25 Tips on Reducing Noise

By: Troy Woodfield

This article contains various tips on how to remove 
unwanted “noises” from your samples. For example: Hisses, 
hums, unexplained explosions, snaps, crackles and pops.

You will notice that this article is entitled: “Reducing 
Noise” and not “Eliminating Noise”. This is because there 
is always some degree of noise in a recording. While there 
are expensive sound reduction tools which will do a better 
job, a lot can be done with a simple PC and appropriate 
sound editing tools.

When you record a sound on your sampler, you are really 
capturing variations in air pressure. A microphone is 
used to capture these changes in air pressure and turn 
them into rising and falling voltages. Next, the sound 
is converted from analogue to digital data, so we end up 
with a digitised waveform. At all stages of this journey, 
there is opportunity for unwanted noise to gatecrash your 
party and ruin your tracks. 

Below are several tips on how to reduce noise.

Tip 1

Minimise the amount of electrical circuitry in your studio (or bedroom!). Why? This reduces the signal path, which in turn reduces the amount of potential exposure to noise.

Tip 2

Poor cable connectors can be a source of noise. The standard trouble-shooting approach is to replace various cables and/or connectors and observe how this affects the noise-ratio. If possible, avoid using connectors and instead utilise cables with the correct plugs at each end. Remember: Each time you remove a connector, you are removing a potential “point of failure”.

Tip 3

Power cables are another source of electrical interference, which can introduce noise, often in the form of a hum. For this reason, ensure your power cables are well away from cables that carry your sound signals. If you have no choice but to make the cables cross, place them at right angles at the point of intersection. This reduces the overlay of electrical fields.

Tip 4

Power transformers should be strategically placed, as they have the same noise producing capabilities as power cables. For example, perhaps you have a ZIP-Disk? If so, ensure the power box is not beside the cables that carry your sound signals. It is easy to simply push all the cables and transformers under your desk, without realising the possible impact on your sounds.

Tip 5

Once you have positioned your signal cables, power cables and transformers correctly, you can tape them into position. ...If you can be bothered! This is probably only a good idea if you don't move things about much.

Tip 6

If you are a technical type and often remove the case of your computer, remember to put it back on. The case provides protection against electrical interference. The same is true for other electronic devices. In addition, the case helps muffle the sound of the computers’ fan, which might otherwise appear in the background of your recordings.

Tip 7

Use Plug-ins. Sound editing software, such as Sound-Forge include “sound removing” functionality which helps remove noise from your samples. This functionality may be built-into your sound editing software OR you can obtain additional DirectX plug-ins, if your [program supports them. Various sites on the Internet offer free DirectX plug-ins for removing different types of noises.

Tip 8

When you record a sample, there is often noise at the beginning and/or end of the recording. This noise is actually present though out the sample, but only becomes noticeable when the sound stops playing. You can choose to keep a “tail” on the end of your sample, to produce a lo-fi feel, but sound-editing software allows you to select and delete sections of the sound, such as the tail, to remove this noise. Alternatively, your sampler may have a TRIM function that does the same job.

Tip 9

Some sound editing tools (such as Cool-Edit) allow you to create a profile of noise. That is, you specify a section of your sample that has only noise (ie: Typically at the start or end of the sound, when the instrument isn’t playing). This section becomes your “Noise Profile”, which can then be used as a filter to remove the noise from the sample. If you are not entirely happy with the results, you can try it a second time, perhaps with different levels of precision set. Once you are happy with the result, you can trim the tail off the sample.

Tip 10

Cheap soundcards produce unwanted noise, as they are affected by the electrical internals of the computer. There is little you can do about this, except research and choose your soundcard carefully. Check with newsgroups / mailing lists / FAQS / Friends to see which card cards will perform at the level you require.

Tip 11

All microphones are not created equal. Some microphones are suitable for low-noise recordings, while others are specially designed to be sensitive. You can protect against unwanted noise by fitting shock-guards to your microphones.

Tip 12

“Swirling” is an effect caused by excessive microphone movement. It is particularly noticeable when using directional “shotgun” type microphones. The movement results in fluctuating volume and possible wind noises. This problem is almost impossible to undo. Therefore try to ensure you are in position before you start recording. This removes the need to walk around.

