"Now, we know that human hearing ranges from 20 Hz to 20 kHz. Since the frequency of the given sound wave is 16.5 kHz, it will be audible to humans." 16.5 is less than 20. How will it be audible?
Yes, sound of the frequency range from 20Hz to 20 kHz, kHz means 1000, so 20kHz = 20,000 Hz and is audible to human beings.
But here it is given 16.5 kHz = 16500 Hz
Now since 16500 < 20000 Hz so 16.5 kHz is audible to human beings.