The basic theory of a large space bandwidth signal analysis by means of a two‐dimensional optical processor is discussed and the synthesis of a near real‐time optical sound spectrograph is presented. In the current state‐of‐the‐art, the realization of an optical sound spectrograph is feasible. It is also concluded that the optical sound spectrograph may offer a broader frequency range of analysis and flexibility in spectrum data handling. The former may be important in ultrasonic signal analysis; the latter may be important in future research in automatic speech recognition, synthesis, and translation.