hertz refers to the frequency (range). Common audio frequency range (for humans) is 20-20K Hz.
that means that sound can vary (in pitch) from 20 cycles per second to 20,000 cycles per second.
When you break it down a low tone (80 Hz.) is considered a bass tone. A high tone (10K Hz.) is considered a treble tone.
the actual measurement of the tone is not good or bad.
It does take a lot more power to amplify low tones than higher ones.