Room acoustics

Question 1

Intensity

Answer 1

Intensity = Power of source / (4 x pi x r squared)

If distance doubles, intensity decreases by 4x
If distance increases 10x, intensity decreases 100x

Question 2

What three things happen to sound when encountering a barrier?

Answer 2

Reflection
Absorption
Transmission

Question 3

Reflection

Answer 3

With smooth hard surface, 90-99% is reflected

Causes reverberations in the sound; different patterns are caused by size and shape of room, objects, and material on surfaces

Question 4

Reverberation time

Answer 4

Overall measure of how long the reverberations last

Question 5

Dry/dead rooms

Answer 5

Rooms with very short reverberation times

Question 6

Live rooms

Answer 6

Rooms with long reverberation time

Question 7

Warm room

Answer 7

Room with a long reverberation time for low frequencies

Question 8

Absorption

Answer 8

Occurs when some of the sound energy is converted to heat in a material

Small fibers = increased absorption
–> sound waves cause fibers to move around; friction between the fibres converts the energy of the motion into heat

Question 9

Transmission

Answer 9

Depends on mass of the barrier
–> more massive per area = less sound transmission, more reflection