5 Ways to Fix Noisy Field Recordings

2012/11/21

The Lobster Nebula, courtesy ESO

This is a sample chapter from my e-Book, Field Recording: from Research to Wrap. Read more about the book.

Capturing recordings with excessive noise is one of the most confusing and frustrating problems new field recordists face when recording sound effects.

Noise is a thick, rushing, steam-like sound that overlaps sound recordings. At higher frequencies it adopts a thin, nasal aspect, known as hiss.

Not all noise sounds the same. Some noise is steady and smooth and somewhat tolerable, or at least unnoticeable. Other forms of noise sputter coarsely.

When noise appears in recordings, it invades sound effects thoroughly, even at low levels. And this is why it is noise becomes an irritating problem: once it arrives, it’s difficult to remove.

Where does this noise come from? How can it be minimized? Can it be eliminated? How much is acceptable? How can you record with clean gain?

I’ll answer each of these questions.

Removing Noise from Sound Effects

Noise is broadband. This means it is spread across many frequencies, including those shared with your sound effects. This is the main reason why it is difficult to remove noise after the fact. It’s not as easy as using EQ to notch out one narrow frequency. Removing noise almost always sucks out good audio with the bad.

In that case, our best option is to catch noise before it occurs. But where does it come from, and how can we prevent it?

The Source of Noise

The majority of noise originates from your equipment itself. It may be your microphone. It is most likely your preamp, however.

Noise comes from the components in equipment. The biggest culprits are semiconductors. Semiconductors have inherent noise, and poorly manufactured ones introduce more of it. Resistors contribute thermal noise. The point to remember is that noise is inherent to components. It is always there as part of recording equipment itself. The components create a quiet “floor” of noise beneath every recording you make. You won’t detect it at a low gain setting. But it is always there as part of the components themselves.

Some components are quieter than others. These cost more to make. Manufacturers of budget equipment use less sophisticated components, which are noisier.

What You Can Do About It

How can you deal with noise? You have five practical options:

  1. Swap Components
  2. Since the source of the noise arises from your equipment itself, your first option is to swap components within your microphone, preamp, or recorder. If you know a savvy engineer, they can replace individual semiconductors and resistors at the circuit board level.

    Upgrading to superior components can cost less than $50. That’s far cheaper than replacing an entire preamp. Of course, the skill to do this is beyond the range of most of us. However, it’s helpful to remember where noise comes from, and what small changes contribute a substantial impact.

  3. Upgrade Equipment
  4. Your next option is to upgrade your equipment. Buying a better preamplifier will reduce noise. Some microphones have inherent noise. Choose one with a high signal-to-noise ratio.

    Cleaner components will introduce less noise. Equipment that uses these components are exponentially more expensive. Be prepared to spend.

    Sometimes your equipment is deceiving. Noise may be introduced only while monitoring. Headphones are powered by their own preamp. It may be poor quality, and introduce noise separate from the recording. This means that you’ll hear noise that is not actually being captured. Just be aware that this is a possibility.

  5. Change Targets
  6. Noise isn’t apparent when a sound effect is loud. It will be barely audible when recording glass shattering, for example. This is because your gain levels will be low when recording loud sounds.

    At other times you’ll record quiet sounds. Examples are forests, winds, room tones, mouse clicks, and so on. You will need to raise your gain substantially to make these sounds audible. The problem? As you increase your gain, you’ll amplify the noise as well. How much? It’s different for each recorder, preamp, and microphone. Some can handle incredible amounts of gain before any noise is apparent. Others introduce noise with the gain just above halfway.

    Often the noise will be louder than the sound you are trying to record. This is something you must avoid, since your goal is to capture the sound effect, not the noise.

    This creates a difficult situation. The problem is that it creates a “wall” of what you can record well with certain gear. Some equipment just can’t capture quiet sounds without introducing noise. It’s not a matter of your skill. It is a physical limitation of equipment.

    So, your first option is to record quiet sounds with noise anyway. I wouldn’t advise this. Noise compromises the vividness and authenticity of field recordings. These recordings won’t strengthen your library, or the projects they join.

    The other option? Don’t record quiet sounds with that gear. Avoid the canyons, fields, and lofts. Wait, upgrade your equipment, then record sounds that are quiet. I know, it’s frustrating to limit your recording options. It is arguably a better option than recording sub-standard sound effects, however.

