AudioEffectBandLimitFilter in Godot – Complete Guide

Audio effects are a crucial aspect of game development, adding an immersive layer to the player’s experience. Sounds can set the mood, signal changes in game states, and even provide essential feedback to the player. One powerful tool for crafting sound in your game projects is the AudioEffectBandLimitFilter in Godot 4. This versatile feature can shape your game’s audio landscape in significant ways.

What is an AudioEffectBandLimitFilter?

What is an AudioEffectBandLimitFilter?

The AudioEffectBandLimitFilter is a specialized audio effect class in Godot 4 that functions within the game’s audio bus system. It serves as a filter that limits the range of frequencies processed, focusing on a specific band around a set cutoff point. This filter allows for precise control over which sounds are emphasized or subdued within your game, giving you the ability to sculpt your audio to match any situation or environment.

What is it for?

This filter is designed to target and adjust frequencies within a specified band while letting those outside of it pass through unaffected. It’s a fundamental tool for creating more refined audio experiences, especially when dealing with complex soundscapes. The AudioEffectBandLimitFilter could be used to focus on the important sounds of a scene, like character dialogue amidst the background noise of a bustling city, or to minimize audio clutter by filtering out unwanted frequencies.

Why Should I Learn It?

Understanding and utilizing the AudioEffectBandLimitFilter can elevate your game’s audio from good to great. It’s not just a tool for audiophiles; it enhances the overall player experience. By controlling which sounds remain prominent and which are minimized, you can direct players’ attention, improve sound clarity, and create more dynamic and engaging environments. Learning to apply this tool effectively can set your games apart and provide a professional edge to your audio design skills.

CTA Small Image
FREE COURSES AT ZENVA
LEARN GAME DEVELOPMENT, PYTHON AND MORE
ACCESS FOR FREE
AVAILABLE FOR A LIMITED TIME ONLY

Setting Up the AudioEffectBandLimitFilter in Godot 4

Let’s start by setting up our AudioEffectBandLimitFilter in Godot 4. First, we need to create an Audio Bus for our game that will house this effect.

var filter_bus = AudioServer.get_bus_index("Master")
AudioServer.add_bus_effect(filter_bus, AudioEffectBandLimitFilter.new())

This code snippet assigns our filter to the master bus. However, you can assign the filter to any bus you have previously defined.

Configuring the Band-Limiting Parameters

Once you’ve set up your AudioEffectBandLimitFilter, configure it to target the frequencies you’re interested in manipulating.

var band_limit_effect = AudioEffectBandLimitFilter.new()
band_limit_effect.cutoff_hz = 1000 # The cutoff frequency in Hertz
band_limit_effect.resonance_db = 3 # The resonance of the filter in decibels
AudioServer.add_bus_effect(filter_bus, band_limit_effect)

This example demonstrates how to instantiate a new AudioEffectBandLimitFilter and set the cutoff frequency and resonance. A cutoff frequency of 1000 Hz selects the middle range of sounds, while a resonance of 3 dB adds a slight emphasis to frequencies at the cutoff point.

Applying the Band-Limiting Filter to Specific Audio Streams

You may want to apply the band-limiter to specific audio instead of the entire bus. To do this, modify an AudioStreamPlayer’s bus setting:

var my_audio_stream_player = $AudioStreamPlayer
my_audio_stream_player.bus = "YourBusName" # Replace with the name of your bus
# Make sure the bus has the AudioEffectBandLimitFilter applied as shown earlier

This code directs the output of a particular AudioStreamPlayer node through your custom audio bus, where it will be affected by the band-limiting filter.

Automating Filter Adjustments

Adaptation to gameplay is key for immersive experiences. Use scripting to change filter settings dynamically based on in-game events.

func _on_Player_Health_Low():
    # Imagine this function gets called when player health is low
    var filter_effect = AudioServer.get_bus_effect(filter_bus, 0) as AudioEffectBandLimitFilter
    filter_effect.cutoff_hz = 600 # Lowering cutoff for a more muffled sound
    filter_effect.resonance_db = 6 # Increasing resonance for more pronounced effect

This function adjusts the band-limiting filter to create a more urgent, muffled audio response when the player’s health is low, highlighting the change in the player’s condition through audio.Let’s dive further into crafting our audio experience with some practical examples and scenarios where you’d want to use the AudioEffectBandLimitFilter.

