The phenomena of repetition of sound caused by reflection of sound waves is called an echo. Echo is a reflection of sound that arrives at the listener with a delay after the direct sound. The delay is directly proportional to the distance of the reflecting surface from the source and the listener. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room and an empty room.

Loudness of a sound depends on the amplitude of the vibration producing that sound. Greater is the amplitude of vibration, louder is the sound produced by it. The amplitude of the sound depends upon the force with which an object is made to vibrate. Loudness of sound is measured in decibel (dB) unit.

The pitch of a sound tells how high or low the sound is. The pitch of a sound depends on the frequency of the sound wave. The greater the frequency, the higher the pitch. The voice of an adult man is of lower pitch than the voice of a baby boy or a baby girl.