Tutorial: Audio

In this tutorial, we will be adding audio to our game to make it more immersive. We will start simply by adding two sound effects to our game: one for when a blaster shoots and one for when an enemy is destroyed. We will go over two different implementations and you can choose which one you prefer.

Blaster Shoot

Whenever the player or the enemy shoots, we want to play a sound effect. So, we will go to the "Player" gameobject which has a blaster, and add an AudioSource component to it. An audio source is a component in Unity that is used to play audio clips.

To play an audio clip, we need to drag and drop a sound clip from the project window into the AudioClip field in the AudioSource component. I have added a bunch of sound effects to the starter project, so you can use any of those. For this tutorial, I will be using the laserSmall_000.ogg sound effect.

Also, we want to make sure that the sound doesn't automatically play when the game starts. In Unity, this option is turned on by default, so we need to uncheck the Play On Awake option in the AudioSource component.

Now, we need to modify our Blaster script to play the sound effect from the AudioSource when it shoots a projectile. Let's get the reference to the AudioSource component in the Start method:

[Tooltip("The audio source that can play the projectile fire audio")]
protected AudioSource audioSource = null;

void Start()
{
    audioSource = GetComponent<AudioSource>();
}

Now, we can play the sound effect in the Shoot method by calling the Play method on the AudioSource component.

public void Shoot()
{
    // ... code to spawn a projectile

    // play the projectile-fired sound effect
    if(audioSource) 
    {
        audioSource.Play();
    }
}

Test it out by playing the game and shooting the blaster. You should hear a sound effect when the player shoots. We can expand it to the enemy blaster by adding an AudioSource component to the "Enemy" prefabs and it should automatically work the same way.

Explosion on Destroy

We have a sound effect for when the blaster shoots by directly accessing the AudioSource component. However, as we expand on our game, we will find it quite tedious to add an AudioSource component to every gameobject that needs to play a sound effect. Wouldn't it be nice if we could just specify the sound effect and the position of the sound effect in the world and have the sound play automatically? This is where our custom AudioManager comes in.

Let's start by adding a new script to our "GameManager" object called AudioManger. It'll have a public function that anyone can invoke to play an explosion sound effect at a given position. So, we need to add a serialized property describing the explosion sound effect and a method to play the sound effect at a given position.

[Tooltip("A reference to the explosion sound effect")]
[SerializeField] AudioClip ExplosionSound;

public void PlayExplosion(Vector3 position)
{
    AudioSource.PlayClipAtPoint(ExplosionSound, position);
}

We can now specify the explosion sound effect in the inspector and call the PlayExplosion function from anywhere in our game. I'm going to use the explosionCrunch_000.ogg sound effect for this tutorial. Next, we need to modify our Health script to play the explosion sound effect when the hp reaches 0.

// ... code to check if hp is 0
if(hp <= 0)
{
    // play the explosion sound effect
    var audioManager = FindObjectOfType<AudioManager>();
    audioManager?.PlayExplosion(transform.position);

    // ... code to destroy the gameobject
}

Test it out by playing the game and shooting the enemy. You should hear a sound effect when the enemy is destroyed. This is a simple implementation of the AudioManager that can be expanded to play other sound effects as well.

Each of the two methods has its own pros and cons. The first method gives the developer more control over the sound effects, but it can be tedious to add an AudioSource component to every gameobject that needs to play a sound effect and configure the properties. The second method is more convenient, but it is less flexible and doesn't give the developer as much control over the sound effects. The most control you get is the position of the sound effect and the volume of the sound effect. So, it's up to you to decide which method you prefer.

Final Scripts

Here are the final scripts for this tutorial for reference:

AudioManager

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class AudioManager : MonoBehaviour
{
    [Tooltip("A reference to the explosion sound effect")]
    [SerializeField] AudioClip ExplosionSound;

    // Play an explosion sound effect at the given point
    public void PlayExplosion(Vector3 position)
    {
        AudioSource.PlayClipAtPoint(ExplosionSound, position);
    }   
}

Blaster

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Blaster : MonoBehaviour
{
    [Tooltip("Additional offset from the source transform from where the projectile is spawned")]
    [SerializeField] protected Vector2 Offset;

    [Tooltip("A reference to the projectile prefab that will be used to instantiate projectiles")]
    [SerializeField] protected GameObject ProjectilePrefab;

    [Tooltip("The audio source that can play the projectile fire audio")]
    protected AudioSource audioSource = null;

    void Start()
    {
        audioSource = GetComponent<AudioSource>();
    }

    // Shoot a projectile from the blaster position
    public void Shoot()
    {
        // apply an offset along the direction in which the blaster is looking,
        // then spawn a projectile from that position with the current rotation of the blaster
        var pos = transform.position + Offset.x * transform.right + Offset.y * transform.up;
        Instantiate(ProjectilePrefab, pos, transform.rotation);

        // play the projectile fire audio
        if(audioSource)
        {
            audioSource.Play();
        }
    }
}

Health

using System.Collections;
using System.Collections.Generic;
using System.Runtime.InteropServices.WindowsRuntime;
using UnityEngine;

public class Health : MonoBehaviour
{
    [SerializeField] protected int hp = 1;

    // Apply damage to the object
    public void ApplyDamage(int damage)
    {
        hp -= damage;

        // if the health drops below zero destroy the object
        if (hp <= 0)
        {
            // play the explosion sound effect before destroying the object
            var audioManager = FindObjectOfType<AudioManager>();
            audioManager?.PlayExplosion(transform.position);

            // destroy the object
            Destroy(gameObject);
        }
    }

    // Apply heals to the object
    public void ApplyHeals(int heals)
    {
        // basically reverse the damage
        ApplyDamage(-heals);
    }

    // Get the health from the health component
    public int GetHP() 
    {
        return hp;
    }
}