Thread: kick arse suppresor ?

Originally Posted by Cigar

Yes, but temperature drops as altitude increases, so there is an indirect effect of altitude.
I read something in a hunting or tramping book years back that stuck in my brain - if I recall correctly, it said temperature drops 6.5 degrees for a 1000m increase in altitude, meaning the temp at the treeline is roughly 8 degrees lower than at sea level, all else being equal.

Yeah but some people get confused because in aviation you have Indicated Airspeed and True Airspeed (IAS and TAS). Airspeed indicators rely on pressure, so as you go higher your TAS increases relative to your IAS. So at 0 alt, the speed of sound is around 660 knots (IAS and TAS ), and at 50000 feet it is ~ 570 knots TAS (due to the temperate drop) and 285 knots IAS (due to the temperature drop and decreased pressure reading).

And for some reason this gets crossed over into the belief that pressure has an impact on the true speed of sound (in air).