As several people have noted, we only sense a tiny sliver of the world. A dog’s sense of smell, for example, can distinguish between caprylic acid and caproic acid in highly diluted solutions (the only differece between the two is an extra pair of carbon atoms on the chain. However, I think it extremely unlikely that they are sensing otherworldly entities.
It’s important to remember two things. First, Occam’s razor tells us to “not multiply entities unnecessarily”, that is, if there are two ways to explain something, the one that requires us to assume the existence of as few things as possible is the most likely to be true. My cat is often scared of the vacuum cleaner. One way to explain this is that he is simply frightened of the sound, perceiving it as a threatening roar. Another is to assume that he hears ghosts in it, which requires the assumption that humans have spirits, which live on after us and haunt vacuum cleaners. Using Occam’s razor, I assume the first explanation to be the correct one.
The second thing is that, if we can’t determine why something happens (why dogs howl at fire-trucks), any two explanations are equally likely, if both are unsupported. For example, perhaps the firetruck carries around an invisible portal of a sort we haven’t discovered, which connects to a universe of giant sentient sponges, and it is their high-frequency squishing that makes the dogs howl. This explanation and the explanation assuming ghosts are equally likely to be true, and the only reason we prefer the ghost one is that there are centuries of culture and myth surrounding it.