The RPi doesn't have an audio input, you need to use I2S via the IO pins or a USB sound card.

Sound Cards For The Raspberry Pi

Wolfson Pi Audio Card

USB Sound Card Resources

kb9mwr.blogspot.co.uk

 

USEFUL?
We benefit hugely from resources on the web so we decided we should try and give back some of our knowledge and resources to the community by opening up many of our company’s internal notes and libraries through mini sites like this. We hope you find the site helpful.
Please feel free to comment if you can add help to this page or point out issues and solutions you have found, but please note that we do not provide support on this site. If you need help with a problem please use one of the many online forums.