Acoustics Flashcards
a series of distinct echoes. they are heard with sufficient loudness compared to the original sound
flutter echo
The power carried by sound waves per unit area in a direction perpendicular to that area.
Sound intensity
it is the ratio of absorbed energy to incident energy and is represented by α, and if the acoustic energy can be absorbed entirely, then α=1.
sound absorption coefficient
formula for sound reverberation
T(subscript 60) =24ln10^1/c(subscipt 20) x V/S(subscipt a)
an area through which sound waves fall to propagate, due to topographical obstructions or disruption of the waves via phenomena such as wind currents, buildings, or sound barriers
sound shadow
occurs when reflected sound rays leap-frog one another and creep along the surface of the curve
sound creep
A measure of acoustic energy emitted from a noise source; expressed in decibels.
Sound power
it is the sound which is produced by an object when it vibrates at the same rate as the sound waves from another object.
sound resonance
it is the difference in decibels between the intensity levels of two rooms separated by a barrier of a given transmission loss.
noise reduction coefficient (NRC)
A form of energy propagated in waves that continues to subsist until filtered through a material turning into heat by friction
Sound
defined as the measure of time after the sound source ceases that it takes for the sound pressure to reduce by 60dB
RT 60
mostly effective for mid-range and treble tones, commonly used in low-height office partitions, wall/ceiling panels, etc.
porous absorbers
(example problem) If the source room has 100 dB and what is transmitted is 70 dB, how much is the STC?
STC 30 dB
A score given to a building’s surface (wall, ceiling, window, etc.) based on its ability to reduce sound coming through it.
Sound transmission class (STC)
It is the technology of designing spaces, structures, and mechanical systems to meet the hearing needs effect of building design on the control of sound.
Architectural acoustics
The pressure level of a sound, measured in decibels (dB)
Sound pressure level
what is used to reduce structure-borne sound transmission?
sealant, with pockets of air in between to allow sound to bounce between them, until it gradually disappears
result of the sound which causes the sound intensity in certain areas to be so low that is already insufficient for hearing
dead spots
The SI unit of intensity
Watt per square meter (W/m2)
Formula for sound transmission loss (STL)
TL = 10 log (1/t)
they absorb sound energy as they dampen the air particles’ oscillation
porous absorbers
the time it takes for the level to decay from -5dB to -65dB
RT 60
Sound where the media is concrete, steel, wood, etc.
Structure-borne sound
any porous or fibrous material such as textiles, fleece, carpets, foam, mineral wool, cotton wool, and special acoustic plasters
porous absorbers
allows sound to pass through without much barrier
acoustical transparency
the limit it takes for the level to decay from -5dB to -35dB multiplied by 2
RT 30
it is the bending and spreading out of light or sound waves around an object
sound diffraction
It is the branch of physics concerned with sound - deals with the production, control, transmission, reception, and effects of sound.
Acoustics
Full circuit by a displaced particle.
Cycle
the repetition of sound caused by the reflection of sound waves from a hard surface back to the listener.
sound echo
sound becomes blurred, distorted, and confusing due to overlapping as well as it cannot be heard clearly.
long reverberation
The number of times the cycle of compression and rarefaction of air occurs in a given unit of time.
Frequency
defines the refraction angle corresponding to the transmitted wave. Thus, depending on the physical properties of each medium, the transmitted wave can be refracted either towards the vertical or towards the horizontal.
Snell’s law
A disturbance or oscillation that transfers energy progressively from point to point in a medium or space without advance by the points themselves, as in the transmission of sound or light
Waves
Frequency of sound vibration; the predominant frequency of a sound as perceived by the human ear
Pitch
a vibrational system that “runs” on sound pressure.
resonance absorber
the direction of the sound that is sometimes brought about by the shape of the hall that concentrates the sound waves to a particular area of the hall creating a sound of large quality
focused sound
Formula for noise reduction coefficient (NRC)
NR = TL+10log (A/S)
where:
A = total acoustical absorption (Sabins)
S = area of a barrier
The log ratio of the incident energy to the transmitted energy.
Sound transmission loss (STL)
it occurs when soundwaves bounce back from the surface of a solid or liquid
sound reflection
Father of modern architectural acoustics
Wallace Clement Sabine
the persistence of sound after it has been stopped due to multiple reflections from surfaces such as furniture, people, air, etc. within a closed surface.
sound reverberation
the phenomenon can affect the audibility of sound in an enclosure
sound reverberation
the limit it takes for the level to decay from -5dB to -25dB multiplied by 3
RT 20
it is used to evaluate the sound efficiency of materials.
sound absorption coefficient
an advance form of reverberation where the sound is clearly and repeatedly after some time until it fades
sound echo
It is usually a vibrating body that converts energy into vibration. It can be made louder or quieter.
Sound source
What can acoustics do?
- To meet hearing needs
- Change the behavior of the users
- Influence perception of space
The back and forth motion of a complete cycle.
Vibration
An aspect of real and virtual spaces that produces an emotional, behavioral, and visceral response in inhabitants; can produce feelings of isolation, warmth, and mystical sense.
Aural architecture
it is the type of surface reflectance often described as a mirror-like reflection of light from the surface. In ___________, the incident light is reflected into a single outgoing direction.
specular reflection
An oscillation in presence of the atmosphere which is capable of being detected by human ear.
Sound
an acoustical defect occurs if there are two parallel reflecting walls
flutter echo
when sound changes mediums (enters a different material) at an angle other than 90 degrees, it is bent from its original direction
sound refraction
used to absorb low frequency sounds
membrane absorbers
A longitudinal pressure wave in air or an elastic medium, especially one producing an audible sensation.
Sound wave
it is the passage of sound from one room to another, or, from the exterior into a room in a building.
sound transmission
Sound which the medium is air.
Airborne sound
It is usually concerned with the human ear. The ______ can be influenced.
Receiver
