Finer points of noise removal and tape hiss

I’m using Audacity 1.3.3-beta to convert an old (1989) audio cassette to digital format then to CD. After hours of tinkering with the new noise removal tool, I still have a problem with tape hiss. I can quiet most of it in places where the artist does not talk or play his instrument. But it “returns” when he speaks up or plays the instrument. These are the only known recordings of a deceased Native American flute player, and I volunteered to help create a digital archive. It’s kind of important. I should be able to solve a simple tape hiss problem, right?

There’s no such thing as a “simple tape hiss problem”. You’re already on the right track.

As long as you’ve selected a good piece of “silence”, the best you can do is fiddle with the sliders to get it sounding as good as possible. Tapes deteriorate and there is a limit to how much good the Noise Reduction plugin can do. You may have to resign yourself to living with some amount of hiss.

You didn’t mention anything about how it was recorded (was the mic a good one? was it recorded outdoors? is the level on the original tape as high as it can be?), but one thing I can mention is that it sounds like this tape may have had some sort of noise reduction added, in which case you should be transferring the tape to your computer by way of a tape deck with noise reduction circuitry. You should also make sure the tape deck is clean and it’s output is set to the highest possible level before it gets to your soundcard.

If you want us to help more, the best thing to do is post a good example (unprocessed with “silence” and talking and music included). You can upload attachments to this board and we’ll fiddle with it and see what kind of settings work best.

Thanks for responding. The tape sounds like it was recorded indoors. My tape deck is clean and the signal to my PC was set at about 75 percent of max volume. I didn’t max it out because I was concerned the deck might generate distortion near its top output.

I’ve uploaded a sample called (253 KB)

I used Audacity 1.3.3 to clean this quite well.

Imported the file, selected the first 2 seconds of audio (this is a great example of the kind of silence you need to use the Noise Removal), Effects → Noise Removal → Get Noise Profile.

Then I selected the whole signal, Effects → Noise Removal → ok. I didn’t even change any other settings and it worked very well.

There’s a little bit of roughness in the right channel when he speaks, but it’s very low in the mix. If that roughness is unacceptable, you can try splitting the stereo track and using the Noise Removal technique on each channel separately (make sure you select a new Noise Profile for each track).

I would have liked to hear some of the flute too to make sure the Noise Removal doesn’t kill that instrument, but you didn’t post any.

I think you’re in pretty good shape though, you’re working with the limits of cassette tape and it manages to sound good regardless. You can even still hear the reverb on his voice (usually the first to go when difficult signals). This is a great example of the kind of signal the Noise Removal works well with, I think I’ll bookmark it for future questions.