Every model of the iPad in the market has an inbuilt microphone for average use of listening to music and contents with audio apps and one can download applications to maximize the use of a microphone. On the first generation the microphone is located on the edge of the device near the headphone port, and in every version of the device speakers are located on the bottom edge of the device to keep them far from the microphone to avoid conflict in input and output cables. This goes to answer the question of does the iPad have a microphone and the truth of the matter is that the microphone has various uses including making it easy for communication when one is using the device to make calls through VoIP, apps like Skype, video calls or face time on iPad 2 or using application that allow voice commands like search and apps for navigation. One can also use the microphone to help in note taking and recording.
To get easy access to the microphone use an iPad cover that allows space for the microphone space uncovered since most of the available cases leave spaces for ports, if you use the device for VoIP calls ensure that the space left for the microphone port is enough to ensure that the calls are clear and communications runs smoothly for both parties.