Long time measurement of long range sound propagation over an ocean surface

In order to obtain data for environmental impact assessment of noise from an airport under development, an MLS test-signal was emitted from a fixed point at the site on the sea and received on the seacoast about 5 km from the source. The measuring system was operated automatically, and the measurements were carried out at every hour and continued for 14 months. The MLS correlation method was applied in order not to annoy the people near the site, since the method succeeded in sound propagation measurements with signal levels lower than the background noise level. During the measurements, some meteorological conditions were also observed simultaneously.