Graphical representation

Particular care was taken in designing the graphical representation of the Harmonica index, in order to simultaneously provide several elements of information about the noise environment in a concise and clear manner.

One score for the noise pollution level

The Harmonica index gives a score of 0 to 10, rounded to one decimal place. The higher the score, the poorer the noise environment.

Two shapes to distinguish between the contribution of background noise and noise peaks

The graphical representation of the index is in two parts, a triangle on top of a rectangle, in order to clearly translate its two components:

  • The rectangle represents the component related to background noise (BGN);
  • The triangle represents the event-based component (EVT), related to noise dynamics and the number of noise peaks that disturb the calm.

Three colours indicates the situation compared to threshold values

The colour of the index (green/orange/red) indicates how the noise environment compares to the WHO's environmental quality objectives and the values recognised as critical for noise. These colours also take the time of day into account, as people are more sensitive to noise at night.


from 6 am to 10 pm

from 10 pm to 6 am

  between 0 and 4 between 0 and 3
  between 4 and 8 between 3 and 7
  over 8 over 7

Four kind of calculation periods per day

The Harmonica index is calculated for hourly time slots for every measurement station from the networks and towns that are part of the NoiseInEU European information platform.

Three average values are also calculated every day: one for the day period (6am - 10pm), one for the night period (10pm - 6am), and one for the entire day (24h).