Valmiki Ramayana Bala Kanda Sarga 24 Shloka 7
Original Shlokaराघवस्य वचश्श्रुत्वा कौतूहलसमन्वित:। कथयामास धर्मात्मा तस्य शब्दस्य निश्चयम्।।1.24.7।।
1 source checked for this shloka
कौतूहलसमन्वितः filled with curiosity, राघवस्य वच: Rama's words, श्रुत्वा having heard, धर्मात्मा righteous minded one, तस्य of that, शब्दस्य relating to that sound, निश्चयम् nature, कथयामास narrated.
At the words of Rama filled with curiosity, the righteous (Viswamitra) narrated the true nature of that sound.