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.
High frequency sounds are usually shrill like a whistle whereas low frequency sounds are more like the deep hum of an amplified bass instrument. The highest frequency that most humans can hear is 20,000 cycles per second or 20,000 Hz. This limit gets lower as humans age. Older people generally donât have as large of a hearing range as younger people.