loudspeaker

n.

An electromechanical transducer which converts an electrical signal into sound.

Also called "speaker" for short.

firecracker

n.

A small explosive charge and a fuse in a heavy paper casing, exploded to make noise, as at celebrations.

Also known as a cracker, noisemaker, or banger.

whisper

v.

Speak softly, using the breath but without vibrating the vocal cords.

(Of leaves, the wind, etc) make soft sounds.

eg.

She was whispering something in her sister's ear so that no one else could hear.