Week 5

Question 1

How is transport defined wrt noise?

Answer 1

Transport - source of noise which impacts life, health, and land value (externalities)

Question 2

How is the Environmental Noise Directive (END) (Directive 2002/49/EC) enforced through the Environmental Noise (England) Regulations?

Answer 2

Defra is required to produce maps showing people’s exposure to the environmental noise every 5 years

Noise mapping informs action plans

The aim is to preserve environmental noise quality where it’s good

The public is informed on environmental noise and it’s effects

Question 3

Define sound

Answer 3

A pressure wave which travels through air and is detected by ear

Surface vibration creates air pressure changes leading to pressure waves

Perceived sound consists of many pressure waves of varying characteristics (ie wavelength) and depends on human ear sensitivity

Question 4

Define noise

Answer 4

A sound which is unpleasant, loud, and disturbs

Question 5

What is amplitude ?

Answer 5

The magnitude of the change in pressure due to the sound wave

Question 6

What is frequency?

Answer 6

Rate of vibrations per unit time (Hz)
Range of perception for young person 20-20,000 Hz

Question 7

What is an octave ?

Answer 7

Interval between one frequency and double that frequency
Characterised by central frequency = 10002^n
Lower freq = f1=fc/sqrt(2)
Upper freq= f2=fcsqrt(2)

Question 8

How is pressure defined ?

Answer 8

F/A [Pa]

Question 9

What range of pressures does human hearing cover ?

Answer 9

2x10-5 Pa to 200 Pa

Question 10

What is sound intensity ?

Answer 10

I [W/m2]
Rate energy is transferred by sound wave p unit area
I= (pressure)^2 / (density * speed of sound)

Question 11

What is sound intensity level?

Answer 11

Sound intensity relative to hearing threshold
I0 = 1*10^-12 (Wm-2)
SIL (dB) = 10log10(I/I0)

Question 12

What is sound pressure level?

Answer 12

Sound pressure relative to threshold of hearing
SIL(dB) = SPL(dB) (approx)
SPL(dB)= 10log10((p^2)/(p0^2))
P0= 2*10^-5 (N/m2)

Question 13

How are SILs added ?

Answer 13

Solve for I for both sound intensities
Ie log10(x)=2 -> x= 10^2
Sum the intensities (sum I)
Solve for SIL with summer intensities

Question 14

How do humans identify source of sound ?

Answer 14

Through having two ears which enables stereo hearing

Question 15

What does perception of sound rely on?

Answer 15

The frequency of the source

Perception of sound not same as sound intensity/pressure level

Question 16

How does weighting change the SIL and SPL?

Answer 16

Approximates sensitivity of human hearing
De-emphasises low and very high frequencies which risk hearing
Units dB(A)
Gain (positive or neg) in dB(A) added to SIL or SPL

Question 17

If SPL or SIL is increased by 10dB and the frequency remains the same how does loudness change ?

Answer 17

It doubles

Question 18

When SPL/SIL is increased by 10dB how does this affect loudness if frequency doesn’t change ?

Answer 18

Loudness doubles

Question 19

What is the loudness ratio?

Answer 19

2^ (SPL/10)

Question 20

How is p/p0 related to SPL?

Answer 20

P/p0 = 10 ^ (SPL/20)

Question 21

How is I/I0 related to SPL?

Answer 21

I/I0 = 10^ (SPL/10)

Question 22

What are the noise metrics in terms of distribution?

Answer 22

Lmax - max SPL in set time
L10 - SPL exceeded less than 10% in monitoring period
LAeq,T - A-weighted energy intensity averaged SIL over time. Assessed by taking average intensity and converted back to SIL

Question 23

What are the noise metrics in terms of time periods ?

Answer 23

Lday - LAeq from 0700 to 1900
Levening - LAeq from 1900-2300
Lnight - LAeq from 2300-0700
Lden- LAeq from 0000-2400 with evening values weighted by +5dB and night by +10dB

Question 24

What is the pyramid of effects for noise ?

Answer 24

Direct pathway: causes hearing loss, leads to stress
Indirect pathway: creates annoyance, leading to stress
Increase in risk factors: blood pressure, cardiac output, blood lipids etc
Increase leads to cardiovascular diseases: hypertension, heart disease,

Question 25

Who regulates noise?

Answer 25

The International Civil Aviation Organisation ICAO