Dear Student
(a)
PITCH - the quality of a sound governed by the rate of vibrations producing it; the degree of highness or lowness of a tone.
LOUDNESS - Loudness is the characteristic of a sound that is primarily a psychological correlate of physical strength (amplitude). More formally, it is defined as "that attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud".
QUALITY - Sound "quality" or "timbre" describes those characteristics of sound which allow the ear to distinguish sounds which have the same pitch and loudness. Timbre is then a general term for the distinguishable characteristics of a tone.
(b)
Time to recieve echo = 3s
Speed = 342 m/s
Distance travelled by sound wave = speed x time = 342 x 3 = 1026 m
So distance of boy from reflecting surface = 1026/2 = 513m
Regards