Arch Sci II Exam 1

Environmental control systems:

Environmental control systems:

• thermal systems (HVAC)

• Lighting systems (most energy consuming)

• acoustic/noise control

Similarities between environmental systems:

• energy in different forms

• physics

• interface with human senses

• impact on human comfort, range and limits

• impact on the building’s overall performance

Noisy sites are sites at which sound intensity level exceeds ___?

70 dB

For good site planning, we should consider off-site sources of noise but not on-site sources of noise (T/F)

False

Sound travels in the form of:

• a mechanical wave

• a rapid fluctuation of air pressure

• a spherical wave front

Speed of sound is constant. For example, speed of sound at sea level is the same as under water (T/F)

False

Low frequency sounds have short wavelengths, and high-frequency sounds have long wavelengths (T/F)

False

Tone is the sound of

a single frequency of sound energy

Noise is

any unwanted sound

Short term exposure to very loud sound may cause temporary loss of hearing, but long-term exposure may cause permanent hearing damage (T/F)

True

We feel pretty comfortable in silent spaces (T/F)

False

Inside the room, all hard and soft surfaces can equally absorb sound. All soft surfaces share the same coefficient of absorption (T/F)

False

When we design spaces for listening, acoustic quality becomes very essential. Longer reverberation times are recommended for smaller spaces (smaller in volume), and shorter reverberation times are recommended for larger spaces (T/F)

False

Three strategies of noise control (in correct order)

reduce noise at source, reduce noise transmission, and masking noise

When it is desired to contain noise in a noisy room (such as a mechanical room), we choose the enclosing walls, based on which rating (of the walls/partitions)

STC (sound transmission class)

role and impact of building systems

• human comfort and productivity

• building performance and energy consumption

• systems and architectural form

• design coordination

Sound travels as

a spherical wave front of rapid fluctuation of air pressure

What is the audible range of frequencies?

20-20,000 Hz

What is bearable range of loudness? (threshold of pain)

130 dB

What frequency is the human ear the most sensitive to?

4,000 Hz

The human ear responds to sound intensity on a ___ scale

logarithmic

Sound is defined as

a rapid fluctuation of air pressure (mechanical vibration)

Sound propagates as

as spherical wave front

Speed of sound increases as

the density of the medium increases and its elasticity decreases

In water, the speed of sound is ___ times faster than air

four

Frequency is defined as

the number of complete cycles per second (Hertz)

Speech has a frequency range of

300-4,000 Hz

Wavelength is

the distance traveled during one cycle of vibration

Sound power is

the acoustic power generated by the sound source (in Watts)

Loudness is

the perceived sound intensity

Resonance is

a natural vibration of a material at a particular frequency as a result of excitation by sound energy at that particular frequency (occurs in ear canal at 4,000 Hz)

Sound meters:

measure only the audible range of frequencies (dBA)

A-weighing:

sound meters that measure sound pressure (intensity) in dBA (most sensitive to mid-frequencies 500-4,000 Hz)

Sound behavior:

sound behaves as a wave (i.e. when strikes a surface could be reflected, absorbed, and transmitted)

Absorbed sound energy is dissipated as

friction, then as heat

Absorption coefficient of a material (alpha):

the ratio of sound energy absorbed to the sound energy impinging upon the surface

Noise reduction coefficient (NRC):

the average absorption coefficient for the middle range of speech

Transmission loss (TL):

a property of construction materials, which represents the reduction in sound intensity level between the incident side and the opposite side of the construction (wall, window, etc.)

Definition of room acoustics:

study of the acoustic environment inside enclosed spaces

Silence is

the virtual absence of sound

quietness is

the comfort level of continuously maintained background sound intensity level

recommended contrast between sound and background noise is

30-40 dB

only ___ frequency sounds act like light

high

reverberation time for lecture rooms

0.5-1 seconds

reverberation time for theaters

1.7 seconds

reverberation time for opera halls

2.2 seconds

design of the back wall should be

covered with sound absorbing finishes (e.g. soft non-stiff materials)

Sound reinforcement systems are required for

rooms larger than 50,000 ft³

outdoor noise in quiet sites should not exceed

70 dB

Sound is produced due to

vibration

sound waves cannot travel through

vacuum

the frequency below the audible range of 20 Hz to 20kHz is referred to as

infrasonic

the number of cycles that a vibration completes in one second is

frequency

select the correct relation between sound, speed, frequency and wavelength

speed = frequency x wavelength

compared to a sound intensity level of 70dB, which intensity level will be perceived as twice as loud?

80 dB

the persistence of audible sound due to successive reflections from surrounding surfaces in the room after the source has stopped is called

reverberation

which of the following is true about “white noise”

• continuously maintained sound

• low intensity sound

echo will be heard when a manifest sound reflection is received after the direct sound by

50 milliseconds

to minimize sound transmission between sound spaces, the wall assembly (between the spaces) must have the appropriate rating of

STC

OSHA stands for

occupational safety and health administration

NC stands for

Noise criterion