Tech Tip Thursday from Facebook

Be careful when using noise reduction in programs like Adobe Audition or Cool Edit. Many of these end up introducing sharp filters which produce a false "ringing" sound that can be misinterpreted as an EVP or other unusual sound.

A better approach is to attempt to reduce as many possible sources of broad-spectrum noise as possible. Heating and air-conditioning systems are among the biggest sources of noise. Central heating and air systems, especially ones with a larger, more aggressive circulation fan, tend to produce wide-band noise (sometimes so much so that it resembles white noise). This is *very* difficult to remove -- but not impossible.

Even though noise-reduction can be tricky, it is possible to effectively use noise reduction -- just be prepared to read and understand how your software's noise reduction feature works and to experiment a lot to get it right. Every audio application is different, so reading the instructions is essential. Also -- one size does NOT fit all. Every location, every situation, and every recording device will bring with it special noise reduction requirements.

Some suggestions:

  • Practice! Record yourself reading out loud in an area where there is some background noise from a fan or air conditioner. Work with your audio program and see if you can remove this noise effectively without drastically altering your voice or introducing "mysterious bell sounds".
  • When investigating, intentionally record 15-30 seconds of silence (nobody talking, moving, or doing anything). This will get a decent "noise profile" for the location. Do this procedure in each area where you're placing audio recorders.
  • Be patient. Getting the right settings can take many tries -- and "automatic" settings rarely are optimal.
  • Document everything you do to your audio files. You won't remember everything you did to a file 6 months later!

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