Most of us can’t bear the sound of nails on a blackboard,but why? Researchers have a possible explanation. It turns out that our adverse reaction to the piercing sound is partly physical. The part of the noise that makes us suffering has a frequency between 2000 and 4000 hertz,a range naturally amplified by the shape of our ear canals. It turns out that we adverse reaction to the piercing sound is partly physical. The part of the noise that makes us suffering has a frequency between 2000 and 4000 hertz, a range naturally amplified by the shape of our ear canals.