  7. Software
  8. A handful of software plug-ins are designed to de-noise hissy audio files. They work by sampling a section of pure noise, untainted by other sounds. This creates a noise profile. The software then subtracts the sampled noise from the entire file. Settings adjust how much, and how sharply, this noise is removed.

    In theory this is an excellent idea. There is a problem, however. All noise is broadband. This means it is spread across many frequencies. Because of this, it is very difficult to remove only the noise and not drag good sound away with it. More expensive software does a better job. A clean noise profile is also helpful.

    The engineer also plays a part. Removing noise without affecting good sound takes years of practice and skill. It’s easy to do incorrectly, especially when you are learning. Working with very noisy sounds, or de-noising improperly, creates aliasing artifacts. This introduces an unnatural “slushy” aspect to processed sounds. It’s also known as “singing robots” because of its cascading, digital tone. Often these artifacts are subtle, and are missed by inexperienced technicians. Even when done well, no-noising contributes a clinical feel to recordings. It may sometimes feel too clean, or sterile. In a sense, the air is sucked right out of these recordings. It’s easy to spot.

    Noise reduction software is undeniably impressive, and has its uses. I mention these caveats because noise reduction software is not a silver bullet. It is not a perfect solution for noisy recordings. It can easily become a crutch for poor equipment, or sloppy technique in the field. Avoid field recording with noise reduction in mind. Instead, do your best to record the cleanest audio at the time. A plug-in is no substitute for superior recording technique.

    Another option is to re-record a noisy sound effect with cleaner gear. In most cases you’ll save time otherwise spent struggling with plug-ins to get good results.

    Think of noise reduction as a last resort. Save it for irreplaceable sound effects.

    When there is no way to avoid noisy equipment or quiet subjects, noise reduction plug-ins will help.

  9. Cross Your Fingers
  10. Noise is easy to spot when listening to an isolated sound effect. Often you’ll audition sound effects loudly. They’ll rarely be used this way in projects. They’ll also be combined with other audio and video. This can have the effect of disguising noise. It’s not as easy to pick out a hissy pasture recording when it is joined by music, cows, birds, and tractors.

    Of course, this doesn’t remove the noise at all. It’s not the best option to live by. Just be aware that sounds with a bit of noise aren’t automatically useless. Consider context.

Unless a recording is rare or exceptional, avoid excessive noise completely. You don’t want so much noise that it distracts from the focus of the recording.

If you hear the noise, it’s likely too much. If you can notice noise in recordings, your clients will, too.

Your Influence

Noisy and hissy recordings can be frustrating. Don’t become discouraged. Use the five tips above to deal with noisy sound effects.

Remember, noise is mostly a limitation of components. It has nothing to do with your skill. You’ll face quiet or noisy recordings often, especially at the beginning of your field recording career. It is common when you have a small budget, too.

This can easily create a trap for field recordists. And no, I don’t mean a technical trap. I mean I mental one.

It would be easy to assume that there’s absolutely nothing you can do in these situations. Avoid this attitude. Don’t let your blooming craft as a field recordist be limited by your perception of the equipment you use.

Refuse to see your recordings as framed by your equipment’s limitations, or it even its strengths, for that matter. Don’t misjudge its impact. This cultivates an attitude of thinking you can’t do anything about the noisy sound you will encounter.

A field recordist has far more influence. Your decisions matter. Select equipment wisely, and modify it if possible. Sharpen your skills using software, but don’t rely on it. And, most importantly, use your input as a creator to influence not only what you can record, but how you do it. A series I wrote earlier has suggestions (article one, two, and three).

What you contribute is just as important as the gear on the shelves. How?

Actively choose bold, expressive subjects. Select people, props, and places that are responsive. Work to pull their vibrant voices into your field recordings. Refuse to settle for limp or noisy sound.

By doing this, you’ll find your creative expression has far more influence than chips, circuit boards, or resistors.

Enjoyed this post? Want to go deeper learning about field recording? I’m publishing an e-Book about field recording next week. Join the free newsletter to learn when it’s published. Read more about the book.

Many thanks to T. Virostek of Straylight Engineering for his assistance with this article.

Thanks also to the readers who proposed this question. Have any questions about field recording or sharing sound? Contact me, I’m happy to help.





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