The Hearing Sensitivity
Human auditory sensitivity cannot perceive all changes in the frequency of sound intensity. Because of this, our ears do not pick up all frequencies.
However, this sensitivity to changes in the frequency of sound intensity is small, a fact that does not allow the human ear to capture the sound frequencies of ultrasound and infrasound , as they are not in the auditory frequency range perceived by the human ear, which is 20 hertz. at 20,000 hertz.
Some studies indicate that the auditory perception of sound intensity variations is approximately equal to 1dB, which means that a 1dB increase in sound level is necessary for us to perceive a small increase in sound intensity.
Infrasound and ultrasound do not cause sensitivity to our auditory system because, as already mentioned, their sound frequencies are outside the auditory range perceptible to the human ear . However, there are animals that can perceive ultrasound. Experiments show that the dogis one of those animals that can perceive ultrasounds that reach up to 50,000 hertz. It is for this reason that they are trained to respond to ultrasound whistles, which humans cannot perceive. Bats are other animals that can also pick up ultrasound frequencies. These animals can emit and hear sound frequencies that reach up to 120,000 hertz.