Distorting Voices – Muffled Neighbours

December 29, 2017

A couple of weeks ago I wrote about distorting voices to sound like olde-timey phonograph recordings for my recently released Sleuthhounds: The Yuletide Tail computer game. That wasn’t the only dialog distortion to make it into the game as there are a couple of places where Homes and/or Ampson are hidden behind walls and so need to have their voices sound muffled.

For the muffled voices I had originally considered various options to actually muffle the voices during recording. However, the more I thought about it, the safer option seemed to be to get a clean audio recording and then muffle it with editing software afterwards.

As with the olde-timey dialog lines, I started by cleaning up the recorded voice lines as best as possible by filtering out background hiss, voice pops, and the like. Such a clean line sounds something like this:

As before, I used the GoldWave audio editing software to then start playing around with the sound of the voice. The tricky thing here was that I needed the voices to sound muffled, as if a given character were speaking from another room, but they still needed to be intelligible.

After a bit of playing around, I found that GoldWave’s low pass filter was the place to be. A low pass filter, as the name indicates, only allows the low end frequencies of a sound through and chops off the higher frequencies. After a few experiments I settled on a lowpass cutoff frequency of 2800 Hz. This distorted the lines to sound like so:

I felt this nicely took off the bright, higher frequencies of the dialog lines without distorting the words being said beyond the point of recognition. When played back in the game, with the appropriate character hidden from view, it helps to accentuate that the character is indeed speaking from another room.

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