Noise

Version 0.11: 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.

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 or loudness, 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.

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	4
The Elven Halls	0
The Lair	3
The Snake Pit	0
The Swamp	0
The Shoals	3
The Spider's Nest	0
The Slime Pits	-5
The Vaults	0
Hall of Blades	-7
The Crypt	-20
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 and the Crypt 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:

• Auxiliary attacks
• Attacking with a weapon of electrocution in shallow or deep water: 15 (1 chance in 3)
• 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).

After obtaining the base value, an amount is added for some weapon brands:

• weapons of flaming: noise_factor is increased by 400/max(1, damage_done).
• weapons of electrocution: noise_factor is increased by 800/max(1, damage_done).

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	0
Blowgun	0
Sling	1
Bow	5
Longbow	6
Crossbow	7

The noise generated by the missile itself depends on the mass of the item. It is sqrt(10*mass/3)+0.5. It is generated at the last square it reached, even if doesn't hit anything.

Missile	Loudness
Needle	0
Stone	1
Dart	1
Arrow	1
Bolt	1
Large rock	14
Sling bullet	1
Javelin	5
Throwing net	3

Example: A character with a bow shoots an arrow. The destination is an empty cell.

Spell noise

See spell noise.

Player shouts

• 12 in normal conditions.
• 18 in Dragon Form.
• 8 in Spider Form
• 4 in Bat Form
• 14 if you have level 2 of the scream mutation.
• 16 if you have level 3 of the scream mutation.

Other sources

• Scroll of noise: 25
• Noisy artefact weapons: 25 (5% chance each turn, only while wielding the weapon)
• The Singing Sword: 0-35 depending on tension.
• Blocking an attack with the Shield of the Gong: 40
• Monster shouts
• Creaking doors: 10 (1 chance in Dexterity + Traps + Stealth/2; "As you open/close the door, it creaks loudly!")
• Alarm traps: 12 (30 in Zotdef)

History

In 0.13 the Crypt won't be so quiet. Its ambient noise will be raised to -3.