The decription of the Silencer (page 311) says that characters receive a -4 penalty to Perception Tests for the purposes of noticing gunfire. According to page 117, the threshold for noticing gunfire is 1, and the threshold for noticing silenced gunfire is 2.

Is this intentional? Are these effects supposed to stack? Or are the authors being overly ambitious by writing two sets of rules to describe one effect? If they stack, then mathematically it takes an average of 10 dice to notice silenced gunfire. If they do not stack, then it takes an average of either 6 or 7 dice to notice the same (depending on which of the two rules one observes). Of course, the -4 rule is harsher and also results in automatic failure for characters rolling less than five dice.

For comparison, it takes an average of 3 dice to notice regular gunfire.

I think I'd also give the perception roll dice for both sight and hearing, so it wouldn't be unheard of to get 10+ dice, so a -4 with a 2 threshold doesn't seem out of place.

Unless my senses flee me, suppressors do make it harder to see muzzle flash.

You can also get an accessory that works only on muzzle flash called a "flash hider."

Also, rememeber that silencers and suppressors do not eliminate the sound of the report from a fire arm, it just reduces the decibel level and happens to make the report unrecognizable as that coming from a firearm out to a certain distance. In essence it reduces and alters the audio signature. Plus, remember that firing regular ammo through a suppressed weapon will still result in a supersonic crack for those rounds which travel at faster than the speed of sound. If you want to have a truly "silent" weapon use either cold loads, rounds which travel slower than the speed of sound normally or a supressed firearm designed to reduce the velocity of the supersonic round to that of less than the speed of sound.

And do us all a favour, don't touch the can without wearing gloves, you'll just leave bits of charred skin all over it.