Who are the listeners? Why are they called the listeners?

It is not quite so clear who the listeners are in this mysterious and nostalgic-feeling poem. The listeners could be ghosts of the people who once lived in the empty home. They could be the animals, such as the birds, who have taken up residence in the home since the humans have left. They could be interpreted as the natural world in general, which has taken over the surrounding area and the house itself.
Whoever the listeners are, they are called this because the traveler does not receive a response as he makes his calls and statements. The listeners simply take in the words of the traveler without a reply. The traveler could be interpreted as the quest for knowledge and/or understanding in our world, and the listeners could be interpreted as the mysteriousness of the universe as we ask questions to it and it makes no response.