The noise you’re seeing is due to high ISO. The camera will do everything it can to keep shutter speeds fast, and one of these is to crank up the ISO so that the camera sensor is more sensitive to light.
If your camera’s have any night modes then switch to that and try it. This will turn down the ISO and images should be cleaner, but you make start to notice blurring in your images. If taking photographs of people then try “night portrait” mode so that the camera fires the flash… this should also help with the demonic red-eye ^_^
If your outdoors try “fireworks” – it was always a favourite of mine – but be warned, you will almost certainty need to use a tripod. Most photographers have trouble shooting blur-free, handheld shots with shutter speeds any lower than 1/60s
Kathy, it’s the camera “slowing down” – at least not in the same sense a computer slows down with too much running – but rather the longer shutter speeds required in low light. Necessary evil I’m afraid.