Help! Getting LO to sleep with noisy siblings

Those who have older kids, how are you managing to get your LOs to sleep for nap and bedtime?🥲 My nearly 1 year old is going through heavy separation anxiety and hates being put in the cot as he knows i’ll leave him so the only way to get him to sleep is to stay with him and be quiet and reassuring. However, I have a noisy 3 year old who means well and hes quiet isnt as quiet as can be 😂 However, the noise just perks my youngest up and nap time is a struggle, he gets overtired and refuses to nap, or if i focus on him, my eldest gets extremely upset that im not giving him attention or helping him and doing this daily is awful. I also live in a masionette/flat so its not the case of leaving one upstairs. the front room is right next to their bedroom and the kitchen so he hears everything