Explanations Regarding Aircraft Noise Measurements


  1. General
  2. Operation
  3. Leq Indication
  4. Interpretation of the Curves
  5. Flight Tracks
  6. Sound Records
  7. Live Camera
  8. Noise Statistics
  9. Station Description
  11. Aircraft Noise Complaints
  12. Map of Region
  13. FAQ's

1. General

Please note:
We work with different types of measurement instruments.
High quality instruments are characterized by the sign '•••' behind the station name.
[Example: Station name "Eppstein •••" means that this station works with a calibrated instrument]

Important note for stations without the tag "•••":
Do not compare our measurements with official noise measurements.
See our measurements - in analogy to a Web cam - as a 'noise Web cam'.


1.1 Cheap instruments (without sign •••) are not calibrated

The respective quality difference is similar to that between good kitchen scales and a calibrated precision balance.


1.2 What can be read from a non-calibrated instrument - and what must not be read ?

This point is only valid for non-calibrated systems!

Individual overflights can be distinctly identified.
The order of noise can be distinctly read.

But you should not use a ruler to measure the exact height of a peak and then say, e.g.:
    This plane had 81.27 dB(A),
What can be said, however, is:
    This plane had about 80 dB(A).


1.3 Error sources

Technological error tolerance is the least problem.

Additional errors may be due to wind, rain, reflections, and interference sources near the noise sensor.


1.4 Time

From July 20, 2002 on, all measurement stations work with 'radio clock time'.


1.5 Updating

The stations work fully automatically.
If everything goes right, each station should log in into the Web at intervals of 1 hour and deliver its new measured values.

Attention: This is not done synchronously, however. For instance, one station may make its update 10 minutes after every full hour, the other 10 minutes before every full hour. In addition, any maintenance operation will change the updating times.

Some stations do not send their values every hour. Respective details will then be found in the station description.


1.6 Hardware

See preconditions for installing a measurement station.


1.7 Software

The measurement stations send their gathered measured values to our server every hour.
When you want to look at a noise diagram, a programme in the Internet server is started that graphically edits the measured data.


2. Operation

We offer 2 different views:

  • the 'classic' view and
  • the 'scientific' view

The 'classic' view is easy to understand, the 'scientific' view offers more information but is also more complex.

The difference between both views:

  • The 'classic' view shows only one curve (the average which is representated from one pixel in the graph).
    Exception: In case of a recognized overflight the peak value of the overflight is shown.

    In the scientific view you see 3 curves: In the middle a solid line with the average (like 'classic' view but without the exception) and an upper and lower dotted line which describe the max. and the min. value inside the average interval.

  • The 'classic' view offers only one zoom level, the other one two. Therefore the complaint function in the 'classic' view is available in the 2 hour view, in the other view it's available in the 30 min view.

Default is the 'classic' view. To switch to the 'scientific' view you should activate the corresponding radio-button.


2.1 Zoom

In whole-day representation, 1 pixel corresponds with 1 minute
In zoom representation 1 (2 h), 1 pixel corresponds with 6 seconds
In zoom representation 2 (30 min), 1 pixel corresponds with 1 second (only in 'scientific' view)

Zoom representation is reached by clicking in the desired area of the graphic or the symbol .

When in zoom representation, you can navigate 2 hours/30 minutes backward/forward by means of the arrows  and .

To decrease the zoom representation, click on .

Important hint:
In the low-resolution graphics we show the average of the compressed time period, eg. 1 pixel in the whole-day representation shows the average of 1 minute.
The means of n values is calculated according to DIN 45641:
  means = 10 * log10 [ 1/n * Σ 10**(0.1*valuei) ]
Please keep in mind the differences in both views.


2.2 Selection of date

In section date navigation, you may navigate one day backward (), one day forward () or to a date you determine via Input.


2.3 Selection of measurement station

In the selection-box 'Other Station' you can select every station.


2.4 Superimposing measurement curves

To better identify overflight noise, you may superimpose the current measurement curve in all representations with the measurement curve of a neighbour station.

To remove the a superimposing station click on Stationname ••• × (below the noise graph).


2.5 Daily, Monthly and Yearly statistics

Daily Statistics will give a tabulated evaluation of all identified overflights as well as several average sound indicators.

Monthly and Yearly Statistics will give a graphic representation of the number of overflights identified per day, a graphic representation of several average sound indicators, and a numeric representation of several average sound indicators (more information, see section 8.).


3. Leq Indication

The Leq (noise-equivalent average sound indication) is a measure to describe mean total noise pollution.

Our Leq values are so-called Leq 3 values, calculated according to the formula:

Whole-day representation:
Leq core night describes total pollution during the dark blue areas of the day.
Leq night describes total pollution during the blue areas of the day.
Leq evening describes total pollution during the light blue areas of the day.
Leq day describes total pollution during the white areas of the day.
Leq whole-day describes total pollution during the whole day.

Zoom representation:
Leq describes total pollution during the indicated 2 hours / 30 minutes.

Attention: Leq values are total-noise Leqs, i.e., the lawn mower, for instance, is included as well !


4. Interpretation of the curves

Please note: Details can be recognized in zoom representation only !


4.1 Blue areas of the day:

The  blue area  marks night time, the  light blue area  marks the so-called evening times of the day, the white area the day period.

Some regions have an additional  dark blue area , which describes special protected night periods (eg. the so-called "Mediation Night" in Frankfurt).


4.2 A long, straight line:

A long, straight line is indicated when there are no measured values. Each maintenance operation, for instance, will produce such a line.

