1

Data used in noise

monitoring and

modelling

Dr Darren Rhodes

CAA

2

Data used in noise monitoring and

modelling

Data inputs

Data provision

Data verification

Third party data

Monitoring

Modelling and validation

3

Data inputs

Numbers and types of aircraft

Different variants of the same type of aircraft can exhibit large

differences in noise level, e.g. different engines, and/or modifications

Position of aircraft

Although aircraft fly standard routes in the vicinity of an airport, the

precise location and variation (dispersion) of a ground track affects

noise exposure on the ground

How much noise is emitted at the source

For take-off directly related to engine power

For landing related to engine power settings and how much noise the

airframe produces, which is related to the aircraft configuration,

position of flaps and landing gear (wheels)

4

Data provision to CAA

As a designated airport, HAL is required under Section 78(8) of the CAA

Act 1982 to provide noise information to DfT or a organisation appointed

by DfT. CAA is that organisation.

Data provided through Noise and Track Keeping (NTK) System

Shared system jointly operated by CAA and HAL

CAA undertakes validation of the system and provides technical advice

on system development

System integrates:

Operational information

Radar information

Noise measurement data

5

Data verification

Operations and aircraft type

Based on NTK system flight planning and radar data feed

Compared with NATS Tower logs

Compared with visual observations whenever attended analysis is

undertaken

Aircraft Position

Radar feed from NATS

Validated against satellite-based position information broadcast by

most aircraft (Mode S ADS-B)

Validated against Flight Data Recorder (FDR) information

Validated against Flight Calibration aircraft

6

Third party aircraft position information

Third party information on aircraft position, based on Mode S ADS-B is

now widely available, e.g. FlightRadar24, FlightAware.

Data is good – used by CAA for validation, but is not perfect!

Output is aircraft pressure altitude at standard pressure (1013.25hPa)

For each 1hPa pressure different, altitude will be out by ~30ft

If not corrected:

At pressures below 1013.25hPa, aircraft will reported by third party

websites higher than they are

At pressure above 1013.25hPa, aircraft will reported by third party

websites lower than they are

Also needs correcting for airfield elevation

Some aircraft with certain Flight Management Systems output erroneous

Mode S ADS-B lateral position data

7

Good Mode S ADS-B dataLX355 (Airbus A320) departure track on WebTrak, 2 December 2014

Court Close

8

Good Mode S ADS-B data

Court Close

LX355 (Airbus A320) departure track on Flightradar24, 2 December 2014

9

Bad Mode S ADS-B data

Court CloseSome aircraft on Flightradar24 are shown with offset tracks. This aircraft actually departed from the southern runway.

BA460 (Boeing 767-300) departure track on WebTrak, 2 December 2014

10

Noise measurements

12 fixed noise monitors, 6 west and 6 east of Heathrow

8 mobile monitors deployed during summer 2014

Each monitor is a precision instrument traceable to international

standards

Annual calibration (with removal)

Noise monitoring largely follows ISO 20906 ‘Unattended monitoring of

aircraft sound in the vicinity of airports’.

Principle measurements are peak level (Lmax) and Sound Exposure

Level (SEL) of an individual flight and hourly aircraft Leq.

Some noise monitors also equipped to measure and record spectral

data and Effective Perceived Noise Level (EPNL)

11

Noise measurements (2)

6m high fixed monitor (with solar panels)

3.5m high mobile monitor

12

Output of a noise monitor

Lmax – departure noise limits

Peak level, good for comparing and contrasting individual aircraft noise levels, but doesn’t address the duration of a noise event

SEL – used for night time

Takes into account the peak level and the duration of a noise event. Better indicator of the amount of noise energy useful for comparing noise event of different duration. More difficult to measure further away from the airport

Leq

Combines the level and duration of each event (SEL) and the number of events over a given time period into a single number. Good indicator on long-term annoyance, but has no information on the distribution of noise levels that make up the Leq

EPNL

Used for validating the Quota Count (QC) system used to limit night flights

13

Output of a noise monitor (2)

Individual noise levels (Lmax or SEL) vary considerably from flight to flight, day to day

Aircraft mass

Engine power setting

Position relative to the monitor (laterally and vertically)

Atmospheric conditions (wind, temperature, relative humidity)

Example 955 B744R measurements over 3 months

Average peak level 92.4 dBA

95% confidence interval of mean 0.2dB

0

50

100

150

200

250

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

10

0

Mo

re

Nu

mb

er

Lmax

14

Model validation

Impossible to monitor in every practical location

Long-standing practice to determine noise exposure around airports through noise modelling

Early models (1960s to 1990s) mostly empirical models based on measurements

1990s transition to models that account for aircraft performance, but in the UK, model still validated against measurements

During summer 2014, 484,759 measurements extracted from NTK system

Examples of model adjustments:

2014 Boeing 737-300 +1dB at 6km from start of take-off

2014 Airbus A330 +1dB at 14km from landing

2007 Boeing 747-400 +1dB beyond 10km from start of take-off

15

Modelling process

Validation of the model databases

Validation of the the number of operations

Establish the number of aircraft and their distribution by:

Runway

arrival/departure

aircraft type

flight path

16

Departure tracks

17

Representation of dispersed flight tracks

18

Representation of arrival tracks

19

Model output examples

Historical average summer day (0700-2300) Leq contours (since 1990)

Historical average summer night (2300-0700) Leq contours (since 2013)

Historical average annual 24hr Lden contours (2003, 2006 and since

2009)

Airports Commission forecasts:

Average summer day and night Leq

Annual annual Lden

Average summer day N70

Average summer night N60

20

Leq validation

21

References

Validating ANCON taken from conference paper

http://www.caa.co.uk/docs/68/Valid_ANCON.pdf

Noise monitor positions

http://www.caa.co.uk/cap1149

NTK Validation

http://www.caa.co.uk/ercdreport0906

Noise metrics for FAS

http://www.caa.co.uk/ercdreport1104

Noise mapping air traffic noise, including Leq validation

(ERCD Report 0306)

http://archive.defra.gov.uk/environment/quality/noise/environment/map

ping/research/aviation/documents/aircraft-noise.pdf

Any Other Business

2 March 2015

23

For discussion

• Chairing of Heathrow Community Noise Forum

• Membership? Have we got it right?

• Frequency of meetings?

• Anything else?

Windsor and

Maidenhead

Slough

Bracknell

Forest

Surrey

Heath

Runnymede

Spelthorne

Richmond Upon

Thames

Hounslow

Elmbridge

South

Bucks

Hillingdon

Ealing

London

councils &

GLA