Nitro-. a combining form or an adjective denoting the presence of niter. Nitro-. a combining form (used also adjectively) designating certain compounds of nitrogen or of its acids, as nitrohydrochloric, nitrocalcite; also, designating the group or radical NO2, or its compounds, as nitrobenzene.
The commonly stated range of human hearing is 20 Hz to 20 kHz. Under ideal laboratory conditions, humans can hear sound as low as 12 Hz and as high as 28 kHz, though the threshold increases sharply at 15 kHz in adults, corresponding to the last auditory channel of the cochlea.
For humans, normal hearing is between â10 dB(HL) and 15 dB(HL) , although 0 dB from 250 Hz to 8 kHz is deemed to be 'average' normal hearing. Hearing thresholds of humans and other mammals can be found by using behavioural hearing tests or physiological tests.hey are not the same as equal-loudness contours, which are a set of curves representing equal loudness at different levels, as well as at the threshold of hearing, in absolute terms measured in dB SPL (sound pressure level).