There is a concept called a koan in Zen Buddhism - it's a question that is not meant to be answered but is meant to try to get you out of your normal thinking patterns - This is a similar thing. Like "What is the sound of one hand clapping."
If it's working you may start wondering if I actually exist.
If you want a physical answer you could answer Yes because sound is vibrations of the air which are caused whether someone is there or not.
Or you could answer No because a sound is more that air vibrations and must be percieved by an observer in the same way that a dog does not have a sight but you can see and thus experience a dog.
Alternatively you could go down the whole Shrodingers cat route where the observer influences the observed event but I wouldn't advise that on a Friday