Harmonic reject filter

[Sim]

Hi all - I'm new to such sophisticated audio editing tools, so please excuse me if I don't know how to accurately articulate my problems - I don't know the correct terms to use yet when describing what my problems are. I have a decent fundamental understanding of sound - I'm a synth player from way back, but that means I'm not as experienced with removing noise as I am with creating it (by manipulating waveforms and such )

I have a recording of a seminar (speech only - no music) which has some bad noise - including low frequency hum, lots of hiss and crackling, and a rather nasty higher frequency hum - which I've discovered actually has harmonics (I tried in vain to isolate the frequency, only to discover that there were lots of them!!).

The Harmonic Reject Filter actually does a nice job of removing the hum (50Hz, Even Only) ... but I'm left with audio which sounds like it has a reverb on it (or is it "flanging" - I'm not quite sure which is the correct term) ... it sounds like someone is speaking down a length of PVC piping ... which is a really cool effect , but isn't exactly natural or conducive to clarity!

I've tried a number of filters and effects to minimise this - but it left the audio rather choppy.

Any suggestions as to the right approach to take ? Should I be filtering other noise before I do the harmonics, or is harmonics best done first ?

[Craig Maier]

What you need to do is to reduce the "Maximum Harmonic" value to the minimum number that is needed to reduce the hum or buzz yet not being intrusive to the signal content. I believe that the system defaults to "500" which is almost always too much, although it is possible to have line frequency harmonic noise which covers the entire audio spectrum. That case would be an extremely bad noise situation to deal with.

Occasionally, when I have encountered induced power line frequency noise having very high frequency spike content (like that produced by a phase controlled light dimmer or a "universal motor" {the kind with brushes}), I have achieved good results with the "Expert Impulse Filter" using the HQ mode with a low value set for the size parameter.