I’m doing this in a publisher/layout program, so this is copy/paste.
Mosquito-Killer4
PURPOSE
Some affordable USB microphones and other USB audio devices can add a constant, irritating, high-pitch whine sound (electronic mosquitoes) to your recording.
http://kozco.com/tech/audacity/clips/USBMicrophoneWhineClip.mp3
The whine sound is very difficult to remove using normal tools, but we found the personality of the whine didn’t change that much computer to computer, so we designed a Nyquist effect to remove it.
INSTALL
Mosquito-Killer4.ny (363 Bytes)
On-line Manual
Follow the link for your operating system then follow the instructions to install Nyquist effects.
http://manual.audacityteam.org/man/faq_installation_and_plug_ins.html#plug-ins
USE
Select the work you want to repair, or all of the work by clicking just above MUTE (on the timeline left).
Effect > Mosquito-Killer4 (8 mosquitoes) > OK.
That’s it. We expect the whine to vanish in one pass with no adjustments and little or no audible sound damage.
COMMENTS AND NOTES
Mosquito-Killer4 is a multi-point Nyquist notch filter designed to search and destroy the most common, objectionable tones in the whine sound.
1000Hz, 2000Hz, 3000Hz 4000Hz, 5000Hz, 6000Hz, 7000Hz, 8000Hz.
That’s usually enough.
The tones are caused by USB electrical housekeeping leaking into the sound.
Please be clear we are surgically removing very tiny portions of show and you may hear some very minor performance changes. The changes are usually so gentle compared to the piercing USB whine that nobody cares.
If you understand Analyze > Plot Spectrum…
http://manual.audacityteam.org/man/plot_spectrum.html
…or timeline Spectrogram View…
http://manual.audacityteam.org/man/audio_track_dropdown_menu.html
…or just keen to experiment, you may find that your whine has fewer than eight significant mosquitoes in it and you can use the effect successfully with a lower number.
The number is adjustable 1 thru 16. As a general production rule, the fewer corrections, effects, enhancements and filters the better.
Best of all is to use a microphone or sound system that doesn’t whine.
If you have troubles, post a message to the Audacity Forum.
https://forum.audacityteam.org/ucp.php?mode=login
.