Simple script which can be used to update the state of an object (like animation) depending on AudioSource outout

AudioSampler.cs

using System;
using System.Collections;
using UnityEngine;

namespace SMS.Tools
{

  public class AudioSampleData
  {
    public float rootMeanSquared;
    public float decibalValue;
  }
  
  public class AudioSampler : MonoBehaviour
  {
    [SerializeField] private int minDbClamp = -75;
    [SerializeField] private int maxDbClamp = 75;
    [SerializeField] private int samples = 256; // samples / audioSampleRate = seconds (256 / 48000) = 5.3ms 
    [SerializeField] private float dbReference = 0.1f;
    [SerializeField] private int sampleThreshold = -15;
    [SerializeField] private AudioSource audioSource;

    private float[] workingSamples;

    private bool isTalking = false;
    
    private void Start()
    {
      workingSamples = new float[samples];
    }

    private void Update()
    {
      if (audioSource == null) return;
      AudioSampleData data = Sample(audioSource);
      
      if (data.decibalValue < sampleThreshold && isTalking)
      {
        // Not enough sound from AudioSource. Play idle animation.
        isTalking = false;
      }
      else if (!isTalking)
      {
        // Sound from AudioSource. Portrait is now talking.
        isTalking = true;
      }
      
      Debug.Log($"dB: {data.decibalValue}. RMS: {data.rootMeanSquared}");
    }
    
    public AudioSampleData Sample(AudioSource source)
    {
      source.GetOutputData(workingSamples, 0);
      float sum = 0;
      for (var i = 0; i < samples; i++) { sum += workingSamples[i] * workingSamples[i]; }
      float rms = Mathf.Sqrt(sum / samples);
      float db = 20 * Mathf.Log10(rms / dbReference);
      if (db < minDbClamp) { db = minDbClamp; }
      if (db > maxDbClamp) { db = maxDbClamp; }

      return new AudioSampleData
      {
        rootMeanSquared = rms,
        decibalValue = db
      };
    }
  }
}