Sound Banks

A sound bank is a named sound. Content never references an audio file directly — it references a bank id, and the bank decides what actually plays.

Banks live in World/sound-banks.xml and are edited in Hydra's Sound Bank editor. They are id‑keyed and merged across active modules like every other resource, so a module can add banks or replace existing ones. See Modules.

The simplest bank

<sound-bank id="ShieldsUp" category="system" instances="2">
  <description>Shields raised</description>
  <alias>sounds/shields-up.mp3</alias>
  <layer source="sounds/shields-up.mp3" volume="1" />
</sound-bank>

That is what a component means when it says activated="ShieldsUp".

Referencing a bank

Banks are referenced by id from component sound slots, model audio cues, effect banks and mission actions, and an FTL drive's Spool-Sound names one too. category groups them in the editor; it does not route the mix. instances caps how many copies can sound at once: left out, it is 2, and 0 means no cap. When the cap is reached, the oldest copy fades out to make room. A bank's own volume scales every layer in it.

instances is a real design decision, not a technical limit. An ambient hum wants 1 — a second copy is just louder. An explosion wants around 10, because in a real fight several land together and a cap of 1 makes a battle sound thin. Laser fire sits in between. Getting these wrong is the most common reason a mix sounds wrong when every individual sound is fine.

Aliases, and why they exist

A bank can declare aliases, and an alias can be a bare file path:

<sound-bank id="LaserFire" category="weapon" instances="6">
  <alias>sounds/laser-fire.mp3</alias>
  <alias>laser-fire</alias>
  <layer source="sounds/laser-fire.mp3" volume="1" variance="300" />
</sound-bank>

This is the compatibility mechanism. Older content that named a raw file path still resolves — it lands on the bank instead, and inherits everything the bank has since gained. So you can improve a sound for all existing content by improving its bank, without touching any of the content that plays it.

When you replace a base game bank in your own module, carry its aliases across or the older references stop resolving.

Layers

A bank can stack several samples, each with its own settings. This is how you build a sound that is more than one recording — a weapon with a transient and a body, an engine with a rumble and a whine.

instances, detune and variance must be whole numbers, and loop must be exactly true or false. A value the loader cannot read drops the bank or the layer it sits on, and that shows only in the server log.

variance is the cheapest quality win available. A repeated sample played identically reads as a machine gun of one recording; a few hundred cents of random pitch spread makes ten explosions sound like ten explosions. The base game's laser and explosion banks use 300. Weapon fire adds a small random spread of its own on top.

Every voice opens from silence over a few milliseconds, and a stopped one fades rather than cutting, so a bank no longer needs attack and release just to avoid clicks. Use them to shape a loop: a slow swell, a long tail.

Variants: one bank, several recordings

A bank can instead name other banks as variants, and playback picks one at random:

<sound-bank id="HullImpact" category="weapon">
  <variant id="HullImpactA" />
  <variant id="HullImpactB" />
  <variant id="HullImpactC" />
</sound-bank>

Content references HullImpact and gets one of the three. This is the better answer than pitch variance when you have genuinely different recordings, and the two combine.

The member is picked first and then played as itself, so its own instances is the cap that applies; set it on each member, not on the container. Variants are one level deep: a member that is itself a container does not play. A bank with both variants and layers plays its variants.

Modulation: sound driven by game state

The most powerful feature, and the least used. A bank can bind a playback property to a live game parameter:

<sound-bank id="Engine" category="engine" instances="1">
  <layer source="sounds/engine.mp3" volume="1" loop="true" />
  <modulate parameter="throttle" target="pitch"  min="-200" max="400" />
  <modulate parameter="throttle" target="volume" min="0.75" max="1" from="0" to="0.4" />
</sound-bank>

from and to are what let you express a knee without an expression language. "Full gain by 40% throttle" is from="0" to="0.4".

Bindings that share a target combine, and not all the same way:

• pitch sums — cents are additive, so two offsets stack into one interval.
• volume multiplies — gains compose, each scaling what the others left.
• filter takes the minimum — the darkest constraint wins, because cutoffs do not add.

The trap follows from the volume rule. A volume binding that reaches 0 multiplies the layer to silence regardless of every other binding. A contributor meant only to lean on the gain wants a non‑zero minimum — min="0.75", not min="0".

Which parameters exist. Every sound can read speed (0..1 of top speed), throttle (0..1) and altitude (raw). A component's ambient loop on the player's own ship can also read the component's own values: Level, Load, Integrity, ChargeFactor, Enabled (0 or 1), Heat and Output (both raw), and any other number the component reports, such as a rotor's Rpm. A raw parameter needs an explicit from and to. An FTL spool bank reads Spool, which runs from 0 at the jump order to 1 at the jump, and its one‑shot layers are stretched to fit the spool. A binding to a parameter a sound cannot read is skipped, and the layer stays at its authored level.

A bank with any <modulate> placed in a component's ambient slot replaces the built‑in engine and power curves rather than adding to them.

The Sound Bank editor cannot edit from, to or layer, and saving a bank in it resets all three. Author those in the XML, and do not open that bank in the editor afterwards, or put them back after you do.

Module-level settings

The wrapper element carries calibration that belongs to the asset set rather than the engine:

<sound-banks master-volume="1" clip-radius="550">

master-volume trims every layer in the module — the control for a set of masters that were recorded hotter than the base game's. It trims down only: keep it, and every product of layer volume, bank volume and master volume, at or below 1, because on a console's own sounds a gain above 1 is read as a percentage and comes out at a hundredth. clip-radius is the positional audio horizon in world units, beyond which a sound is not heard. It applies to sounds placed on objects in the 3D view; a console's own sounds have no position. The fall‑off is linear and reaches silence well inside the radius, at about half of it for a typical cue. A module working at a different scale needs a different horizon.

Each bank uses its own module's settings. A module that sets neither gets 1 and 550, not its parent's values.

Saving and reloading

A save in the Sound Bank editor takes effect on the server at once. Consoles that are already open fetched their banks when they loaded, so reload them to hear the change. A hand edit to sound-banks.xml needs a module reload from the Game Master console, which cannot run while a mission is playing, or a server restart; a module reload also tells open consoles to fetch the banks again.

When you audition right after a page load, the first sound fades in with the console itself over about a second. Play it twice before you judge it.

Practical advice

• Set instances from how often the sound really overlaps. It is the difference between a battle and a stutter.
• Add variance to anything that repeats. Weapons, impacts, footsteps.
• Give loops an attack and release that suit them. The engine prevents clicks; the ramps are for shaping.
• Keep aliases when you override a base bank, or older content stops finding it.
• Fill in description. It round‑trips through the editor, and it is what makes a bank list navigable a year later.