Hydra: a sound radar that detects vehicles that are too noisy
On January 5, 2022, the government introduced an experiment with sound radars in the mobility orientation law. The objective was to test the effectiveness (and therefore the precision and accuracy) of these radars for several years in key locations chosen in different cities in France.
Hydra: a radar with 9 heads to relieve those of residents
It is the company Bruitparif, helped by the Île-de-France region, which developed Hydre, this sound radar whose name is directly inspired by on-board technologies. Because the monster has 8 microphones and 2 cameras. It can thus quickly detect the dominant noise source in the environment, and measure the distance at which it is located.
Since noise is a sound wave, it is essential to know how far away the source is. The measurement carried out by Hydra is accompanied by a recalibration to obtain an equivalent measurement at a distance of 7.60 m.
This is what the Hydra radar looks like. © Bruitparif
If, after this recalibration, the sound level exceeds the threshold of 85 dB, the radar uses its video recordings to identify the vehicle and records its license plate. The issued document then indicates the noise level, the photo of the vehicle and the license plate number.
The Hydra radar camera is capable of recording license plates. © Bruitparif
Already tested in several European cities, Hydra is in the certification phase at LNE. Its implementation is planned for 2025.
Why 85 dB?
Without going into too much detail, the measurement of sound level is spread, in the case of human hearing, on a logarithmic scale ranging from 0 dB to 120 dB. The decibel (dB) is a dimensionless unit of magnitude, defined as ten times the decimal logarithm of the ratio between two powers, used in telecommunications, electronics and acoustics.
Thus, it was found that exposure for 2 hours per day to a threshold of 85 dB leads to irreversible deterioration of hearing abilities. It is accompanied by tinnitus. According to the World Health Organization, in 2050, one in four people will suffer from hearing problems.
Luckily, democratization noise canceling headphones and earphones (RBA) could help disprove this analysis.