4.3 How is aircraft noise distinguished from other types of noise ?

See also 4.5 Detection of overflights.

typical loud overflight:
a near overflight lasts 2 to 3 min.

typical series of overflights

'extreme' lawn mower directly in front of the sensor
much too long for an overflight

loud car
much too short for an overflight

normal lawn mower with overflight

 Shortly before half past four in the morning:
Birds welcome the new day

4.4 Colour bars under the measurement curve

Wind direction:

The colour bar below the noise graph describes the wind direction.
The main directions:  North ,  East ,  South  und  West .
If you move the mouse above a colour, the system shows you wind direction and wind speed.

For Frankfurt, in particular, operation direction Fraport is indicated as follows (up to February 2004):

The upper colour bar indicates the wind direction (as with all other regions).
The lower colour bar indicates the calculated operation direction:
operation direction 25 = takeoff towards West
operation direction unclear (preference 25)
operation direction unclear
operation direction unclear (preference 07)
operation direction 07 = takeoff towards East

Attention: The operation direction indicated is based on an evaluation of wind data. As air-traffic controllers have some scope of decision, erroneous calculations might occur.

For Frankfurt, in particular, wind direction and operation direction Fraport are indicated as follows (from March 2004 on):

The upper colour bar indicates the wind direction (as with all other regions).
The lower colour bar indicates the operation direction based on Fraport data:
operation direction 25 = takeoff towards West
operation direction 07 = takeoff towards East

4.5 Detection of overflights

Overflights are detected in an asynchronous background process (every 5 min). Hence some time passes until overflights have been calculated.
Overflights are marked by an O or a X on the noise peak.

Important hints:
  • Overflights are calculated by means of a mathematical procedure that interprets noise curves. This procedure will not detect all overflights with 100% precision.
    Therefore, it may (and will) occur that noise peaks are falsely marked as overflights – and it may (and will) occur that actual overflights remain unidentified !!!
  • It is not job of the overflight detection to detect every overflight!
    Only those overflights should be detected which can be part of a noise calculation. The DIN demands a minimum difference between the basic loudness and peak of 15 dBA. In some individual cases we can reduce the difference to 10 dBA – less is impossible.
  • In some stations we have additional algorithms for the overflight detection. The final calculation needs sometimes up to 2 days.
  • In situations with more than one calculation pass we mark the temporary detected overflights with:
    X = provisionally
    O = final
    In case of unclearness (overflight yes/no) we recommend to use "Superimposing measurement curves" of two neighbour stations (see 2.4) or the analysis of the flight tracks (siehe 5., not in all regions possible)

4.6 An additional tip

You had best note down some overflights at your residence and compare them with our curves. If you live in the neighbourhood of one of the measurement stations, you will soon develop a feeling for the interpretation of the curves.  

5. Flight Tracks (not in all regions possible)

In the noise graph you will find a yellow horizontal bar "Flight tracks" if there are flight tracks in our database.

After a left mouse-click in this bar, we show you all flight tracks of the selected time (±7,5 min).

Flight tracks which differ only ±90 sec of the selected time are shown in bold black.
A click on such a bold black flight track shows you the details of the flight.


6. Sound Records (only with stations in 'high-end' technology)

In the noise graph you will find a blue horizontal bar "Details" if sound records are available.

A mouse click directly above a peak gives you detailed information including the sound recording.


7. Live Camera

In some noise graphs you will find a blue horizontal bar "Pictures"

A mouse click shows you the picture from this time.


8. Noise Statistics

We offer daily, monthly and yearly statistics.
Basis for all calculations is the overflight detection. This means that stations with a poor overflight detection produce poor statistics.

Only peaks which are shown with a 'O' in the graph are part of the statistics.

Peaks which are marked with a 'X' (provisional) or without any mark are not part of the statistics.


9. Station Description

To get a description of the measurement station, click on the link Station description below the noise graph.
Not all operators send us a description.

Note: For reasons of data safety, we do, on principle, not answer any questions regarding the measurement stations (exact address, name, etc.)
The complete information that station owners have compiled with respect to their station will be found under station description.



Station owners can comment their measurement curves. In that case, you find below the noise graph a link  Comment.
Click on this link to read the comment.


11. Aircraft Noise Complaints

In the highest zoom representation, an electronic complaint system is available (not in all regions).
Complaints are sent via e-mail.

First, in the highest zoom representation, you have to click on the overflights you want to complain about - then click on the link Send Aircraft Noise Complaint.

A detailed guide is found in the complaint instructions.


12. Map of Region

For many regions, there is a map of the region:
In that case, you will find the link Region Map.

Example: Frankfurt
On the region map, you will find a map witht
   the positions of the stations,
   the set flight routes per operation direction and
   the actual flight routes per operation direction.

We can only realize these maps of a region in cooperation with the station operators, as we do not know the respective site.
So please understand that we do not offer them for any region.


FAQs (frequently asked questions)


How can I print diagrams ?

All feasible ways of doing that are via other programmes, e.g. via 'Word':
1.   Start Word
2.   File/Page setup/Paper size/Landscape/OK
3.   Right mouse click anywhere in the diagram, then choose COPY in the context window
4.   In Word: Edit/Paste
5.   In Word: left doubleclick on picture, then, in the appearing window, choose tab SIZE, and in field 'width', enter 25.
6.   In Word: Print
This description only holds for IE 5.5 and Word 2000 - but with any other version known to the author, things work almost the same way.


I would like to have more detailed information on a measurement station
On principle, we do not give more information than that presented in the station description.


Why we do not measure at place xy ?
We never operate stations by ourselves.

Operators are private persons, NGOs and municipalities. They buy, install and operate the stations.

Therefore they decide the location of the measurement station.