在Silverlight 4中支持了麦克风设置的调用，在本节中我们将调用麦克风设备，然后进行录音，并且将录制的声音存取为Wav音频文件。

        第一步、首先我们从AudioSink类派生一个音频接收器类：WavAudioSink。其代码如下所示：

public class WavAudioSink:AudioSink
{
    // 设置需要记录的内存流
    private MemoryStream _stream;
    // 设置当前的音频格式
    private AudioFormat _format;

    public Stream BackingStream
    {
        get { return _stream; }
    }

    public AudioFormat CurrentFormat
    {
        get { return _format; }
    }

    protected override void OnCaptureStarted()
    {
        _stream = new MemoryStream(1024);
    }

    protected override void OnCaptureStopped()
    {
    }

    protected override void OnFormatChange(AudioFormat audioFormat)
    {
        if (audioFormat.WaveFormat != WaveFormatType.Pcm)
            throw new InvalidOperationException("WavAudioSink只支持PCM音频格式");

        _format = audioFormat;
    }

    protected override void OnSamples(long sampleTime, long sampleDuration,
        byte[] sampleData)
    {
        // 新的音频数据到达，将它们写入流
        _stream.Write(sampleData, 0, sampleData.Length);
    }
}

   第二步、然后我们将编写一个保存音频的函数类，以保存读取到的音频数据：

public class SaveWAVHelper
  {
    public static void SavePcmToWav(Stream rawData, Stream output, AudioFormat audioFormat)
    {
        if (audioFormat.WaveFormat != WaveFormatType.Pcm)
            throw new ArgumentException("Only PCM coding is supported.");

        BinaryWriter bwOutput = new BinaryWriter(output);

        // -- RIFF 块
        bwOutput.Write("RIFF".ToCharArray());
        // 包的总长度
        // 计算的数据长度加上数据头的长度没有数据
        // 写数据(44 - 4 ("RIFF") - 4 (当前数据))
        bwOutput.Write((uint)(rawData.Length + 36));
        bwOutput.Write("WAVE".ToCharArray());

        // -- FORMAT 块
        bwOutput.Write("fmt ".ToCharArray());
        // FORMAT 块的长度 (Binary, 总是 0x10)
        bwOutput.Write((uint)0x10);
        // 总是 0x01
        bwOutput.Write((ushort)0x01);
        // 通道数( 0x01=单声道, 0x02=立体声)
        bwOutput.Write((ushort)audioFormat.Channels);
        // 采样率 (Binary,  Hz为单位)
        bwOutput.Write((uint)audioFormat.SamplesPerSecond);
        // 字节每秒
        bwOutput.Write((uint)(audioFormat.BitsPerSample * audioFormat.SamplesPerSecond * 
            audioFormat.Channels / 8));
        // 每个样品字节: 1=8 bit 单声道, 2=8 bit 立体声 or 16 bit 单声道, 4=16 bit 立体声
        bwOutput.Write((ushort)(audioFormat.BitsPerSample * audioFormat.Channels / 8));
        // 每个样品字节
        bwOutput.Write((ushort)audioFormat.BitsPerSample);

        // -- DATA 块
        bwOutput.Write("data".ToCharArray());
        // DATA数据块的长度
        bwOutput.Write((uint)rawData.Length);
        // 原始PCM数据如下
        // 复位rawData地位，记住它的原点位置
        // 恢复底。
        long originalRawDataStreamPosition = rawData.Position;
        rawData.Seek(0, SeekOrigin.Begin);
        //追加到输出流中的所有数据从rawData流
        byte[] buffer = new byte[4096];
        int read;       
        // 循环读取字节数据
        while ((read = rawData.Read(buffer, 0, 4096)) > 0)
        {
            bwOutput.Write(buffer, 0, read);
        }
        //开始写入数据
        rawData.Seek(originalRawDataStreamPosition, SeekOrigin.Begin);
  }
}

      第三步、然后再MainPage.xaml中我们添加三个按钮，分别是开始记录音频、停止录制音频、保存音频文件三个按钮。

<Grid x:Name="LayoutRoot" Background="White">
        <Button Content="开始录制" Height="28" HorizontalAlignment="Left"
                Margin="30,15,0,0" Name="btnRecord" VerticalAlignment="Top"
                Width="71" Click="btnRecord_Click" />
        <Button Content="停止录制" Height="28" HorizontalAlignment="Left"
                Margin="150,15,0,0" Name="btnStopRecord" VerticalAlignment="Top"
                Width="71" Click="btnStopRecord_Click" />
        <Button Content="保存音频" Height="28" HorizontalAlignment="Left"
                Margin="268,15,0,0" Name="btnSaveWav" VerticalAlignment="Top"
                Width="71" Click="btnSaveWav_Click" />
    </Grid>

 第四步、最后在MainPage.xaml.cs代码中我们进行录制、停止、保存音频的操作如下所示：

public partial class MainPage : UserControl
    {
    public MainPage()
    {
        InitializeComponent();

        btnRecord.IsEnabled = true;
        btnStopRecord.IsEnabled = false;
        btnSaveWav.IsEnabled = false;
    }

    //声明私有变量
    private WavAudioSink _wavSink;
    private CaptureSource _captureSource;
    private SaveFileDialog _saveFileDialog = new SaveFileDialog() 
        { Filter = "Audio files (*.wav)|*.wav" };

    private void btnRecord_Click(object sender, RoutedEventArgs e)
    {

        //初始化_captureSource
        var audioDevice = CaptureDeviceConfiguration.GetDefaultAudioCaptureDevice();
        _captureSource = new CaptureSource() { AudioCaptureDevice = audioDevice };

        //有默认设置的设备且可以用来录制音频
        if (CaptureDeviceConfiguration.AllowedDeviceAccess ||
            CaptureDeviceConfiguration.RequestDeviceAccess())
        {
            //判断当前没有开始录制音频
            if (_captureSource.State == CaptureState.Stopped)
            {
                //初始化WavAudioSink
                _wavSink = new WavAudioSink();
                _wavSink.CaptureSource = _captureSource;
                //开始录制音频
                _captureSource.Start();     

            }
        }


        btnRecord.IsEnabled = false;
        btnStopRecord.IsEnabled = true;
        btnSaveWav.IsEnabled = false;
    }

    private void btnStopRecord_Click(object sender, RoutedEventArgs e)
    {
        //如果当前状态为开始录制，则停止录制
        if (_captureSource.State == CaptureState.Started)
        {
            _captureSource.Stop();
        }


        btnRecord.IsEnabled = false;
        btnStopRecord.IsEnabled = false;
        btnSaveWav.IsEnabled = true;
    }

    private void btnSaveWav_Click(object sender, RoutedEventArgs e)
    {
        if (_saveFileDialog.ShowDialog() == false)
        {
            return;
        }
        //保存Wav文件
        Stream stream = _saveFileDialog.OpenFile();
        SaveWAVHelper.SavePcmToWav(_wavSink.BackingStream, stream, _wavSink.CurrentFormat);

        stream.Close();

        MessageBox.Show("你的音频已经保存");


        btnRecord.IsEnabled = true;
        btnStopRecord.IsEnabled = false;
        btnSaveWav.IsEnabled = false;
    }
}

       通过以上步骤我们就可以开始调用麦克风录制音频文件了，本实例采用Silverlight 4.0+VS2010编写，如需源码请点击 SL4Audio.zip 下载。其效果图如下所示：