Does a Falling Tree make a Sound When Nobody is there to Hear it?

As it presupposes dualism (between “things” (dharmas) in themselves and “things” as represented) the representational view of knowledge and experience is definitely rejected in Zen Buddhism, as it is in Mahayana Buddhism generally. In Zen, all real dharmas (things, beings, instances, events, etc.) are actualized (not re-actualized, or represented) insofar as they are experienced by sentient beings.

So then, the falling tree makes no sound if no one experiences it, and in fact, there is no such thing as a falling tree that no one experiences. A tree, a human being (or any dharma) is only a real dharma if someone (a “self” or an “other”) experiences it. One obvious implication of this is that whatever (or whoever) does experience beings (or other dharmas) must also be real. This aspect of reality is one of the central topics of Dogen’s Shobogenzo.

When speaking of consciousness of self and other, there is a self and an other in what is known; there is a self and an other in what is seen.
Shobogenzo, Shoaku Makusa, Hubert Nearman

In Buddhism, as we know, experience and experiencer are nondual, and each is (like all dharmas) one with the whole universe. But the Zen masters certainly do not let matters rest there; they constantly exhorts us to look deeply and come to understand how the myriad dharmas differ, relate, and interact with each other and the rest of the world. Dogen’s Shobogenzo, for example, is a marvelous demonstration of how this task is accomplished.