What’s That Noise?

 

Wind and Surf Capture, Oregon Coast

 

In our post, Pre-Production and Field Recording, we talked a bit about pre-production and things to think about before recording audio. In our summary, it came down to planning ahead and thinking about what could cause unwanted signals from being recorded and how to mitigate some of them.

But what other noise might we consider? Before we dive in, let’s talk a little about dynamic range.

In the context of audio and music, dynamic range demonstrates the ratio of sound from lowest to highest in audio equipment and musical instruments. This is measured in decibels (dB). It allows us to understand the maximum output signal and to rate a system’s noise floor.

Why is this important? When thinking about your recording levels, there are a myriad of sounds being recorded at any given time. Your equipment, no matter the quality, has a self-noise that makes up your Noise Floor. The environment around you constitutes an additional amount of audio that you are recording. And finally, your reference or source signal (the sound you actually want to record) makes up the rest.

For example, you may get a bit of hum or low level noise from your cables or your digital audio recorder. You may also have some self-noise coming from your microphone. As we increase the gain, these levels become more prominent. But because these levels should generally be lower than our source signal, they may go unnoticed or be candidates for some equalization and noise reduction in post-production to lessen their impact to the overall recording. However, the more we can attenuate the noise in our recordings before post, the less headaches we will likely have.

The trick here is to make sure that your source signal is recorded at the highest possible level, well above the noise-floor and environment. As you increase the gain, you are getting more of the signal you want. A good rule of thumb is to use your ears AND eyes during recording. Your meters are there for you to get a sense of the level at which your signal is being recorded, and your headphones are used to get an overall sense of your environment. That is why we want to determine our levels by the meters and not our headphones (which are almost always adjustable to their own output levels and do not represent the level of our recording). Also remember to not clip your recordings. In the context here of digital recording, any time your meter goes “RED” your levels are too high and the audio signal will result in distortion or clipping. There is no easy method to recover a clean version of the audio once it has been distorted.

Summary

  • Interpret and gauge your recording levels with your eyes
  • Understand your environment and the sounds being recorded with your ears
  • Noise-Floor consists of equipment self-noise such as microphones, digital recorders and cabling.
  • Environment noise consists of wind, rain, dogs, trains, cars and the like.
  • Dynamic Range demonstrates the ratio of sound from lowest to highest in audio equipment and musical instruments.

Some terms and specifications for microphones to keep in mind

Max SPL
The point where the microphone distorts. Characterized by clipping, crackling in the recording.

Higher ratings tend to be better, but there are microphones that have lower Max SPL that are used for vocals, acoustic instruments that do not need to have a high Max SPL.

Self noise (Equivalent Noise)

The amount of noise the microphone itself creates. Characterized by hiss, white noise.
Lower ratings are better
< 16dB

Dynamic range
The range between self-noise and Max SPL.
Higher ratings are better
> 128dB

Signal to Noise ratio
The range between self-noise and the reference signal.
Higher Ratings are better

Happy Recording!

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