Drastic indeed. I'd think a piece of tape and some dense foam would do nearly as well, and leave the mic available if ever wanted to use it again.
That, and willful damage of the iPad might void your warrantee, just bit.
That's an excellent idea! I've got some dense closed-cell foam - and hey, everybody has gaffer tape, right
OK, I've tried a rough and ready experiment on blocking the internal microphone with some closed cell foam. It really helps!
I cut a small cube approximately 5x 5 x 5 mm and taped it over the mic input hole with gaffer tape. The difference was considerable, although you could still just hear the finger clicks I was using as a rough test. But without the foam the finger clicks were loud enough to clip the input of the track.
Now I've got no data on the dB difference between the two tests but the difference was huge. All the tests were done in MultiTrack Daw, with the input set at 0dB. I might try using a metronome to try to quantify the difference more accurately, and upload the results to SoundCloud so you can judge for yourselves.
And this wasn't anything special in the foam - it was just some stuff I had laying around for another project. Nor was the gaffer tape anything special - in fact it's really cheap stuff, Norton Bear Brand, which is about as cheap and nasty as you can get.
I'm going to see if I can get some really high quality heavy duty acoustic closed cell foam, and my plan is to glue it over the mic hole using silicone sealant. I'll have to be really careful to make sure that the sealant doesn't get into the hole itself in case I ever want to remove the foam.
Of course, for a more permanent (and no doubt more effective method) you could also inject the mic hole with silicone sealant - a hypodermic syringe would probably do the job well. But I wouldn't like your chances of ever getting it out again.
Hope that this helps other people with this problem!