What if my hypothesis is that there is no difference?

That can still be your hypothesis. What you ate doing next is to plan and do an experiment. If your experiment matches with no difference, a theory can be formed. No difference is a possible result.

The speed of  sound:   sound travels  at different speeds depending on what it istraveling through. of the three mediums (gas, liquid, and solid)  sound waves travel the slowest through  gases, faster  through  liquids, and fastest  through  solids.