How loud was a Brown Bess (musket)?

A friend of mine is writing a story which takes place in about 1775. At one point, one of the characters hears someone fire a shot using a Brown Bess (British military musket) from a distance of perhaps half a mile. She does not have a clear line of sight back to the shooter, who is behind her. Perhaps her vision is blocked by trees or a hill.

How loud would the shot sound to her? What would it sound like? A comparison to a modern-day noise is acceptable.

Big bore muskets have a sound signature similar to a 12 gauge shotgun, IME. The report is more of a “boom” than an earsplitting “crack” like a high powered rifle.

My son shoots a brown bess.
To some extent it depends on how large of a load of gunpowder they used.
From 1/2 mile away it would be clearly audible, even through trees, tho not really loud.
I’m finding a hard time thinking of a comparison - maybe it would sound similar to a handclap.
Scum is right - it does not have a rifle’s crack.
From a distance it sounds more like a pop, if that makes any sense.

Is it because a musket ball is subsonic, and thus no crack?

A camcorder isn’t exactly a hi fi sound recording device, but there are videos on youtube like this one that show a brown bess being fired:

http://www.youtube.com/watch?v=SJMbxZ1k9NQ

The sound is going to be pretty muffled a half a mile away and without a clear line of sight, but would still be quite recognizable as a gunshot. As the others said, more of a pop than a crack.

The sound a gun makes comes primarily from the rapidly expanding gas exiting the muzzle. The more gas you have, and the higher pressure it is under, the louder the gun will be. Blackpowder weapons, like the Brown Bess, operate at much, much lower pressures than a modern smokeless high powered rifle. The supersonic bullets contribute, but the majority of the noise is from the powder gasses.

Thank you for the information, gentlemen and/or ladies.

Robert