Acoustics

Question 1

What is sound measured in?

Answer 1

decibels, dB (a logarithmic scale)

Question 2

What are the two major aspects of sound?

Answer 2

sound conditions within spaces and sound transfer between spaces

Question 3

What is sound?

Answer 3

• we hear sound as a response to pressure on the ear drum

- 20-100,000,000μpascals

Question 4

What is the sound threshold of pain?

Answer 4

0-130dB

Question 5

What does an increase of 10dB do each time?

Answer 5

doubles the perceived nose

Question 6

What is the difference between dB and dBA?

Answer 6

dB - for pure sounds

dBA - weighted average

Question 7

How does sound change with distance?

Answer 7

sound decays with distance - double the distance away and the sound reduces by a factor of 4 - a reduction of 6dB

Question 8

How are frequencies divided?

Answer 8

the sound we hear is made up of a range of frequencies - normally divided into octave bands

Question 9

What does good acoustics within a space depend on?

Answer 9

1. direct and reflected sound transmission from the course to the listener
2. volume and shape of space - the sound path is too long, sound may be inaudible
3. absorption of the sound by surface materials
4. conditions are expressed by “reverberation time” the time it takes for sound to fall in level by 60dB

Question 10

What materials absorb sound?

Answer 10

people, furniture, finishes, acoustics panels

Question 11

What does a high frequency mean in terms of wavelength?

Answer 11

small wavelength

Question 12

What ca affect the sound conditions and sound transfer?

Answer 12

function
material
required distribution
avoidance of external noise

Question 13

What devices can be used as sound absorption solutions?

Answer 13

• acoustic ceiling panels
• corrugated acoustic form
• plywood
• felt acoustic panels

Question 14

How does sound transfer between spaces?

Answer 14

1. when sound strikes a wall, a small amount is transferred through to the other side
2. the difference between incident and transmitted sound, expressed in dB is the sound insulation
3. if we know the desired internal sound level, and the external sound condition, the required performance of the wall can be determined

Question 15

What are flanking sounds?

Answer 15

flanking noise is noise reaching a room by an indirect path (think windows doors etc) - sound transfer between spaces through flanking transmission

Question 16

How can you improve resistance to the passage of sound?

Answer 16

• using acoustic glazing

- reducing the effect of openings (buffer zones to reflect the sounds, using heavy doors etc.)

Question 17

What can be some of the causes of unwanted sound transfer between spaces?

Answer 17

• gaps and cracks can be a particular problem
• badly fitting windows significantly reduce their performance
• natural (and mechanical) ventilation paths often need some acoustic treatment

Question 18

What are some of the implications of sound for designers?

Answer 18

• location of quiet rooms in relation to noisy rooms and external noise sources
• separation of noisy rooms from quiet spaces (what do you do with music practice rooms/recording studios)
• floors of activity rooms
• performance spaces - materiality
• natural ventilation and external noise sources

Question 19

What effects does the Environmental Noise (England) Regulation 2006 No. 2238 state should be considered?

Answer 19

• individual objection
• irritation
• disturbance
• personal concern
• annoyance/upset at times
• personal nuisance to an individual

(the Environment Agency Guidance state noise should not be so loud that it gives reasonable cause for annoyance to persons in the vicinity)