Today there are almost as many audio cleanup software products as there are applications for them. They can scrub distracting background noise out of interview footage, reduce wind noise from outdoor location shots, or clean up clicks and pops on vinyl recordings.

I recently took a look at Bias SoundSoap Pro, a whimsical name for a powerful new restoration and cleanup software. Originally sold as a prosumer product named SoundSoap, the pro version provides four individual tools to clean up vinyl records, cassette tapes, noisy location recordings, and even studio recordings.

SoundSoap Pro is a plug-in for any compliant audio program such as Bias Peak or Steinberg Cubase, Cubase SL/SX, or Nuendo. I tested it in Peak, the sound mastering software also developed by Bias. I had been planning to revive some old reel-to-reel recordings anyway, and so had an actual project on which to test drive SoundSoap Pro.

My reel-to-reel tapes are all music recordings of various bands I was in a very long time ago. Surviving members of the bands maintain that our solos are not worthy of audio, but I'm the one with the tapes, and so the restoration begins.

SoundSoap has set out to make the interface and process of cleanup as simple as possible, and for most basic restoration tasks you can achieve good results after spending about an hour on the tutorials. These, by the way, are very useful.

Naturally, it makes sense to bring in the cleanest possible signals. I played the 1/4in. source tapes on a restored Akai GX-625 open reel machine. The Akai was connected via Monster cable to an Edirol UA-5 converter box, a professional A/D audio interface. This was connected to my Mac G4 via USB cable, which is far cleaner than the notoriously noisy mini-pin input found on most PCs. I could have converted the audio at 24 bit, but let's be serious, I'm transferring live recordings made in clubs with less than stellar acoustics. CD-quality 16-bit 44KHz was adequate for the test. I transferred all the tunes to Freeverse Sound Studio 3 and saved them as individual AIFF files. Next, I imported them into Peak.

Once in Peak, the waveform for each file is visible and you can select sections to loop, a normal feature in an audio editing app and very useful — as will soon become clear. Soap is found in the plug-in list on the menu bar. When opened, Soap appears as a floating palette with four tabbed filter categories along the bottom of the window. From left to right the options are Hum & Rumble, Click & Crackle, BroadBand, and Noise Gate. The Soap manual recommends working from left to right, applying each applicable effect to the audio file in sequence.

There are a few things that make Soap easy to use. First is the interface layout, which is relatively intuitive, and second, all the filters operate in realtime. This is critical because you can test various parameters and listen for the results even if you don't know exactly how the settings are affecting the signal from a theoretical point of view. Naturally, a good set of headphones or monitor speakers is critical.

Not every recording requires each of the four tabbed options. Click & Crackle, for instance, is most likely to be used on vinyl recordings and did not apply to my reel-to-reel recordings. Beginning with the first filter, I began looking for hum or rumble to remove. The tapes were relatively clean in this respect. While it was possible to remove some overall ambience and boominess, this was more of an EQ issue than a noise removal issue. So while there were ways of pulling down some of this unwanted sound, it also pulled out some of the music.

This is always a possibility, even when targeting narrow frequency ranges, and the Noise Only button is the way to find this out. Noise Only isolates the noise the applied filter and parameter settings eliminate. If you hear even faint music, you've gone too far and have to pull the cleanup effect back.

The BroadBand filter turned out to be the main tool required for most of my recordings and made a huge difference. This filter allows you to sample the background sound (Learn Noise button) and then subtract it from the overall sound profile. Fortunately, I could find isolated room ambience to sample for most of the tracks. Since the separate recordings were made in the same room and conditions, I could save the correction profile that Soap creates and apply it to other tracks as long as the recording conditions were the same. The profile is created by sampling a small section of the track either with a snapshot (a momentary sample) or by selecting a half-second section of the track. Peak lets you loop this section for playback.

SoundSoap's BroadBand filter analyzed the unwanted room and system hum on my tape and immediately made a best-guess correction. The difference was dramatic. The results show up on an interface that looks like a parametric equalizer. This provides 10 bands with two sliders per band — one is for Reduction level and the other is for Threshold. This allows you to refine Soap's first basic attempt to remove noise. The first correction removed unwanted noise by my subjective estimate of 80 percent.

The final filter, Noise Gate, allows removal of offending sounds below a selected volume threshold. Noise Gate was useful in removing what sounded like an intermittent wind noise.

Each tabbed filter section (BroadBand, Pop & Crackle, etc.) has a button that lets you turn the specific filter on or off while you are working. This helps you hear how any filter is contributing to the overall correction. For my source material, Noise Gate offered minor improvement because BroadBand had done most of the work. It is also typical in noise removal work to do multiple passes and take multiple sound samples throughout a file, however, restoration requirements are entirely dependent on your source material. For some recordings a single pass may be just fine, but if conditions change in the recording, then you probably should attack this section with an addition pass.

After doing the tutorials, I cleaned up the first song in about half an hour. This included learning enough about Peak to use Soap. After that it took about 10 minutes to clean up each song file. The improvement to the recordings was stunning and a big success.

There is still more value to be had from SoundSoap that Bias could easily add in the form of additional documentation. The manual and tutorials are basic, and provide tutorial audio files for three types of common noise problems. The majority of basic parameters in any of the four filter types is reasonably explained while working through the tutorials. But there are also several other options in each filter — for instance, Attack, which adjusts to the speed of change in volume — that are less than intuitive. Additional tutorials would be helpful in learning the subtleties of noise reduction.

Other than that, SoundSoap Pro is easy to use, provides very good results, and is reasonably priced at $599 (dongle required). Mac OS X and Windows XP versions are available, and the plug-in works with VST, RTAS, DirectX, and Audio Units compatible host programs.

You will find similar noise reduction technology in other programs, including Adobe Audition. However, SoundSoap Pro is aimed at professional media makers, whether they are professional sound engineers or not. The interface and workflow are intended to get you up and running quickly without having to learn an entire sound editing package. SoundSoap Pro is a good product for indie filmmakers, for example, or editors, directors, or producers using other desktop media applications.

SoundSoap Pro is good at removing hum and other electronic noise from badly recorded location audio, for example, motor sounds, mic hiss, fluorescent light hum, line buzz from bad connections, and other narrowband interference. These are all-too-common problems with location sound, so SoundSoap Pro can be a quick recovery tool. While it cannot perform miracles, it can remove many types of common audio noise to the point of inaudibility at normal playback volume.