Driving FMOD Parameters from Unity: Teleport Sound Example

Introduction⌗

In this tutorial, you’ll build a reactive teleportation sound system by controlling FMOD parameters from Unity using C#. You’ll learn to:

• Create and automate parameters in FMOD
• Instantiate and attach FMOD events in Unity
• Dynamically set parameter values via C# scripts
• Trigger sound transitions via Unity collision events

FMOD Parameters are made up of a range of values that can be adjusted in real-time inside our game. This allows us to create dynamic audio that responds to gameplay events, such as a player entering a teleporter.

FMOD Setup⌗

Before diving into code, we’ll first build the teleporter event in FMOD. This event demonstrates how to use both built-in and user parameters to control sound behavior dynamically.

Goal⌗

We’re designing an event that:

• Loops a magical hum sound for a teleporter object.
• Uses the built-in Distance parameter to fade out low frequencies as the listener moves away.
• Uses a custom Trigger parameter to fire a secondary teleport sound when the player enters the teleporter.

When done, your FMOD setup will let Unity control when the teleport sound plays—while FMOD automatically handles distance-based EQ changes.

1. Create the Event⌗

1. Open FMOD Studio.
2. In the Assets Browser, find Teleporter Loop Stereo 01 under Audio Bin → Interactables → Teleporters.
3. Create a new event named Teleporter in the SFX/Interactables folder.
4. Drag Teleporter Loop Stereo 01 onto Track 1 at the beginning of the timeline.

2. Loop Region and Asynchronous Playback⌗

1. Create a loop region around the first second of the timeline. This keeps the playhead cycling near the start while the loop plays.
2. Select your sound instrument and:
   • Enable Async playback. This ensures the sound plays to completion even if the playhead remains in the loop region.
   • Enable Loop While Playing.
   • Enable Cut (cut playback when untriggered) — so when the loop region deactivates, playback stops immediately.

3. Add and Automate the Distance Parameter⌗

The Distance parameter is one of FMOD’s built-in parameters. There are six built-in parameters: Distance, Direction, Speed, Orientation, Elevation, and Cone Angle.

Built-in parameters automatically update based on the listener’s position relative to the sound source in 3D space.

See more information here: FMOD Built-In Parameters

To add and automate Distance:

1. Click the “+” icon → choose Add Parameter Sheet → New Parameter.
2. Name it Distance and choose the Built-In type for Distance.
3. On your track, insert a 3-Band EQ effect (right-click near the track fader → Add Effect → EQ → 3 Band EQ).
4. Right-click the Low Gain knob on the EQ and choose Add Automation. Then click Add Curve and select Distance.
   1. You have now connected your Distance parameter to the low-frequency gain control on the EQ.
5. You’ll see a red automation curve appear under the track.
6. Draw the curve so that as Distance increases, the low end fades out.

This simulates real-world behavior—low frequencies carry farther, so as the player gets closer, you regain that low-end presence.

4. Create the Custom Trigger Parameter⌗

Now we’ll add the parameter Unity will control.

1. In the Parameters tab, click “+” → Add New Parameter.
2. Choose Discrete type (whole-number values).
3. Name it Trigger.
   • Discrete values are ideal for toggling between on/off or state-based conditions.
4. Set its range:
   • Min: 0
   • Max: 1
5. In your event:
   • Place the second sound (Teleporter Walk Through 01) under the same track or on a new one.
   • Go to the Loop region and open its Trigger Conditions panel.
   • Set it to play when Trigger = 1.
6. For the looping hum track:
   • Open its Condition Sheet and add a condition to disable playback when Trigger = 1.
   • Add a short fade-out automation for smooth transition.

When Trigger switches from 0 to 1, the looping hum fades, and the teleport sound plays once.

5. Fine-Tune Spatialization⌗

1. On the Master Track, open the Spatializer effect.
2. Adjust Min Distance and Max Distance values so the attenuation curve fits your in-game scale (e.g., smaller values for tight interior scenes, larger for outdoor).
3. Preview using the 3D Preview window in FMOD to confirm how the sound falls off with distance.

6. Save and Build⌗

Finally:

• Save the project.
• Assign your event to the Master Bank.
• Build your banks (File → Build → Build Banks).

You’re now ready to load this event in Unity.

7. Test in FMOD Before Unity⌗

Play your event in FMOD:

• Drag the Distance slider to watch the EQ automation respond.
• Set Trigger = 1 to hear the teleport sound override the loop.

You should observe:

• The low-end fading out naturally as Distance increases.
• The teleport sound firing instantly when Trigger hits 1.
• The loop stopping cleanly when the parameter condition disables it.

This confirms everything is wired properly before moving to C# integration.

Unity Scene Setup⌗

• Find the teleporter in the scene. Its the TransitionStart game object.
• Make sure the teleporter has a Box Collider (or whatever shape), set to Is Trigger.
• Place your player (e.g. “Ellen”) in the scene. This will make our sounds easier to test.
  • Find Ellen and change her transform position to X: -145, Y: 21.3, Z: 43.
  • Alternatively, copy the position of the TransitionStart object then paste it into Ellen’s transform, then adjust the X position by -5 to start just outside the trigger.
• Disable or remove other objects so they won’t interfere during testing by unchecking their active state in the Inspector.

C# Script: F_Teleporter.cs⌗

Create a script under your Scripts/FMDO Scripts folder named F_Teleporter.cs and attach it to your teleporter object (the same object holding the trigger collider). Here’s the full script:

using UnityEngine;

public class F_Teleporter : MonoBehaviour
{
    
    FMOD.Studio.EventInstance tHum;
    void Start()
    {
        tHum = FMODUnity.RuntimeManager.CreateInstance("event:/SFX/Interactable/Teleporter");
        FMODUnity.RuntimeManager.AttachInstanceToGameObject(tHum, gameObject, GetComponent<Rigidbody>());
        tHum.start();
    }

    // Update is called once per frame
    void OnTriggerEnter(Collider other)
    {
        // Could also use other.CompareTag("Player") for more robust checking if the Player game object had the tag "player"
        if (other.name == "Ellen")
        {
            tHum.setParameterByName("Trigger", 1, false);
        }
    }
    
    void OnDestroy()
    {
        tHum.stop(FMOD.Studio.STOP_MODE.IMMEDIATE); 
        tHum.release(); 
    }
}

Key Points⌗

• CreateInstance(path) must match exactly the FMOD event path.
• AttachInstanceToGameObject(...) aligns spatial 3D behavior (so position/distance is tracked).
• setParameterByName("Trigger", 1f, false) changes your Trigger parameter.
  • The false flag means you don’t bypass seek speed — FMOD seeks based on your parameter settings.
• release() frees memory and ensures no audio leaks after object destruction.

Testing & Debugging⌗

1. Hit Play in Unity.
2. Move the listener close to the teleporter — you should hear the ambient loop with full low frequencies.
3. As you back away, low frequencies fade (due to the Distance → EQ automation).
4. Walk into the trigger: the teleport sound plays, and the loop stops or fades.

If things don’t work:

• Confirm the collider is set to Is Trigger.
• Double-check your player object’s name (or change the script to use a tag).
• Ensure the FMOD event path is correct and that the event’s bank is loaded.
• In FMOD Studio, verify your parameter mapping and that Trigger = 1 is correctly wired.