How can I put an audible notification on a yard gate?
This feels like an XY problem - you imagine a squeak would work, so you ask about how to make a squeak.   Instead, ask &quot;how to alert a blind person when someone opens the gate&quot;
I'd go with an Infrared interrupter beam right behind the gate, like a shop.  Have it wired to a chime inside, and do lube the gate properly to help it last longer.
If you want to be fancy, a wireless or portable chime unit could be ideal, at the cost of needing a charge or new batteries periodically.