The human auditory system does not perceive different frequencies with equal sensitivity ; signals around 1 -- 4 kHz sound loudest for a given intensity .
The human auditory system processes frequencies in a roughly logarithmic fashion approximated by the Bark scale .
The human auditory system , which processes frequencies in a roughly logarithmic fashion approximated by the Bark scale , does not perceive different frequencies with equal sensitivity ; signals around 1 -- 4 kHz sound loudest for a given intensity .