We present a large scale effort to build a commercial Automatic Speech Recognition
(ASR) product for Arabic. Our goal is to support voice search, dictation, and voice
control for the general Arabic-speaking public, including support for multiple
Arabic dialects. We describe our ASR system design and compare recognizers for five
Arabic dialects, with the potential to reach more than 125 million people in Egypt,
Jordan, Lebanon, Saudi Arabia, and the United Arab Emirates (UAE). We compare
systems built on diacritized vs. non-diacritized text. We also conduct
cross-dialect experiments, where we train on one dialect and test on the others.
Our average word error rate (WER) is 24.8% for voice search.