Every CS2 map has different audibility, so you must practice a lot on different maps and carefully check the specifications of them. On some maps you can hear the enemy due to thin walls, or due to wooden boards that can be really loud if someone’s running. Learn CS2 Models Hitboxes W...
Opening a door while aiming down your gunsights lets you peek through--and maybe toss in a flashbang or grenade. Sprinting or sliding into a door, or using a melee attack, lets you kick it in, potentially disorienting people on the other side, but it's a loud approach that gives away...