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In Prison Break SE1E5 "English, Fitz or Percy", Attorneys Veronica Donovan and Nick Savrinn bring a video tape of a murder, in where the suspect is seen on tape shooting another man with a gun in an underground parking lot, to a video expert to analyse the video for any proof it was doctored.

The expert claims that the visual aspects of the tape are spot on but when he inspects the audio track of the tape at the moment the gun is fired, he notices that the gunshot sound "dies" as soon as the gun is fired. He then tells the attorneys:

The problem with your eyes is that they play tricks on you. But your ears don't lie. Here's the audio track from the tape, sound pretty true right? But noise is a lie. See it just doesn't die like that. Stripped down those levels should be dancing. A room that size would give you a blam, blam, blam, blam. You know? Like one off each wall, split second after each other. On yours, the reverbs bouncing at the same time. The sound of the gunshot wasn't recorded in that room."

Is there any truth behind what he says? That if the a gun was fired in a large room that the sound wouldn't just "die" instantly but remain for a while.

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Short answer is YES.

There is a whole science of Reverberation which has to be taken care of while designing certain buildings such as theater, cinema halls and auditoriums.

In layman's term,

Larger the room, echo will be persistent for some duration. And smaller the room, sound will be absorbed by objects present or by walls and dies faster.

As the video shows that Lincoln Burrows shot a man sitting in a car in parking lot, the sound should had bounced over the concrete walls multiple times and echo should had been recorded by the camera.

But as the sound and video were morphed in a smaller room by secret service the sound effect is not similar to that of parking lot.

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Rahul already gave the answer, an underground car park will have significant reverb decay time, but I'm adding this so you can try a fun experiment…

Every time you walk into a room or especially a large space, do the clap test.
Try not to make people jump though;)

One clap, loud as you can - listen to the sound you get back.

Even just around the house you'll get different decay times. A carpeted living room or bedroom will be very short, bathroom, kitchen and stairwell will be longer.
A classroom, church, warehouse, underground car park will be noticeably longer.
You can even try it outdoors - ever wondered why sometimes you hear a dog bark then you hear its distinct echo? Same principle, just with fewer reflective surfaces - individual walls and buildings, each adding one discrete reflection.

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