Here is the answer to your problem and what was my problem. I will tell you how to do it yourself or who to use and what to tell them if you are not able to do it. I remember when the flasher on my car was too loud and I did not like the noise. Now the signals are electronic and you cannot lower the volume or wrap the flasher with cotton and tape.
Here is what you do: tap into the left power wire for your turn signal and run it to a 12 volt DC buzzer and run the other connector on the buzzer to a vehicle ground. Do the same for each side. Any radio installer or remote start installer can do it for you.
If you want to do it order two buzzers from Amazon (Cole Hersee 4099 $17 each). Watch a video on how to change bulb in the turn signal of your car to see how to get at the wire. I prefer rear signals. Watch video on how to use a T wire splicer. You can order a bunch on Ebay. Splice the wire that is the power wire…Not the black one which goes to ground. Run the wire to the buzzer you buy somewhere in the car for you to hear it…not in the trunk because it may make it too quiet. I put a pillow over the buzzer because it was too loud in my back seat. Run the other wire from the other buzzer connection to a bare piece of metal on the car. When you turn on the signal it will buzz loud. Do it on each side so each both buzzer sound when needed.
That is all there is to be able to hear the turn signals. Good luck