You will find some code samples or libraries on CodeProject:
http://www.codeproject.com/search.aspx?q=sound+visualizer&doctypeid=1[
^].
Unfortunately, you did not tag your platform, language and other preferences; it would give you too wide search criteria. Add some keywords related to your preferences to the query, to limit your search.
It's pretty likely that your platform is .NET; you probably want to use VB.NET but should not limit your choice with VB.NET, because code in any .NET language would be equally helpful. Yet, you did not put any constraints on the UI library to use. Anyway, then it's even easier to find:
http://www.codeproject.com/search.aspx?q=sound+visualizer+%28%22.NET%22+OR+%22C#%22+OR+%22VB.NET%22%29&doctypeid=1[
^].
Good luck.
—SA