Usually in comedy and animation, a large grin is sometimes accompanied by a sound like a squeak, bling, or an upwards sliding note. It's usually used to accent the happiness behind the expression or, in the case of a twinkle or bling sound, to exaggerate the sparkly whiteness of the teeth. Contrariwise, there are also Audible Frowns that sound much more unhappy.
Many cartoons use this, and is used occasionally in live-action for smiles that are especially sparkly or silly. Some people in real life make a funny squealing sound when they make an extremely joyful smile.