Enhancing Environmental Ambiance

Consider a scene within a dense forest in your game. You want to highlight the sound of a flowing stream while subtly reducing the forest’s ambient noise to create a serene atmosphere.

var env_bus_index = AudioServer.get_bus_index("Environment")
var stream_filter = AudioEffectBandLimitFilter.new()
stream_filter.cutoff_hz = 1500 # Higher cutoff to accentuate the stream's ripple
stream_filter.resonance_db = 4 # Slight resonance boost to make the stream stand out
AudioServer.add_bus_effect(env_bus_index, stream_filter)

Creating a Radio Effect

If you want a character’s voice to sound as if it’s coming through an old radio, you can tweak the filter to narrow the frequency range, mimicking the radio speaker’s limitations.

var radio_effect = AudioEffectBandLimitFilter.new()
radio_effect.cutoff_hz = 800
radio_effect.resonance_db = -24 # Reducing resonance simulates the tinny radio effect
AudioServer.add_bus_effect(voice_bus_index, radio_effect)

Filter Sweep for Dramatic Transitions

Next, let’s automate a filter sweep, which can be used for dramatic effect, perhaps during a transition from one game level to another.

var filter_sweep_time = 5.0
var sweep_timer = Timer.new()
sweep_timer.wait_time = filter_sweep_time
sweep_timer.autostart = true
sweep_timer.connect("timeout", self, "_on_sweep_timeout")

func _on_sweep_timeout():
    var start_frequency = 200
    var end_frequency = 10000
    var transition_effect = AudioServer.get_bus_effect(transition_bus_index, 0) as AudioEffectBandLimitFilter
    
    # As the timer runs, smoothly interpolate from the start to the end frequency
    transition_effect.cutoff_hz = lerp(start_frequency, end_frequency, sweep_timer.time_left / filter_sweep_time)

Here, we’re using a timer to execute the sweeping effect over a span of five seconds, transitioning all the sounds on a bus from a low cutoff frequency to a high one, simulating an audio ‘zoom’ effect.

To get a reverse sweep, simply swap the start and end frequencies and adjust the lerp function accordingly.

Dynamic Response to In-Game Actions

Lastly, let’s dynamically adjust filter settings in response to in-game events. For instance, when entering combat, you might want to increase the intensity of the soundscape.

func _on_combat_entered():
    var combat_bus_index = AudioServer.get_bus_index("Combat")
    var intense_combat_filter = AudioServer.get_bus_effect(combat_bus_index, 0) as AudioEffectBandLimitFilter
    
    intense_combat_filter.cutoff_hz = 5000 # Raising frequency for higher intensity
    intense_combat_filter.resonance_db = 12 # More resonance to create a sharp, focused sound

This sudden change in the audio filtering will make the combat experience more visceral and focused, by ensuring the more intense frequencies are at the forefront, while the ambient sounds are pushed to the background.

By utilizing these examples and integrating the AudioEffectBandLimitFilter into your game, you’re taking significant steps in enhancing your audio design and overall player immersion. And remember, experimentation is key – don’t be afraid to play around with the settings to find the perfect audio landscape for your game!When working with audio in your game, there’s a myriad of ways to leverage the AudioEffectBandLimitFilter for different scenarios. Let’s explore more examples, demonstrating the power of this tool in action.

Simulating Underwater Effects

One common use case is creating an underwater audio effect. When the player dives into water, you might want to simulate how sound travels differently underwater by adjusting the audio filter.

func simulate_underwater():
    var underwater_filter = AudioEffectBandLimitFilter.new()
    underwater_filter.cutoff_hz = 400 # Low cutoff to simulate water density
    underwater_filter.resonance_db = 1 # Minimal resonance to keep it sounding 'drowned out'
    AudioServer.add_bus_effect(AudioServer.get_bus_index("Underwater"), underwater_filter)

As soon as the player enters the water, call `simulate_underwater()` to instantly transition the audio perception, creating immersion.

