At 85 dB you’ll have hearing damage from long term exposure without hearing protection. Normally considered 8 hours a day 5 days a week. So 2000 hours in a year. Higher sound levels have a lower threshold so shorter times. 120 dB is the threshold of pain, so immediate hearing damage. Also, dB are a 10x log scale. So every 10 dB is an order of magnitude increase. So the siren is actually about 3000x louder than when you should start wearing earpro.
Only really counts for feet and inches. But yes, having your base unit be divisible by halves, thirds, quarters, sixths, and twelths with whole numbers of sub units is highly useful when fabricating objects when you don’t have access to modern tooling and supplies. In fact I would argue base 12 is the superior numerical system that was abandoned for metric and we have lost something in the meantime. Though Jan Misali might disagree with his love for sexinal.
Imperial units do have another advantage to this day, though. When talking about machining bolts and threads Imperial use threads per inch or threads per unit length while metric uses the pitch of the thread, so mm in-between threads. This decision means that when machining imperial nuts and bolts we by default pick whole numbers of threads per inch which due to the circular nature of lathes means that a simple clock dial can keep the lead screw synchronised with the head. Since metric uses pitch we pick numbers like 1.25mm pitch which does not always synchronous well with the lead screw and head and requires some odd gear ratios to cut specific threads.