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Created December 9, 2019 21:56
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Pooling sound effects in Tetra

Here's a quick example of how you can pool instances of a sound effect in Tetra! There's a few advantages to doing this:

  • You cap the number of identical sounds that can play at once, which avoids you accidentally calling play in a loop and blowing out your speakers (not speaking from experience, honest 😅).
  • It gives you a central place to apply variations to the sound - e.g. you could make it so the pitch gets set to a slightly randomized value each time.
  • It's probably slightly more performant than spawning new SoundInstances every time (as always, avoid premature optimization).
use tetra::audio::{self, Sound, SoundInstance};
use tetra::input::{self, Key};
use tetra::{Context, ContextBuilder, State};
struct SoundPool {
// This isn't used, but you could hold onto it in case you want
// to resize your pool later?
sound: Sound,
instances: Vec<SoundInstance>,
next: usize,
impl SoundPool {
fn new(ctx: &Context, sound: Sound, instance_count: usize) -> tetra::Result<SoundPool> {
let mut instances = Vec::with_capacity(instance_count);
for _ in 0..instance_count {
Ok(SoundPool {
next: 0,
fn play(&mut self) {
let instance = &self.instances[];
// If we've looped back to an instance before it stops playing,
// rewind it and play again.
instance.stop();; = ( + 1) % self.instances.len();
struct GameState {
pool: SoundPool,
impl GameState {
fn new(ctx: &mut Context) -> tetra::Result<GameState> {
audio::set_master_volume(ctx, 0.4);
let sound = Sound::new("./examples/resources/powerup.wav")?;
let pool = SoundPool::new(ctx, sound, 3)?;
Ok(GameState { pool })
impl State for GameState {
fn update(&mut self, ctx: &mut Context) -> tetra::Result {
if input::is_key_pressed(ctx, Key::Space) {;
fn main() -> tetra::Result {
ContextBuilder::new("Pooling Sounds", 640, 480)
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