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Toy that produces the sound of a mooing cow From Wikipedia, the free encyclopedia
The moo box or moo can is a toy or a souvenir, also used as a hearing test. 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 meowing of a cat, the sound of a bird, or the bleat of a sheep.
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The moo box consists of a block and a bellows. The bellows is sealed to the bottom of the box and to the block. The block is heavy and perforated, and used to actuate the bellows, producing the sound.
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. After passing the blade, the air passes through a duct of variable length, which determines the pitch of the sound.
The toy can be used to perform the Moatti test to test infants' hearing at different frequencies, conceived by doctor Lucien Moatti. It uses four boxes at different frequencies, all calibrated to generate a sound pressure level (loudness) of sixty decibels at two metres. The test can be used to screen the hearing of children aged from six to 24 months.
The tester knocks down the boxes out of sight of the child. If the child hears the sound, they will turn their head towards it.
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