A sound engineer by the name of Belli Dura Despicio on YouTube has recreated the terrifying sound of a World War 1 era drumfire. This is an audio simulation of five minutes in a World War 1 trench line.
A preparatory bombardment is conducted directly before an assault. The intent of the bombardment is to degrade and at the very least decimate the defenders position, which will theoretically give the attackers an advantage going into the attack. Thinking about this from a doctrinal perspective, it makes sense that a preparatory bombardment should be used on any hardened position with a large number of defenders that you are sending your attacking force into.
The unforeseen side effect of a massive preparatory bombardment however is show-cased quite well in this five minute recreation of the sound a drumfire preparatory bombardment creates. Even if you do not completely decimate or degrade your enemy with this type of fire mission, you certainly induce a level of shock that demoralizes the enemy heavily. On top of this, you probably destroy their ability to communicate effectively with anything outside the use of a high-pitched shrill from a whistle.
Imagine if you will, this five minutes of sound, lasting for several hours or days. Close your eyes once the drumfire sound begins, and just imagine yourself sitting in a trench, hungry, cold, and covered in mud. Now, imagine that this is the noise you have been listening to for the past several days, and imagine that every impact sent a shockwave through your body like a small earthquake.
War is Hell.