How do I avoid noise when speaker is further away?

Question

When the speaker is further away from the microphone, noise gets louder as (that is my assumption) the compressors wants to compensate for the missing loudness.

An audio sample can be found here:

Example of noisy audio recording

The microphone is a Neumann U87, the pre-amplifier is a Manley.

How do I solve this situation?

Or would the noise be absent if a perfectly clean environment would be used? I do not know in which environment this audio has been recorded, but if she is close to the microphone, no noise can be heard at all.

Answer 1

All analogue electronics generates some level of noise, and digital recordings also introduce a small amount of dither noise in order to accurately record signals.

When you record sound from a microphone, you are recording the person speaking, but also the sounds present in the room, the indirect sound of the person speaking reflecting off the objects in the room, and the noise associated with the analogue and digital systems being used.

What we're listening for is the ratio between the desired signal and the undesired noise. Generally when recording with high quality microphones (like the U87) and a good pre-amp, noise is likely to be introduced by poor microphone placement, the wrong directional pattern being used on the U87, or recording levels being too low at some point within the signal chain before the audio is recorded.

U87s have a directional pattern setting which can change the response of the mic between omni, cardioid, and figure of 8. In an echoey room with no acoustic absorption, a recording of a person speaking in front of the mic set to a 'cardioid' pattern will have a greater proportion of direct to indirect sound recorded. The trade-off is that 'figure of 8' and 'omni' have slightly better frequency response patterns.

Even if you recorded in an anechoic chamber, there would be no room noise, but there would still be noise caused by the analogue and digital circuitry. If your gain is set too low on the pre-amp or any other gain module before the signal is recorded, an undesirable level of noise would be introduced to the signal path. If the digital level that you record at is set too low, you will also be introducing more noise into your recording, as the ratio of your signal to the quantising and dither noise introduced by sampling the signal digitally will be worsened.

Practically speaking, your audio clip doesn't sound that bad to me. You could try noise reducing the recording using Adobe Audition's built in noise reduction tools. You could re-record with your subject closer to the mic (but they sound pretty close mic'd already given the amount of mouth noise), and you could check your recording levels throughout your signal chain.

Answer 2

It's easy to forget that like sound quality, electronics vary wildly in the amount of self-noise they produce. In most recording situations, this doesn't end up being a significant problem because we're recording instruments and voices that allow us to reduce gain to lower levels and NOT amplify the noise as much.

In situations where we're recording a very quiet (or distant) sound source, self noise quickly becomes an issue. Noise is compounding: the self noise of your microphone is amplified by your preamp (which adds its own noise), then all of that noise may be amplified through your compressor (which adds its own noise), and on it goes.

Put a dynamic mic in front of an electric guitar amp, and your gains will be so low through the whole recording chain that any self noise never makes an appearance. Put a "vintage" tube mic (often noisy) in front of a whispering actor, run that into a "vintage" preamp (often noisy) and you may have as much noise as voice at the end of the signal chain.

For the cleanest recordings possible, you need to start with a microphone with high sensitivity and low self-noise.

Two affordable examples:

• Rode NT2A, self noise 7 dBA
• Audio-Technica AT4047, self noise 9 dBA

Then you need to run that into a low-noise preamp (most decent solid-state preamps today fit the bill, check out the Grace M101). Preamps designed for ribbon mics (typically very low sensitivity) are usually very clean with gobs of gain and low self-noise.

If you still have noise in your recordings, active noise removal plug-ins have come a long way and will do a fantastic job cleaning up most audio files.