The intensity squeezing bandwidth of a light-emitting diode was measured as functions of a driving current, junction capacitance, and operation temperature. It was found that the squeezing bandwidth was linearly proportional to the current and inversely proportional to the capacitance and the temperature in a low current regime. The experimental results provide evidence for a pump-noise-suppression mechanism in a constant-current-driven p-n junction due to a ''macroscopic Coulomb blockade effect'' [A. Imamoḡlu and Y. Yamamoto, Phys. Rev. Lett. 70, 3327 (1993)]. © 1995 The American Physical Society.