It may seem odd that we have to refer to noise as an integral part of musical compositions and/or recordings. But that is how it is: noise is absolutely tied to music and to sounds. Where is the difference between a noise and a musical sound? We could define noise as those sources, with enough sound pressure to become audible, that are foreign to our intention; in other words, unwanted sounds.

Obviously, noise tends to follow us (musicians) wherever we go (and I'm not talking about the neighbors who consider our mastery to be noise). Both live and in the studio we have to pay close attention to this aspect to achieve the best definition and avoid distracting our listeners with unwanted sound sources that muddy our performances and turn them "gray."

If it is important live, in our studio it will be even more so. Live sound is "thicker," and the visual appeal, together with the rougher definition of the sound, makes noise go more unnoticed (which doesn't mean it shouldn't be dealt with). In the studio, however, any unwanted sound source muddies and disturbs in a considerably noticeable way, especially bearing in mind that if we store a small amount of noise on every track we record, we will accumulate a number of small signals that will eventually add up in our final mix and production, becoming a "significant" hum.

It may seem somewhat obvious to you, but I think it is an important enough subject to be covered in one of our chapters, since there are classifications of noise and specific methods for eliminating it, which I describe here and strongly recommend for achieving better results in our recordings.

Classification of noise
A first classification, according to sound pressure level:

- High intensity (> 90 phons): very annoying noises that must be eliminated
- Intermediate intensity (between 40 and 90 phons): bearable but annoying noises
- Low intensity (< 40 phons): almost physically imperceptible but recognized by our psychology.

- Noise according to its nature:
- Background noise: generally the combination of several nearby or distant sources.
- Random noise: fluctuating noise.
- White noise: noise that affects a large number of frequencies evenly, constantly and almost symmetrically.
- Continuous noise: noise that, measured in octave bands, shows no fluctuations over time
- Constant intermittent noise: like the previous one, that is, constant but with unmeasurable interruptions.
- Periodic noise: noise with periodic interruptions.
- Repetitive noise: noise with repeated impulses.
- Pink noise: like white noise but with a constant slope of -3 dB

Noise in "everyday language"
It may be useful to translate all these noises into somewhat more "homespun" terms, with examples of the most typical hums and sources in our "home" studio.

Among the most common elements, most of them described in this section, we will find elements of our studio that are generally the cause of most noise.

As I said in the opening paragraphs, it is essential to be especially careful when recording, taking as many precautions as possible to reduce noise on each track. Often a little noise goes almost unnoticed and is let through, which in the end means our session will contain the sum of all those little hums, which will end up "blatantly" present.

As I suppose you know, most unwanted sources will occur mainly in our audio recordings, since MIDI is generally silent.

The most dangerous sources will be:
- Our computer monitor. Enemy number one, which has the constant "bad habit" of ruining our recordings by emitting a "repulsive" amount of unwanted sound signals in combination with other devices. Among the homemade solutions, we can first switch off the monitor right at the moment of "recording," or second, move the source that conflicts with the monitor as far away as possible (at least during the recording stage): mics, guitars, etc.

- Effects processors. Especially for guitar: boosters, tubes, gain, distortion, sometimes even flangers, choruses, delays, etc. Normally these effects, added to the noise of the amp + the mic and ambient noise, generate enough noise to ruin any recording for good. Logically, everything will depend on the quality of our gear, since manufacturers keep improving and solving these problems better and better in the high-end versions of our "studio appliances."

In any case, the electric guitar is a close friend of noise, especially when we want real sounds (and not "cheesy" ones) and avoid the sacrilege of running it straight into a line input. Forgive me, readers who like to record guitars direct, but the sound you get grates on my particular ears.

I want solutions...
My recommendation is to have a good preamp or a good effects processor with a variety of amp simulators. The results are excellent. This way we avoid mics, noisy amps, etc., making it feasible to record the instrument direct, eliminating noise and complications without losing the power and sound of a well-amplified guitar.

We can also take the measure recommended in point a), that is, switch off the monitor momentarily while recording guitars with heavy distortion.

- Power supplies and electrical gadgets. This problem is relatively easy to solve:
Preferably use the original power supplies for each device, those specially designed by each manufacturer, avoiding "dollar store" adapters, which tend to give us an open bar of noise.
Keep transformers and power supplies as far as possible from the recording sources, the monitor and the multi-effects units.

- Cabling. It may seem ridiculous to you, but I remember the last concert I attended, where there were a couple of battle-scarred cables (you could tell at first sight), and the guest artist (performer) lost all his feeling while playing because he was really uncomfortable with the noise, spending the whole concert worrying about the unbearable noise instead of giving his all on the instrument.

Getting back to our studio, sometimes a slight "botch job" in our connections (say, a homemade splice, etc.) seems to work fine, with no noise and no problems. However, this is another source that will generate unwanted signals, because as our studio grows, the tangle of cables gets bigger and bigger, and these temporary fixes fill our cabling system with "wounds," which in the end makes it absolutely impossible to locate where that horrible hum is coming from, the one singing "raspy" backing vocals behind our lovely singer.

Solution: I recommend going to your usual supplier with a list of all the connections you need for your studio, spending five or ten thousand pesetas on proper new cables, and finally devoting a couple of hours to replacing the entire cabling system, if it is full of Band-Aids.

External and internal noise sources picked up by our microphones.

External sources include:
- Noise from community activities: crowds, schools, loading and unloading, shopping arcades, etc.
- Noise from industrial activities.
- Road traffic noise
- Air traffic noise
- Etc.

Internal sources:
Those generated inside our room or building.
- Impact noise
- Video equipment, television
- Stereo equipment
- Household appliances
- Plumbing
- Elevator noise
- Ventilation systems
- Air conditioning systems
- Electrical installations: switches and lighting systems.

It is common to hear one of the noises caused by one of these components in a recording that had come out perfect in our mic take.

The truth is that these sources are the hardest to disguise in a home studio. My recommendation: soundproof your room, or soundproof a booth for mic recording.

Given the high cost of good soundproofing and the amount of space it requires, most of us will be forced to take alternative measures, somewhat "makeshift" but effective:

- Locate your room in the quietest part of the house, away from traffic and street noise.
- Away from household appliances and internal noise in your living space.
- Do your mic sessions at the quietest times of day in your surroundings.
And, logically, close windows and doors and do everything you can to avoid ambient noise.

Conclusions
I know this chapter may seem somewhat obvious at first glance. But I can assure you that it is far more relevant than it might seem for achieving the best quality in our recordings. I recommend, if you don't already do so, that you take every measure, even to an exaggerated degree, to reduce noise on every take: those described here, plus specially designed devices and filters (noise gates, etc.).

I am sure anyone can ultimately tell the difference between a master or copy recorded with precautions against noise and a set of careless recordings colored by intense little noises which, admittedly, will give them a certain improvised character thanks to the dissonance in the chords and scales of that well-known maestro: NOISE.