Valmiki Ramayana Sundara Kanda Sarga 57 Shloka 20

दीनमनसः dejected at heart, ते they, सर्वे all, काननौकसः with eagerness, वानरेन्द्रस्य chief of vanara's, पर्जन्यनिनदोपमम् like the thundering of clouds, निर्घोषम् noise, शुश्रुवुः heard.

All the vanaras who were feeling dejected and waiting anxiously heard the noise of Hanuman that sounded like a thundering cloud.