Dark Souls III categorizes its sound into different types, denoted by a letter. Sound files are found in Game > Sound, and are contained within sound banks (.fsb). The Dark Souls Sound Inserter (DSSI) is the easiest way to view and modify these.

Sound Type Associated Banks Description
Ambient (a) sm Ambient sound, like wind, water drips, and cave sounds.
BGM (m) sm, smain Music.
Body (b) ? ?. Japanese text translates to "Armor Material Dependent" (床材質依存)
CharacterMotion (c) c####, main, smain Sounds made by the character associated with the ID.
Foot Effect (e) main Sounds made by feet when moving.
FrontEnd (f) main FrontEnd sounds. For example, moving in an item menu.
Ghost (g) ? ?
Material (z) main ?
Multi-channel Streaming (y) xm ? Sounds like ambience.
Object (o) m, main, sm Sounds associated with objects.
PolyGeki (p) m, rm Sound in cutscenes, plus some other sounds (?).
SFX (s) m, main, sm, smain General sounds, including spells, status effects, etc.
Voice (v) main, smain, vm Sound used in voice lines.
XMaterial (x) ? Material-dependent sounds. Japanese text translates to "Floor Material Dependent" (床材質依存)
Sound Bank Description
c#### Contains sounds associated with characters.
m## Contains map-bound sounds.
main Contains variety of sounds that can be played in any map. There are 3 total: one for base game, and one for each of the DLCs.
sm Mostly contains ambience and music. A couple of other sound types can occasionally be found here.
smain Contains sounds that play in the startup menu, plus some more (?). There are 2 total: one for base game, and one for DLC1.
rm Contains sound used cutscenes (remo), plus some more (?).
vm Contains sound used in voice lines.
xm Contains multi-channel streaming sounds.

***Note that, with the exception of main sound banks, sound banks are either character or map-bound, meaning they will not play unless the character is loaded in or the player is in the associated map, respectively.