A long read but I hope you enjoy :)!

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My first bike was an ecoped (lasted 3 weeks and 1200 kms and totally fell apart) anyway, it too had a beepy signal so what I did was opened the front dash and placed a small piece of cotton held by tape over the speaker - pedestrians can still hear it but it was wayyyyy less obnoixious lol

my turn signals don't beep but whenever i would turn off my daymak gatto i got a loud 3beep message from the alarm. i opened the bike for the first time to change the batteries and had a go at figuring this out as well.
by process of elimination i was able to find which connection controlled this and now the ONLY thing i hated about my ebike is gone. unless all your wires are sealed around the controller you should be able to do the same

typically there are 2-3 purple/blue/green wires leading to the alarm speaker...one of these is what you're looking for

red's and whites and blacks you want to be more careful with...wires that is.