In the Logic menu, find the if true block.
Put it inside your on radio received event, at the end after all of the code you used before.
Also in the Logic menu, find the comparison block 0 = 0.
Put it on the if true block, so that it replaces true.
Edit this new block, so that your statement reads: if signal-strength >= 7.
You can add something into the space inside the if block now. Whatever you add inside, will happen only if the signal strength is 7 or higher (so only if you are close to the treasure).
Explore the Music menu for different sound options!