I was recently out doing a demo with the JBL VerTec rig that I often talk about.
The room was a traditional shoe box sanctuary that was very reverberant. The walls were plaster, the ceiling also plaster and had a slight smooth arch to it.
The balcony wall was glass that stretched from side to side with a flat plaster wall above the glass. One nice thing was that the reverb was relatively full frequency and smooth.
In fact, congregational singing and the organ both sounded spectacular.
As I was setting up the system for a Thursday night rehearsal the pastor of the church came in and began turning on the air conditioning units. The air conditioning consisted of eight large wall-mounted interior units that were mounted where the walls butted up to the ceiling.
As the pastor fired up the first unit, I immediately took notice of how loud the unit was (think of those window air conditioning units that go into houses x 10).
By the time he fired up all eight units I found myself talking with the pastor having to push my voice to get above the noise. I estimated that there was well above 70 dBa of air conditioning noise!
As I continued setting up the system I found myself thinking about a conversation I had with my friend Vance Breshears (senior consultant at Acoustic Dimensions).
A few months earlier Vance had been in town, at an “audio geek” lunch with me and several other friends, and he had talked about a class he was teaching on acoustics. Specifically, he referred to acoustics as “signal-to-noise ratio.”
I wondered just how much signal I would need in order to get the system “over” the air conditioning, and what kind of problem this would pose in the reverberant space.
It turned out to perform pretty well, providing very good intelligibility despite the background noise. I was surprised as to how good it actually sounded.