A Little Hiss Never Hurt Anyone!

Unless that hiss is coming from a nearby rattlesnake!!!

Fortunately, we're talking about this in the context of restoration and mastering!

Hiss can come from many sources: two primary ones are analogue recordings – either reel-to-reel, vinyl or cassettes; or gradual noise build-up from a recording equipment chain.

The first solution most people think of is to apply a noise reduction plug-in.

But I've received files from “helpful” clients where the process was so over-applied that the recording sounded like it was done in a bird sanctuary!

Needless to say, I've had to return said files and ask for un-processed versions.

Obviously, there is a tendency for some to go overboard with this stuff!

You may be interested in some surprising test results....But first!.

Here are some ideas on how to approach hiss reduction:

First and foremost, ease back! Many, many times just 2–3 dB reduction is enough to push it into the background.

Next – is the noise constantly audible throughout the song? Or just the quieter passages?

I think you might already know my solution: just apply a little reduction to the quieter passages only!

Another overlooked solution is to apply multi-band downward expansion. This is an 'upgraded' version of the standard gate. iZotope's Ozone plug-in allows you to do just that:

As a starter, using all four bands engaged, in the 2k to 10k apply a very gentle slope (ratio) below the threshold that you set by using your ears and Ozone's histogram meters – about 1 : 1.1 or 1.2 – in that region. In the upper most band you could apply a slightly more 'aggressive' ratio like 1.5 or thereabouts. You may also need to adjust the crossover points, too.

Have you ever considered using just a simple EQ?! A 1 or 1.5 dB wideband cut at the 3k-8k region can do wonders sometimes. Not necessarily a high shelf either. Find out why, later.

I mentioned a gate already, but I usually have little luck with those on music files.

So I may manually reduce the sections where there should be 'silence' – it's a lot more work but it offers the most control and reliable results.

And, of course, I don't mean reduce to total silence.

As always, you need to use your ears to make sure the results are as natural sounding as possible.

You may be beginning to think I might have some kind of love affair with hiss!

Quite the contrary!

Let me share something interesting with you that, like me, your own experience can verify.

At a recent Audio Engineering Society meeting I attended discussing, oddly enough(!), noise reduction techniques, the presenter offered these very ear-opening test results:

Listeners were given two audio files to listen to. The first file had music with all high frequencies above 6kHz effectively removed. This is similar to what music sounded like on AM radio.

The second file was the exact same file but - with a little bit of white noise added. (You know what that sounds like, right?!)

The listeners were not told these details, of course, but were simply asked which of the files they felt had more musical information in it.

Over 80% responded with the reply that second file had more music in it!

Are you starting to catch on?!

Are you beginning to understand why a little hiss is all right?

Try it – and hear for yourself!

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