Do People Hear At Different Frequencies?

Yes, most definitely!  The older someone gets, the less of a frequency they can hear.  For example, kids can hear the "Mosquito Ringtone" on their phones, but adults cannot.  Also, there ARE people that can hear dog whistles.  I do not understand why people are freaking out saying that humans cannot hear dog whistles, because they CAN.  I have proof of that because I CAN HEAR THEM.

In general people hearing from 20 to 20,000 Hertz where one Hertz (Hz) is one vibration per second and higher Hertz values equate to higher pitched sounds. People vary in their personal sensitivities for a range of reasons. Difference in genetic inheritance affect hearing ability just as they do our other traits so the figures given are only rough averages.

People have been recorded as detecting sounds of 22,000 Hz and higher. As people age or their hearing is damaged by exposure to loud noise they become less able to hear high frequencies; so that a normal middle aged man is likely to only hear as high as 13,000 Hz. Hearing tends to deteriorate more slowly in women so females may often be able to hear higher pitches than same-aged males. Many animals communicate at frequencies outside our audible range such as elephants who use lower frequencies (infrasound) and rats who use higher frequencies (ultrasound).

Yes, when you grow older, your tolerance to noise would be weaker and weaker, and you can't tolerate louder noises, so you will hear frequencies at a lower level.