Complete and total hiss removal is pretty much a bad thing. First, some background...
Hiss can come from many sources. Two primary ones are analogue recordings:
In all cases we’re talking about a steady, unchanging, persistent ‘wash’ in the audio background that annoyingly threatens our listening enjoyment!
Depending on the file, a simple editing solution can be applied. Surprised? If the noise is audible at the start and end of a file, a careful and artfully applied fade is all that would be needed. For ‘silent’ passages or rests in the music, a careful lowering of volume in that region can be very effective! I love simple solutions...
Another one is to apply equalization. This can work quite well with older recordings from the early half of the 20th century. The musical content tends to drop above frequencies of 7-8 kHz. By applying a gentle dip at those areas, we can minimize its impact. The ‘trick’ is the balancing of harmonics.
However, for those times when we’re not so fortunate, another solution would be to apply multi-band downward expansion. Here the frequencies where the noise is the most prominent are isolated and a gentle ratio is applied. This gently lowers the level once the signal goes below a pre-determined threshold.
Think of this as a combination of the first two solutions automated. Music is constantly changing. This method adapts to the change when set correctly.
Specialized software from iZotope, Sonnox and Waves, for example, takes our multiband downward expander solution to the nth degree! Here, the frequency spectrum is split up into a much higher number of bands. The thresholds are set by an envelope. It can be set either manually; by adapting to the audio; or by taking what’s called a noise-print at the start or end of a file. The amount of noise reduction is determined by the user setting.
Here’s where a lot amateurs fall into trouble! The goal has never been total hiss removal. The aim is to minimize its impact on the audio we want to listen to.
I promise I have no love affair with hiss!
Quite opposite, in fact!
A while back, at an Audio Engineering Society meeting dealing with noise reduction techniques, the presenter offered these very ear-opening test results:
Listeners were given two audio files to listen to:
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 beginning to understand why complete and total hiss removal is a bad thing?
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