Bottomless Pit and Speed-less Sound! What If?

A description about what if a bottomless pit existed... where would it practically exist? What if the speed of sound currently at 340m/s suddenly decreases to 340mm/s?
Have you ever considered the possibility of things that go beyond our reality? Events that take place in the realms of our imagination only. To accurately predict the nature of events that cannot ever occur naturally? This has been going on and on for ages, like a snowball rolling down the hill, with more and more people thinking simultaneously. Consider some theories about the earth. People believed the earth to be a solid mass thoroughly, whereas, some believed it to be having a top layer consisting of solid for hundreds of kilometer and remaining, a molten mass. The deepest hole drilled is about 7.5 km down, and the deepest mine into which man has traveled is 3.5 km down (a gold mine in BixBurg, the Transvaal, South Africa). The earth's radius is 6,400 km. We don't really have the deep level digging equipment that could cover even a reasonable part of this number.
It was in the 18th Century that there emerged a concept in the minds of the mathematician Maupertuis and the philosopher Voltaire. They dreamed of tunneling right through earth. Of course, no tunnel of this nature has been dug yet. However, let us consider for science's sake that this tunnel has been dug. What will happen when one falls down in this 'bottomless pit'? Assume that the drag present due to air is absent. You will never ever crash into the bottom, yet, you will experience the thrill of falling. There is no bottom in this pit. You keep falling and falling until you reach the acceleration produced by gravity, i.e., appox. 8 km/sec, until you reach the center of the earth, and then you feel a change of sensation. Now, instead of falling down, you feel as you are being thrown up (like on a fireman's blanket) You simply overshoot and continue to fall or rather shoot 'up' from the earth's center, and gradually your speed decreases, until you reach the opposite end. Now, you must have something to hold on tightly for your life or you will start going down once again. This process can continue continuously like a pendulum, considering that we have neglected the air drag in this case. If you consider the air drag, you will slow down gradually, and eventually stop at the center of the earth. So, how long would a one-side journey take? Approximately an hour and a half. Flammarion, a French astronomer who brought up the project again after Mauperturis and Voltaire remarked, "This would be possible if and only if the well were dug from one pole of the earth to the other. Any other location would have us take into account the earth's rotation. We know that every point on the earth rotates 465m/sec at the equator, and 300m/s at the latitude of Paris. Since circumferential velocity increases, the further away we are from the axis of rotation, a plumb line dropped in a well will deflect eastward from the vertical. If we dug our bottomless well at the equator, we should have to make it very wide or very inclined, because a body dropped into it from the surface would fly way east of the center of the earth. Further if the mouth were on a South American plateau, two km above sea level, while the outlet were at ocean level, the opening would fly out at the other end two kilometers up. However, if both openings were at ocean level, you could grab the person by the hand when he appears at the mouth, because here, his speed would be nothing. In the previous case, you would better beware of the traveler hurtling by.
Well, enough about the earth. Let us consider one more imaginative case for the sake of science. As taught to us in our school days, sound moves at appox. 340m/s in the air. Suppose some worldwide experiment occurred and changed the speed of sound to 340mm/sec, which is even less than the speed at which we walk. The consequences, first, to hear anything clearly, you will have to hold yourself rock steady. You dare not move in the direction of sound or you will be hearing the sounds all garbled. Slow music will gain a new meaning... literally. A hitchhiker will never rely on his ears for getting a ride, nor will the horns of our vehicles be of any use.
A friend of yours is walking back and forth across the room while talking to you. His location will always be different from the direction of his speech. God forbid, he doesn't walk towards you while talking to you. What you will hear next is his voice in reverse order. First, you hear the words he has just uttered, then the sounds uttered just a bit before, and then the sounds uttered earlier, and so on and so forth.
An explosion would be detected very late in the neighboring block. Guns wouldn't need silencers. Army machines can go undetected in enemy area [as far as 'hearing them approach' is used]. July 4th wouldn't be the July 4th we know of. Thunderclaps would take approximately 150 hours to reach us after they occur. The world will be even more chaotic with sound effects in bullet time!
Definitely, while sitting in my bedroom, I feel relaxed when I hear my pet dog banging at the front door of my living room, and glad that such an experiment has not occurred, and hopefully will never occur.