I use these kind [1][2] of silicone ear-plugs to sleep, although I buy them in local pharmacies. Last week there was a festival where I live, with loud music and DJs at least 4:00 am, and it damped the noise by a lot, enough to let me sleep.

They are a bit uncomfortable to use at first, but I got used to them in 2/3 nights.

[1] https://kathmandu.imgix.net/catalog/product/6/1/61247_earplu...

[2] https://www.amazon.com/Reusable-Silicone-Earplugs-Reduction-...