Whismur

“Normally, WHISMUR’s voice is very quiet - it is barely audible even if one is paying close attention. However, if this POKéMON senses danger, it starts crying at an earsplitting volume.”

— Pokémon Ruby

“WHISMUR is very timid. If it starts to cry loudly, it becomes startled by its own crying and cries even harder. When it finally stops crying, the POKéMON goes to sleep, all tired out.”

— Pokémon Sapphire

“Its cries equal a jet plane in volume. It inhales through its ear canals. Because of this system, it can cry continually without having to catch its breath.”

— Pokémon Emerald