Sound transmission into incubators in the neonatal intensive care unit.
To measure the attenuation of sound by modern incubators. LEQ, LMAX, LPEAK, and frequency distribution were measured simultaneously inside and outside two recent model incubators. The attenuation of sound (outside minus inside) was 15 to 18 dBA with the motor off and 4 to 8 dBA with the motor on. There was a significant difference between incubators in their attenuation of sound. Octave band analysis showed attenuation in frequency bands of > 31.5 Hz with the motor off. With the motor on, the sound level inside the incubator was higher than outside at frequency bands of < 250 Hz. Caring for infants inside modern incubators reduces "averaged" sound exposure to levels near those recommended for the neonatal intensive care unit. Lower frequency sounds are louder inside the incubator and arise from the incubator motor.