If a tree falls in the forest and no one hears it, does it make a sound?
perception n. act or faculty of perceiving; intuitive recognition; action by which the mind refers its sensations to external object as cause. perceive v.t. apprehend with the mind, observe, understand; apprehend through one of the senses; regard mentally in a specified manner.
Concise Oxford Dictionary
We can rephrase this in audio engineering terms:
If an acoustic transmission is not perceived, does the waveform exist? If there is a concert without an audience, will we get paid?
The subjective side of acoustical reception includes the experience of human hearing, i.e. perception. Unsurprisingly this is a subject of ongoing discovery and debate. ...