There is a growing need for safe methods to insulate sleeping people from intrusive environmental noises so that they can get a decent night's sleep. This invention solves the problem of how to provide a sleeping enclosure with a high degree of insulation against environmental noises while also providing assured ventilation within the enclosure. It features an active ventilation means and a passive ventilation means that are physically linked so that there is always one of them providing ventilation. This linkage combines the superior sound-insulating properties of active ventilation (such as a longer air conduit for reduced intrusion of environmental noises into the enclosure) with the superior safety properties of passive ventilation (such as not being vulnerable to power failure or mechanical failure).