Sound Laundry from Algorithmix is a bundle of real-time audio restoration plug-ins that runs on the Windows platform. Included in the package are the

Sound Laundry from Algorithmix is a bundle of real-time audio restoration plug-ins that runs on the Windows platform. Included in the package are the Analyzer, DC-Removal Filter, De-Noiser, De-Scratcher, and High-Lowpass Filter tools. You also get the AlgoTest tool, which lets you determine the residual noise level of your sound card, and the AlgoRec tool, for recording WAV files with built-in proprietary lossless audio compression. The bundle touts high-quality 80-bit internal signal processing, coupled with speedy performance, low CPU load, and an easy-to-use interface.

Unfortunately, in its quest for simplicity, Algorithmix has made Sound Laundry more difficult to work with. The incomplete interface and proprietary plug-in format greatly reduce productivity. I tested the product on a 300 MHz Pentium II, with 64 MB of RAM, and all the while I was wishing that these were DirectX plug-ins. That would have allowed me to use them from within my favorite digital audio-editing software.

MINOR SETUP PROBLEMTo begin with, I had a problem authorizing the program. I went through the installation process, during which I had to type in a required CD-key number. The number was accepted, but the plug-ins still ran as unregistered copies. After a few attempts I contacted Algorithmix, and the company's response was quick and helpful. It turns out that the setup procedure has a small bug: authorization won't work unless you elect to add icons to your desktop for each of the plug-ins. I had unchecked that option each time I tried installing the program because I don't like desktop clutter. Allowing Setup to add the icons solved the problem. Algorithmix says it will fix the bug in the next version.

THE PLUG-IN STATIONBecause of their proprietary format, the Sound Laundry plug-ins can be run only via the included PlugIn Station (see Fig. 1), the command center where you input, process, and output audio. The PlugIn Station provides three methods of processing: Live, Real-Time, and Off-Line. Live Processing lets you take an audio signal from your sound card's input, process it with the Sound Laundry plug-ins, and hear the results through your sound card's output without generating an intermediate WAV file. This method lets you use your computer as a live signal processor.

I experienced a slight delay between the input signal and the processed output signal, but this is to be expected. All sound cards exhibit some amount of latency, so this is not the fault of Sound Laundry. As a matter of fact, the program allows you to adjust the number of device buffers as well as their size in samples, so you can find the right balance of least latency without signal dropouts.

Another problem I encountered was a slight echo of the input signal introduced into the output signal. The echo had a very low amplitude, but it was still audible when the input signal ceased and the delayed output signal sounded. Whether Sound Laundry caused this, I can't be sure.

Real-Time Processing is similar to Live Processing except that the input is derived from a preexisting WAV file rather than a live signal. When you use Real-Time Processing, you're prompted to select an input file. Then any processing you do is applied to the file in real time as it plays. Any parameter changes that you make are also reflected in playback. This allows you to make fine adjustments and hear the results instantly. You can bypass any processing during playback to hear an unaltered signal, or you can use the Difference feature to listen to the disturbances being removed instead of to the signal that's being processed.

When you've found the right settings, you can switch to Off-Line Processing. Here you must select an input file and an output file. Then all plug-in parameters are disabled so that changes cannot be made, and the file is processed. In addition to WAV files, Sound Laundry accepts MP3 files and files created by its own AlgoRec tool, although it can output only to WAV format.

After you've chosen a processing method, the PlugIn Station lets you select which plug-ins you want to apply to the signal. You can chain up to four plug-ins in any order by selecting them from the drop-down plug-in menus. Why a fifth menu wasn't included puzzles me. After all, there are five plug-ins, and most users have the available computer power to use them all. In fact, I was able to process a stereo file with all four plug-in menus selected without exceeding a CPU load of 48 percent.

Sound Laundry has no preset functions. (This will change with the newly announced v. 2.5.) You can't save individual plug-in parameters or the settings in the drop-down plug-in menus. You must start from scratch every time you launch the program, although the last settings used and the last window positions are saved when you exit.

THE PLAY STATIONIf you choose the Real-Time Processing method, the PlugIn Station opens a companion window called the Play Station (see Fig. 2). This part of the program lets you control audio playback of your input file. I found the Play Station confusing at first. It has a row of buttons at the bottom that, from left to right, seem to indicate stop, play, loop, markers 1 and 2, rewind to beginning, rewind to marker, play, cue, fast-forward to marker, and fast-forward to end. But in fact, the End button ends the current session, and the button marked with a green triangle acts as both a stop and play button.

The loop and marker buttons are as they seem, but the remaining buttons select either Play or Cue mode. In Cue mode, what look like rewind and fast-forward buttons are actually high-speed playback buttons. Instead of instantly moving to a point within the file, they just play the file backward or forward at 45 or 165 speed. I have no idea why they are included.

The Speed lever, however, lets you adjust playback speed and make rudimentary corrections to pitch. Finally, the Current Position lever lets you move to any point within the file, but playback always starts at the beginning unless you place markers and activate Loop mode.

