People had asked this many times and that is why they came up with methods and standards that will answer these type of questions. You can look it up in the NIST or the National Institute for Standards and Technology.
Answer:
Many things, but i think a toaster...
Explanation:
P waves are faster S wave are slower P waves can pass through both solids and liquids S waves bounce of solids
The strumming is mechanical energy
the notes heard is sound energy
so use D
