Don't know if this will help, but received this info in an NCH email yesterday:
Audio Tip: Remove Background Noise
If you record meetings, lectures, interviews, or even yourself practicing the guitar, you might end up with some unwanted background noise. Clean up those recordings using WavePad audio editor.
- From the Effects tab, click the Cleanup button and select Noise Reduction, Audio Spectral Subtraction. Click the preset drop-menu and select voice or music, then click OK to apply.
- From the Effects tab, again click the Cleanup button and select Noise Reduction, Multi-band noise gating. Select a preset, then click OK to apply.
- If using the presets don't give you the best results, try using lower levels on each type of reduction.