The phrase "audible gasps" means that people can hear and notice the sound of surprise or shock that comes out of their mouths when something unexpected or amazing happens. Full definition
Unsurprisingly this statement drew audible gasps from the usually composed Barbican audience. (treehugger.com)
Peters: I heard audible gasps in the theater while Shuri was explaining the vibranium delivery system to Agent Ross in the Panther's lair. (theringer.com)
I heard audible gasps at this point, and other moments, during a recent media screening. (washingtonpost.com)