Noise

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Version 0.14: This article may not be up to date for the latest stable release of Crawl.


Noise in the dungeon can wake sleeping monsters. Monsters that hear a sound will generally wander toward it; if you get involved in a fight, monsters can come from all different directions to see what the fuss is about, potentially overwhelming you.

Contents

Noise propagation

When a noisy action happens at a position, the noise will propagate to all the adjacent cells. Each time it advances a cell, the intensity suffers an attenuation. When the intensity reaches a value less than 1, the noise is inaudible and it won't propagate further.

The attenuation depends on the following factors:

  • The cell type:
Cell type Attenuation
Empty -0.85
Statue or Idol -1.70
Tree or Mangrove -2.55
Closed/Secret door -6.80
Wall -10.20
Permanent wall -infinity
  • The direction: In diagonal, the attenuation is 41% higher (sqrt(2)~1.41).

This means that in open areas the radius of the area affected by a noise is: loudness/0.85 = loudness*1.176.

The following picture was generated by compiling the game with the option DEBUG_NOISE_PROPAGATION enabled. It shows which squares are affected by a simple shout. In this case, the intensity was 12 and the ambient noise was 0.

Noise grid example.png

Ambient noise

Ambient noise makes sounds harder to hear. This idea is implemented in the game by adding, or subtracting, a branch-specific amount to loudness. The effective loudness is:

effective_loudness = loudness - sgn(ambient_noise)×{3d(abs(ambient_noise))/3 - 1}
Branch Ambient noise
The Dungeon 0
The Temple 0
The Orcish Mines 0
The Elven Halls 0
The Lair 0
The Snake Pit 0
The Swamp 0
The Shoals 3
The Spider's Nest 0
The Slime Pits -5
The Depths 0
The Vaults 0
Hall of Blades -7
The Crypt -3
The Tomb -10
The Hells 0
The Realm of Zot 0
Pandemonium 0
Portals 0

In most branches, this effect is minimal. Certain branches, however (the Tomb in particular), greatly amplify even the slightest noise. While characters in heavy armor probably won't care, stealthy characters that are used to sneaking around will find that even the noise generated by their attacks attracts attention.

Sources of noise

Melee combat

A successful stabbing is always silent, otherwise the loudness is:

 noise_factor * damage_done / 400

This value is capped at 12. Noise is generated even if you miss your attack (in that case loudness is 1).

Other sources of noise in melee combat:

Calculation of noise_factor

The base value of noise_factor depends on the damage type of your weapon: 150 for unarmed combat; 125 for slashing or crushing; 100 for slicing or chopping; 75 for piercing or stabbing. If your weapon has multiple damage types, the game will chose one of them randomly (you can look up the damage types of any weapon here).

Auxiliary attacks

If you get an auxiliary attack, that attack also makes noise and its noise factor is:

Auxiliary Attack noise_factor
Constriction 10
Kick 100
Headbutt 100
Beak 75
Tail Slap, Stinger 125
Punch, Claws 100 (75 if Blade Hands is active; 125 if you have tentacles)
Bite 75
Pseudopods 125
Tentacles 100

Ranged combat

There are two sources of noise when you shoot a projectile: the launcher and the missile.

The noise generated by the launcher is always made at your position even if you miss the shot.

Launcher Loudness
None (i.e. Throwing) 0
Blowgun 0
Hunting sling 1
Greatsling 3
Shortbow 5
Longbow 6
Hand crossbow 2
Arbalest 7
Triple crossbow 9

The noise generated by the missile itself depends on the base damage of the item. It is damage/3, rounded down. It is generated at the last square it reached, even if doesn't hit anything.

Missile Loudness
Tomahawk 2
Javelin 3
Large rock 7
Throwing net 0
Needle 0
Stone 1
Sling bullet 2
Arrow 2
Bolt 3

Example: A character with a bow shoots an arrow. The destination is an empty cell. (Note that this image is out of date. The arrow would make 1 more noise in recent versions.)

Noise-grid-ranged-combat.png

Spell noise

See spell noise.

Player shouts

Other sources

History

Prior to 0.19, the Lair's ambient noise was 4, and the Orcish Mines's was 3

Prior to 0.13, the Crypt's ambient noise was -20.