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SF Make Noise Reduction A Breeze:
A Software Review by Read G. Burgan
Published In RADIO WORLD December 8, 1999:

Sonic Foundry’s Noise Reduction 2.0 Plug-In
Read G. Burgan

If you digitally restore vinyl recordings and other analog sources, Sonic Foundry’s Noise Reduction 2.0 plug-in may be your most important digital restoration tool ever.

I evaluate digital noise reduction software on three criteria: 1. Effectiveness; 2. Ease of Use and 3. Efficiency. I give Sonic Foundry’s latest entry into the noise reduction market high marks in all of these areas.

This is not Sonic Foundry’s first entry into the noise reduction software field. I have been using SF’s original noise reduction software on a daily basis since it was first introduced. Much of my work consists of digitally restoring sixteen inch electrical transcriptions from the 30’s, 40’s and 50’s, and SF’s noise reduction software has been an effective tool for this.

But SF’s latest entry is head and shoulders above it’s previous noise reduction software. How? First in removing pops, clicks and other impulsive noise.

SF has completely redesigned it’s declick algorithm. The previous version was effective in removing larger pops and clicks, but not very effective in removing smaller clicks and the “crackle” so often associated with shellac records and ET’s.

The pop/click tool has been renamed “Click and Crackle Removal.” The interface contains three sliders: Sensitivity, Click Shape and Maximum Click size. SF provides several presets to get a user started, including basic settings for 78 rpm and vinyl recordings.

Since the results can be previewed in real time, it is easy to maximize the settings by selecting a sample of the material to be declicked and then adjusting the sliders while listening in the preview mode. My experience has been that once I find a setting that works, it will work pretty well on all similar material.

SF has also added a Noise Level click box, with three settings: low, medium and high. In the low and medium settings, the software separates the music into noise and non-noise portions. By doing this, the software is better able to discriminate between noise and program material.

The interface also has a “low level rumble” box which, when checked, removes low frequency material below 30 Hz. Some old recordings contain a lot of low frequency energy that could conceivably confuse the declick algorithm.

SF has also added a “Keep Residual Output” box. When this is checked, you can hear exactly what the software is removing during the preview mode. By using this feature, you can insure that only pops and clicks are being removed.

How well does the Click and Crackle Removal Plug-In work? Incredibly well. Declicking is probably the most difficult and frustrating of the vinyl restoration chores. Most declick software will remove the most egregious pops and clicks, but then you’re left to manually remove the remainder -- a thankless, time consuming task.

I find that by running SF’s declick plug-in twice (each time with different settings), I am able to remove all but a handful of pops and clicks and related noise from a fifteen minute ET. What’s left can usually be removed by rerunning the declick software with different settings on just the offending portions of the WAV file.

SF’s Click and Crackle Removal plug-in saves me a whole lot of time by “automatically” removing nearly all of the pops and clicks in the entire file, and it does so with a minimal amount of artifacts. This is particularly true on material containing spoken voice.

Traditionally, declick software will distort the spoken voice if set too aggressively, and if set too conservatively, leaves too many pops and clicks. For my money, SF has created an algorithm that is able to remove a maximum number of pops and clicks without creating unwanted distortion and other artifacts. It is certainly the best I have used to date.

The other key ingredient in any noise reduction software is a tool for broadband noise reduction: vinyl surface noise, air conditioning noise, street noise, etc. SF’s original broadband noise reduction tool was very good, but the latest version is better by a country mile.

The noise reduction onscreen interface hasn’t changed much. But SF has added two new features: “Reduction Type” and “Noise Bias.” And these two features make all the difference.

Broadband noise reduction works by taking a sample of the noise (For example, the “silent” portion when a person pauses between sentences, etc.). It then creates a noise print of the noise that is then used as the basis for removing noise.

The problem is that low volume program content is often embedded in the noise, and as the noise reduction software removes the noise, it often “chips” away at the program material itself creating unwanted artifacts.

This was true of the original SF noise reduction software, and although one could compensate for this by taking several small “bites” of noise and using new noise prints with different attack and release settings, it took a lot of time and the results weren’t always predictable.

To solve this problem, SF has created three additional algorithms, each one working differently than the original. These algorithms allow one to apply the noise reduction much more aggressively, with little or no adverse effects on the low level program material.

The “Noise Bias” slider allows for fine tuning the relationship of the noise print to the program material. Its effect is similar to manually moving the noise print envelope up or down, but the effect is more subtle and the result more pleasing.

How well does the new noise reduction plug-in work? Astonishingly well. I used to apply the noise reduction plug-in three times to an average Electrical Transcription WAV file. Now, for the most part, I can set the noise reduction to 70 dB or higher in a single pass, and the final result is a noise free recording with virtually no artifacts.

SF has also added a “Click Peak Restoration” function. This is designed to restore digital material that was recorded at levels high enough to produce clipping. SF gives the caveat that it should only be applied to material with minimal clipping, and my tests confirm that. In cases where the clipping is moderate, it may make the difference between a useable and unusable recording

I do have one criticism of SF’s latest noise reduction software, and that concerns their aggressive copy protection. In the past, SF has required users to enter their own unique serial number before the software can be installed. If you back up your hard drive and use the backup for reinstall, the Sonic Foundry software won’t run and has to be reinstalled. I considered that an unnecessary but acceptable nuisance.

Now SF has taken copy protection to a higher level. You still need a unique serial number to install the software, but once installed, the software will only run for seven days unless you register it at their web site. When you do this, SF creates a unique identity for your computer, and you have to input that identification number into the SF onscreen registration box in order to eliminate the seven day cut off.

If you change your motherboard or your operating system, the identity of your computer changes, and you will have to go back to Sonic Foundry for a new authorization code. You also cannot run the software on any other computers you may own without obtaining additional authorization codes. One only wonders what will happen if SF should go out of business or decide to no longer support this product. One could easily be left with a product having a seven day life.

While I understand the underlying factors that impel Sonic Foundry to intensify its copy protection, they are clearly moving in a direction that is contrary to the majority of software manufacturers. There must be a better way to protect their intellectual property rights without adversely affecting the needs and convenience of their users.

That said, I still believe that SF has about the finest noise reduction software currently available for the PC that I have tested.. SF’s Noise Reduction 2.0 is a Direct-X compatible plug-in that should work on any PC based digital editor that uses Direct-X plug-ins, including SF’s own Sonic Foundry, Vegas Pro, Cakewalk Pro, Steinberg Wavelab and IQS SawPro. It has a retail price of $399.

The version I tested was downloaded from their site, along with the accompanying 67 page manual that I then printed out. I tested the software on Pentium II class computers with processors ranging from 300 MHz to 400 MHz and with a minimum of 64 meg of ram.

For further information, contact Sonic Foundry at 1-800-57-SONIC or e-mail them at sales@sonicfoundry.com or write to: Sonic Foundry, Inc., 754 Williams Street, Madison, WI 53703. Home Page: http://www.sfoundry.com

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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 rgb@chartermi.net.