It's almost certainly the case. In my mic measurements, I wrapped the mic in plastic and duct tape, then buried it in several hundred pounds of a sand and cat litter mix. "Soundproof boxes" generally aren't, especially at low frequencies.
I liked the laser jig. My method was a lot cruder, a hanging ping pong ball, moved away during measurement.
Thank you for providing me with the idea to make a sound insulation box.
I couldn't use the sand to resume this measurement, but instead I did the best I could.
I made a small box using 60T MDF (30+30).
And I added sound absorber.
And I wrapped this box around in a blanket to put it back in a big box.
Finally, I put it in a box and sealed the entrance.
This box has become a pretty good piece of equipment, at least for me.
I used the SPL calibrator for all microphone measurements.
It is impossible to accurately check the performance limit of my SPL calibrator.
At least the relative comparison using the Earthworks M30 data sheet is as follows:
There is little difference between the official datasheet and the DIY measurement data.
Let's get down to business.
M23
M23R #1
M23R #2
M30 #1
M30 #2
M50
One curious thing is that a small amount of distortion was found in all M23 microphones (including R).
And coincidentally, I was able to measure the Minidsp UMIK-1 and UMIK-2 microphones at the same time.
You can see that UMIK-2 has the smallest self-noise.
All measurements are now complete.
Each microphone goes back to its owner's arms.
It's a clear limitation that this is just a relative comparison in the same environment, but I hope you enjoyed it nonetheless.