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###Stealth - Alerts Alerts are noise and instantly turn people in hearing range uncool. In the context of this game, alerts mean that neither the orientation of the head nor obstacles make any difference and that the person becomes uncool instantly without becoming suspicious first.

###Human observers become alerted by the following:

###Stealth - Alarm There are 4 different ways alarm can be raised:

Stealth - Alerts

Alerts are noise and instantly turn people in hearing range uncool. In the context of this game, alerts mean that neither the orientation of the head nor obstacles make any difference and that the person becomes uncool instantly without becoming suspicious first.

Human observers become alerted by the following:

Stealth - Alarm

There are 4 different ways alarm can be raised:

• Glass breaking (range: 12 m)
• ECM feedback (range: 100 m)
• Gunshots (range: 25 m when enemies shoot, usually 45 m with player weapons)
• Gunshot impacts (range: 1/4 of the gunshot noise)
• Grenade/Flashbang explosions (range: 100 m)
• Trip mine explosions (range: 50 m)
• Taking fall damage (range: 2.5 m)
• Civilian screams upon becoming uncool and at various other times (range: 2 m)
• Footsteps by a sprinting criminal (range: 4.5 m, sometimes 4.5 m * sqrt(2) = 6.4 m)
• Civilian or enemy screams when experiencing moderate or heavy hurt or death (range: 6 m for clients without Shinobi aced, 0.25 m with Shinobi aced, 0 for host without Shinobi aced). Even handcuffed guards scream.

In contrast to the other noise sources, footsteps require line of sight: They do not propagate through solid walls, but they do propagate through glass. Just sprinting for a split-second is enough to alert people. The origin of the noise is your first-person camera.

Unless you shoot in the sky, every gunshot ends with a gunshot impact. The noise origin is the impact location.

If your gun has issued a gunshot alert (i.e. you have fired your gun), subsequent gunshot alerts by the gun will be blocked for 1.5 seconds, unless the origin of the alert differs by more than 5 meters. Whether you fire your CAR-4 once or 15 times to control civilians with Control Freak, they both issue just a single gunshot alert. There is a separate but pretty much identical block for gunshot impact alerts, where the 5 meters rule has a greater effect.

All player weapons have an alert range of 45 meters with the following exceptions: Brenner, KSP and R93 have an alert range of 40 meters. The Thanatos has a range of 35 meters. The saw is a gun like any other and has an alert range of 35 meters when not using up the blade, else 150 meters.

All weapons with an alert range of 45 meters have their alert range reduced to 1 m when silenced (thus their gunshot impacts have a mere 0.25 m range). Weapons with an alert range of 40 meters or less have their alert range reduced to 0 when silenced (i.e. R93 and Thanatos).

• Glass breaking (range: 12 m)
• ECM feedback (range: 100 m)
• Gunshots (range: 25 m when enemies shoot, usually 45 m with player weapons)
• Gunshot impacts (range: 1/4 of the gunshot noise)
• Grenade/Flashbang explosions (range: 100 m)
• Trip mine explosions (range: 50 m)
• Taking fall damage (range: 2.5 m)
• Civilian screams upon becoming uncool and at various other times (range: 2 m)
• Civilian or enemy screams when experiencing moderate or heavy hurt or death (range: 6 m without Shinobi or Hidden Blade aced, else 0.25 m). Even handcuffed guards scream. Non-lethal melee attacks against civilians cause no scream.

Unless you shoot in the sky, every gunshot ends with a gunshot impact. The noise origin is the impact location. Technically, gunshot impact alerts are of the same type as gunshot alerts. As a result, gunshot impacts may cause alarm on day 1 of Big Oil, but they can also be used together with Control Freak to intimidate civilians.

When your gun has issued a gunshot alert (i.e. you have fired your gun), subsequent gunshot alerts by the gun are blocked for 1.5 seconds, unless the origin of the alert differs by more than 5 meters. Whether you fire your CAR-4 once or 15 times within 1.5 seconds to control civilians with Control Freak, they both issue just a single gunshot alert. There is a separate but pretty much identical block for gunshot impact alerts, where the 5 meters rule has a greater effect.

All player weapons have an alert range of 45 meters with the following exceptions: Brenner, KSP. MG42, R93, Thompson, Queen's Wrath, Lion's Roar, minigun, Lebensauger have an alert range of 40 meters. The Thanatos has a range of 35 meters. The saw also causes gunshot and gunshot impact alerts and has an alert range of 35 meters when not using up the blade (2 m if silenced), else 75 meters (8.5 m if silenced). The flamethrower has an alert range of 300 m. The grenade launchers and RPG do not cause gunshot alerts.

All weapons with an alert range of 45 meters have their alert range reduced to 1 m when silenced (thus their gunshot impacts have a mere 0.25 m range). Weapons with an alert range of 40 meters or less (except saw) have their alert range reduced to 0 when silenced.

Uncool civilians cannot hear anything but gunshots (and gunshot impacts) caused by the players. Control Freak basic fully intimidates civilians when hearing a single gunshot alert. When hearing too many gunshots of players without Control Freak basic in quick succession, untied civilians will stand up no matter their intimidation level (only Dominator aced blocks this). This being said, due to the 1.5 seconds cooldown it is virtually impossible for a single player to make a civilian freak out and flee.

Uncool enemies cannot hear anything but gunshots (and gunshot impacts) caused by the players. Technically, they were supposed to listen to explosions and glass breaking caused by the players as well. However, the function used by HE rounds, hand grenades and the grenade launchers explicitly claim that the cause of the noise is the group of civilians and enemies, but not the players. As a result, any alerts caused by that function are ignored by uncool enemies. Breaking glass also does not work correctly and is ignored by enemies. Thus enemies behave like civilians in that regard and will react to gunshots only (and maybe trip mines). Enemies prefer to target players whose alerts have been heard and may also decide to shoot due to alerts.

Excerpts from 'Dispelling Common Misconceptions' Reddit /r/paydaytheheist post by KarateF22:

• Civilians are alerted by bags: They only care about body bags and only at close range. Guards, gangsters, and cameras do care about all bags, however.
• You can stop a camera alarm after detection with ECM or by killing the operator: False. Operators aren't even alerted when the camera is; once a camera fully alerts stealth is guaranteed to fail in 7 seconds.
• Grenades sound the alarm on Big Oil Day 1: Hilariously they do not. Gunshots and the saw still will however, so be wary of that.
• Shinobi Ace is useful: Kinda. It works as claimed for clients in a game. However, there is currently a bug where hosts always silently kill targets, regardless of having the skill or not, which makes this much less useful if you host frequently.