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.
There are still plenty of sounds in the world that you canât detect. The low range of human hearing starts around 20 hertz, and tops out at about 20,000 [PDF]. By contrast, bats can hear ultrasonic sounds with frequencies up to 110,000 hertz. Other animals, like elephants, hear sounds many times lower than those a human can perceive. And as people age, their hearing gets even worse, eliminating even more sounds from the range of audible noises. Here are just a few sounds most people are missing out on: