There is a science to noise. I’m in a building where noise carries through the floors to a quite extraordinary degree.
I suggest you take a multifaceted approach. There is no fix, if it wasn’t noisy neighbours it could be a barking dog, drum or trumpet practise, overhead aeroplanes or raucous music and revving engines. You can of course mention to the neighbours that they have no privacy and that you and your clients can overhear their personal life. That would be courteous and then I’d put stressing about the neighbours out of your mind and focus on things under your control.
It sounds like your clients have no privacy for arriving and leaving your cabin. How can you screen them? Can you plant some shrubs or ornamental grasses or put up decorative outdoor screens with climbing annuals to scramble through the screen? How about a sail or parasol! If your clients aren’t noticed by your neighbours this may help reduce your stress and anxiety.
I spend a few hours every quarter adding to my music playlist. I use license free music and I’ve created playlists for different treatments to create additional ambiance and experience. I also have a vortex fan which creates white noise that’s non intrusive. By using the fan I can muffle the individual words of a conversation and then play music over the top. You can also get sound apps with the sound of waves and rain and music which combines both. Different types of sound confuse the brain so that it cannot focus on one particular type of sound.
You could consider noise cancelling headphones for your clients and invite them to select a piece of music, perhaps incorporate this ritual into your treatment.
You can call in soundproofing experts and ask for their advice about installing sound insulation. It’s a specialist task and not something to diy without advice, although fitting is something that a competent diyer can handle. Sound insulation usually improves heat loss and reduces thermal gain so you may find the cost is partially offset by an improvement in comfort and reduction in heating and cooling costs.
You should also investigate your windows and see if these can be replaced or improved with secondary glazing. Some buildings are basically echo boxes and amplify noises. My building is like this. Everything vibrates in resonance with the noise so that it’s louder on my floor!
I totally sympathise because no-one needs this hassle and expense, but it will have to be done. Think about the school holidays! In the meantime, when my upstairs neighbour starts her hoover just as I’m in the middle on an Indian Head massage for a bereaved client. I simply ground myself and vocalise a meditation incorporating “the sounds of life, and the living around us”. I’ve been in meditations on zoom with children accidentally included in the live audio and I found the combination of the restful voice of the facilitator and the “joyful sounds of children” strangely calming. The experience of being led through this vocal intrusion, taught me how to better manage my irritation and frustration with things outside my control. So it’s not all a disaster. Your clients come to you for a respite. Give them the gift of learning how to relax even if it isn’t as quiet as a library.