Especially, unclearness of the patterns on the 'dotaku to hear,' which is thought to have been created due to a treatment such as polishing, not due to degradation over time in the ground from a burial through to an excavation, possibly shows that they were repeatedly dug out and polished every time a ceremony was held (Makoto SAHARA).
特に「聞く銅鐸」の紋様の不鮮明さは埋納時から発掘までの土中での経年劣化ではなく、磨く等の行為によるものとされており（佐原真）、祭りの度に繰り返し掘り出し磨かれたためという。