Timbre and pitch are sound characteristics that aid in distinguishing various voices. Consequently, due to differences in the timbre and pitch of sound waves, one can recognize the voice of a friend, even when they are sitting among others in a dark room.
∆ABC is an isosceles triangle in which AB = AC. Side BA is produced to D such that AD = AB (see Fig. 7.34). Show that ∠ BCD is a right angle.

(i) The kind of person the doctor is (money, possessions)
(ii) The kind of person he wants to be (appearance, ambition)
Sound is a vibration that propagates the mechanical wave of displacement and pressure, through a medium can be of any matter. In other words, the sound is the thin line between Music sound and Noise.
Sound can be divided into two types depending on its frequency. The following are:-