Some people have compared iPhone speaker volumes, to see which one of Apple's amazingly popular telephones produces the loudest sound. The result might very slightly interest you.
The iPhone 6 is the noisiest of all Apple's mobiles, outputting at a maximum of 105.4 decibels from its onboard speaker. The iPhone 4 was the quietest, managing just 92.9 back when there was a lot of fuss about people hurting their ears by listening to things too loudly. So you weren't going deaf back in 2010, it was just a quieter speaker. [iClarified via Independent]