Why do Aria and Suzu always play the drum and whistle?


When Shino explains the school's rules, Aria and Suzu always play a drum and
whistle. Why is that? Is this a reference to anything? Or is it just a
Seitokai Yakuindomo thing?

![subtitles: "article two, clause
three!"](https://i.stack.imgur.com/IAvZt.jpg)




no reason. it's a direction.  
The measure is "three-three-seven hand clap"(san-san-nana-byoushi in
Japanese).  
There is no element that indicates the relevance of this direction in
"Seitokai Yakuindomo".

