You can use '.NET Voice Recorder' which exist at CodePlex, it is a sample application demonstrating how to use NAudio to record audio on the .NET framework
see link https://voicerecorder.codeplex.com/
Alternatively I heard that, vinmm.dll is also used to capture sound.
you can check below link for more details
Editor, DotNetSpider MVM
Microsoft MVP 2014 [ASP.NET/IIS]