Refers to a lingering sound after the original source has stopped, often used in literary or descriptive contexts.
The echo of the bell faded into the mountains.
The reverberation of the church organ lingered for a long time.
Compound of 余 (yo, 'remaining, lingering') and 響 (kyō, 'sound, echo'). The exact historical derivation is uncertain, but the kanji composition transparently conveys the meaning of a lingering sound.