Humm.

[murray]

Hi to all ...i am having a small problem with removing....HUMM...from a program ...from the RADIO archives...it is a USAF...recruiting program running time 15 minutes,,,, 1963 ERA .. i have cleaned it to a point ...that there is something sounding like a....transformer ....humm...do you have a solution in DC7... to solve this problem ...i am asking the brains of the world elctronics for advice....murray. ....

[Craig Maier]

Sometimes, this is a terminology issue. I usually refer to "Hum" as the fundamental component of the line frequency, and only the fundamental. But, some folks consider the fundamental plus the first five harmonics of the line to be hum.

So, if you are dealing with what I call "Hum" you can identify its frequency using the spectrum analyzer and simply apply the Notch filter set for that frequency. But, if there are harmonics, you need to use the Harmonic Reject Filter. Sometimes you need to run one pass for Odds and a second Pass for Evens with the harmonic number set for around 5.

If you have what is commonly referred to as "Buzz" the number of harmonics may be much higher than 5. You will have to determine that using either your ears in conjunction with the Harmonic Reject Filter or via the spectrum analyzer.

I hope that is of some help to you.

ps - - - sometimes, the Continious Noise Filter will find and attenuate the Hum or Buzz automatically when you use Auto-Spectrum mode in conjunction with high settings of FFT.

[Dan McDonald]

You should also be able to see it by running the spectrum analyzer, especially if it's bad enough to notice while listening. That helps identify the harmonics also.

Dan