As far as I can tell, it is a hollywood invention. Unless the British government has some secret technology up their sleeves.
"Gunshots are loud because superheated gases expand rapidly and produce shockwaves as they escape the gun's chamber. Silencers contain a series of expansion chambers that cool and dissipate the gases before they leave the barrel.
A silencer is a lot like the muffler on your car (in fact, both were invented by the same guy). Screwing a silencer onto the barrel of a gun doesn't "silence" the explosive bang, it just muffles the noise. That's why folks in the gun industry call them suppressors instead of silencers.
The decibel level of an un-suppressed 12-gauge shotgun is 160 decibels, louder than standing on the runway when a jet is taking off (150 decibels). The Occupational Safety and Health Administration (OSHA) sets 140 decibels as the threshold of pain, although it takes far less than 140 decibels to inflict long-term hearing damage with repeated exposure.
According to a fact sheet from SilencerCo, a Utah-based silencer manufacturer, a 12-gauge shotgun equipped with a silencer registers 137 decibels and a silenced .22 rifle is muffled to 116 decibels, slightly louder than an ambulance siren. Still loud, just not eardrum-busting loud. "
So my whole life has been a lie? T_T
Those silencers appeared so frequently in movies and games that I figured there were some that could do that.