Valmiki Ramayana Sundara Kanda Sarga 47 Shloka 19

ततः then, कपिः Hanuman, रणचण्डविक्रमम् showing fierce valour, विवृद्धतेजोबलवीर्यसंयुतम् endowed with excessive splendour, power and energy, घनतुल्यविक्रमम् who had valour equal to a cloud, तम् him, कुमारम् अक्षम् prince Aksha, संयुगे in battle, प्रसमीक्ष्य after observing, हर्षात् happily, ननाद roared

Then Hanuman saw prince Aksha, endowed with excessive splendour, power and energy advancing in a fierce manner like a cloud in the battle. Then Hanuman happy (to see the heroic prince) roared like a clap of thunder.