C# Speech Recognition

Что не так может быть в коде? Не распознает голос

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Speech.Recognition;
namespace Speech
{
    public partial class Form1 : Form
    {
        SpeechRecognitionEngine recorder = new SpeechRecognitionEngine();
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            Choices choices = new Choices();
            choices.Add(new string[] { "one", "two" });
            GrammarBuilder gb = new GrammarBuilder();
            gb.Append(choices);
            Grammar grammar = new Grammar(gb);
            recorder.LoadGrammarAsync(grammar);
            recorder.SetInputToDefaultAudioDevice();
            recorder.SpeechRecognized += recorder_SpeechRecognized;
        }
        void recorder_SpeechRecognized(object sender, SpeechRecognizedEventArgs e)
        {
            if (e.Result.Text == "one")
                MessageBox.Show("You used one");
            else if (e.Result.Text == "two")
                textBox1.Text += "You used two";
        }
        private void Enable_Click(object sender, EventArgs e)
        {
            recorder.RecognizeAsync(RecognizeMode.Multiple);
            Disable.Enabled = true;
        }
        private void Disable_Click(object sender, EventArgs e)
        {
            recorder.RecognizeAsyncStop();
            Disable.Enabled = false;
        }
    }
}