THE DE-SCRATCHERThe De-Scratcher plug-in is really three tools in one (see Fig. 3). It provides de-clicking, which removes large spikes in the audio signal; de-crackling, which removes crackles and smaller clicks that are left behind after the de-clicking process; and de-plopping, which removes low-frequency disturbances in the signal due to mechanical resonances and can be turned on or off. De-clicking and de-crackling can be adjusted via sliders that range from 0 (no processing) to 100.

As your audio is processed, you can monitor the overall click and crackle level on the Scratch Level meter. The more clicks and crackles detected, the higher the Scratch level will be. You can also monitor the separate click and crackle levels, which are graphically displayed on the Scratch Scope as red and green lines, respectively. The Scope displays the last 12 seconds of signal. The higher each line appears from the bottom of the Scope, the higher the click or crackle level.

I found the De-Scratcher very effective. Sound Laundry includes a demo WAV file, which contains a number of disturbances. Using De-Scratcher I was able to remove most of the clicks and crackle from the "dirty" file without any adverse effects on the audio.

THE DE-NOISERThe De-Noiser, on the other hand, requires the user to expend a fair amount of effort in order to achieve good results (see Fig. 4).This plug-in provides adjustable Threshold and Noise Reduction Amount parameters for removing continuous background noises such as hiss. It also has a Noise Level Meter and a Noise Scope, which function similarly to the De-Scratcher's Scratch Level Meter and Scratch Scope. The De-Noiser uses the popular noise-print method for processing and provides two preset prints-white noise and pink noise-which enable you to quickly remove background hiss. You can also capture a user print from your audio file for more accurate processing, but herein lies the problem.

To capture a noise print, you have to hunt and peck your way through your file to find a good piece of "silence" that contains only a fragment of the noise that you're trying to remove. Locating a sample of noise with the Play Station is cumbersome, because it gives you no way to graphically view and select a portion of the file. If there is enough silence at the beginning or the end of the file, you may get lucky. But even then, you have to capture on the fly and hit the Stop button in time so you don't include any of the actual audio in the print.

Furthermore, if you succeed at capturing a good print, you have no way to graphically edit the noise print itself. I've worked with many noise-reduction products, and those that use the noise-print method have always included a way to edit the noise print. These issues are major oversights in Sound Laundry. (The new version of the software includes a waveform editor, which should make finding a noise print much easier. Other improvements in the new release, such as noise-print smoothing and editing, will also help considerably.)

With a good noise print, however, De-Noiser gave me some decent results. I tried it with a vocal track that contained some air-conditioner noise in the background. After a bit of a struggle, I obtained a good noise print, and the plug-in removed all the noise with only a slight coloration of the audio material. But getting a good sound still takes a lot of trial and error. Luckily, you can adjust the fast Fourier transform block size and FFT overlap, which are parameters that aren't adjustable on many products. I was also able to clean up the included demo file very nicely after finding the right combination of FFT, Threshold, and Noise Reduction Amount settings.

THE OTHER PLUG-INSSound Laundry gives you three more plug-ins, which are nice to have but less necessary than the De-Scratcher and De-Noiser. The DC-Removal Filter simply removes DC offset from the input signal. Left and right meters show the level of DC offset in each channel, and a reset button lets you reset the meters. I have no complaints about this plug-in except that most Windows audio editors already provide a DC-offset removal function. (Algorithmix has recently announced a DirectX version of the De-Scratcher and the De-Noiser, which will enable you to use the technology directly within many host audio applications.)

Because the Noise Scope provides only a basic display of the De-Noiser's levels, the Analyzer is included for showing a more accurate frequency spectrum. You can set it to display the input and output of the De-Noiser as well as the High-Lowpass Filter. You can also use it to display your captured noise print superimposed over the other signals. (You still can't edit the noise print, though.) Adjustable frequency and amplitude scales allow you to zoom in or out for a more or less detailed display. You can switch the amplitude scale between logarithmic or linear, and a Decay parameter controls the fallback time of the display.

The High-Lowpass Filter-the most useful of the three additional plug-ins-acts as a highpass and lowpass filter, with adjustable parameters for each. What makes this plug-in special is its use of linear-phase filters, both of which have continuously adjustable slopes from 0 to 24 dB per octave. This gives you some nice high-end filtering possibilities. The highpass filter has an adjustable cutoff frequency of 20 to 180 Hz, and the low-pass filter can be adjusted from 2 to 20 kHz. The plug-in provides a graphical display of the filter, and you can adjust the parameters by dragging the appropriate filter point with the mouse. At the same time, the corresponding numerical values are shown below the graph, although you can't adjust these numbers using the computer keyboard.

THE ENDWith some effort, you can use Sound Laundry to remove a number of anomalies from your audio signals. But the product is more difficult to use than its documentation claims. Although the program comes with no printed documentation, the online Help files explain the functions of each part of the program quite well. And the CD includes a comprehensive PDF manual, which explains in detail how to use the plug-ins.

Sound Laundry's main problem is its lack of DirectX support. With DirectX, users could simply run the plug-ins through their favorite Windows audio-editing application rather than having to deal with the cumbersome Play Station. Algorithmix should also add graphical noise-print selection and editing to the De-Noiser plug-in. Without those features, however, capturing an accurate print is very difficult.Otherwise, Sound Laundry provides some good processing power. If the new release is all that Algorithmix says, then the program will compare well with the other professional solutions on the market.