unity Couldn't acquire device ID for device name Built-in Microphone

using UnityEngine;  
using System.Collections;  
  
[RequireComponent (typeof (AudioSource))]  
public class MicrophoneCapture : MonoBehaviour   
{  
    // Boolean flags shows if the microphone is connected 
    private bool micConnected = false;  
  
    //The maximum and minimum available recording frequencies  
    private int minFreq;  
    private int maxFreq;  
  
    //A handle to the attached AudioSource  
    private AudioSource goAudioSource;  
   
    void Start()   
    {  
        //Check if there is at least one microphone connected  
        if(Microphone.devices.Length <= 0)  
        {  
            //Throw a warning message at the console if there isn't  
            Debug.LogWarning("Microphone not connected!");  
        }  
        else //At least one microphone is present  
        {  
            //Set our flag 'micConnected' to true  
            micConnected = true;  
  
            //Get the default microphone recording capabilities  
            Microphone.GetDeviceCaps(null, out minFreq, out maxFreq);  
  
            //According to the documentation, if minFreq and maxFreq are zero, the microphone supports any frequency...  
            if(minFreq == 0 && maxFreq == 0)  
            {  
                //...meaning 44100 Hz can be used as the recording sampling rate  
                maxFreq = 44100;  
            }  
  
            //Get the attached AudioSource component  
            goAudioSource = this.GetComponent<AudioSource>();  
        }  
    }  
  
    void OnGUI()   
    {  
        //If there is a microphone  
        if(micConnected)  
        {  
            //If the audio from any microphone isn't being captured  
            if(!Microphone.IsRecording(null))  
            {  
                //Case the 'Record' button gets pressed  
                if(GUI.Button(new Rect(Screen.width/2-100, Screen.height/2-25, 200, 50), "Record"))  
                {  
                    //Start recording and store the audio captured from the microphone at the AudioClip in the AudioSource  
                    goAudioSource.clip = Microphone.Start(null, true, 20, maxFreq);  
                }  
            }  
            else //Recording is in progress  
            {  
                //Case the 'Stop and Play' button gets pressed  
                if(GUI.Button(new Rect(Screen.width/2-100, Screen.height/2-25, 200, 50), "Stop and Play!"))  
                {  
                    Microphone.End(null); //Stop the audio recording  
                    goAudioSource.Play(); //Playback the recorded audio  
                }  
  
                GUI.Label(new Rect(Screen.width/2-100, Screen.height/2+25, 200, 50), "Recording in progress...");  
            }  
        }  
        else // No microphone  
        {  
            //Print a red "Microphone not connected!" message at the center of the screen  
            GUI.contentColor = Color.red;  
            GUI.Label(new Rect(Screen.width/2-100, Screen.height/2-25, 200, 50), "Microphone not connected!");  
        }  
  
    }  
}