For example, of the two words lion and lioness, lion is unmarked for gender (it can denote either a male or female) whereas lioness is marked, since it denotes only females. b. Explicitly characterized by or having a particular linguistic feature.
20 Hertz to 20,000 Hertz is the frequency response range that a human can hear. So in answer to your question 20 Hertz would be the lowest pitch a human can hear.
Compared to humans, dogs and cats have a much different range of hearing. Humans can hear sounds in the 64 Hz (low sounds) to 23 kHz (high sounds) range. By comparison, a cat has a range of about 45 Hz to 64 kHz and a dog has a range of about 67 Hz to 45 KHz.