Did you know?
The human ear is a very sensitive pressure sensor. It picks up incredible small pressure fluctuations and translates those in conjunction with the brain into 'sound'. The human ear has a sensitivity peak at around 4000 Hz. At 10,000 Hz almost twice as much energy is required to create the same loudness sensation. At the lower frequency range more and more sound energy is needed to create the same loudness sensation. At 20 Hz almost 70 dB more sound is needed.

The human ear is most sensitive to frequencies in the 4000 Hz range.

At 20 Hz the human ear needs 70 dB of sound just to be able to hear it.

Already in the cave dwellers era, people hollowed out tree trunks of certain lengths and excited the air column inside by hitting the trunk. The length of the tree trunk determined the frequency of the sound produced. They quickly figured out that a longer trunk produced a lower tone, resulting in a much larger broadcast area.