Austman – Clearly, you know your building, but the point I was making is that a performance-based assessment of air quality may reveal that the existing ventilation system is over-doing it, and that you may be able to reduce the frequency of its operation and/or slow the rpm of the fan/s in order to reduce the noise and operational costs. I expect that adjustments of that type (as opposed to changes) to the ventilation system wouldn’t affect existing approvals.
Anyway, it’s something to keep in your back pocket if the acoustics assessment doesn’t lead to improvements that resolve the complainant’s issues, which if it helps at all, he/she is contributing to by 1/12.