Imagine what it would be like to look at the music during a mix. Or better yet, to visually dissect the sounds on each track. That is the goal of Metric Halo Laboratory’s SpectraFoo Visual Audio Monitoring System. This real-time audio analysis software can analyze up to 24 channels of audio simultaneously.

While SpectraFoo is available in different software formats, I auditioned it within the Pro Tools environment. My test system consisted of a 266 MHz Apple G3 running Pro Tools 24. Minimum requirements for SpectraFoo include a PowerPC-based Mac with OS 7.5.3 or higher and a Digidesign Pro Tools III Core system with software Version 4.0 or later.

Features

SpectraFoo is based on the concept of synesthesia — the experience of multiple sensations at one time, e.g., the association of specific audio pitches with different colors in the spectrum.

One of the key ingredients in this audio analysis system is the fast Fourier transform (FFT). FFT has been used for years in hardware-based audio analyzers. In fact, the Fourier transform was developed by mathematician Jean-Baptiste-Joseph Fourier in the early 1800s. It was devilishly difficult to calculate. Today’s "fast" Fourier transform is a computer algorithm based upon Fourier’s work that can do the job in a snap. SpectraFoo is the first audio visualization system to provide high-resolution spectral and phase information synchronized in real time.

While using the Power Mac’s RISC processor, the program works in conjunction with the Pro Tools DSP Farm Card. This setup provides a high-resolution, high-speed, multithreaded environment for analyzing audio signals. When processing the dual-channel 64k point FFTs, SpectraFoo updates its display 42 times per second. At the program’s highest resolution, bin widths as small as 2 Hz or 3 Hz can be displayed. Keep in mind, processing power is also dependent upon the specs of the computer system being used.

A real-time rack of 10 audio instruments comprise the program’s spectrum analyzers. Any and all of the instruments may be displayed on the screen at once. They may be turned on or off, soloed, resized, zoomed in or out; images may be frozen on-screen and parameters can be changed in real time.

In use

In addition to the colorful meters and graphs, there is an accompanying text-based detail window. This lets the user change parameter settings for the corresponding display. For example, to analyze frequencies between 250 and 500 Hz in the spectrograph, simply move the on-screen sliders to this range.

Speaking of the spectrograph, this instrument features a continuous three-band color-coded display. Real-time, average and peak audio signals may be shown individually or at the same time. While running under Pro Tools at 48 kHz, the horizontal axis spans a frequency range of DC to 24 kHz and the vertical axis displays a power level in dB.

Like the spectrograph, the spectrogram analyzes frequency and power but adds the element of time. By using fours colors, the screen looks like a continuous abstract painting moving from right to left. The density of each color represents the power of that particular frequency. This display is particularly useful in identifying problem areas of frequency component overlaps — like a kick drum and bass guitar. Frequencies and power-scale range may be adjusted in the detail window.

The level meter is a basic and handy tool for measuring audio levels. Have you ever wondered about the accuracy of your DAT machine’s meters? Check it against the SpectraFoo level meter — you may be surprised. The three-in-one meter displays peak, RMS and VU levels graphically and numerically. For audio signals above 0 dB full scale, the display flashes red and lists the number of clipped samples.

Three time-base displays in SpectraFoo also appear as graphs scrolling from right to left. Power history compares peak levels against average RMS levels. And the ratio between these two levels is the perceived volume of the audio. Also similar is the power balance display. When the first input channel is greater than the second, the display turns green and increases above the graph’s horizontal line. Conversely, when the second input is greater, the display turns red below the line.

The envelope history is a moving sample-editor-envelope. Anyone who has worked with a DAW will recognize this type of waveform. All three graphs work well together. Most importantly, they provide a visual representation of the amplitude and balance between left and right channels.

The next analysis instrument is a single-trace oscilloscope. This free-running scope shows the active waveform against a background grid. Adjustable parameters include magnification of the oscilloscope trace and a time-scale slider for the grid. Freezing the oscilloscope in place looks much like a stock market graph.

The phase torch, a tool that compares phase relationships between two channels, is mesmerizing to the eyes. Shown as a circular diagram, five different frequencies are each represented by a different color. When the channels are in phase, there is a fountain of colors aligned with the negative Y axis. This tool is worth its weight in gold. In addition to being beautiful to look at, this graph can be a lifesaver in multimiking situations where accurate phase relationships are a must.

Also addressing stereo and phase issues is the Lissajous scope. Configurable in oscilloscope or vectorscope modes, the Lissajous displays the input signal’s amplitude along with the width of the stereo field. SpectraFoo also can show Lissajous patterns, which display the phase and amplitude relationships between the left and right signals of a stereo pair. Lissajous patterns (named for another 19th-century French mathematician, Jules Antoine Lissajous) give an idea of the width and spaciousness of a soundfield. This information is useful in identifying such problems as sibilance and low-end boominess.

Finally, there is a time code clock that locks to external time code or the computer’s internal clock.

Summary

Metric Halo Labs has released a new software upgrade called SpectraFoo Radical 3. Some of the new features include dual-channel modes for spectrum analyzers and oscilloscopes, impulse response measurement, multicapture data slicing and measurements of acoustical parameters. In addition, there is support for various hardware cards, and files can now be saved in Digidesign’s Sound Designer II format. Interestingly, this new version works both as a plug-in or a standalone application.

SpectraFoo is not limited to recording and mastering projects, however. Other applications include analysis of live sound acoustics, electrical engineering measurements, speech therapy, medical diagnostics, forensic audio analysis and as an educational tool for audio curriculums. The list goes on.

If the idea of looking at your music appeals to you, give Metric Halo Laboratory’s SpectraFoo a look-see. Definitely two thumbs up.

J. Arif Verner can be found in his digital production studio, Infinite Sound, when he is not writing for Pro Audio Review.