loud buzzing sound on playback

I am using Mac OS X version 10.5.8 and am trying to record tapes from a Nagra 4.2 tape recorder. Audacity records the sounds, but when it is played back, most of the sound is drowned out by a loud buzzing sound. Where does this sound come from and how can I eliminate it? I have looked at Noise Removal, but am not sure that I can identify areas of the recording that have the noise only, as the tapes are of low-level noises that are mostly drowned out by the buzzing. I would be grateful for any help. Nicholas

Tapes from a Nagra, but are you playing them back on a Nagra? You’re listening to the pilot tone. Nagra tapes have a world-class speed correction system that puts a pilot tone in the third track in the middle of the tape. It’s the tape speed control track. Our company used to make equipment that could “fake out” the pilot tone so people could make sound-sync movies of video (notoriously hard to do in the US). If you’re not using a Nagra on playback, you will get the pilot tone mixed into the show and other distortions.

You could try the notch filter. The standard tone is 60.000 (as I remember). You’re far better playing the tapes on a real Nagra which has custom equalization, track dimensions, and voice compression. Also, the notch filter may fail if the tone isn’t at 60.000 and that’s not guaranteed on a different machine.


Many thanks - that would seem to explain the buzzing sound. Our first problem is that I have tapes with intermittent recordings on them that I want to edit down to the bits I need and was hoping to use Audacity to do this. Our second problem is that all we have is the Nagra, the tapes, the MacBook Pro and no experience. I will try the notch filter and see what happens. We need to re-use the tapes as they seem to be very hard to get over here (in the UK, that is). Nicholas

You have a Nagra and it was playing the tapes like that? Do you know anything about the tapes? I’m trying to remember if the older mono Nagra is compatible with stereo Nagra tapes. I just don’t know without making a lot of calls.

Yes, I wouldn’t be shocked to find it hard to buy Scotch 808.

You should be careful that the tape binder isn’t falling apart. Look for brown or reddish brown deposits through the tape pathway. That’s the oxide, and the show falling off the tape polyester backing.



I knew it was something like that.