manner - but at least you then have better confidence that your test mic hasn't deviated over the coming weeks/months/years.
I haven't gone down this path yet, but do have 5x WM-61 capsules, and two 2nd hand ACOP polarised mic and combo preamp units plus interface that I was going to use for comparison testing, as the ACOP mic's have datasheet very flat frequency responses, and I have a Cirrus calibrator for 1/2" instrument mics to add in some further comparison. Of course if the various responses deviate too much from each other then you won't have much confidence.
I haven't gone down this path yet, but do have 5x WM-61 capsules, and two 2nd hand ACOP polarised mic and combo preamp units plus interface that I was going to use for comparison testing, as the ACOP mic's have datasheet very flat frequency responses, and I have a Cirrus calibrator for 1/2" instrument mics to add in some further comparison. Of course if the various responses deviate too much from each other then you won't have much confidence.