Propane Gas Fireplace Roaring Sound
Papatots is right, in suggesting that this is a potential hazard. Especially with propane. Propane has a flame speed of 32" per second, that's why propane appliances have an 11" water column (pressure). Fireplaces will often have plenty of secondary air to complete combustion regardless of the pressure but that doesn't mean you want any deviation from the manufacturers allowable tolerance. An easy thing to look for is called "lifting" not like hitting the gym, but the flame, if the flame has a visible gap between itself and the burner the pressure is likely to high.

Disclaimer
In any case these things demand respect. Don't play around with fuel burning appliances unless you understand the dangers. Propane can be very explosive and a delayed ignition on a propane fired fireplace can easily result in a tempered glass grenade.