Question

answer the above questions 17&18..

Answer 1

We can hear from 20Hz to 20kHz. but dogs can hear infrasonic i.e sounds leeser than 20Hz, therefore even hearing the slightest of dusturbances, which we can't detect, the dogs can and hence they start barking

Answer 2

no one should be able to heard the sound because humans can heard sound of frequencies in the range 20Hz to 20 kHz . the frequency of sound mention there is not in this range. so.....

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