Tip 13

If you are working with analogue recording devices, remember that each time a recording is copied, the amount of hiss increases. Noise reduction schemes, such as Dolby can reduce hiss, but on the original recording only.

Tip 14

Programs such as Cooledit use filtering to remove noise. The basic principle is that low pass filters remove shrill tones and allow the low frequency sounds to pass through. High pass filters remove the bass tones and allow the high frequency sounds through. This filtering affects both the noise and the sound signal that you are attempting to clean.

Tip 15

If you have cheap headphones, you may experience “Headphone leak”, whereby the sounds escape from the headphones and become unwanted noise in your recording. The solution is easy: Get new headphones OR turn the volume down or off when recording.

Tip 16

When you apply compression to a voice, for every Db of compression you apply, the noise during quiet sections is increased by the same amount. Ie: Start with as little noise as possible.

Tip 17

Ask your vocalist to stop humming.

Tip 18

If you have a ZIP-Disk, you may experience the “Click of Death” (COD). This is an often referred to phenomena, whereby a “click” sound appears in sounds stored on a Zip-Disk. Many people are sick of this topic appearing on various news-groups. So if you’re interested, have a read: Click of Death Info This site includes a free software utility to test whether you have the COD problem.

Tip 19

General noise can be hidden using gates and expanders. However, they cannot do magic, so if the noise is too high, the sound of it turning ON and OFF can become very noticeable. Try increasing the gate-release time to reduce this.

Tip 20

This is an obvious tip. When you record live sounds, be sure to eliminate unnecessary background noise. For example, turn off unnecessary equipment, close all the doors and ask those present to remain quiet and still. Even small movements, squeaking of chairs, sniffing or rustling of papers can be captured unintentionally. Consider doing a silent count-in with your fingers, as seen on television, so everyone knows to be silent. However, be warned: You WILL look like a complete plonker.

Tip 21

You can use EQ settings to reduce noise. For example, if you have a hum at 50 or 60Hz, filter it with EQ on a very tight bell curve or shelve the EQ off at around 100hz. (Tip from: Geg Hopkins). However, remember that you will be affecting not just the noise, but also the sound as well. What matters here is signal/Noise ratio. Ie: We want to lose more noise then signal.

Tip 22

Don’t eat excessive amounts of baked beans.

Tip 23

To the best of my knowledge, there is currently no good, affordable tool which can remove a vocal from a recording. Geg Hopkins wrote to the Akai list, stating: "This is fantasy. Call Scotland Yard, they have High end, low quality result forensic software. There are cheap Karaoke (whatever) machines around that do it..they do it by Phase. Not very successfully. If you get some sophisticated software running like the CEDAR machines which are heavy, about $14,000 or more, they can help, the PC versions are about half that! Even then, the result is very tunnel effect. Sound Forge and syntrillian... yeah, but again crap! Best is to run your track through a board (mixer). pan both channels to mono and then reverse one phase on one channel. Providing the vocals were put in the mix fairly central, you will get rid of some of it. If the vocal has reverb on it.. you will be left with the reverb sound on top of the back track. If you are trying to do it the other way around, LIke only be left with the vocals.. No can do! Basically, not possible for high quality results, that I know of.. Maybe someone knows different!" (End of quote, thanks Geg).

Tip 24

If you are experiencing clicks in your samples, it may be due to your samplers memory. I haven't experienced this myself, but others have writen to the AKAI list, stating that the unwanted clicks disappeared when they replaced their Samplers RAM. You can test your RAM by removing it and working with just the on-board memory. If the problem goes away, then the RAM SIMMS are at fault. Of course, remember that you may be breaking your warantee by opening the case. Avoid mixing different types of memory. If you're dealer has given you mismatched memory SIMMS, I'd ask them to exchange it.

Tip 25

If there is a click at the start or end of your sample, you can often remove it by changing the samplers START and/or END points for that loop. What percentage of the above tips did you already know about? 0-9%: You do not create music. You produce noise. Sorry, what was that? I can’t hear you? 10-89%: Well done! I hope you got one or two new ideas from this article. Even if they do not work, it will make you feel good about yourself and your set-up. 90-100%: You are very good at reducing noises ...but probably do not have a girl friend. - Troy

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