Except the answer is no. Assuming ‘no one is around to hear’ means no living beings, so no fluffy bunnies or owt, either.
The falling tree creates vibrations in the air, which causes our inner-ear gubbins to vibrate, which in turn, the human / animal brain interprets as ‘sound’.
No one around, no ear, no brain = no sound.
That’s just twisiting the definition of the word sound. E.g. does an ultrasonic sanner make a sound, yes. Can we hear it, no. Does this make a difference, No. How about those high frequency devices that they proposed to deter young people gathering in groups. If it’s but there are no young people to hear it is it making a sound, yes.