- Tom Kelly
Room Reverberations and Why It'll Ruin your Mixes, your Edits, and your Podcast
We all know that reverberations are bad for a podcast, but very few people understand JUST how badly it affects your sound.
In audio production, we rely on our environment to shape our sound. I often say you can think of your voice in podcasting like water, it'll take the shape of your room. In music production, rooms will often be engineered specifically for the room sound and the reverberation, but most bedrooms, basements, and closets we are recording our podcast in were build with no mind to the acoustics of the space. Generally the acoustics will be terrible, and therefore need to be controlled with some kind of absorptive materials.
You'll often see in Facebook group and online forums to tack a bunch of 1" foam panels to your wall, throw some carpet all over your reflective spaces, or line up 1-2 pillows behind your microphone, but you'll find throughout this video that while those methods MIGHT do SOMETHING to your audio, it can often be more harmful than anything.
1" foam panels, carpet, pillows, window drapes, etc are all very thin and not very dense material, so what will end up happening is you'll absorb some of the very high end frequencies, but it'll allow all those lower frequencies, 1kHz and blow to pass right through. Pair that with a small room and standing waves that are similar to fundamental frequencies of the human voice and you'll find yourself with a podcast that sounds like it's being pumped through 2 15" subwoofer in a Caddy on spinning rims. You're essentially EQing the high end out of your reverberation, and these early reflections sum themselves together with the source recording (ie your voice) and causes a REALLY boomy sound that's terribly hard to get rid of in post, and it a monster to edit around. While proper and effective acoustical treatment techniques are a video for a different day, it's important for you to understand how damaging room reflections and reverberations are to your podcast.
The graph below depicts the Noise Reduction Coefficient, or NFC of 1", 2", and 3" foam made from the same manufacturer. On the y-axis we have the NRC which ranges from 0.0 to 1.0, and we can think of .2 as 20% absorption and .8 as 80% absorption. Then more depth we have, the better these materials will absorb lower frequencies because low frequency sounds have a MUCH longer wavelength and require a deep and more dense material to capture its longer waves.
The human voice holds a lot of power in its first fundamental, around 150Hz, and we can see 1" foam does virtually nothing in that frequency range. There's a HUGE different between 1" and 2" foam, but we can also see that 3" foam is absorbing about 80% of those really damaging frequencies, and as explained in the video, we can run into some disasters if we're not absorbing enough of that 125-250Hz range.
In the video below, I very thoroughly run through what reverberations are, why your carpet on the wall isn't doing enough, and how difficult (see also: impossible) it is to edit around long reverb times, and how damaging it is to your sound as a whole.
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De-esser Vocal Rider
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Microphone: Shure SM7b
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