When we hear thunder in a storm, we feel a shudder. The same happens when we stand on the edge of a cliff. Or are when we are listening to the organ in a cathedral. We feel melancholy, startled, heavy... Sensations that we cannot explain—or perhaps we can.
Some scientists believe that behind these perceptions are sounds that we do not hear, but that our organism picks up: infrasound, also known as black noise.
What is black noise, and how does it affect our health?
Infrasound is an acoustic wave whose frequency is less than 20 Hertz. They are sounds that we do not hear, as our ears perceive frequencies approximately between 20 Hz and 20 kHz. But even if we don't hear this black noise, it can have consequences for our health.
It is true that infrasound does not hurt our ears, as would be the case if we were standing very close to a plane as it takes off. But even though our hearing organs do not technically hear them, they are absorbed by our organism. These inaudible sounds are acoustic waves. When we put our hand on the fridge door, even when the engine is not running, we feel a tremor. And that vibration reaches the floor. Through the air and the floor, they are absorbed by our whole organism.
So when our body absorbs these infrasonic wave frequencies, the cells of our heart, our lungs and the neurons of our spinal cord and brain vibrate.
That oscillation then 'turns into heat, and our organism then considers it as something harmful, like a fever.' And what does our immune system do when the temperature rises? Catecholamines (a type of hormone) are triggered and, therefore, stress arises.
Where do black noise emissions come from?
Nowadays, these infrasounds usually come from household appliances, such as refrigeration and ventilation equipment in shops, machines, wind turbines... The rolling of vehicle wheels, especially tractors, buses and lorries, generates infrasound.
In fact, drivers are the ones who suffer the most, although it seems that these imperceptible oscillations also reach homes near roads, motorways and highways. Ever noticed that when you drive for hours, you feel irritated, but you don't know why. The answer is the absorption of the vibration of the car.