Interesting technical challenge from a pod-friend
Obviously, one edits with their ears, but a spectrograph can be enlightening.
A friend has been struggling with their audio quality as they embark on an exciting new project. They sent me a file which had a bizarre high frequency hum and on inspection in RX looked like this.
The mic in question is an Electrovoice RE320, a dynamic mic that cuts off at 18kHz, but as you can see there is strong signal even over 20kHz! It’s also very smooth the whole way to cut off with no bands suggesting resonance or reverb. This is very unusual
It’s been present in previous recordings from them, but not quite so egregious, well within listenable tolerances for a podcast. Their new product needs another level though.
For comparison, take a look at one of my recordings. Bearing in mind my microphone is a Samson Q2U, so like 20% of the price and includes USB and preamp circuitry, so definitely of lower quality.
The Samson has a 15kHz max frequency and you can see the drop off starts before then, from around 5kHz and carries on a little beyond 15kHz.
So, any guesses?
Take a minute….
Okay, when chatting with the friend it emerges that their apartment is awash with wifi signals. They are even sometimes aware of a high-pitched ringing in their home. So it seems like their recording electronics are picking up and recording electronic noise which is manifesting as this squealing hum.
So I did a bit of polishing and the results look like this.
The obvious thing is simply EQ’ing a bit of a curve into the high end and using a low pass filter at the top end to control the squeal. It needs some more work, but is already a major improvement.
A test for podcast editors and producers.
1) There’s something else distinctive about my friend’s recording. It made diagnosing the issue a little more difficult. Can you tell me what it is?
2) I made another creative choice that’s apparent in the final picture, can you identify it?