I work in LTC w/dementia patients on the 3p-11p shift and I can tell you, in my experience, noise greatly affects most of my dementia patients! And not in a good way.
Change of shift often is met with "noise", the chatter of the oncoming/off going employees, the shuffling around, the overhead pages..I notice a lot of the residents who might have been sitting quietly just as we walk on the floor are very agitated and anxious within 10 minutes of us walking on the floor.
The TV or radio being too loud can also set them off. But in the same token at times, a TV or radio set to a low volume with a soothing type sound works wonders to calm an agitated dementia patient.
At the change of shift as I walk onto the floor, as i pass the radio, I turn it off or turn it down low, I make sure the TV isn't blasting, and I try to keep my voice down. The less background noise the better the resident is.
Later in the shift, I remind my staff to try to keep the tone/volume of their voices down, especially around 'sundowners time". Loud talking, laughing etc tends to perk up the dementia resident who might have been quiet prior to.
Dinner time tends to wind up some of the dementia patients, again, the kitchen staff bringing the trays to the floor, their laughter and chatter, the noise of moving residents to their dining area, etc. I try to have my easily set off residents in an area that isn't ground zero for the noise, they tend to be more relaxed if they aren't in the center of all the noise and movement.
With that said, yes, noise definately affects my patients with dementia. Now I said noise, not sound. Hushed background sounds like a radio set on an easy listening station on a low volume actually will calm most of my residents, talking to them in a calm, soft voice will calm them as opposed to a normal to loud voice. The "bubble" machine (what i call it) that makes soft water sounds will lull a lot of my residents into a peaceful state and sometimes a nap.
Sound can have good and bad effects on a dementia resident.