There are two options - go low or go high. Lower frequencies than humans can hear - below 20Hz - are known as infrasound. They're used by animals including elephants, whales and hippos to communicate.

The human ear is best at registering sounds above the frequency of 20 hertz. Anything below that is called infrasound. Horror movies like "Paranormal Activity" use sounds right around that 20 ...

Earthquake and infrasound activity was also detected two minutes prior to the collapse of Anak's southwestern flank. When this mass slid into the sea, it sent a wall of water, up to 4m high ...