Importing and Playing Sound Effects

Introduction to Sound Design in 2D Video Games

Audio accounts for more than half of a video game's perceptual impact. A jump animation or a hit against an enemy may feature flawless pixel art, but without synchronized auditory feedback, the action feels disconnected and lacks weight. In game development, this tactile and sensory responsiveness is commonly referred to as 'game feel' or 'juice.' Sound effects (abbreviated as SFX) provide crucial feedback, confirming to players that their inputs have been received and processed by the system.

Up to this point, our retro platformer project already includes movement mechanics, collisions, basic patrol enemies, coin collection, and a complete graphical user interface. However, all these interactions unfold in complete silence. In this lesson, we will begin assembling the game's audio layer by learning how to import sound files, understanding how GameMaker manages audio assets in memory, and using the built-in audio_play_sound function to bring jumps, hits, and pickups to life.

Audio Formats and the Sound Asset in GameMaker

In GameMaker, any audio file you include in your project is managed within the Asset Browser as a Sound asset. Before importing audio, it is essential to understand which file formats are best suited for snappy sound effects versus continuous background music tracks.

The two standard formats widely used in GameMaker development are WAV (.wav) and OGG Vorbis (.ogg). WAV files contain uncompressed or minimally compressed PCM audio, preserving pristine fidelity without requiring CPU cycles for real-time decompression. This makes them ideal for short, immediate sound effects (typically under 1 to 2 seconds), such as a coin chime, a jump bounce, or a quick explosion. In contrast, OGG files employ efficient lossy compression, drastically reducing disk space and download size, making them the industry standard for long music tracks and continuous ambient loops.

When you create a new Sound asset in the Asset Browser (right-click a folder and select Create -> Sound), the Sound Editor opens. Here you can name the asset following a consistent naming convention (such as the snd_ prefix), import the audio file from your drive, and configure its compression type and playback attributes.

💡 Memory Tip: Selecting 'Uncompress on load' decompresses the entire audio file directly into system RAM when the room initializes. For short sound effects (such as jumps or gunshots), this guarantees zero playback latency and prevents frame drops during gameplay.

The Core Function: audio_play_sound

In modern versions of GameMaker, the primary function used to trigger sounds in game space is audio_play_sound. Its base syntax accepts several arguments specifying the asset to play, its priority, and whether it should loop:

// Classic function signature:
audio_play_sound(soundid, priority, loop);

Let's break down each parameter in this function call:

1. soundid: The identifier of the Sound asset as defined in the Asset Browser, such as snd_salto or snd_moneda. 2. priority: A numerical value (integer or float, commonly ranging from 0 to 100) indicating the relative importance of this sound compared to others. Operating systems and audio middleware have a hardware limit on simultaneous audio channels (hardware voices). If the game attempts to trigger more sounds than available channels allow, GameMaker halts the lowest-priority sounds in favor of higher-priority ones. Crucial gameplay cues, such as UI clicks or player damage, should have higher priority (e.g., 10) than background environmental details (e.g., 1). 3. loop: A boolean value (true or false). Passing true causes the sound to repeat indefinitely until explicitly stopped through code. For one-shot sound effects such as jumps or impacts, this argument must always be false.

In modern GameMaker runtimes, audio_play_sound also supports optional extended parameters, including gain (volume), time offset, and pitch modulation:

// Extended signature available in modern GameMaker:
audio_play_sound(index, priority, loop, [gain], [offset], [pitch], [listener_mask]);

This overloaded call allows you to adjust volume and playback speed/pitch directly on the same line of code—an invaluable technique for preventing repetitive sounds from causing ear fatigue.

Practical Implementation 1: Jump Sound in obj_jugador

In previous modules, we established the player's vertical movement logic, governed by variables like vspd (vertical speed), grav (gravity), and jump_spd (jump impulse). Now we will hook our snd_salto sound asset to trigger at the exact instant the player lifts off the ground.

Next, open obj_jugador and navigate to its Step event, specifically where the code checks if the player pressed the jump key while grounded:

// Object: obj_jugador
// Event: Step

// Input polling (defined in earlier modules)
var _key_jump = keyboard_check_pressed(vk_space) || keyboard_check_pressed(ord("W"));

// Jump logic when grounded
if (en_suelo && _key_jump)
{
    vspd = -jump_spd;
    en_suelo = false;
    
    // Play jump sound effect
    // Priority 8 (high tactile importance), non-looping (false)
    audio_play_sound(snd_salto, 8, false);
}

Notice that audio_play_sound is placed inside the keyboard_check_pressed check. If we had used keyboard_check (which returns true every frame the key is held), the engine would attempt to restart the sound 60 times per second, causing a harsh stuttering artifact known as audio machine-gunning.