21dB addresses acoustics at Harissa basilica
Published: MEA
LEBANON: Beirut-based consultancy 21dB has recently completed the first phase of a project to improve the acoustics at the Our Lady of Lebanon basilica in Harissa. This initial phase was based around electroacoustic correction within the venue.
The basilica is a cavernous concrete space with an RT of 12s. The primary challenge for the consultants was to deliver intelligible audio. ‘Before we started work on the basilica, many companies have tried and failed to compensate for the acoustic deficiencies with electronic means,’ recalled Fouad Bechwati, principal at 21dB. ‘By the time we came in there were many speakers installed all over the basilica but speech intelligibility was poor everywhere.’
The main system at the basilica was a pair of Duran Audio Axys Intellivox DSX500 column arrays. However, these had not been setup appropriately. This meant the first job for 21dB was to use the manufacturer’s DDA software to run a simulation of the basilica.
‘We had to first build a 3D model of the basilica which proved much harder than anticipated due to its irregular shapes and curves in all directions,’ said Dr Bechwati. ‘We then managed to complete the simulation and upload the new beam steering setup files just in time for the August 15th Assumption of Mary holiday which included a series of masses planned over the whole day at the basilica.’
The success of this first phase was demonstrable by the improvement in STI experienced at the basilica. ‘The average STI value measured across the Basilica went from 0.2 before the setup file was uploaded to 0.55,’ noted Dr Bechwati. ‘All other speakers were dismounted the next day and the only ones that remained are the two 5m long columns by Duran Audio.’
The result has also been appreciated by staff at the basilica. ‘The improvement was so noticeable that the head priest told me when he first heard the new sound: "You cannot believe for how long we have been suffering because of bad acoustics. We are completely thrilled to have met you and cannot start to think of ways to thank you for what you have done for us",’ said Dr Bechwati.
With the first phase of the project complete, 21dB will now move on to address the acoustic treatment. ‘What remains to be done is to reduce the reverberation times of the basilica so that music performances can be hosted,’ explained Dr Bechwati. ‘For that we will be running an Odeon simulation to evaluate the acoustic environment and propose the right solutions required.’