I used to record important technical meetings and demos using Camtasia Studio, using a Mic to capture the speaker voice.

Sometimes we invite attendees by asking them to call us in the meeting, and they would call on a cell phone then we switch it to loudspeaker so we can hear and talk to them and also record the conversation on Camtasia.

The problem I am having now is that playing back those recording produces the regular noise that results from the microphone being close to the mobile phone (the kind of noise you hear when your mobile phone rings and it is near a speaker).

Any advice on removing this noise?