CalibrateNoiseTogether is an Android application that supports the distributed and opportunistic calibration of the microphone embedded in - or connected to - a mobile phone. CalibrateNoiseTogether is intended to operate in a fully decentralized way and thereby leverages the presence of the nearby phones that monitor the same noise level so as to perform a multi-party calibration while enhancing the overall accuracy gain. For this purpose, the mobile phones exchange measurements to determine a calibration function, which describes the relationship between the non-calibrated measurements and the calibrated one(s) and thereby enables correcting the measurements of the non-calibrated phones(s). Once calibrated, the phone can, in turn, be used to calibrate others. Such a dynamic calibration, which is also known as multi-hop blind calibration, allows calibrating sensors under their deployment conditions and without involving the end-user.