Hardware Software ModSyn Music Interview Event Books Videos Store

SpectraFoo - Metric Halo Laboratories

July 1998 By Cherise O'Neill.

Although digital audio monitoring software is used primarily by sound engineers, for checking to see exactly what's going on within a sound, it is also becoming a must have tool for anyone serious about getting the most out of their music, especially the electronic music maker who is now capable of producing virtually any sound under the sun and more than ever really needs to see what's going on. So before taking a look at some of the stunning visuals lets take a moment to give you an idea of the principals behind realtime audio visualization and analysis.

SpectraFoo actually takes advantage of a phenomenon known as Synesthesia, a talent that very few people have which allows them to associate certain pitches with certain colours. Invariably they'll have perfect pitch and can actually see a sound as well as hear it. But thanks to SpectraFoo anyone who can see colours and shapes on a computer monitor can now experience this amazing phenomenon.

So that's the phenomenon that SpectraFoo takes advantage of, but how does it do it?

To answer that question we have to go back to around 1804, to the time when French mathematician Joseph Fourier was developing a way to study heat transfer. What he did was basically figure out a way of converting a continuous record, involving amplitude vs. time, into a record of amplitude vs. frequency. Shortly afterwards his Fourier Transform was modified, and made capable of dealing with sampled rather than continuous waveforms. And then, even later (not too long ago actually) an algorithm of the Discrete Fourier Transform was developed, capable of being calculated on a digital computer. This was, and still is, called the Fast Fourier Transform (FFT) and is the analysis engine on which SpectraFoo is based.

Although many other audio analyzers also use the FFT algorithm to provide information for the user, SpectraFoo is the first audio visualization system to provide high resolution spectral and phase information which is absolutely synchronised to the live signal. And the faster the processor the smoother the animation.

So what do these"high resolution visualizations actually look like?

Heartbeat analysisWell here's a look at what a single unborn child's heartbeat looks like (left), slowed down by around 80% and observed using a tool called a Spectragram, just one of the many tools in SpectraFoo's extensive arsenal.

We cleaned up the original recording, made with a handheld Sony dictaphone, using Arboretum's Ionizer before analyzing it, so all you're seeing is the actual heartbeat without much noise. Notice the different colours. These indicate the amplitude, or power, of the signal. The blue bits hanging down are the lower frequencies, which are still very a important element of the overall sound but not quite as dominant as the greens, yellows and oranges.

Here's what music looks like (right), a section from an excellent ambient album called The Silent Shore by Robert Scott Thompson.

Notice how the information moves vertically this time, from bottom to top. This is the way the default Spectragram window looks. The scale at the base of the window shows the frequency, and as with the heartbeat the colours signify amplitude or power. This particular sound is a warm fat synth pad with many different constituent elements. You can see the way the lower frequencies taper off to the left, the heavy mid section (where most of the action is taking place within this particular section) and the various layers of harmonics in the upper regions.

Again, this is a tool which is not only invaluable for those who make it their business to fine tune large PA's or state of the art studios, but also for those just beginning to learn about how sound actually works, such as students, hobbyists and even seasoned musicians who are making the switch to digital based recording and processing (i.e everyone). The Spectragram essentially gives the user the ability to see the dynamics that make up a sound and is easily configured to focus on any area that may need special attention.

Lissajous Phase AnimThen there's a Lissajous Phase Scope (left), which lets you see the width of a stereo field. It's particularily useful when checking for possible polarity problems within a mix, something which can often go unnoticed until someone points out that something sounds odd a few days after your CD has shipped out to the distributor (believe me, it happens).

The example on the left, which is just a looped animation to show you what it looks like when running, shows the scope in X-Y mode (as opposed to the other mode which is Vector). Everything looks fine but could easily be showing polarity problems which only a highly trained ear could otherwise detect.

Another invaluable tool is the Oscilliscope (right), a must have item in most audio analysis situations and also the basis of the Lissajous Phase Scope. Capable of being configured in exactly the same way as its real life counterpart, allowing you to freeze the action and really see what's going on.

Another great tool is something called a Phase Torch which is used to compare the phase difference of two channels. You can see what it looks like in the screenshot of the Virtual Rack below the title. It's the scope in the top right hand corner.

The most amazing thing about SpectraFoo is the ease with which we were able to get the whole thing up and running and, most importantly, actually analyzing.

Installing the software was as easy as it usually is when installing on a Mac. Insertion of CD-ROM, double clicking of the icon that appears and double clicking install.

From clicking the install button to actually having SpectraFoo up and ready to go took about a minute. We didn't even need to insert an authorization diskette, which should make all those new iMac owners even happier than they already are.

After firing it up we selected a few different analysis tools from the Master Control, removed the installer CD-ROM and popped in an audio CD. Selected CD from the Audio I/O menu and all of a sudden the screen came to life as the CD started up.

Obviously one of the primary uses for SpectraFoo will be as a tool kit for measuring audio as and when it happens, or even watching what's happening to the sound from a CD while it's actually playing. But SpectraFoo can also capture audio as well as open existing sound files. This is a feature which will come in very useful when it comes to mastering your music just before putting it onto a CD.

The screenshot on the left shows the SpectraFoo Virtual Rack, which is literally a rack that holds all the tools you need to analyize audio. You can have as many modules as you like, each one operating independantly of the other and with its own separate controls. Because we only have a 14" screen hooked up to our power mac the maximum number of modules, from left to right, was limited to two, but with a 17" or larger screen you can literally fill it with as many modules as you like, all running at the same time.

So that's our overview of SpectraFoo. Obviously the technical depths to which we could have delved are immense, but our mission is to enlighten those of you who may be new to all this rather than scare you away with technical jargon. There are several other tools we didn't dare attempt to simplify, such as the Power History and digital Metering functions, yet these will prove useful in anyone's digital desktop studio if the time is taken to understand the principals behind them. In the meantime here are the system requirements and below them is a link to the Metric Halo Ladoratories website where you can download a fully functioning demo.