Dirac will work with most Windows compatible sound devices. A full-duplex card is recommended. USB based sound devices, such as the Triton, can also be used.

To improve the measurement quality, or to obtain a frequency spectrum, you can use the internally generated MLS or swept sine signals, connecting the soundcard's line output to an omnidirectional loudspeaker sound source through a power amplifier. An example of an omnidirectional sound source is the Pyrite and an example of a power amplifier is the Amphion.

To measure the speech intelligibility (STI, % ALC, STIPA, RASTI, STITEL) of unamplified talkers, you can connect the sound device output to a mouth simulator or a small loudspeaker with a directivity characteristic similar to a human speaker. To test a speech relaying sound system, you can connect the sound device output directly to the system input or use a CD or MP3 player with provided MLS or sweep signals. An audio CD containing selected stimuli is available here.

Using the input level calibration and the speech filters built into Dirac, accurate speech intelligibility measurements can be performed. Dirac can add artificial noise spectra to these measurements, or you can enter your own SNR values to aid in what-if analyses. 

You can obtain additional parameters by using both line input channels. For instance, you can obtain LF, using an additional bidirectional microphone, LFC, using a sound intensity probe, or IACC, using a measurement head. By using an additional omnidirectional microphone, you can double the number of measurements in the same time.

Sometimes it is convenient to use excitations other than an impulsive, MLS or swept sine signal. Dirac supports a wide range of broadband source signals, such as pink or white noise and music. With this method you can measure not only single channel parameters, but also the LF, using a switchable microphone.

Dirac supports automatic system calibration in a reverberation room (diffuse field) according to ISO 3741. It is also possible to perform free field system calibrations. System calibrations only impact post processing, and need not be completed before starting field measurements.
The level calibration allows measurement of the Leq.

The measured impulse responses are saved as standard Windows .WAV files, that include information for unambiguous identification and interpretation of the impulse response. Extensive signal editing features with unlimited undo can be used to extract the relevant portions of an impulse response, or to remove unwanted signals.

The calculated parameter graphs and tables can be printed or saved as ASCII files that are easily imported into a spreadsheet. The graphs and tables can also be copied to the clipboard, for inclusion in reports. A user-defined selection of parameters, (including group averages and other statistics), can be calculated and saved to disk for all files in a project, in a single operation.

Several post processing options provide support for scale model measurements and auralisation. The subtraction method as prescribed in ISO 13472-1, NF S 31-089 and CEN/TS 1793-5 can be used for in-situ reflection and absorption measurements using the Zircon probe.

For more information download the Dirac product data sheet, or try Dirac using the demo version which you can download here. We also have some technical notes describing the use of Dirac.