In this tutorial, I will show you how to play an audio file in Unity and, more importantly, how I resolved an issue related to overlapping audio playback from an Audio Source.
Video Transcript
Hello everyone! In this tutorial, I will show you how to play an audio file in Unity and, more importantly, how I resolved an issue related to overlapping audio playback from an Audio Source. Before we proceed, please note that the solution presented in the video is just the one I adopted for this problem, but there are likely other (and potentially better) solutions out there; so, don't take the information provided here as the definitive approach!
The tutorial was created using Unity 2022. Specifically, I want to play a footsteps audio file (sourced from the first Prince of Persia game, by Jordan Mechner, which was my first PC gaming experience) when the character moves within the scene. This may seem like a straightforward task, but as we will discover, it conceals a minor challenge.
To play the footsteps audio, the first step is to attach an Audio Source object to the character. Within this object, we will define the specific audio file to be played and configure other playback properties.
An Audio Source is a component that needs to be added to an object within the scene. This could be the character, a door, a ball, or even an invisible object—useful for playing an audio file when the character enters a specific room or gets near a particular item.
For the audio to be heard by the Main Camera, the Camera needs to have an active Audio Listener component. In new Unity projects, the Main Camera typically comes with an active Audio Listener component by default, as it is assumed that users will want to hear audio files. If the default Audio Listener is missing, it can be added through the Inspector of the Main Camera object.
In my scenario, the audio file needs to be linked to the character.
Within my project, there is a Player object that serves as the parent of the Main Camera. The movement script is associated with the Player object, while the camera is equipped with a script to enable looking around. Consequently, I will attach an AudioSource component to the Player object.
Upon accessing the tab of the newly created component, you will immediately see the AudioClip field, which is initially set to 'None.'
Additionally, there is a checkbox labeled "Play on Awake" that is selected by default. This option plays the audio file when the game starts, which can be beneficial in certain scenarios. However, it isn't necessary for our current use case, so I will deselect it.
Importing an audio clip into the project is quite straightforward: simply drag the audio file from a File Browser window into the Project tab or choose it from your disk through the Assets - Import New Asset window.
Unity is compatible with various audio formats, such as mp3, and it will display a musical note icon alongside the corresponding element within the Project.
As you can see, my project already contains several audio files intended for playback at different moments. Among these files, the one we're specifically interested in is "PoP---walk".
To proceed, I first select the Player in the Hierarchy.
Next, I click and hold the button down on the PoP---walk asset in the Project.
Finally, I drag this element into the AudioClip box of the AudioSource component associated with the Player.
As previously mentioned, the sound should be played when the character moves.
To achieve this, I will open the script responsible for handling the character's movement and insert the required code.
First, I create an AudioSource variable and initialize it within the Start function by associating it with the Player's AudioSource component.
To do this, I write the following code:
private AudioSource playerAudioSource;
and, inside the Start function:
playerAudioSource = GetComponent();
I also need to create an AudioClip variable to associate with the audio file that needs to be played. I'll call this variable myAudioClip and use the SerializeField attribute because I want it to be visible in the Inspector.
After saving the script file, the next step will be to drag the "PoP---Walk" asset into the myAudioClip field of the script within the Inspector.
Immediately following the definition of playerAudioSource, I write the following line of code:
[SerializeField] private AudioClip myAudioClip;
After saving the script, I return to the Unity Editor and proceed to drag the "PoP---Walk" asset into the myAudioClip field of the script, as previously described.
At the moment, the audio is not being played.
Within the Update function of the script, there are some instructions to detect the user's keypresses, which control the character's movement.
Specifically, when the user moves the character, the value of Input.GetAxis for Horizontal and Vertical (which I have renamed x and y for convenience) can be either -1 or 1, depending on the direction.
In this case, I could write the following code:
if ((Mathf.Abs(x) == 1) || (Mathf.Abs(z) == 1))
playerAudioSource.PlayOneShot(myAudioClip);
and try to run the game; however, doing so would be a significant mistake because Unity would play the audio file during EVERY FRAME OF THE GAME!
The result doesn't improve if we merely move the PlayOneShot function inside a Coroutine and add a one-second delay command (yield return new WaitForSeconds(1)). The issue remains that Update will call the Coroutine at every frame, leading us back to the same error.
The Coroutine, therefore, is not necessary; instead, we need to implement a simple check on the AudioSource: play the audio only if the AudioSource is NOT already playing it.
This can be done within the Update function by writing the following code inside the if block that checks the values of x and y:
if (!(playerAudioSource.isPlaying))
playerAudioSource.PlayOneShot(myAudioClip);
Now we can save the script, start running the game, and observe (or, better yet: listen to) the result.
Before concluding this tutorial, I'd like to share a thought: the AudioClip field of the AudioSource component can, of course, be modified via script.
This means you can use this AudioSource to play a standard footsteps sound file, but also replace the audio clip during the game with another one if, for example, the character is walking on gravel, on the shoreline, or other surfaces, which can be identified using Colliders.
Additionally, if your character can fly, you can disable the AudioSource so that no sound is played.
Well, that's all for this tutorial; I hope it was helpful! See you soon!