Cyclic delay diversity (CDD) is a simple and elegant technique to exploit transmit diversity in a MIMO-OFDM system by artificially increasing the frequency-selectivity of the equivalent channel. In this paper, we study the application of CDD in digital audio broadcasting (DAB), which is well motivated by the mismatch analysis between the channel inherent diversity and the capability of the DAB channel coding and interleaving. Simulation of DAB with CDD in rural area and typical urban area is carried out; the results demonstrate the advantage of CDD in creating a more uniform coverage area compared to the system without CDD. We further devise a lower bound which allows justification of tradeoff between the design parameters and the performance improvement