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.
Hearing range describes the range of frequencies that can be heard by humans or other animals, though it can also refer to the range of levels. The human range is commonly given as 20 to 20,000 Hz, though there is considerable variation between individuals, especially at high frequencies, and a gradual loss of sensitivity to higher frequencies with age is considered normal. Sensitivity also varies with frequency, as shown by equal-loudness contours. Routine investigation for hearing loss usually