AU2
AU2 transforms subsonic noise to sounds.
Ground vibrations are transfered by a bridge to 5 strings tuned in a pentatonic scale. An electro-magnetic pickup converted the string-vibrations into electric signals. The signals are amplified and passed on to a line-out, where headphones and recording-devices can be plugged in.
AU2 is specially for use in areas with strong ground vibrations, such as bridges or metro stations.