I’ve been using these filters for several weeks, but I’ve been looking forward to actually testing them to see if they’re actually doing anything.

I recorded some samples with and without the makeshift filter. I’ll be honest, there’s not a life-changing difference between the two. However, there is a small difference. The first two samples are of me singing a few lines.

Here they are:

Vocal WITHOUT Filter

Vocal WITH Filter

Obviously, neither vocal sound is all that bad. In fact, I would argue that on the quieter parts there’s pretty much no difference.

(click to enlarge)

However, the vocal recorded with the filter sounds a bit tighter to me on the louder parts. On the words “like” and “colors” you can definitely hear the sound my voice bouncing around the room.

While the first set of samples is a bit subtle, the next two were a bit more revealing for me. All I did was crank up the gain on the preamp and simply recorded the mic for around 15 seconds — once with the filter, once without.

Here they are:

Silence WITH Filter

Silence WITHOUT Filter

The best way to listen to these is to open them up and switch back and forth between the two while they are playing. You can do this in QuickTime by just selecting back and forth between the windows. Or you can just import them into a DAW and solo each one.

As you can hear, the filter does nothing for the low frequency noise in the room. However, it does roll off quite a bit of the high frequency noise. I measured the two waveforms and found that the recording with the filter is 0.6 dB quieter than the other.

That’s certainly not a huge difference, but once you add compression to the vocal and the entire mix, this noise will be made louder. Cutting out the high frequency “hiss” could really make a difference in the sound of a final mix.

Conclusion
As I recorded these samples, I was a little disappointed that the differences weren’t more obvious. But as I thought about it, it makes perfect sense. Foam doesn’t do anything to stop low frequencies. It’s a high frequency absorber.

Even though the results won’t take your breath away, I decided it would still be good to post them. After all, this is real life. Sometimes you make changes to your studio that don’t improve things all that much. Or maybe the improvement is a subtle one.

Either way, until I build some really nice gobos for myself, these little foam filters will get a lot of use.

 
Joe Gilder is a Nashville-based engineer, musician, and producer who also provides training and advice at the Home Studio Corner. Note that Joe also offers highly effective training courses, including Understanding Compression and Understanding EQ.

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