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Intelligent Devices Pro Audio Analyser 2.0

Audio Analysis Software By Paul D. Lehrman
Published February 1997

PAUL D LEHRMAN discovers things he never knew about his recordings...

Computers make wonderful tools for music production. As recorders, editors, MIDI and studio controllers, signal processors, and sound designing systems, they have made themselves invaluable in every aspect of audio. One area, however, in which they have lagged behind has been analysis of recorded sound. Many digital audio programs allow visualisations of waveforms and some, like Alchemy and Sound Designer, have spectrum and/or three‑dimensional Fast Fourier Transform displays, but these are static displays, which can only look at an instantaneous slice of sound. True real‑time audio analysis, usually handled by a rack of pricey dedicated hardware, involves looking at audio signals as they are played or produced, through multi‑mode level metering, instantaneous displays of the relative levels of different frequency bands within the audio spectrum, and two‑dimensional displays of the relative phase of stereo signals.

This is what Intelligent Devices' Pro Audio Analyzer (PAA) software does, but instead of dedicated hardware, it uses a Macintosh computer, working either with the built‑in audio hardware of a Power Mac, or one of Digidesign's audio cards.

The software comes in two versions. The stand‑alone version is for use with external analogue or digital audio sources, which can be brought into a Power Mac through the computer's own 16‑bit 44.1kHz audio inputs (or an internal CD player), or into any NuBus Mac equipped with an Audiomedia II card or a Pro Tools I or II system. The TDM version is a plug‑in for Pro Tools II or III systems (both NuBus and PCI) with at least one TDM card. It shows up as an insert, either in mono on a channel, or in stereo on an auxiliary input. Even though the processing that the plug‑in version does on the signal is not as apparent as, say, a compressor, it uses up one DSP.

The Features

The program's display is in four sections, which can be viewed all together, or in various subsets.

  • The leftmost part of the display has five vertical level meters: vertical peak and average (VU) indicators for each stereo channel, in green and yellow, with a pair of red clip 'lights' at the top of each one; and a central meter which can be switched to show the average or peak levels of either the sum of the two channels (with a 6dB pad, which keeps it more or less at the same level as the individual channel meters), or the difference between them. The meters can be made to look like LEDs (large segments), plasma displays (small segments), or continuous displays. They cover a range of 96dB, which means they're almost always showing something — input noise, convertor noise, hum — unless you're playing a signal that consists of mathematical silence. Above the coloured segments are small white bars for peak hold indication. The release rate for the meters and the decay rate for the peak hold indicators are separately adjustable over a range of four speeds. An input trim control adjusts the input signal in eight steps over about a 20dB range. The steps are uncalibrated, but the 'zero' position is clearly marked.

The two clip lights atop each meter — one goes on at the first sign of clipping and stays on until you reset it, the other resets itself after a while — can be set to turn on anywhere from 1dB to 0.05dB below maximum level, so if you want to be daring, you can try to push your levels really, really close to the max. Below the meters are numeric peak indicators, which show, to the nearest 0.1dB, the highest level encountered since they were last reset.

  • Over to the right of the level meters is the spectrum display, which divides the audio range from 43Hz to 20kHz into 24 bands, each approximately 1/3‑octave. Individual vertical bars show the instantaneous level in each band — either the two halves of a stereo signal side by side, or the summed mono signal. A switchable reference 'legend' shows heights from ‑70 to ‑2dB, and the gain of the display can be raised 6 or 12dB. Peak hold indicators are here too. Their decay time, the display's update time, and the main release time are all adjustable. Using a slow update and decay rate can give you a good picture of the overall spectral balance of a recording over time — very useful when mixing.
  • Below the spectrum is the waveform monitor, which will be familiar to anyone who's used a digital audio editor. It scrolls the waveform as the audio plays, and can show two channels in parallel, summed mono, or the difference signal (L‑R), at any of three speeds, or reverse. In addition, any points at which the signal clips are displayed in red and stay that way, showing the clipping history of a piece over a fairly long period of time.
  • Finally, there's the phase scope. This generates dots representing the instantaneous stereo position of the signal, against either a vertical or diagonal axis. The dots can be either of two sizes, and there are three magnification scales. A 'phosphor emulation' can be switched on that causes the dots to die away slowly, and a 'length' feature controls the overall time a dot stays on screen — at the longest length, they turn into little snake‑like things. An overlaying grid can be switched on and off.
This description of PAA's features really doesn't do justice to the great usefulness of the product.

The update speed is not directly controllable, and unfortunately it's not very fast. I found this feature to be the least useful of the bunch: it can give you an idea of the overall stereo spread of a mix, and also show you when things are seriously out of whack, but if you're looking for the source of a balance or phase problem, the slow update speed makes it less than ideal. Apparently, this display is given lowest priority of the four, and although there's a slight speed improvement when all of the others are switched off, it's still no substitute for a real oscilloscope set up to monitor L vs R.

