There's a stereotype of Chinese table tennis coaches that they often do just two things during a practice session - watch the player's feet and listen to the contact. (I often do this as well.) The latter tells the coach if the player is making good contact. Top players contact the ball consistently the same way for each given shot, which leads to consistency. Developing players do not have this consistency, and so their contact varies - and their contacts sound different.
While a coach can hear this difference, as a player you should be able to feel it. When, for example, you loop a ball at a certain speed and spin, it should both feel and sound the same every time. The same is true for other shots, such as blocks. With experience, you should be able to recognize the feel of a good shot - and the feel of a mishit. Focus on the ones with the right feel and strive to replicate it every time.
We all have watched top players, but perhaps next time try listening?