Everybody: This question of whether or not we can hear very low frequencies (say 15 Hz) keeps confusing many people.
I hope I am giving away no secrets when I reveal that music is a complex superposition of many frequencies. :) To understand the basic physics involved, let's take a simple example, when there are just two frequencies present: 100 Hz, 15 Hz.
So you start with 100 Hz and that you can hear. Now, adding 15 Hz you might think that being inaudible it would make no difference to what you hear. However, the way physics of waves works, the mutual interaction (or superposition) of the two frequencies also produces 85 Hz and 115 Hz (difference and sum), and these extra frequencies are audible!
(In a somewhat different context, had the two frequencies been close to each other, the brain would perceive the difference as a "beat", which is why musicians are always tuning their instruments to one another's)
So, even if you cannot hear 15 Hz by itself, you can hear its interaction with other frequencies. The frequency is not audible, but its presence is. It is like "seeing" the air because you can see the leaves move. I hope that makes some sense.
I hope I am giving away no secrets when I reveal that music is a complex superposition of many frequencies. :) To understand the basic physics involved, let's take a simple example, when there are just two frequencies present: 100 Hz, 15 Hz.
So you start with 100 Hz and that you can hear. Now, adding 15 Hz you might think that being inaudible it would make no difference to what you hear. However, the way physics of waves works, the mutual interaction (or superposition) of the two frequencies also produces 85 Hz and 115 Hz (difference and sum), and these extra frequencies are audible!
(In a somewhat different context, had the two frequencies been close to each other, the brain would perceive the difference as a "beat", which is why musicians are always tuning their instruments to one another's)
So, even if you cannot hear 15 Hz by itself, you can hear its interaction with other frequencies. The frequency is not audible, but its presence is. It is like "seeing" the air because you can see the leaves move. I hope that makes some sense.