some questions about auditory system

[ahmet]

can we say that the bold curve shows the hearable treshold at the same time?

for instance the sound specigically in these intervals are not hearable  by human's ear.

between 0-40 dB and between 0-50 hertz.

after 10.000 hertz and between 0-18 hertz.

 

and could  someone provide more contexts about hearable sounds (diagrams,graphs with numeric parameters would be great)?

thanks