1. What is the difference between this two pictures

2. Project 2 Measurement and analysis of environmental parameters
Lighting
- Measurements
- Calculation
Thermal comfort in ECJ classroom
Noise measurement
Report
Daily oscillation measurement (HOBO)

4. Objectives Learn about basic acoustic in buildings Noise Phenomena
Terminology
Noise
Quantities
Sources in building
Reduction techniques

5. Sound –air pressure oscillation
Amplitude

6. Frequency of Sound

7. Octave band frequency Sound 15 Hz – 15 kHz Human conversation
Octave frequencies
8, 16, 32, 63, 125, 250, …. Hz

8. NOISE Usually defined as "unwanted sound“
Sound waves described by following parameters:
frequency
human ear can hear between 20-20KHz
most sensitive 3 KHz
amplitude - magnitude of pressure variation (pmax - pmin)

9. Decibel Sound Pressure Level - SPL SPL= 10 log(p/pref)2 [ dB]
p – air vibration pressure – sound
pref - reference pressure (20 μPa or 10-9psi)
Speed of sound c=340 m/s
Example:

10. General perception of sound

11. Sound Perception
120 dB - Pain limit

12. Noise Criteria - NC Define acceptable background noise spectra
Defined for octave band 63 Hz – 8000 Hz
Generally
NC = A weighted noise level – 5 dB

14. Adding decibel quantities
dB=10 log x
2 equal sources
dB= 10 log (x+x) =10 log(2x) =10log(2) +10log(x)
= 10log(x) + 3
n equal sources
dB= 10logx+10log(n)

15. Acoustic in a building
Every element of building design and construction affects its acoustical characteristics
Acoustic principles should influence
choice of finish materials in rooms,
location of these materials in a building,
building design.

16. Room acoustic Behavior of Sound in an Enclosed Space
shape
dimensions
construction
Major sources of absorption/reflection in a room:
Ceiling
Floor
Furniture

17. Factors Influencing Acoustical Environments
How is space to be used?
e.g. office, hospital, theater, auditorium, library reading room
Type of noise sources?
voice, music, impact sounds.
Predictability of source?
expected sounds less stressful than unexpected sound.

18. Parameters which define Acoustical Environments
Sound absorbing/reflecting qualities of interior surfaces.
Reflection time - echoes vs. "dead" space
Source location/locations
Receiver characteristics/expectations

19. Sound reflection and absorption
Absorbed sound is turned into heat energy
Absorption coefficient ()
ratio between absorption of a material and open window
 = 1.0 all sound energy is absorbed
Reflection - Echo
persistence of sound after it has stopped - echoes
Reflection Time (Tr)
period required for sound level to decrease 60 dB after sound
source has stopped producing sound

20. Sound control by Absorption
Convoluted Egg Crate Acoustical Foam

21. Noise Sources in HVAC System

23. Noise Control
Noise Control for Roof Top HVAC Equipment

24. Noise Control Duct silencers - Absorptive Dissipative
Use sound absorptive material

25. Noise Control
Elastic connections
Ducts – fans
Pipes - pumps

26. Active Noise Silencer

27. Wall sound insulation Gypsum board Insulation blanket Frame (stud)
Damped Resilient
Channel
Gasket

28. Wall sound reduction as function of Frequency
Low frequency sound
- More difficult to reduce
- Damped Resilient Channel
High frequency sound
- Can be reduced easier with sound insulation materials such as fiberglass

29. Wall Absorption

30. Window Sound Insulation
Glazing
Frame
Gaps

31. More about Acoustics
Tao and Janis
Chapter 18 and section