Cortana Inbuilt Mic

I read that someone can get a response more than 10 feet away but there must be a distance where it becomes inaudible due to reverb and signal to noise ratio the further away you are from the onboard mic

A post from another forum reckoned quote ‘I've bought a mic for about 5$ from a Toy store and when i tried to record i could hear my brother talking 2 rooms away with the door closed’. I cant see how this is possible just using a cheap mic unless he was using a preamp

How far is it possible to speak to cortana, would background noise from other rooms be able to trigger it?

 

*Im not sure if the man using the $5 mic was using it for cortana or just general recording. Im refering to an inbuilt mic on a laptop

If you put the mic gain up to 100% in windows would it be possible for cortana to make sense of words spoken from another room?