They are nuts if they claim that 81 to 85 dB is less than the average large church. They may have peaks that hit 90 or 95 also. I have followed church sound levels for 20 years. I have my own sound meter to check sound levels.

Foam ear plugs can only reduce about 26 to 30 dB at most. I could not be in 80 to 85 dB even with the foam ear plugs. I finally had to stop attending services in the auditorium.

A big issue in most auditoriums is poor sound design. Echos can cause as much problem as volume. The trade offs between form (style) and substance (sound quality) can be immense.

I have a friend who is one of the foremost church sound engineers in the USA. He routinely has customers who demand setting sound levels far above his recommended levels. He has worked in most church auditoriums in the SF Bay Area and Northern Calif. He has designed system on both coasts. They will complain and he will show up and they turned things up too high.

You will be fighting an uphill battle with this. Get some sound canceling head phones (Bose type) is you can. Or, maybe the church will get a set to keep on hand for needs like yours.