Why are exploding HHO bubbles louder then pure HHO? We tried my electrolyzer with a friend today, we filled a small bottle with HHO gas, and set it on fire. It was loud but not a big deal, like a firecracker. Then we added some soapy water and created HHO bubbles instead of filling the bottle with HHO underwater. Then we lit the bubbles and it exploded so loud that for a while all we heard was just ringing. It was way too louder than when before, same gas same bottle, we even tried it twice with same result.
Im wondering why is it so unbelievably louder. I thought that maybe the sound just traveled in a different way, because the bottle was turned in the opposite way (towards the ceiling instead of towards the floor), but im not sure.
 A: Some ideas you might want to consider or explore:
1. Bottle
You take a 1 litre water bottle made of PET and filled with water. You invert it and place it into a tank of water over electrodes that are producing oxygen and hydrogen gas. You collect the mixture of gases until all the water has been displaced from the bottle. You take the bottle from the water tank and move it to another location, you apply a source of ignition (e.g. a match) to the open mouth of the bottle.


*

*You lost some gas while moving the bottle from the tank to another location (it was replaced by mixing with nitrogen and other gases in the surrounding air.

*The shape of the bottle limits the spread of the ignition through the gas inside the bottle, the ignition spreads from the opening and travels along the length of the plastic bottle.

*The bottle itself resists the expansion produced by the burning gases and perhaps limits the rate at which the reaction proceeds 
2. Bubbles
You dispense with the bottle, add some detergent to the water and allow the oxygen and hydrogen to form bubbles at the surface
You ignite the bubbles.


*

*Some of the hydrogen and oxygen does not form bubbles but is invisibly present around the bubbles. This leads you to underestimate the volume produced

*you are not good at visually estimating 1 litre of bubbles. You have more than 1 litre of collected gas.

*The bubbles are not contained in a (moderately) rigid container. This means the reaction can spread faster - producing a more concentrated (louder) sound wave.
In General
You will see I have had to invent a description of your procedure because you only described it in very vague terms. You did not describe in detail the apparatus you used or the procedure you followed. you did not explain how you measured and verified the volumes of gas involved. 
I have made a number of hypotheses - you should also. Some of these hyptheses will turn out to be false on testing. I would think about how you can test all these hypotheses. I would think about how I can make good records of everything done. I would ask myself what sort of controls I can introduce. I would think about how I could make a more objective measurement of the loudness of the explosions and how to fix the distance of the measuring equipment from the site of explosion.
Hint
"way too louder than when before" and "so unbelievably louder" are not SI units :-)
