Testing, Testing

1/12/2017 9:53:00 AM
By Craig Anderton
Craig Anderton

Let’s salute the unsung hero of modern recording software: test and measurement. In the days of tape, your test gear was VU meters that sorta indicated when something was happening, a volt-ohmmeter in case you had to fix a cable or check for patch bay shorts, and if you had the bucks, a dual-trace oscilloscope or Audio Precision AP-1. Fortunately, you did have the world’s most sophisticated test equipment—your ears—but they can do only so much.

Before continuing, let’s address those who scoff at “listening with your eyes.” While measurement doesn’t substitute for technical and artistic judgment, ear training happens much faster when you can correlate what you hear to what you see. For example, before digital delays, I had only the vaguest idea of how long a delay was. But after dialing in delay times for all these years, I can say “add about 40 ms of delay” and know it will be at least close to that amount.

TESTING INSIDE THE DAW

DAWs continue to add features that assess what’s happening with audio. One of the most important is comprehensive metering that can show and hold both peak and average readings, as well as set the meter range—for example, 12 dB to see what’s happening with the master bus, or 90 dB to reveal low-level noise on an input signal.

Spectrum analysis has also transitioned from expensive hardware to everyday software; it’s not uncommon for EQ and other plug-ins to include a spectral display. DAWs that also have a mastering orientation, like Samplitude and Studio One Pro, typically take this further with the ability to hold peaks and switch to different display types (e.g., change resolution or FFT analysis characteristics). Correlation, balance, mid-side and phase meters are working their way into more and more DAWs; if something’s missing, add sophisticated plug-ins from companies like Blue Cat, Brainworx, Voxengo, iZotope and several others.

Bob Katz’s loudness- and headroom-based K-System metering has become a de facto standard for calibrating studio monitors, with the goal of consistent recordings having sane levels of dynamic range, as based on the intended delivery (e.g., broadcast, home theater, etc.). Furthermore, metering in general is becoming more important than ever due to more rigorous broadcast standards. Without getting into the details of various definitions (LKFS, LUFS, LU, etc.), standards like ITU BS.1770-3, target levels, true-peak metering and the like, suffice it to say that before audio leaves the mastering phase, it has to be in compliance with these standards.

DEDICATED SOFTWARE

There are also dedicated software programs. The Windows-only, “old standby” RightMark Audio Analyzer simplifies measuring crosstalk, THD, frequency response, IM distortion and other audio interface attributes. ARTA makes programs (again, Windows only) for signal generation, impulse response measurements, THD analysis, and triggered storage scope functionality; with a calibrated microphone, you also have an SPL meter. TrueRTA is another Windows-only favorite whose basic package provides real-time audio spectrum analysis, signal generation, a digital level meter, crest factor meter and even a dual-trace oscilloscope.

There are also more specialized programs, like the Room EQ Wizard (for Windows and Mac). It can generate test tones, measure SPL and impedance, check frequency and impulse responses, generate spectral decay plots and calculate reverb times, and quite a bit more. If that sounds too much like work and you just want a quick spot check of various frequencies or a swept tone, just “ask the internet” and you’ll even find sites with free online signal generators.

OUTSIDE THE COMPUTER

If you’re not around a computer, you still have options. There’s Phonic’s PAA6 palm-sized audio analyzer, as well as several smartphone apps (many depend on a calibrated mic, but you can still get “ballpark” results from a smartphone’s internal mic). Software is a big part of making affordable, stand-alone test gear a reality.

Naturally, you don’t always want to obsess over specs; after all, we’re aiming for an end result that has an emotional impact on an audience. But knowledge is indeed power—and the more you know what’s going on with your audio, the better. One of my favorite “parlor tricks” for newbies is playing a swept sine wave and watching the expressions of horror as they realize how bad their room acoustics are—but fortunately, software has kept pace with the more rigorous needs of pros as well.

Author/musician Craig Anderton’s official web site is now live at craiganderton.com, and his latest album, Neo, has been uploaded to his re-designed video channel at youtube.com/thecraiganderton.

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