system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:While on a phone call, how can you hear sounds like an alarm but the other person on the other line is unable to?
gpt
Newer phones use noise cancelling which is very good at rejecting sounds that don't come from directly in front of the phone's mic (where your mouth is). 

Alarm sounds (I assume based on your premise) are coming from farther away and aren't pointed directly into the mic. Us sound guys call that "off axis".