Loud horn to scare squirrels

I've had it!  I've put up all kinds of physical obstacles to prevent 
squirrels from getting to the bird feeder outside my study window, but the

gymnastic squirrels keep outsmarting me and mastering the obstacles.

I'd like to be able to push a button on my study desk when I see a
squirrel 
climbing up to the feeder, and have an ear-splitting horn next to the
feeder 
blast him.

I've googled (actually froogled) horns, but don't know what I'm seeing.  I

would be grately deepful if you could recommend a relatively inexpensive 
setup.

Thanks
Tim Carr