Question

What is timber of sound

Answer 1

timbre means those characteristics of sound which allow the ear to distinguish sounds which have the same pitch and loudness. 

Answer 2

In music, timbre (TAM-bər, also known as tone color or tone quality from psychoacoustics) is the perceived sound quality of a musical note, sound or tone. ... In simple terms, timbre is what makes a particular musical sound have a different sound from another, even when they have the same pitch and loudness.