There have been valid research showing the effect of pink noise on calming and improving the sleep quality of children. 

 

Heartbeat sound is a natural source of pink noise, which is featured by a mix of high and low frequencies (i.e. PQRST waveform).

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Beatnik MRI Noise Canceling Muffler is equipped with a pair of in-ear earbuds that transmit continuous pink noise to the user, achieving the effect of psychological comforting.

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