One of the most time-consuming aspects of noise barrier measurements for EN 1793-5/6 and EN 16272-5/6 is the correct positioning of the microphone array in relation to the barrier and the sound source. More often then not, there is very little maneuvering space for the tripod, especially when the ground is not flat. Also, measuring and correcting the distances from the source to each of the microphones can be tedious.

Recently, AE has released mechanical and software tools that should help make it much easier and quicker to perform this task.

The mechanical solution consists of 4 adjustable spacers that can be used to fix the distance between the (non-flat) barrier and the microphone array. Typically, the microphone array would be lifted by ropes that run over top the barrier. The drawings below give an impression of how the array is positioned in front of a sloping barrier using spacers and rope.

The spacers can easily be attached to the MA24 microphone array, and can be adjusted from 174 to 392 mm. Existing Zircon MA24 owners can order a set of 4 spacers free of charge.

For more information on the mechanical aids for array placement, see Technical Note 18 - Zircon MA24 placement.

To correctly position the source in front of the microphone array, DIRAC 7.1.8875 has been updated with an Aligner option. This option can be found in the measurement window on the new Align tab:

The Align tab is only visible when the sound device has 10 or more input channels, and the new array receiver is selected. Note that a loopback channel must be set for the Aligner to work.

When the Aligner is activated using the Run button, DIRAC will make continuous IR measurements to measure the distance between the source and each of the microphones. The positioning of the array is visualized in real time with the 5 circles, representing the corner microphones (1, 3, 7 and 9) and the center microphone (5). The deviation from the nominal distance in [mm] is given by the number in the center of the circle. A deviation within the tolerance limits given by the standard is indicated with a green circle. When the distance is too large, the circle is red, when it is too small the circle is blue.

To make it easier to see the alignment from a distance, selecting the Expand button will open a larger sizeable window with the same 5 circles:

The distance measurements by the Aligner have been optimized for the Zircon V2 system with the LS24 loudspeaker source and MA24 microphone array. Other hardware may require a software configuration change. Please contact us for details should you wish to use the Aligner feature with other hardware.