64 watts = 18.1 decibels. If by 'set' you mean you have two 64 watt speakers then they will create 36.2 decibels.
70-100 decibels
120
The iPhone can produce a maximum of 100 to 115 decibels.
43db
There is a few generators that will produce less than 60 decibels. That is about the same decibels as background music. These are good to use if you live in an apartment or have very close neighbors.
At 80% load factor you can support 60 fixtures.
20 decibels
207 decibels.
20 to 50 decibels (dB).
85 decibels maximum.
in what
That depends only on the distance where you are hearing the Big Ben and where you are measuring it. Don't come to close.