Is it normal to hear a really loud pulsing sound when partial hanging and to not go unconscious after 40 seconds?
It's normal if you don't apply enough pressure. You're probably only blocking the jugular veins, so blood keeps flowing in your head, but not out. This causes pressure to build up in your head, and you don't go unconscious fast enough.
If you apply enough pressure on your neck, you should lose consciousness within about 5–15 seconds. If that's not the case, it's not worth trying any longer. Instead, you could try to reposition the rope or apply more pressure. It's also important to do it
suddenly. If you do it slowly, the same thing happens: you'll just feel pressure building up.
Warning: if you do this, you'll likely die. So do it only if you're 100% sure you want to end your life.
If you just want to practice, don't fix the rope to an anchor point. Instead, just hold the other end in your hand. By doing it this way, you'll automatically release the rope as you start to pass out, so it's safe. If you do this, make sure there're no sharp objects around in case you fall.