Question

1. why do people sometimes cup their hands around their mouths when yelling loudly outside? 29. what causes the distortion of sound in a poorly designed hall? 30. why do porous materials act as sound absorbers?

Explanation:

1. Cupping hands around the mouth helps to direct sound waves forward, reducing sound dispersion and making the sound travel further.
2. In a poorly - designed hall, sound distortion can be caused by factors such as multiple and irregular sound reflections from walls, ceilings, and other surfaces, creating echoes and interference patterns.
3. Porous materials act as sound absorbers because sound waves cause air in the pores to vibrate. Friction between the air and the material converts the sound energy into heat energy, thus reducing the sound intensity.

Answer:

1. To direct sound waves forward and reduce dispersion.
2. Multiple and irregular sound reflections creating echoes and interference patterns.
3. Sound - induced air vibration in pores converts sound energy to heat energy through friction.