You can hear the audio that is passing through PAA, and control it via a dialogue box accessed with option‑clicks or, in the stand‑alone version, on a menu. You can select stereo, mono, or the difference signal, or put the sum on the left and the difference on the right. There's also a 20dB pad and a mute switch.

The Good, The Bad & The Ugly

This description of PAA's features really doesn't do justice to the great usefulness of the product. Simply by allowing you to look at music, while you're hearing it, in such a wide variety of ways and from such different angles, it can teach you a tremendous amount about how to mix music as you play favourite (or unfavourite) CDs through it, and watch the levels and spectral balances over time. When it comes to mixing your own music, by dint of being faster and more critical than just about anything else out there (certainly anything that costs less than several thousand dollars), PAA makes it easy for you to maximise your levels, and thus get the best dynamic range out of digital recording without encountering the unconscionable horrors of clipping. If you paired PAA with a good digital dynamics processor, like Waves' L1 Ultramaximizer, you'd have an unbeatable combination for making mixes that scream without screeching.

Although PAA is highly recommended for those who are serious about knowing what they're putting on tape or CD (and who have a fast Macintosh), there are a few ways in which it could be improved. The owner's manual, written by Intelligent Devices president (and audio columnist) Stephen St Croix, has a tutorial that reads like a magazine piece: breezy, clever, with plenty of amusing asides, and also informative and thought‑provoking. Unfortunately, that's all there is: there are no instructions on what you need to run the software, or how to set up your hardware or the Mac's treacherous System Folder. For seasoned Pro Tools users, this is not too much of a problem, but for new Power Mac owners, who want to see what's going on with their CD collections or their own mixes, it's pretty off‑putting. Neither is there a reference section, or even a picture describing what everything does. There is a list of keyboard commands, but it leaves out some of the most important ones, which you have to find by digging through the dense text. And the number of spelling mistakes is pretty embarrassing too.

Some less‑visible features are clumsy and don't work too well. There are command keys for setting many of the functions, which can be reconfigured by the user. Unfortunately, you can't just change one command key: if you want to change any of them, you have to change all of them, and the reconfiguration window doesn't show the default assignments, so you have to remember what they are (not all of them are in the manual) and enter them all in by hand. To make matters much worse, when it is in reconfiguration mode, the TDM version responds incorrectly to the Mac keyboard: when you tell it to assign a function to 'c', it thinks you're typing 'option‑shift‑6'. The choices of command‑key defaults also leave something to be desired: the space bar turns the spectral display on and off, but in Pro Tools, it happens to be the main transport control. When PAA is open, the key's transport function is disabled!

The manual tells you that if you put PAA's window in the background on a Pro Tools screen, it won't work well, but it doesn't mention that you can't. This is actually a problem with all TDM plug‑ins, but it's particularly annoying because PAA's window is so big. (There's no re‑sizing of the window per se, although you can choose not to display some sections.) If you have a small monitor and want to do things like operate Pro Tools' transport controls, or bring PAA in and out of an insert point in the Mix window, you have to do a lot of sliding things around.

In a strange violation of Macintosh interface guidelines, there's no title bar in the stand‑alone version — to move the window, you have to hold down the command key while you click and drag it. Another anomaly of the stand‑alone version is that you cannot shut down your Mac when it is running; you have to specifically quit the application first.

The Verdict

Rough edges aside — and at least some of these will undoubtedly be cleaned up in future revisions — Pro Audio Analyzer is a marvellous tool for anyone serious about audio. If you work with sound, you'll find a use for it: studio designers will use it to tune rooms, live sound engineers will look for hot spots and feedback points in performance spaces, mastering engineers will spot anomalies and imaging problems, broadcasters will make sure their signals are providing maximum punch; the list goes on. You may be tempted, as company president St Croix says he was, to spend hours looking at other people's recordings to see why they sound good — or not so good. It would be time well spent: with any luck, you'd learn to apply the principles thus discovered (the good ones, that is) to your own recordings, which should stand you in very good stead in the long run.

Neater Meters

The manual makes a strong point of saying that Pro Audio Analyzer is far more accurate and reliable than any other digital metering system because it will show a clip as short as a single sample, whereas other systems (like the meters on a DAT deck) might pass several clipped samples in a row before they acknowledge the problem. I was able to fool PAA sometimes, sending it signals just below clipping that caused the red lights to fire, and sending it single‑sample clips that didn't, but it got it right nearly all of the time. The usefulness of this feature was borne out when I fed the system a sine wave that just clipped at the very top: PAA's red lights blinked furiously, while a Tascam DA30 MkII DAT deck was placidly telling me I had 3dB of headroom left.


  • Spectrum display provides excellent picture of
  • Shows very short clips very accurately.
  • Allows you to get the best dynamic range out of a digital system.


  • Phase scope update speed not fast enough.
  • Manual could be more detailed.
  • Command key implementation needs work.


An extremely useful audio tool with lots of uses, and an excellent mix learning aid to boot!