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I have a snoring girlfriend. To interrupt her snoring, I make a sound similar to the very brief sound gas makes when opening a soda can or bottle (had a snoring brother, I know this technique works very well):

Here is a recording of the slound: https://instaud.io/3hJH

enter image description here

Sometimes her snoring wakes me up in the middle of the night (eg 3AM), so I make that sound, and she immediately wakes up and asks me from a very clear and aware voice: "why did you just pshiiished me?".

The sound I make is around 150 ms long, so I don't understand how someone who is being awakened and transitioning from sleep into consciousness would have the ability to distinctively recognize it.

Sometimes she'll even complain that I interrupted a nice dream she was in, which leads me to believe her sleep level was quite deep.

Can someone explain how a snoring/dreaming person can be awakened by a very brief sound (~ 150 ms long) and be able to distinctively recognize that sound as she transitions from sleep into consciousness?

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Short answer
The auditory system remains active during sleep.

Background
Filtering of sensory input during sleep is a recognized phenomenon and indeed the senses are typically lulled during sleep. This phenomenon is, at least partly, caused by thalamic gating. Thalamic gating is caused by the thalamus entering a state in which slow-wave activity disrupts or even blocks incoming sensory input (Coulon et al., 2012). However, the auditory system remains active during sleep and during the full sleep/wake cycle auditory stimulation will evoke responses in various parts of the central auditory system beyond the thalamus (Issa & Wang, 2008).

In fact, when supra-threshold stimuli are intense enough, they invariably result in wakefulness. Auditory stimuli result in so-called K-complexes in the cortex, which are believed to be functional and specialized sensory responses during sleep (Velutti, 1997).

Hence, when you ask...

The sound I make is around 150 ms long, so I don't understand how someone who is being awakened and transitioning from sleep into consciousness would have the ability to distinctively recognize it.

...the answer is that the auditory system is active enough to process and recognize the sound. Further, the typical modulation frequency of speech is about 4 Hz (Leong & Goswami, 2014), i.e., the typical syllable length is about 250 ms, meaning that sounds with a duration of 150 ms are long enough to be processed.

References
- Coulon et al., Pflugers Arch (2012); 463(1): 53-71
- Issa 7 Wang, J Neurosci (2008); 28(53): 14467–480
- Leong & Goswami, Front Hum Neurosci (2014)
- Velutti, J Sleep Res (1997); 6: 61–77

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  • $\begingroup$ Yes, maybe I wasn't specific enough in my Q. We know the auditory system remains active during sleep, otherwise we wouldn't wake up to alarm clocks. What I'm interested in is how one can identify so distinctly such a brief sound, which implies that within a few ms, they go from asleep to awake so they can hear that sound. Or is it that a description of the sound is created by the auditory system while asleep (= a "phiiish" sound) and delivered to the subject when it becomes awake, hence why my girlfriend knows what sound I made although she never consciously heard it? Hope I make sense. $\endgroup$ – Max Feb 12 at 18:17
  • $\begingroup$ @Max what I'm trying to say is that you don't have to be awake to hear the sound. $\endgroup$ – AliceD Feb 12 at 20:03
  • $\begingroup$ @AliceD - I think that what Max is saying is that ok, the K-complexes might determine whether the sound represents danger or not (wake up now or don't worry, carry on sleeping) but would they help determine exactly what the noise is and what (or who) created it, based on a sound burst of a few milliseconds? $\endgroup$ – Chris Rogers Feb 12 at 23:08
  • $\begingroup$ @ChrisRogers: thanks for clarifying. Indeed I get you don't have to be awake to hear a sound (once again, waking up to alarm clocks), what I'm surprised by is how precise the recollection of the sound is when we know from XP it can take us a few seconds to be fully conscious when waking up but the sound lasts a few ms, so I am wondering whether the auditory system does a sort of pre-processing of the sound and then delivers the info to us when we're fully conscious, thus allowing us to know exactly which sound there was ("phiiish") enough though we are not (fully) awake when it occurs $\endgroup$ – Max Feb 13 at 6:47
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    $\begingroup$ @Max - prior knowledge seems paramount. Who else can make the noise but you? Further, 200 ms is the typical syllable length, hence long enough to contain information up to the lexical level. Answer edited. $\endgroup$ – AliceD Feb 13 at 7:03

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