Answer :

reflection of sound can be defined as bouncing back of sound wave when it strikes the hard surface like walls , metals ,etc.

multiple reflection of sound can be defined as when the reflection of sound take place more than once  it is utilized in working of various devices like stethoscope , bulb horne , etc. 
avi010

Reflection of sound:-

the bouncing of light from hard surface.

multiple reflection of sound :-

the bouncing of light multiple times .