The birth of birdsong

The earliest bird that definitely made a noise was the Vegavis iaai, which lived in Antarctica about 67 million years ago. Fossils show the presence of a syrinx, the avian equivalent of the larynx or “voice box” in humans, in its windpipe, just above the lungs. This indicates that it was able to quack or honk.

Birdsong began to rapidly evolve from those quacks and honks, about 30 million years ago, when Australian plants adapted to their steadily drying climates by excreting the sugars they produced, as nectar or plant sap. Australian birds quickly evolved to tap into these new resources: they began to taste and seek out sweetness, grew larger, more aggressive, cleverer and, they became vocal.

The loudest boom

The loudest sound ever produced on Earth was probably the shrieking, hissing crash of the Chicxulub impactor, as it struck present-day Mexico 66 million years ago, wiping out most of the planet’s non-avian dinosaurs (among numerous other species) and sending shock waves over land and sea.

Chicxulub was an asteroid larger than Mount Everest, and it struck Earth at 20 times the speed of a bullet. It drove itself so far into the Earth, that in moments, the rim of the 100-km-wide crater was made up of peaks higher than the Himalayas are today; they soon collapsed amid the chaos.

The sound of the Chicxulub crash would have been at least 500,000 times louder than what is perhaps the loudest sound in human history: that of the 1883 eruption of the Krakatoa volcano.

This explosion sent pressure waves rippling around the Earth. It pushed a tsunami 45 metres high on to the shores of nearby Java and Sumatra, killing an estimated 120,000 people.

The captain of the Norham Castle, a ship stationed 64 km from Krakatoa, wrote that the explosions burst the eardrums of over half his crew.

More than 160 km away, the sound was measured at about 172 dB, over eight times the threshold for pain in humans, and about four times as loud as a jet engine if one were standing right next to it.

Notes in space

While the Northern Lights or aurora borealis do not in themselves make any noise, in the right conditions, they can give rise to electrical discharges 100 metres or so above the ground that sound like gentle crackles and bangs. These sounds have been described by indigenous peoples and travellers in the Arctic for centuries, and were first recorded by scientists in the early Aughts.

Seismometers placed on Earth’s moon enable researchers to measure shudders and groans caused by meteor impacts. These are measured as vibrations within moon rock, since the moon itself is an utterly silent place. Sound needs a medium to travel through, and without a significant atmosphere, it cannot travel there.

The atmosphere on the surface of Mars, meanwhile, is about 100 times less dense than on Earth.

The cold air, which is primarily carbon dioxide, would reduce the speed of sound, which would serve to lower the pitch of the human voice. But the thin atmosphere would raise the pitch, by about as much. So, though the waves would travel slower, humans would sound pretty much the same on Mars as they do here on Earth.