What is meant by “the people pounded into submission”?

PLEASE ANSWER THESE QUESTIONS. THANKS IN ADVANCE.

“Shut up, shut up, shut up!” It was a plea, a cry so terrible that Montag
found himself on his feet, the shocked inhabitants of the loud car staring,
moving back from this man with the insane, gorged face, the gibbering, dry
mouth, the flapping book in his fist. The people who had been sitting a
moment before, tapping their feet to the rhythm of Denham’s Dentrifice,
Denham’s Dandy Dental Dertergent, Denham’s Dentrifice, Denham’s
Dentrifice Denham’s Dentrifice, one two, one two three, one two, one two
three. The people whose mouths had been faintly twitching the words
Dentrifice Dentrifirice Dentrifrice. The train radio vomited upon Montag, in
retaliation, a great tonload of music made of tin, copper, silver, chromium,
and brass. The people pounded into submission; they did not run, there
was no place to run; the great air train fell down its shaft in the earth.

Questions :

What is meant by “the people pounded into submission”?