In an experiment,

(a) When Anhad adjusts the signal to the loudspeaker to give a sound of frequency 200 Hz then the air between Anhad and the loudspeaker vibrates with the frequency of 200 Hz.

(b) Both the ear of Anhad recives the sound. His right ear recives the sound by the sound waves coming directly from the loudspeaker (through air)where as his left ear recives the sound from sound waves reflected from the wall of classroom.