Start by downloading the free NIOSH app for measuring sound with your cellphone.

https://www.cdc.gov/niosh/noise/about/app.html

Then go around your house when it is quiet, noisier, and noisy to measure the sound levels. Include when running the dishwasher, washing machine, or vacuum cleaner. Read up on how to minimize sound transmission in a retrofitted house. It's more complicated than a few sentences of advice can solve for you.

Often, attic build-outs have relatively low ceilings. That might limit things. Start with a lot of insulation in your attic floor between the rafters. Pick an insulation that's good at dampening sound. Use expanding foam around holes to things like fans and utilities.

You also need to make certain the framing can handle the conversion. Attics are frequently just over ceiling joists with no expectation of the loading required for livable space, and then you mention a bathroom and tile. That will add a lot of weight. Your foundation may even need to be redone.

The head height, after you add the required insulation depth, and beef up the joists, needs to be 7'. That means you start with more than 8' to make all that work. https://www.thisoldhouse.com/attics/21018914/read-this-before-you-finish-your-attic#:~:text=The%207%20and%207%20rule,requirements%20that%20supersede%20this%20rule.

So Iassume you have all permits in place so please post plan of the space for us to see. Soundproofing between floors is best dealt with at the begining of a build . There are sound muffling flooring materila probablt the best look for some meant for condo install between floors . Usually some type of waffle under floor and then the new flooring on top Waht floor do you have in th rest of the house ?