From Majiastic Computer:
Microphone Pass-through Emulator is designed for the newer sound cards that the direct playback from microphone to speaker is disabled, such as Realtek HD sound cards. This means you cannot hear what you speak to your MIC from your speaker. This playback feature is a very important or must-have for some applications like Karaoke software or sound mixing programs. Without this feature, you have to spend a lot of money and time to setup a big system with an extra mixer. This program pass the input from microphone through your speakers directly in background to emulate playback features. You can control the output volume and an option to load other programs after running (V1.4 only). Version 1.5 and later support ASIO and DirectX drivers in order to provide lowest recording latency.
If you're looking for a software where you can direct audio from a microphone directly to your speaker just use Virtual Audio Cable. Set the line in as your microphone in use and the line out as your speaker and you're good to go.