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.
I hope this helps you. Dogs hear at a wider range of frequencies than humans. The low end of the range is similar to humans (humans hear down to about 20 Hertz, or cycles per second, dogs are at about 40 Hz). But at the high end, they are quite different.