Question

Thermocol is a:
A. Good reflector of sound
B. Good absorber of sound
C. Bad absorber of sound
D. Good conductor of sound

Answer 1

Hint: Substances that are good absorbers of sound usually have a lot of mass and are thick so as they can dissipate the sound energy between the layers of the material. They may also have pores that can trap the sound energy in them and dissipate it. Good reflectors of sound are usually hard materials without a lot of pores which cannot trap sound energy but reflect it back.

Complete step by step answer:
A good reflector of sound, reflects sound waves that hit it, therefore, they are instrumental in propagating sound waves and changing their direction. They are usually hard and do not have a lot of pores on their surface. They can cause echoes since they reflect the sound wave into another direction often sending it back to the source.

On the other hand a bad reflector of sound (or a good absorber) absorbs the majority of the sound waves that it encounters. It may also have pores that trap sound energy and dissipate it in other forms of energy such as heat.

Good absorbers of sound are used in preventing echoes in places like amphitheatres and auditoriums. This is why the walls and floors of auditoriums are draped with fabric curtains and carpets.
Thermocol has a hard upper surface which makes it a very good reflector of sound.

Hence, the correct option is A) a good reflector of sound.

Note: Students might be tempted to think that since thermocol can be broken easily that it must not be able to reflect sound. Also, many are of the belief that thermocol has a lot of free space or pores in it. To an extent, that is true, however, the upper surface of thermocol rarely has any pores and is quite hard. Therefore, it acts as a good reflector of sound.
Students must not get confused and think that it is a good absorber of sound.