What's that Hiss? Field Recorder Self-Noise Guide

 

Most definitions of self-noise can be as hard to understand as it is to listen to.

 
 
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When I was first getting into field recording, “self-noise” was a term that kept popping up. It seemed like it was really important when shopping for microphones and field recorders.

Everyone was saying to watch out for high self-noise levels, and to purchase the lowest self-noise microphone you could afford.

So what is it? Researching the definition might leave you more even more confused. Most articles are filled with wiring diagrams and too much technical jargon. This post will attempt to explain self-noise in easily understood terms.

What is Self-Noise

Self-noise is the sound produced by a device when powered. This sound is always present when the device is active, even if there is no ambient noise. It is produced from the internal circuitry and can be heard as a faint hiss in the background of your recordings.

Self-noise, also referred to Equivalent Input Noise (EIN), is an important factor of recording devices. Depending on subject matter, a certain level of self-noise can be tolerated but when that threshold is crossed, it is annoying at best and unbearable at worst.

Generally, the louder the sound and the closer it is to your microphone, the less you have to worry about self-noise affecting your audio quality.

Conversely, recording quiet or far away sounds can emphasize self-noise levels.

Comparing self-noise to recorded sound levels is called the “signal to noise ratio” (SNR) and is a popular statistic on microphones and recorders.

The signal is the audio you are recording. To maximize clarity, you need to boost the loudness of your signal as much as possible.

For far away sounds, use a parabolic reflector or a shotgun microphone to do this.

For quiet sounds, use the most sensitive microphones possible.

By increasing the loudness of your signal, your device’s noise will be much less noticeable in the final recording.

Why Does my Microphone Make Noise

When I was first learning about all this stuff I wondered “Why the heck does my field recorder make noise? Why didn’t the manufacturer mute it?”. The unfortunate truth is, all electrical devices make noise.

The sound you hear is generated by electrons moving around in circuits. The audio signal passing through your device picks up this sound as “noise.”

Technology will continue to invent ways to limit self-noise, but as long as electrons are moving, there will always be some system noise present (electrons only stop moving when the temperature reaches absolute zero). Since electrons need to be moving for electricity to work, this creates a “catch-22” situation.

What is a Good Self-Noise Rating

When shopping for a new recorder of microphone, make sure you look under the “specifications” for the self-noise, equivalent input noise (EIN) or signal-to-noise ratio (SNR).

Self-noise (dBA) EIN (dBu) SNR (dB) Rating Description
≤ 10
-130 ≥ 82
Ultra Quiet Extremely low self-noise. Undetectable even under the most critical recording conditions.
11-15 -126 78-81 Very Good Very slight noise discernable when recording the quietest signals.
16-19 -119 74-77 Good Good enough for most purposes. Noise noticeable in quieter recordings.
20-23 -110 70-73 Fair Noise obvious when recording anything below speaking level.
≥ 24
-100 ≤ 69
Poor Not recommended unless you only record waterfalls, alarms and jets (very loud signals).

If you are shopping for an external microphone, this information is usually provided.

Unfortunately, the same does not hold true for field recorders. Many manufacturers either do not specify this information or they do so inaccurately. Because of this reason, I frequently reference the independent testing done by Avisoft Bioacoustics.

They have systematically tested most field recorders on the market. Their results are compiled in a list ranking from quietest to loudest EIN. Check it out here.


Conclusion

All microphones make noise. Depending on the loudness of your subject, your tolerance for self-noise will vary.

If you do have noticeable noise in your recordings, try moving your mics closer to your subject to increase its signal strength.

If getting closer is not an option, try using a parabolic reflector or a shotgun mic.

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Thanks for reading,
-Jared


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