Understanding the Noise Floor!!!

Kenny’s Tip of the Day - Understanding the Noise Floor!!!

The Noise Floor is defined as the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system, where noise is defined as any signal other than the one being monitored.

In other words, if you are recording your instrument, whether it be a voice, acoustic guitar or a clarinet, there is going to be unwanted sound that gets mixed in with the desired signal. Your microphone picks up everything.

It could be the air conditioning in your room, a fan, outside traffic, the ambience or reverb of your room and even the hiss that the electronics in your mic preamp (audio interface) produce. All of these things create noise and the level where this noise sits is called your Noise Floor.

So why am I writing this? Everyone knows to avoid recording noise. If they can. That is true, but there is a common misconception I see floating around and I thought it was worth clearing up. That is that we can lower this Noise Floor by changing the Gain of our Mic Preamps.

Sorry to say, but this technique will not work. In many situations, the Noise and the wanted signal are connected. They are tied together. And they can’t be disconnected unless you manually move some things around. Or change the performance.

One thing I read recently was this idea that you can record quietly (and therefore record less noise) and then bring up the audio file in your DAW so it’s now louder but the noise is not. That defies the laws of physics.

Let’s say that your instrument is producing sound at +10dB and the noise in your room is producing sound at +2dB. Then the distance from your wanted sound to your unwanted sound is 8dB. This is known as your Signal to Noise Ratio.

So if you boost this recording with your preamp by say 50dB, what do you end up with? The instrument is now 60dB and the noise is now 52dB. The Signal to Noise Ratio hasn’t changed at all. It’s still 8dB. Do you see where I’m going with this? You can’t do anything to change the current situation by using just volume adjustments. The instrument and the noise are connected. So recording louder or softer is not a useful solution.

But there are many things you CAN do. When dealing with fans or air conditioning, you can turn those off when recording. I have a ceiling fan that I use but I set it to “low” whenever I’m recording voiceover for my tutorials. This reduces the signal to noise ratio as I have reduced the fan noise, but my voice is still the same level.

You can also treat your room to keep some of the neighborhood sounds from leaking into your recording space. Again. Reduce their level while keeping your instrument or voice levels the same.

Another important solution is Mic Placement. The closer your instrument is to the mic, the louder your instrument will be. While the noise level in your room will stay consistent. So we’ve again changed the signal to noise ratio. We raised the signal as compared to the noise.

The volume of your instrument is also an important factor. While you usually aren’t going to tell your singer to sing louder you can make a guitar amp louder if noise is an issue. Or raise the level on your Hammond Organ. This again will make your signal louder, while the noise floor has stayed the same. You can now turn down the preamp on your mics and the noise will be quieter in relation to the desired sound.

Microphone Choice also plays a part. Some microphones (called omni-directional) pick up sounds from all sides of the mic. This is great for capturing the ambiance of a room more effectively but also brings up the noise. If your instrument is placed on only one side of this mic, it will be picking up a lot of unwanted signal. Choosing a Cardioid mic (which only picks up sound from the front and rejects sound from other sides) is a much better choice in a noisy environment. Especially for quieter sounds like vocals or acoustic guitar.

After the recording, you can employ such solutions like a Noise Gate, which will turn off the audio when the instrument isn’t playing. This can be very useful for things like vocals and drums but you also want to keep in mind that a noise gate only turns off the noise when the instrument stops playing. So you haven’t actually changed the noise floor. It’s still there and at the same ratio. You just don’t notice it as much as it disappears during the spaces in the performance.

There is also some very good noise reduction plugins that will capture the noise and analyze it so it can be reduced even while your instrument is playing. REAPER has a plugin called ReaFIR (Free) that does this very well. This can change the tone of your recording so you do want to monitor the sound change and use it sparingly but this is a very effective way of reducing noise.

I should also mention that an enemy of reducing the noise floor is a compressor. A compressor works by bringing up the volume of quiet parts and reducing the volume of loud parts. It’s very useful for creating a balanced instrument level but it can wreak havoc on a problematic noise floor. It raises and lowers the noise floor making it more difficult to use noise gates and noise reduction software.

For this reason, I would hesitate to use a compressor while recording (printing the effect) unless you know for sure that your noise floor is low enough for it not to be a problem. You can always use a compressor AFTER the solutions I mentioned and it will be more effective in that position. You can however just monitor with a compressor and not record the result at the time of recording.

If you’d like to learn more, check out all of my videos over atwww.groove3.com

I hope this message finds you well. Kenny Gioia