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Civil Engineering > Unit 1 Sound > Flashcards

Unit 1 Sound Flashcards

1
Q

What is Reverberation Time

A

The time taken for sound to decay (1)

Sound absorbed by interactions with the surface of a room

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2
Q

What are sound waves

A
  1. Transvers and longitudinal
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3
Q

What is wavelength (m)

A

The distance from one point on a wave to the same point on the next wave.

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4
Q

What is amplitude (m)

A

The maximum extent of a vibration measured from the point of equilibrium

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5
Q

What is frequency (Hz)

A

The number of waves passing a point per second

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6
Q

What is the formula for wave speed

A

Wave speed (m/s) = Frequency (Hz) x Wavelength (m)

v = f x λ

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7
Q

What is the formula for period (s)

A

Period (s) 1 / Frequency (hz)

1 / f

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8
Q

What is the formula for measuring the speed of sound

A

Speed (m/s) = Distance (m) / Time (s)

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9
Q

Characteristic of sound

A
  1. Cant travel through a vacuum

2. speed of sound is slowest in gasses, faster in liquids and fastest in solids

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10
Q

What is amplitude/Loudness and what is it measured in

A
  1. Size of vibration which determines how loud the sound is

2. Measured in decibels

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11
Q

What is the difference between sound and noise

A

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

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12
Q

What are the factors that cause a difference in sound

A
  1. Tone
  2. Pitch
  3. Intensity
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13
Q

What is tone

A
  1. Refers to sound quality
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14
Q

What is pitch

A

subjective impression about the highness or lowness of a tone.

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15
Q

What is intensity

A

Amount of energy that is transported past a given area of the medium per unit time

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16
Q

How can noise effect poeple

A
  1. May cause annoyance
  2. May cause hearing damage

Acoustic environment must be designed to avoid detrimental effects

17
Q

What are the negative affects of Nosie

A
  1. damage to hearing
  2. Disturbance of sleep
  3. Poor performance of tasks
  4. impaired alertness
  5. Increased fatigue
18
Q

How do we reduce sound

A
  1. Design it out before it becomes a factor
  2. Reduce it at source
  3. Insulate sound
  4. PPE to be worn where exposure exceeds 85db
19
Q

What is refection

A

Molecules of air pushed further apart

20
Q

What is sound

A

A form of energy, which is transmitted through air as a pressure wave

21
Q

What factors affect acoustics

A
  1. Sound reduction indices
  2. Reverberation Times
  3. Noise Criteria indices
22
Q

What value represents the threshold of hearing and sensation of pain

A
  1. 0.00002 N/m² Threshold of hearing

2. 20N/m² sensation of pain

23
Q

What is sound intensity

A

Power of sound wave per unit area (w.m²-2)

24
Q

What is reverberation

A

Multiple random blended repetitions of sound

25
Q

What is reverberation time

A

the time required for sound in a room to decay

26
Q

What is sound absortion

A

The conversion of sound to energy

27
Q

What is airborne noise ?

A

Sound waves transmitted from a source to a receiver through the air

28
Q

What is structure-borne noise

A

Noise caused by vibration from within the building by footsteps or machines. The vibration is directly transferred through the buildings structures and materials

29
Q

What three ways does airborne sound travel

A
  1. Through openings in a structure
  2. By direct transfer through the structure
  3. By direct transfer along the structure
30
Q

How can the building/ design layout control noise

A
  1. By positioning rooms which are less sensitive to noise to act as screens between noise sources and quite areas.
  2. Use higher density materials
  3. Double glazed windows, thicker flooring/ wailing
31
Q

How can airborne sound be controlled

A

Through tick dense walls, Carpets using fibreglass quit in cavity wall and ceiling any air passaged around windows doors etc.

32
Q

What is sound absorption

A
  1. the transfer of sound waves’ kinetic energy into thermal energy

Curtains, furniture and other textiles contribute to total absorption. Also known as natural absorption.

33
Q

Explain two reasons for the need to consider ‘noise criteria indices’ when
designing the new building

A

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)

Civil Engineering (9 decks)

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