Julia, won’t you clarify what ‘walla’ is?

I can't present 'walla' as the only correct variant of translation, errare humanum est, you know, nevertheless I have found it as a translation of expression 'шум толпы'. I might have made a mistake, then I apologize. In a case you dug deeper into details I'm eager to listen.

Here are some references: https://en.m.wikipedia.org/wiki/Walla

Да, Julia, Александр, in walla - не очень частотное выражение...

https://translate.academic.ru/walla/en/ru/

3 walla
1) Общая лексика: слуга, служащий, хозяин, шум толпы
2) Индийский язык: парень, человек

in walla - в шуме толпы

https://books.google.com/ngrams/graph?content=in+walla&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cin%20walla%3B%2Cc0

Perhaps walla is a proper word, but it’s in Hebrew, as I could understand from a Google search. Neither for English nor for Russian speakers walla is familiar. Google Ngram Search only shows the Walla Walla College:
https://www.google.ru/search?q=%22walla%22&tbm=bks&lr=lang_en&gws_rd=cr,ssl&dcr=0&ei=28LjWYP1GoXt6QTtzbiYDg
So, I believe walla is not the proper word for this translation.
I would suggest simple ‘noise of the crowd’, quite popular nowadays:

https://books.google.com/ngrams/graph?content=noise+of+the+crowd&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cnoise%20of%20the%20crowd%3B%2Cc0

Julia, as for your reference to Wikipedia, it says Walla is an audio effect used on radio, filming etc. So it’s just a specific professional term, even a kind of slang known only to specific people.

murmur of the crowd vs noise of the crowd:
https://books.google.com/ngrams/graph?content=murmur+of+the+crowd%2Cnoise+of+the+crowd&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cmurmur%20of%20the%20crowd%3B%2Cc0%3B.t1%3B%2Cnoise%20of%20the%20crowd%3B%2Cc0

Hope I could help you😊

Julia, thank you for the reference.
... In American radio, film, television, and video games, walla is a sound effect imitating the murmur of a crowd in the background...