Can permanent sensorineural hearing loss be caused by sleeping with an ear against a train window?

A patient presented to the authors with unilateral sensorineural hearing loss after falling asleep with his ear tightly pressed against a window of a moving train. This study set out to determine whether a train could generate sound levels of sufficient intensity to cause such a hearing loss. A sound level meter was used to measure the sound levels produced at the window of a moving train. Further measurements were made with a rubber attachment on the microphone, that simulated the effect of the ear stuck to the window. The sound levels were found to be amplified by the attachment but not to levels that could cause a hearing loss over a short period. In a second experiment eight healthy volunteers all perceived an increase in sound levels when their ears were pressed against a train window. It seems unlikely that sleeping with an ear against a train window can cause hearing loss, but it cannot be ruled out.