Intensifying Boss Fight Tension

For invigorating boss fight sequences, tweaking the audio to become more aggressive can enhance the tension and focus on the fight itself.

func boss_fight_audio():
    var boss_fight_bus_index = AudioServer.get_bus_index("BossFight")
    var boss_fight_filter = AudioServer.get_bus_effect(boss_fight_bus_index, 0) as AudioEffectBandLimitFilter
    boss_fight_filter.cutoff_hz = 7500 # Emphasize high-tension frequencies
    boss_fight_filter.resonance_db = 8 # Strong resonance for dramatic effect

Invoke `boss_fight_audio()` when the boss fight initiates to change the audio landscape, making the battle feel more immediate and intense.

Creating a Safe Zone Calmness

Conversely, in areas where you want to evoke calmness, like a safe zone or healing area, the filter can help in smoothing out the game’s soundtrack.

func rest_area_audio():
    var rest_area_bus_index = AudioServer.get_bus_index("RestArea")
    var rest_area_filter = AudioEffectBandLimitFilter.new()
    rest_area_filter.cutoff_hz = 1200 # A smoother range for tranquility
    rest_area_filter.resonance_db = -12 # Subtle resonance for a mellow feel
    AudioServer.add_bus_effect(rest_area_bus_index, rest_area_filter)

In the safe zone, players will experience a mellow soundscape, giving them a much-needed auditory break from the game’s action.

Dynamic Audio Transitions Between Environments

Switching audio settings as players move between environments can make the game world feel more alive. Consider a scenario where a player moves from a forest to a cave:

func transition_forest_to_cave():
    var cave_bus_index = AudioServer.get_bus_index("Cave")
    var cave_filter = AudioEffectBandLimitFilter.new()
    cave_filter.cutoff_hz = 600 # Damping higher frequencies to mimic sound in a cave
    cave_filter.resonance_db = 2 # Just enough resonance to emphasize echoes
    AudioServer.add_bus_effect(cave_bus_index, cave_filter)

Call `transition_forest_to_cave()` to smoothly transition your audio from the forest’s wide frequencies to the cave’s muffled echoes.

Affecting Player Perception with Audio Filters

Imagine manipulating audio to influence player’s perceptions or to indicate status effects such as confusion or disorientation:

func confuse_player_audio():
    var master_bus_index = AudioServer.get_bus_index("Master")
    var confusion_filter = AudioEffectBandLimitFilter.new()
    confusion_filter.cutoff_hz = 2000 # Narrower frequency range
    confusion_filter.resonance_db = 5 # To unsettle the player with unusual acoustics
    AudioServer.add_bus_effect(master_bus_index, confusion_filter)

These examples provide just a glimpse into the vast creative potential that the AudioEffectBandLimitFilter holds. Try out these examples and see how they transform your game’s audio landscape. With every new line of code, with every tweak of a frequency, you are crafting an aural experience that can define the mood, enhance storytelling, and captivate your players. Let your imagination guide you, and remember, in the rich world of audio design, the only limit is the range of frequencies you choose to explore!

Continue Your Game Development Journey

You’ve taken a step into the vast world of audio design with the AudioEffectBandLimitFilter in Godot 4. The journey doesn’t end here; this is just the beginning of crafting unique audio experiences for your games. To keep growing your skills and dive deeper into game development with Godot 4, we invite you to explore our Zenva Academy’s Godot Game Development Mini-Degree. You’ll gain access to a comprehensive curriculum that covers everything from fundamental principles to more advanced concepts.

Whether you’re just getting started or building upon existing knowledge, the mini-degree is designed to empower you to build your own games at your own pace. With a vast array of Godot courses available, you can tailor your learning experience to your interests and career aspirations. Embrace the challenge, unlock new possibilities, and transform your gaming ideas into reality with Zenva.

Conclusion

As you’ve seen, mastering the art of audio with Godot 4’s AudioEffectBandLimitFilter can have a profound impact on the player experience. By carefully shaping the soundscapes of your games, you breathe life into the worlds you create. The examples provided here are just the starting point – your creativity and the tools available in Godot 4 define the limits.

Don’t let the journey stop with audio. At Zenva Academy, our Godot Game Development Mini-Degree is ready to take you further, offering you the keys to unlock a treasure trove of game development knowledge. Continue crafting incredible experiences and grow as a developer with us – your next game-changing course awaits!

FREE COURSES
Python Blog Image

FINAL DAYS: Unlock coding courses in Unity, Godot, Unreal, Python and more.