To jangle is to make a metallic sound like a bell, a bunch of keys, or spurs on cowboy boots. Little kids waiting for Santa Claus might wake up abruptly, thinking they've heard his sleigh bells jangle on the roof.
A jangle is similar to a jingle, a ringing, bell-like noise, but it's typically a bit harsher or more discordant. You might contrast the delicate jingle of silver bracelets with the jangle of an enormous ring of keys. The word can also be used figuratively: something that makes you feel uneasy or upset jangles your nerves. An earlier definition of jangle was "talk excessively, chatter" or "slanderous conversation, gossip." The "harsh sound" meaning first arose in the 15th century.