Question

if reflection of sound causes echo,then why sound boards are used??won't the reflections of sound by sound board produce echo?

Answer 1

Sound board is used to send the sound towards audience in big hall or auditorium. This works on the basis of laws of reflection of sound waves.

Sound board is a big concave board and is set in such a fashion behind the stage that speaker is at the focus. Sound coming from speaker falls over sound board and gets reflected towards the audience. As a result, the audience sitting in the hall even at far distance from the speaker can clearly hear what the speaker is saying.

Additionally, the ceiling of the auditorium is also made curved so that it also acts like sound board. The curved surface of the ceiling reflects the sound waves and facilitates better hearing.

Answer 2

Because it absorbs the sound waves............

Hope you understand :)