Sound of existence

5:50, Saturday.
As the sun rises and begins to color dull orange the east sky over the beige building, more songs of birds can be heard. But, listen hard, in the background of the merry soprano chirp, there is a gut-resonating bass noise echoing through the town. That may be the sound of people's activity, how prevailing and penetrating.
Last week I went to Osaka and heard a similar noise in a hotel room near the station. It was so faint and at such a low pitch that it felt more like a vibration. But somehow it seemed like trying to reach somewhere in my soul, so familiar and nostalgic that I felt as if remembering what I heard before I was born.
Not long ago, somebody told me that the word "Aummmmm", when pronounced at a very bass tone, is exactly like the sound of the universe.
A sound that thrusts through 13.6 billion light years of time and space, through the stars, the Sun, the Earth and every one of us. That's grand to imagine. If there were such sound, it would definitely be like what I'm hearing now.
The sound of existence. If only I could hear it.