Here's the audio of a single muzzle loading civil war rifle, shooting a real minie ball with 60 grains of powder, cloned 13,000 times with computers and timed to fire randomly in 25 second intervals. This gives us a rough approximation of what Pickett's charge must have sounded like based on eyewitness accounts.
— Gettysburg Picketts Charge rifle audio from actual recorded gunfire:
This is what the artillery must have sounded like during a 2 hour bombardment at Gettysburg. Researchers say it was the most cannons fired in a single battle until world war I.
....And the 700 Cavalry soldiers firing their carbines every 10-15 seconds.
Turn your volume WAY down.
This can only give us an approximation of how Hellish Pickett's charge was. Songs have said that Lincoln from his desk in Washington could feel the earth shake and hear the roar of the cannons.