Moo box

When turned upside down, it produces a noise that resembles the mooing of a cow.

The toy can be configured to create other animal sounds such as the meow of a cat, the chirp of a bird, or the bleat of a sheep.

When the box is inverted, the block falls away from the bottom, filling the bellows with air.

When the box is turned right side up, the air is expelled through a vibrating blade (which makes it a free reed instrument) producing the sound.

It uses four boxes at different frequencies, all calibrated to generate a sound pressure level (loudness) of sixty decibels at two metres.