I think they decrease echo and reduce noise, they do this by either absorbing vibrations or by scattering the sound so that echoes arrive at different times rather than reverberating as a standing wave. An echo is a reflection of a sound that arrives at the listener with a delay after the direct sound. The delay is usually proportional to the distance of the reflecting surface from the source and the listener.
2 Answers. The mass of a pendulum's bob does not affect the period. Newton's second law can be used to explain this phenomenon. In F = m a, force is directly proportional to mass.
