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TerraSonde Audio Toolbox

TerraSonde's Audio Toolbox ($999) is a DSP-powered, multifunction handheld device that does acoustic analysis, audio tests, troubleshooting and calibration.

The cost-to-horsepower ratio of DSP has made it possible to perform previously unthinkable tasks at truly affordable prices. Not so long ago, countless individual pieces of test equipment could easily cost five figures or more. And many of these devices were not even designed for audio. Only designers and manufacturers could afford such luxuries and we mere mortals had to use only our ears as tools. Don’t get me wrong I’m not minimizing ears – in some cases we can hear things we can’t even measure.
Product PointsApplications: Troubleshooting; calibration; acoustic analysis

Key Features: Uses built-in or external mic; SPL meter; signal generation; RTA; MIDI helper

Price: $999

Contact: TerraSonde at 303-545-5848


+ Pro and consumer I/Os

+ SPL meter

+ Phase checker


– Case is sharp around the edges

The Score: A great, feature-packed audio tool for a fair price.

TerraSonde’s Audio Toolbox ($999) is a DSP-powered, multifunction handheld device that does acoustic analysis, audio tests, troubleshooting and calibration. Four main menus set the stage for an amazing amount of in-depth functions. The review sample I have is Version 2 and it has many new features and functions not available in the previous version. Newer software versions can be downloaded and installed into the Toolbox for free during the first year or you can send the ATB (Audio Toolbox) to TerraSonde for a complete hardware/software upgrade for $75.

In early ’00, TerraSonde will be releasing the Audio Tool Box Plus, which will be packaged in an anodized-aluminum chassis with a built-in rechargeable battery system and a removable microphone. A rackmount version, powered on 120/240 VAC, will also become available shortly. All units share the same set of software features.

The acoustic analysis section has six functions, starting with the sound level meter. A giant upgrade from the Radio Shack meter that many of us use regularly, the ATB has a large numeric display for SPL and can measure ANSI-type 0, A, B and C weightings, in addition to unweighted or flat. These are all true RMS measurements.

With the standard built-in microphone, the range is 100 dB (30 to 130 dB) and can be extended another 35 dB with the optional external mic. A signal generator outputs sine or square waves from 10 Hz to 20 kHz in octave, one-third-octave or fine modes and pink or white noise. A nice addition here would be one-third-octave filtered pink noise – maybe future software upgrade? Slow, fast, impulse and peak modes, as well as long term SPL averaging up to 24 hours, make the ATB extremely flexible.

The next function is the real time analyzer (I can see now I’m not going to make it through all the functions). The RTA can accept low or high mic level inputs in addition to a line input. Either full bandwidth 20 to 20 kHz or low, which covers the low-frequency band from 10 to 332 Hz, may be selected for analysis. The latter is nice for subwoofer setup.

At any given moment, the band with the highest dB reading is displayed on the screen. Averaging speed is also adjustable. A variable output pink noise generator lets you set the reference while a vertical cursor can be moved around to read out the exact dB level of any bar on the screen.

The energy time graph generates a pulse at the output that can feed to an amp/speaker. The internal microphone receives this signal and lets you measure time in ms or distance in feet, inches, meters or centimeters. This is very useful for speaker setup or setting delay times in multiple speaker setups.

Reverb decay time computes reverb decay for a room referenced to the standard RT60 time, which is the time it takes for reverb to decay by 60 dB.

The polarity tester can be used to check speakers, microphones or any audio electronics for that matter. Absolute polarity with speakers is oftentimes not detected when they are in phase with each other.

One of my favorite tools in the Toolbox is noise criteria (NC), which can be used to measure the acoustical noise floor of a room. This is probably the most overlooked specification in pro audio when you consider the kind of dynamic range we deal with in equipment. It is not unusual to find control rooms or recording spaces that have an NC in excess of 50 dB. To have a 60 dB listening dynamic range window, one would have to be listening at 110 dB or higher! Not good for your health. Fans, computers, HVAC and outside traffic all contribute to this pollution and we get used to it or just choose to ignore it. Taking the ATB around and looking at NC readings shows you just how noisy some rooms are.

Test functions include a signal generator, which also includes an impedance meter as a subfunction.

The level/frequency meter has four functions, including a stereo level meter, a stereo frequency counter, a stereo dB bar graph meter and a stereo VU bar graph meter. Signal/noise ratio compares the noise floor of a device to the full-scale signal and computes the signal-to-noise ratio. Frequency responsemeasures the response of a device by measuring the response of the center frequency of each one-third- or one-twelfth-octave band in the audio spectrum. Sample scopeis like an oscilloscope that runs at the maximum system sample rate of 48 kHz and shows the incoming signal on a graph. It can also be used as a phase meter when used in the X/Y mode. Distortion meter is very useful for measuring distortion in speakers, individual drivers as well as matching complete systems.

Session helpers include an instrument tuner, tempo computer, MIDI helper, MIDI transmitter and timecode tools (which include a generator, reader and calculator). Hum cancellation actually samples the hum and removes it.

Utilities consist of a monitor amplifier for driving headphones from a line input, a cable tester (both wiring test and audio test are performed) that can also be used to check continuity, power test (used to check phantom power and battery level), and transmit data (which is used to dump data to a PC or Mac).

In use

An LCD display provides clear, easy-to-read letters and graphs, even without my glasses. The entire Toolbox can be controlled with a single encoder knob that is extremely easy to use. The left side has stereo inputs that are both balanced XLR-1/4″ combo and unbalanced RCA. The outputs are on the right side of the unit and are XLR and 1/4″, as well as RCA. The 1/4″ headphone jack can also be used as a stereo line output. Three MIDI connectors are provided as well.

Physically the ATB is black plastic and is a little rough (and sharp) around the edges.


It would take many more pages to fully describe all of the functions of the Audio Toolbox but this should give you an idea of the depth of audio testing that can be done with this great little product. At $999 it is very good value. Nice Job.