The loudest fire alarm I’ve heard is my Wheelock 7002T-12. It’s so loud I can’t be in the same room with it without hearing protection or covering my ears. Haven’t heard any other mechanical horns besides scoreboard horns, which were all Federal Signal Vibratone 350s so can’t really compare it to anything else. It is definitely much louder than a Vibratone 350 tho. As for the electronic horns, that would be the System Sensor SpectrAlert Advance as it’s almost as loud as my 7002T but I can still handle it up close without having to cover my ears. It is still very loud and painful though. The second would by my Wheelock MT-24-MS, My school’s Wheelock/Siemens ZNS-24s, Siemens UMMTs, and my Gentex SHG-24-15/75WR