gistfile1.txt

using System;
using System.Collections;
using UnityEngine;

[RequireComponent(typeof(AudioSource))]
public class Alarm : MonoBehaviour
{
    [SerializeField] private float _changingSpeed;
    [SerializeField] private float _delay;

    private AudioSource _audioSource;
    private Coroutine _coroutine;

    private void Start() => _audioSource = GetComponent<AudioSource>();

    private void OnTriggerEnter(Collider other)
    {
        if (other.TryGetComponent(out Player _) == false)
            return;

        if (_coroutine != null)
            StopCoroutine(_coroutine);
        _coroutine = StartCoroutine(FadeVolume(1));
    }

    private void OnTriggerExit(Collider other)
    {
        if (other.TryGetComponent(out Player player) == false)
            return;

        if (_coroutine != null)
            StopCoroutine(_coroutine);
        _coroutine = StartCoroutine(FadeVolume(0));
    }

    private IEnumerator FadeVolume(float targetVolume)
    {
        if (targetVolume < 0 || targetVolume > 1f)
            throw new ArgumentOutOfRangeException(nameof(targetVolume));

        var wait = new WaitForSeconds(_delay);

        while (Mathf.Approximately(_audioSource.volume, targetVolume) == false)
        {
            _audioSource.volume = Mathf.MoveTowards(_audioSource.volume, targetVolume, _changingSpeed);
            yield return wait;
        }
    }
}