Sound is present everywhere on Earth, whether we can hear it or not is another matter. The only place where there can be no sound is perfect vacuum. The absolute minimum sound that can be theorized is -23dB caused by Brownian motion of minute vibrations of atoms in a gas or a liquid. Anything quieter requires perfect vacuum.
Microsoft now holds the record for the quietest place on Earth at an amazing -20dB. To set the quietest record on Earth requires an anechoic chamber, which essentially and insulated room that attempts to minimize and completely absorb reflections of sound from within. Microsoft engineers set off to achieve -16dB in Microsoft’s anechoic chamber inside building 87 but ended up recording a sound of -20.6dB, the smallest magnitude in history and much lower than was originally anticipated.
The previous record was -13dB set by Anechoic Test Chamber at Orfield Laboratories but Microsoft engineers totally blew that record away in an engineering marvel. This sound recorded is the closest to Brownian motion than any other record. To achieve such silence, every object in the room and any other connections leading to it must be precisely engineered. Even the smallest wire can cause vibrations that can distort the silence. The entire chamber is designed with sound absorbing wedges that help mitigate the minute amounts of sound that penetrate the thick concrete walls of the building. The whole foundation of the room is isolated from the rest of the building as it sits atop of noise-reduction springs to further dampen any noise contamination.
The sound of absolute silence is quite frightening and a terrifying experience to withstand negative decibels because our ears and our minds are simply not used to such silence. Even when we go to sleep in our not so noisy bedrooms, we can hear the fan, the breeze, our breathing and the occasional horn of a car from far away. To withstand negative decibels can be dangerous and no human has been able to spend more than 30 minutes in this chamber without supervision. Those who have done it tell us that at one point, you start hearing your own heartbeat and your own blood flowing inside your arteries at which point one might be driven mad an inflict self-harm.
To put this silence into perspective, the loudest noise ever known to man is of the 1883 eruption of the Krakatoa Volcano in Indonesia that ruptured the ear drums of fishermen 40 miles away. The sound travelled around the Earth 3 times. If you witness a rocket take off at 100m distance, the sound you’ll hear will be of 170dB, which you will not actually hear because your ears will be ruptured at 150dB. Hearing a plane take off at 25m produces a sound of 150dB which you will hear if you survive being blown apart by the jet’s exhausts. Normal conversation is 60dB, rustling of leaves is 20dB and human breathing is 20dB. Clearly, attempting to achieve -20dB is an engineering marvel.