(Unity)効果音の音量をスクリプトで動的に調整する

(スクリプト)

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

public class EnemyShotShell_Sound : MonoBehaviour
{
    public GameObject shellPrefab;
    public AudioClip sound;
    private int count;

    // 効果音
    private AudioSource audioX;

    private void Start()
    {
        // 効果音
        audioX = GetComponent<AudioSource>();
    }

    private void FixedUpdate()
    {
        count += 1;

        if (count % 20 == 0)
        {
            GameObject shell = Instantiate(shellPrefab, transform.position, Quaternion.identity);
            Rigidbody shellRb = shell.GetComponent();
            shellRb.AddForce(transform.forward * 1000);
            Destroy(shell, 5.0f);

            // 効果音の発生
            audioX.PlayOneShot(sound);

            // 音量調整
            audioX.volume = 0.3f;
        }
    }
}