Noise

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

• Note: Severely outdated. Noise now spreads in a square, many branches have been changed, noise meter added

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.

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

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.

Beware that this picture is based on the old noise model where noise propagates less far on diagonals. Now, the area would be approximately square.

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}

The Swamp, the Shoals, and the Desolation of Salt are loud, with ambient noise +6. The Crypt, the Tomb of the Ancients, and the Slime Pits are quiet, with ambient noise -6. All other branches have ambient noise 0.

This effect is significant but not drastic. Shouts will not travel far in loud branches, whereas usually minor noises, such as attacking, may be sufficient to attract monsters in quiet branches.

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:

• Auxiliary attacks
• Noisy randarts: 20 (1 chance in 20)
• Attacking with a weapon of chaos: 15 (1 chance in 200)

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.)

Spell noise

See spell noise.

Player shouts

Different forms have different shouting volumes.

• Shouting in Bat Form, Bat Swarm Form, Fungus Form or Wisp Form has a loudness of 4
• Shouting in Spider Form or Sun Scarab Form has a loudness of 8
• Shouting in Scroll Form or Serpent Form has a loudness of 10
• Shouting in Dragon Form has a loudness of 18
• All player species and all other forms' shouting has a loudness of 12.

Additionally, each level of the Scream mutation adds 2 loudness.

Other sources

• Qazlal worshipper at piety ******: 16
• Scroll of noise: 25
• The Singing Sword: 0-35 depending on tension.
• Blocking an attack with the Shield of the Gong: 40
• Monster shouts
• Monster spells with the Noisy flag
• Creaking doors: 10 (1 in 8 + 4 * Stealth / 3); "As you open/close the door, it creaks loudly!")
• Alarm traps: 40
• Using the Horn of Geryon: 15

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.