If you have a guitar without tune module on it, you can use your smartphone to become an auto guitar tuner.
With an auto guitar tuner you don't use your hearing, let the smartphone detect and say that the tone is too low or too high, and then you set the tuning key of the guitar to get the right tone.
For this purposes I recommended you to use the smartphone application named Guitar Tuna. It support for Android and also iOS,
Go to Google Play Store (Android) or App Store (iOS) and search the app with keyword: guitar tuna.