Serialize

SaveAudioClipToDisk.cs

public static void SaveAudioClipToDisk(AudioClip audioClip, string filename)
{
    //create file
    BinaryFormatter bf = new BinaryFormatter ();
    FileStream file = File.Create (Application.persistentDataPath+ "/" + filename);

    //serialize by setting the sample, frequency, samples, and channels to the new AudioClipSample instance
    AudioClipSample newSample = new AudioClipSample();
    newSample.sample = new float[audioClip.samples * audioClip.channels];
    newSample.frequency = audioClip.frequency;
    newSample.samples = audioClip.samples;
    newSample.channels = audioClip.channels;

    //get the actual sample from the AudioClip
    audioClip.GetData (newSample.sample, 0);

    bf.Serialize (file, newSample);
    file.Close ();
}