Yeah I can hear a slight thud every time the blocks collide with a wall! (I'd consider the level completion noise more of a bell jingling sound but it's good too!) Level 20 is a great example of the thud sound effect because if a move causes the red barriers to open and if there are blocks up against that wall, they fall through and land at a slightly different time than the initial thud from that same key press. Created some really nice pitter-pattering in my opinion! Anyways the sound is definitely coming from your game so I'm not sure why you wouldn't be able to hear it?
Also yeah I don't think you need to do anything to prevent brute forcing, it's just another way to play! Didn't make it any less fun for me cause I would still end up having to slow down and think about it if I felt like I was caught in a loop of no progression lol. Limited spins would honestly make me less motivated to push through, I think.