(1) Due to the function of cotton, the sound transmitted from the watch to the cylinder can be absorbed, so that the sound can only (probably) propagate vertically upwards.

Through the reflection of the sound by the flat mirror, people who can't hear the sound of the watch can hear the sound again.

It shows that sound can be reflected like light. When the sound meets the plane mirror directly above the barrel mouth 10cm, it will be reflected back and the ear can hear the surface sound.

(2) After the sponge replaces the flat mirror, the sound is weakened, indicating that the sponge absorbs some sound, and the flat mirror has a smooth surface, which is beneficial to reflecting sound.

So the answer is: (1) incident angle; Yes; (2) reflection; absorb