We hear different types of sounds around us. Some sounds are pleasant to the ear, whereas some are not. Such unpleasant sounds are called noise. The sounds which are pleasant to hear are called music. Some sources of sound produce pleasant sounds or musical notes while others produce unpleasant sound or noises. Musical notes are sounds that are easy to listen to because they are rhythmic. The waves that carry these notes change smoothly and their wave patterns occur at regular interval of time.

Key terms

• Noise: Unpleasant sound
• Musical note: sounds which are pleasant to hear