Our infrasound array detects a lot of signals coming from almost all directions. The most part of them are of human origin that is clearly seen in distribution plots of number of signals by days of week and by day times.
The infrasound array often register signals from open-pit mining explosions.
Places of explosions signals from where were registered are shown in the map below.
In addition, we sometimes detect moments when planes cross sonic barrier and Doppler effect from planes and helicopters flying under the sensors of our infrasound array.
In 2002 we detected signals from Finland from old amunition destruction explosions. Place of the explosions was found by seismic signals (see fig. below).
Recordings of the explosions for 9 day, aligned by explosion times, are shown in fig. below.
It is clearly seen that the signals appeared several times after each explosion. It corresponds to waves propagated in different athmospheric layers. Travel times of the waves vary significantly depending on athmosphere conditions.
Of course, not all acoustic signals can be explained by human activity. Hypotheses exist that we registered waves generated by ocean storms and even bolides and auroras.