Can Sounds Affect Animals While They Sleep?

Though the body repairs itself during sleep, it does not stop the ears from retaining full functionality.

Most animals, like humans, slip into unconsciousness when they sleep. However, unconsciousness doesn't prevent them from registering sounds. Though all animals have different thresholds through which vibrations must pass before sound is interpreted, ears continue to register vibrations through sleep.

Low-Threshhold Sleepers

Cats' ears are sensitive so they can respond quickly to prey.

Most animals do not sleep deeply for eight solid hours as people do. Instead, some animals, such as cats and dogs, are able to sleep lightly for long periods of time, hence the term "catnap." Furthermore, they are easily woken by sounds, as they have retained their ancestors' ability to be alert at a moment's notice.

Birds

Birds are able to hear sound, though they will not wake unless it is threatening.

According to the October 27, 2000, edition of Science Magazine, researchers discovered that songbirds, when exposed to a recording of their own singing during undisturbed sleep, they more or less sang along with the recording in their heads, as the neurons that fire in their brains at that time are identical to the patterns of neurons when they actually sing.

Invertebrates

Though dragonflies may not be able to hear, the receptors on their bodies are able to sense vibrations that we interpret as sound.

Many scientists argue over whether invertebrates sleep, but it is clear that most at least slip into a lowered state of consciousness. In this state, invertebrates with hearing abilities, such as cicadas, can quickly be brought out of lowered consciousness in the presence of sound.

References

• Science Magazine: Song Replay During Sleep
• Britannica Online: Organs of Sound Reception in Invertebrates