introduction to architectural acoustics

1. Acoustics
“A science that deals with the production, control, transmission,
reception, and effects of sound.”

2. • Sound is reflected, transmitted, or absorbed by the materials it
encounters.
• Soft surfaces, such as textiles, and Matt insulation, tend to absorb sound
waves, preventing them from further motion.
• Hard surfaces, such as ceramic tile, gypsum board, or wood, tend to reflect
sound waves, causing ‘echo’. Reverberation is the term used to describe
sound waves that are reflected off of surfaces.
• Dense, massive, materials, such as concrete or brick, tend to transmit
sound waves through the material.
• High frequency sound waves (think of a high whistle) are not capable of
being transmitted through massive, heavy, material.
• Low frequency sound waves (bass) are transmitted through massive
materials.

3. Hearing range of some animals

4. Decibel levels
• 0 The softest sound a person can hear with normal hearing
• 10 normal breathing
• 20 whispering at 5 feet
• 30 soft whisper
• 50 rainfall
• 60 normal conversation
• 110 shouting in ear
• 120 thunder

5. Decibel levels
• The human ear's response to sound level is roughly logarithmic (based on
powers of 10), and the dB scale reflects that fact.
• An increase of 3dB doubles the sound intensity but a 10dB increase is
required before a sound is perceived to be twice as loud.
• Therefore a small increase in decibels represents a large increase in
intensity.
• For example - 10dB is 10 times more intense than 1dB, while 20dB
is 100 times more intense than 1dB as perceived by humans.

6. Decibel levels
• 130dB - Jack Hammer (at 5ft)
• 120dB - Rock Concert / Pain threshold
• 110dB - Riveter or a Heavy Truck at 50ft
• 90dB - Heavy Traffic (at 5ft)
• 70dB - Department Store or a Noisy Office
• 50dB - Light Traffic
• 30dB - Quiet Auditorium
• 20dB - Faint Whisper (at 5ft)
• 10dB - Soundproof room / anechoic chamber

7. An anechoic chamber is a space in which
there are no echoes or reverberations.
The surfaces absorb all sound, and reflect none.

8. Acoustics: sound
• Sound is a mechanical wave and therefore requires a medium in which it
can travel.
• Acoustics is classically divided into sound and vibration.
• Sound refers to waveforms traveling through a fluid medium such as air
• Vibration describes energy transmitted through denser materials such as
wood, steel, stone, dirt, drywall or anything besides a fluid.
• It is not heard as much as felt, due to its extremely low frequency, which is
below the range of most human hearing.

9. The speed of sound versus the speed of light
• sound travels at 1130 feet per second at normal room temperature.
• light travels at 299,792,458 meters per second, which is roughly
974,325,489 feet per second (974 million feet per second!!)

10. Sound Waves:
amplitude & frequency (cycles)

11. Bonded acoustical cotton; recycled cotton, class A non flammable
Melamine Foam Acoustical Panels: fiber free, Class A fire retardent

12. Fabric wrapped panels provide good acoustical absorption

13. ACOUSTIC FOAM

14. Helmholtz

15. Reverberation Time
• Reverberation time refers to the amount of time required for the sound
field in a space to decay 60dB, or to one millionth of the original power.
• In simple terms this refers to the amount of time it takes for sound energy
to bounce around a room before being absorbed by the materials and air
• Reflections are an important part of acoustical design for music
performance venues.
• For effective musical acoustics, the reflections have to arrive within the
correct time window, and from the correct direction.

16. • The reflections help to boost the level of acoustic instruments and human
voices in the audience area.
• They also influence timbre and help define the apparent size or
perspective of the instruments.
• The critical time interval we're talking about is a very brief 0.3 seconds

17. Sound ray diagram of New National Theatre, Tokyo (May 1986

18. Stage
The area where the players perform; usually a raised platform
Ryman Auditorium

19. Three Types of Stages
• Proscenium Stage
• Thrust Stage
• Arena Stage

20. Proscenium Stage

22. Thrust Stage

24. Arena Stage

26. Everything else is called Flexible Staging
If it doesn’t fit into one of the three stages, it is Flexible.