vtchopperdude said:
the 5.56 with the 762 can on it sounds like a 22LR and you can shoot it all day without hearing pro and be fine
No, if you shoot it all day without hearing protection you're giving yourself permanent hearing damage. It might not be noticeable to you, but it's still happening. Your 5.56 rifle with that silencer on it is around 135 dB, which is louder than a jackhammer and is well above the threshold for permanent hearing damage.
The silencer industry uses the term "hearing safe" to describe any silencer under 140dB. This is a deliberately misleading term, and it's a misrepresentation of the rules for noise exposure. The 140 dB threshold is what OSHA uses for the upper limit of the safe dB threshold for a one-time impact noise. But that doesn't mean any sound below that is safe and won't cause permanent hearing loss.
Here are the decibel guidelines for daily exposure as described by the American Hearing Research Foundation (emphasis added):
"Habitual exposure to noise above 85 dB will cause a gradual hearing loss in a significant number of individuals, and louder noises will accelerate this damage. For unprotected ears, the allowed exposure time decreases by one half for each 5 dB increase in the average noise level. For instance, exposure is limited to 8 hours per day at 90 dB, 4 hours per day at 95 dB, and 2 hours per day at 100 dB. The highest permissible noise exposure for the unprotected ear is 115 dB for 15 minutes per day. Any noise above 140 dB is not permitted.
[...]
Combined use [of ear plugs and muffs] should be considered when noise exceeds 105 dB. Note that for such situations, it may be that there is no type of hearing protection that will stop a very loud noise from affecting you."
http://american-hearing.org/disorders/noise-induced-hearing-loss/
In comparison, a centerfire rifle with a silencer is usually in the 135 - 140 dB range. A centerfire pistol with a silencer and subsonic ammo is usually in the 125 - 130 dB range. And a .22 with a silencer and subsonic ammo is usually in the 115 - 120 dB range.
Using the formula provided by the American Hearing Research Foundation, the maximum allowed exposure time per day for your suppressed 5.56 would be under half a second. [EDIT: Actually it would be just over 56 seconds. Apparently I calculated incorrectly. But that's still not a very long time. And remember, that's the maximum exposure time per day, but that doesn't mean a shorter duration can't cause hearing loss.]
Now, I'd be interested to know how the recommended exposure levels translate to an intermittent sound like gunfire. I'm not at all claiming that the exposure times allowed for each dB level directly translate to gunfire. But those numbers still show that suppressed gunfire can cause hearing loss, it just probably takes longer than a constant noise would take.