Cancel Location Noise

While it's not a perfect technique good quality sound can be obtained in noisy environments by recording a second track away from the voice talent. This track is inverted and added to the original source to eliminate the background noise.

On location, record the voice talent in a noisy environment with a high quality, narrow pickup microphone. This will be the primary audio.

Use a second microphone, recording to an independent audio channel than the voice talent, away from the talent. The goal with this microphone is to record the ambient noise without any of the voice talent in the recording. In noisy environments, this isn't difficult!

Capture both channels and export them independently - we need to process each one differently. Soundtrack Pro can be used for this purpose, or use a dedicated audio workstation like Pro Tools or Nuendo. This example is from Soundtrack Pro but the principle is the same for any workstation.

• Set up the project so the two tracks are on adjacent tracks. This works best if they have been exported as independent Clips.

• Control-click (or right-click) on the off-mic channel - the one without the voice talent - and select "Open in Editor" from the contextual menu.

The Clip opens in the Soundtrack Pro Clip editor.

• Choose the Process menu and select "Invert". This processes and inverts the phase of the waveform.
• If you have exported the track as an independent Clip, choose the File menu and select Save, or use Command + S on the keyboard.

Switch back to the Multi-track view and play. The inverted background noise should cancel out the background noise from the talent's track, making it clearer. The results with this method are superior to what can be obtained only in post production.

Without that second track to invert, we can use Soundtrack Pro's tools to reduce noise, but the results will be better with a second channel.