This is the 5962nd most frequent Japanese word.
わいわい
Lively, noisy, and cheerful chatter or commotion.
Here, "わいわい" is used to depict the cheerful and lively noises children make while playing together.
子供たちは公園でわいわい遊んでいました。
The children were playing noisily in the park.
In this context, "わいわい" conveys the bustling, cheerful atmosphere of the festival with many people talking and laughing.
文化祭では皆がわいわい楽しんでいました。
Everyone was joyfully enjoying themselves at the cultural festival.
Here, "わいわい" implies the energetic and lively interaction among friends during gatherings and sharing joyful moments.