Communication. Conceptual image showing sound waves moving from one woman's mouth to another woman's ear. This represents the sound waves that are made when speaking and heard when listening. The human ear can hear sounds in a frequency range of 20 to 20,000 Hertz, and sound levels ranging from 0 to 130 decibels. Human speech ranges from 300 to 4000 Hertz in frequency, and is around 65 decibels loud.