Mr. Brown is an expert at imitating all sorts of noises. There isn't a sound Mr. Brown can't do, from a hippo's gumchewing to a goldfish's kiss. The noisemakers are graphically illustrated and the "sound effects" are printed in big lettering.
A city of Whos on a speck of dust are threatened with destruction until the smallest Who of all helps convince Horton's friends that Whos really exist.