Over the years, DIRAC 6 has been improved in small steps to keep it up to date, but the time has come for larger updates that affect many parts of the software. Changes that not only add new features now, but also prepare the way for all that is yet to come. For now, DIRAC 7 is the result of these changes, and here we'll show what some of these changes are and how they can help you measure better and faster.

Multi-channel measurements
The most prominent change is the support for multi-channel measurements. This change is immediately visible in the measurement window when you have set up a multi-channel device:

Note that you can now select a sound device setup on the Device tab. This selection can be saved in a measurement setup, allowing you to prepare setups for different devices, and quickly switch between them, all from within the measurement window.

When the options on the Project tab are set correctly, previews of the measured files will appear in in the project window. This allows you to quickly judge if all channels are as expected. Double clicking on one of the previews will open the corresponding IR view.

The new Channels tab allows you to enable/disable individual channels, and to specify each channel's properties. To play back a stimulus during the measurement, the output channel needs to be selected. This replaces the internal/external stimulus selection in earlier versions of DIRAC.

Other properties that can be set for each channel are the position number, the angle, the source-receiver distance, the channel gain and a microphone frequency response correction.
For microphones that use 2 channels, such as intensity probes, the grouping of channels will be indicated, and the distance between the microphone capsules can be set.

It should be noted that for each single transducer microphone, DIRAC will produce a separate single channel .wav file. For intermittent measurements these files contain a second channel with the background noise. For microphones with 2 transducers (e.g. probe, omni-bi-directional or HATS), DIRAC will produce a dual-channel .wav files, with a channel for each transducer. Intermittent measurements are at this time not possible with multi-transducer microphones.

Improved VU meters

The red (negative) values below the VU meters indicate that the input channels are uncalibrated, and display the input value relative to 0 dB full scale. Channel 1 in the image to the left is calibrated and displays the current level in [dB]. The peak value is displayed with a single horizontal line (yellow in the picture above), the RMS value is displayed with a solid bar, and numerically below the VU meter. At the top of the VU meter you can see the clip indicator which is cleared automatically at the start of each measurement, or when you click on it with the mouse pointer. The different areas of the VU meter can be set up by left-clicking on the meter, which displays the VU options dialog.

New stimuli

In the stimulus dropdown you will find a new set of bandlimited stimuli. These are meant to get more energy into the frequency range of interest, and to prevent damage to loudspeakers. Playback of the stimulus now starts with a quick fade-in and ends with a fade-out to make it a little less unpleasant. At the end of each measurement, DIRAC will play a sound via the default speaker (usually the laptop/PC speaker).

All stimuli can be used in intermittent measurements. There is now also a separate tab in the signal generator that allows you to create .wav files with the stimuli:

When using an e-sweep stimulus, DIRAC will automatically disregard the distortion products that normally appear near the end of the IR while calculating parameters where this is relevant, such as the INR and the RT.

The ECHO stimulus can now also be played from within DIRAC. When the ECHO stimulus is selected, a 'Voice' button appears that serves the same purpose as the voice signal in the HBK 4720 Echo device. This can be useful when measuring the STIPA where the signal is fed directly into the PA system.

Wireless measurements using the HBK 2255 and HBK 2755
DIRAC can communicate with the HBK 2255 Sound Level Meter and the HBK 2755 Smart Power Amplifier using a WiFi connection. Once selected in the sound device setup window, DIRAC will automatically find the available devices and establish a connection. The found devices are displayed on the new Wireless tab of the measurement window.

Multiple SLMs and amplifiers can be connected simultaneously, although for playback only a single amplifier will be used at a time. Having multiple SLMs without any cabling can greatly reduce the time required for measurements.

Loopback channel
For accurate source-receiver distance measurements, the delay between playback of the stimulus and the recording must be know. The device setup window contains a button that can be used to calibrate the source-receiver distance using a loopback cable, or a loudspeaker and a microphone at a known distance from each other.

Not all sound devices have a stable delay, and for the most accurate timing a loopback channel can be used for the measurement. The loopback channel should receive the stimulus signal, and will be used to deconvolve the response from the other active channels.

Real Time Analyzer
DIRAC now has a Real Time Analyzer window. It is available from the IR view toolbar (the animated icon next to the recording button), or by double-clicking on one of the VU meters in the measurement window.

Updated standards
DIRAC has been updated to support IEC 16268-16:2020 and ISO 3382-3:2022. Also, support for measurements using the EN 1793-5:2016 standard has been improved.

Other improvements
DIRAC 7 features many more improvements, such as the playback marker in the IR view, new parameters, support for the 65536 Hz sample rate and a new licensing system that allows for floating licenses. These and more will make measuring easier, faster and better.