Microphone — detect speech start & end

Is it possible to detect when user stops to speak to the microphone? I use this code, but I don't want user to press button, I want it to be stopped or started automatically. using UnityEngine;
using System.Collections;

 [RequireComponent (typeof (AudioSource))]  
   
 public class SingleMicrophoneCapture : MonoBehaviour   
 {  
     //A boolean that flags whether there's a connected microphone  
     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;  
   
     //Use this for initialization  
     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 '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!");  
         }  
   
     }  
 }