Hardware And Software Reviews
Eliminates 'De Noise':
A Noisy Proposition
Read G. Burgan
It seems like only yesterday that I labored over the transfer of a particularly noisy sixteen inch broadcast transcription. I used all of the hardware in my audio arsenal, including a one third octave equalizer and a graphic equalizer. No matter what combination of filtering I used, I could not eliminate the noise without drastically affecting the sound itself. It was a frustrating situation with no satisfactory solution.
That was then and this is now. If there’s one area where digital audio has had a dramatic impact, it’s in the area of noise reduction. In the past several years several software companies have developed digital noise reduction software that eliminates all kinds of noise while leaving the sound itself intact. One of the latest of these is Steinberg’s DeNoiser, that works with most any PC-based digital audio software using Direct-X plug-ins. There is also a Mac version available.
DeNoiser takes a different approach than most of the noise reduction software currently on the market. Most noise reduction software works by taking a noise sample from a sound file and then removing anything matching the noise sample. DeNoiser does not take a noise print. Instead it applies an algorithm that it uses to reduce unwanted noise.
Steinberg describes the process this way: “DeNoiser is based on spectral subtraction. Each section of the frequency spectrum that has an amplitude below the estimated noise floor, is reduced in intensity by use of a spectral Expander. The result is a noise reduction that does not affect the phase of the signal.”
There are several potential advantages to this approach. One is a fast learning curve. Most conventional noise reduction software has a multitude of variables that affect the final result, and mastering them all can require a lot of experimentation.
DeNoiser has only three onscreen slider controls. In less than five minutes, one can easily figure out how the controls affect the final product. This is a real time saver.
Since DeNoiser doesn’t require a noise print, you don’t have to wander through your sound file looking for a “silent” portion that is typical of the offending noise you want to remove. When you press the preview button, DeNoiser begins to dynamically analyze the program material and applies its own algorithm as it plays the file.
Each of the three controls can be adjusted during the preview process, and the resulting change is heard in real time. The Level control is a threshold control that determines the level at which the noise reduction is applied. The noise level is graphically represented on the screen by a yellow line, and all you have to do is set the Level control’s green line slightly higher than the noise line.
The Reduction slider determines how much noise reduction is applied. It can be set anywhere from 0 to 20 dB. Finally an Ambiance slider allows you to fine tune the noise reduction to minimize the affect on ambiance in the sound file.
Without a doubt this is one of the easiest and fastest noise reduction modules I’ve come across. Does it work? Yes . . . and no. Let me explain.
I tried DeNoiser on several kinds of noise that you might expect to find in a radio station or sound studio environment. To test DeNoiser, I used Sound Forge 4.0d as digital audio host for the plug-in. On tape hiss, it does relatively well. On vinyl recordings, I found it much less effective than other comparable noise reduction software.
To find out why, I used Sound Forge’s Spectrum Analyzer software to look at the noise in several sound files before and after processing by DeNoiser. Here’s what I found.
Most of DeNoiser’s effect takes place at 4,000 Hz or higher. At those frequencies, there is an average apparent noise reduction of about 11 dB when the reduction slider is set for 20 dB of noise reduction. Below that point, the noise reduction tapers off to virtually nothing. For one test I used a reel-to-reel recording of a newscast I did when I was in public radio back in the early 70’s. Like many studios put together on a shoestring, it left a lot to be desired.
There was a prominent hum at 65 Hz, and after one application of DeNoiser, the 65 Hz hum was still as prominent. A second application of DeNoiser reduced the higher frequency noise even more, but made no dent on the 65 Hz hum or other low frequency noise.
I found the same thing true when I tried DeNoiser on sixteen inch broadcast transcriptions. It reduced the higher frequency noise substantially, but made little or no dent in the low frequency surface noise that often accompanies phonograph records.
When I ran the same material through the noise reduction software I normally use with a setting of 20 dB of noise reduction, I found that both DeNoiser and my other software removed about the same amount of noise in the higher frequency areas, but the other software also removed an equal amount of noise all the way down the lowest frequency in the spectrum, resulting in a noticeably quieter sound file than with DeNoiser.
However, DeNoiser does seem to have less affect on the ambiance and creates less artifacts. This was particularly noticeable where a person takes a breath. My usual software tends to subtly reshape these sounds, giving them a slightly artificial affect.
Most noise reduction software provides the ability to remove up to 100 dB of noise in one pass, versus DeNoiser’s maximum of 20 dB of noise reduction. However, in my experience attempting to remove more than 20 dB in a single pass will almost invariably create artifacts and the best approach is to apply about 20 dB in successive passes anyway.
The bottom line is that DeNoiser is easier to learn and use than most other noise reduction software currently available, but is limited in its effectiveness to those frequencies that are at or above 4,000 Hz. It will definitely reduce certain kinds of noise in your sound recordings, and if time and speed are important considerations in your work, you should consider DeNoiser for your audio arsenal.
DeNoiser has a retail price of $399 and an average street price of approximately $289. For more information, contact: Steinberg North America, 9312 Deering Avenue, Chatsworth, CA 91311 (818) 993-4161 email: firstname.lastname@example.org website: www.us.steinberg.net
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Read Burgan is a free lance writer and a former public radio station manager who can be reached at (906) 296-0652 or through e-mail at email@example.com.