Harnessing Digital Technology to Improve Audio Clarity

Pouvez-vous m’entendre sur le balcon?

Notre Dame de France (NDF) is not, as you might expect, in Paris but in London – in fact just off Leicester Square. It is the home church in London for the French speaking Catholic community and, naturally, the Sunday services are in French (with some English translations as required).

Unfortunately, the acoustics are such that it is pretty difficult to be heard, as the reverberation time of a circular domed building, with reflective hard surfaces, is long. The sound amplification system has a very tough job to cut through and project voices clearly and intelligibly into the congregation.

Add to that a varying congregation size ranging from 12 up to 500 and you can begin to understand that the ministers, readers and singers had a problem with being heard clearly anywhere, let alone on the circular balcony!

Father Des Hanrahan, responsible for selecting and installing a new sound syste, said “We suffered with poor intelligibility in the very reverberant acoustics and a Hearing Loop system that had failed. We struggled with unpredictable radio microphone dead-spots and it was difficult to adjust volume levels when the church was full.”

Directional Loudspeakers Deliver Clarity not Overspill

The solution was first to upgrade the radio microphones (and move them on to frequencies that didn’t clash with a lot of adjacent theatres) and replace the (failed) Hearing Loop amplifier.

In a second phase fourteen loudspeakers distributed around the church were replaced with only four very directional ones. The circular balcony presented a particular challenge as minimal overspill into the rest of the church was required. This was solved very elegantly with two circular shaped loudspeakers strategically placed behind pillars on either side of the building; these radiated out of both the “front” and “back” but not to the sides, thereby producing minimal overspill into the rest of the domed church. 

Auto-Mixing Filters Sources

Finally a new mixer was installed that automatically turns off an individual microphone when not being spoken into, thereby preventing that microphone from picking up and broadcasting reverberant sound.

Father Des Hanrahan summarised “The automatic levelling system now handles the wide dynamic range incurred by different users who read and sing. The new loudspeakers are visually discreet and it’s significant that the congregation is not really aware of there being an amplification system, thus implying that the sound is clear and natural sounding”.