There are a few different ways to remove background hiss/noise from your recordings. These are
noise removal features that are present in some recording programs,
noise gate, and
manual editing.
However, depending on your recorded material, you may be limited in which method you can use:
- If the noise can be heard while your recorded track is sounding (ie, you hear both together), then you are pretty much stuck using an actual noise removal feature to try to remove the noise.
- If the noise cannot be heard while your recorded track is sounding (your recording drowns out the noise so it can't be heard), then you are not limited by any method and can choose which ever you want to get the desired result.
Below I will list the pro's and con's of each method.
But before I begin, I must say that it is always best to make every effort to
fix the noise at the source. Try to track down what is causing the noise and see if you can fix it. These noise removal techniques should be used as a LAST resort as they all have their drawbacks that will mess up your audio in some way, shape, or form.
Noise Removal Feature:
Some recording programs (such as Audacity which is free) have a noise removal feature that removes the frequencies causing the noise/hiss. To do this you select a short section of the noise and there should be an option in one of the menus called "get noise sample" (or something similar to this) which will collect the sample of the noise. Next, select the whole track and choose the noise reduction feature. The noise sample is used in the noise reduction feature to remove only the frequencies where the noise is located.
Unfortunately, the noise usually covers a wide range of frequencies, so method basically takes out a large chunk of the frequency range. It can also cause some very strange artifacts when used heavily, so you will definitely want to experiment with the settings to find the best compromise. Sometimes the artifacts made by the noise removal is more annoying than the noise that it was trying to remove.
Noise Gate:
Some recording programs may have a noise gate as one of the built in effects. Even if it does, I would recommend first trying the
FLOORFISH from Digital Fish Phones (part of the fish fillets bundle). This is the best noise gate plugin I've used and it's FREE.
All the noise gate does is mute the volume when it drops below as certain value. So when you are not playing the noise gate turns down the volume so there is ZERO background noise. When you start playing the signal goes above the threshold and the noise gate turns your volume back up to normal. This provides no weird artifacts when the signal is above the threshold because it is only affecting the signal when you are not playing.
This however will not be very effective if you can still hear the noise while you are playing. As the noise gate turns on and off, the background noise will go in and out and IMO, this is more annoying than just letting the noise go throughout if it is very noticeable.
The only draw back to this method is the noise gate can (and likely will) reek havoc on any notes you hold too long. Normally (without a noise gate) when you hold out a note the volume will decrease smoothly down to nothing. With a noise gate however, it will very very choppy when it gets around the threshold volume. Because while your volume may be decreasing on "average", it will still have some fluctuations in the volume which can cause the noise gate to toggle "on and off" several times as the volume fluctuates above and below the threshold. While you won't be able to completely get rid of this, you can experiment with the attack and release settings to will allow for more time (while holding the note) before it starts toggling.
Manual Editing
This method takes the longest and can be quite tedious, but it can also provide the best results as you can customize the fade ins and fade outs specifically to each individual note. This method is the same as the noise gate in that it won't work if the background noise can be heard while you are playing. This is only to remove noise during "silent" parts.
This method is simple in concept, but as said above is quite tedious to actually do. Basically all you have to do is make an edit point on either side of the silent gap where the noise can be heard, and delete the section with the noise. Then add fades to the sections before and after it so that they flow smoothly and don't sound like they are getting "chopped off" when you delete the noise section.
You can also use this method in combination with the noise gate (letting the noise gate take care of most of the work) and only use the "hand method" to fix the parts that need it.
Here are some pictures to help illustrate the manual noise removal method.
NOTE: While I will be demonstrating this method in Reaper, since this is a general noise removal tutorial I won't go into the specific commands used in Reaper not all programs operate in the same way. I will however be adding another Reaper tutorial that will cover editing for those who are interested in Reaper.
First, locate the noise that we want to remove.
Place the cursor at the start of the noise....
...and drag a range until the end of the noise.
NOTE: As you will see below, you can make adjustments after the edit you do not have to set the range perfectly at the begging and end of the noise, just get it close and do your fine tweaking afterwards.
Now split on both sides of the range.
Delete the noise.
Take a listen to the edit and adjust the fade in/fade out as needed (way over emphasized to show what I did).
Remove the range.
You can also adjust the start and end of the audio clips as needed.
