It varies a lot with the type of brake you are using and shooting position. The most efficient brakes I've used have the ports angled somewhat to the rear but the muzzle blast can be brutal because the noise is also being directed towards the shooter. Radial discharge brakes follow behind them in noise directed back at the shooter. For the best combination of efficiency, muzzle flip reduction and noise directed back at the shooter I want a side discharge brake with the rear ports angled ever so slightly forward with additional ports at or above the 10 and 2 Positions to keep muzzle flip to a minimum. After trying more than a dozen different types of brake over the years I've settled on the Northwest precision muzzle brake in the slotted version. I find noise wise it's entirely tolerable even if I find myself needing to make a quick shot without time to put on hearing protection.