Sound

Question 1

List noise issues

Answer 1

Site noise (during construction)
Equipment noise
Background noise
Noise transmission from environment

Question 2

How do room acoustics vary?

Answer 2

Rome volume
Shape and proportions - affect sound paths
Finished and furnishings
Layout
Special treatment (reflectors, absorbers, diffusers)
Electronic sound systems (placement etc)

Question 3

Define sound

Answer 3

Vibration in a plastic medium which returns to its natural state after the force has been removed

Longitudinal waves

Measured in Hz

Question 4

Inverse square law

Answer 4

How sound intensity decreases with distance

L1/L2 = (D2/D1)^2

L is sound intensity (w/m2)
D is distance from sound source (w/m2)

Question 5

Decibels

Answer 5

Measure sound volume

Question 6

Sound intensity level

Answer 6

Li=10log(l/lo)

Li is sound intensity level in db
I is sound intensity
Lo is reference sound intensity (10-12)

Question 7

Sound absorption

Why don’t sound levels from w source not reduce with distance indoors?

Answer 7

Because of reverberation

a>0.5= sound absorbing
a

Question 8

Types of sound absorbers

Answer 8

Porous materials - convert sound energy into heat by friction

Vibrating or resonant panels - convert sound energy into vibrational energy dissipated by internal damping and radiation

Volume resonators - reduce sound energy by friction and by inter reflections within cavity

Question 9

Mass law for homogenous building materials

Answer 9

Transmission loss between a noise producing space and a receiving space increased for each doubling of surface weight of the separating walk

Greater the weather of the building material, greater the resistance to motion and less sound energy transmitted

Question 10

What is noise reduction between rooms dependent on

Answer 10

Area of wall transmitting sound
Absorption in receiving room
Transmission loss in common wall

Question 11

What is difference between reflection and diffusion

Answer 11

Reflection is the return of a sound wave from a surface

Diffusion is the random scattering of a sound wave from a surface

Question 12

Why should concave surfaces be avoided where even distribution of sound is a priority?

Answer 12

Concave surfaces tend to focus sound

Question 13

Reverberation time

Answer 13

Persistence of reflected sound energy in an enclosed space

Sabines law
T=0.16V/A

T is reverberation time in seconds
V is room volume in m3
A is total sound absorption

Question 14

How do you calculate total sound absorption?

Answer 14

A= sum of S.a

S is surface area in m2
a is sound absorption coefficient of a material surface in Sabins

Question 15

How can you describe acoustic situations?

Answer 15

Source > path > receiver