Unit 1 Sound Flashcards
What is Reverberation Time
The time taken for sound to decay (1)
Sound absorbed by interactions with the surface of a room
What are sound waves
- Transvers and longitudinal
What is wavelength (m)
The distance from one point on a wave to the same point on the next wave.
What is amplitude (m)
The maximum extent of a vibration measured from the point of equilibrium
What is frequency (Hz)
The number of waves passing a point per second
What is the formula for wave speed
Wave speed (m/s) = Frequency (Hz) x Wavelength (m)
v = f x λ
What is the formula for period (s)
Period (s) 1 / Frequency (hz)
1 / f
What is the formula for measuring the speed of sound
Speed (m/s) = Distance (m) / Time (s)
Characteristic of sound
- Cant travel through a vacuum
2. speed of sound is slowest in gasses, faster in liquids and fastest in solids
What is amplitude/Loudness and what is it measured in
- Size of vibration which determines how loud the sound is
2. Measured in decibels
What is the difference between sound and noise
Sound - vibrations transmitted through air or another medium capable of being detected by humans ears
Noise - A sound that is loud, unpleasant, unexpected, or undesired
What are the factors that cause a difference in sound
- Tone
- Pitch
- Intensity
What is tone
- Refers to sound quality
What is pitch
subjective impression about the highness or lowness of a tone.
What is intensity
Amount of energy that is transported past a given area of the medium per unit time
How can noise effect poeple
- May cause annoyance
- May cause hearing damage
Acoustic environment must be designed to avoid detrimental effects
What are the negative affects of Nosie
- damage to hearing
- Disturbance of sleep
- Poor performance of tasks
- impaired alertness
- Increased fatigue
How do we reduce sound
- Design it out before it becomes a factor
- Reduce it at source
- Insulate sound
- PPE to be worn where exposure exceeds 85db
What is refection
Molecules of air pushed further apart
What is sound
A form of energy, which is transmitted through air as a pressure wave
What factors affect acoustics
- Sound reduction indices
- Reverberation Times
- Noise Criteria indices
What value represents the threshold of hearing and sensation of pain
- 0.00002 N/m² Threshold of hearing
2. 20N/m² sensation of pain
What is sound intensity
Power of sound wave per unit area (w.m²-2)
What is reverberation
Multiple random blended repetitions of sound
What is reverberation time
the time required for sound in a room to decay
What is sound absortion
The conversion of sound to energy
What is airborne noise ?
Sound waves transmitted from a source to a receiver through the air
What is structure-borne noise
Noise caused by vibration from within the building by footsteps or machines. The vibration is directly transferred through the buildings structures and materials
What three ways does airborne sound travel
- Through openings in a structure
- By direct transfer through the structure
- By direct transfer along the structure
How can the building/ design layout control noise
- By positioning rooms which are less sensitive to noise to act as screens between noise sources and quite areas.
- Use higher density materials
- Double glazed windows, thicker flooring/ wailing
How can airborne sound be controlled
Through tick dense walls, Carpets using fibreglass quit in cavity wall and ceiling any air passaged around windows doors etc.
What is sound absorption
- the transfer of sound waves’ kinetic energy into thermal energy
Curtains, furniture and other textiles contribute to total absorption. Also known as natural absorption.
Explain two reasons for the need to consider ‘noise criteria indices’ when
designing the new building
Noise criteria indices are specific for a type of use of a room (1) and are linked to the maximum recommended noise level for a specific use (1)
Building regulations set performance standards for noise levels (1) which can be met by specifying appropriate materials (1)
