If you feel like your infant can hear all the noises from outside their window and everything that's going on inside the house, there are some things that you can do. You want to be sure that you can stop them from being woken up during the day and night from outside noises, but do it in the safest way possible. Here are some things that you can look into at a low cost and will be safe for the baby.
There have been studies that show it isn't always great to use a white noise machine in your child's bedroom to help break up some of the noise and to help them stay asleep. Instead, you should consider using a ceiling fan or installing a small fan that rotates and can be set upon the dresser. This can help control the temperature of the room and also add some noise to the space so your baby doesn't hear everything going on outside the room.
Blackout curtains that block out UV rays to help keep a room dark and to help control the temperature can also be used to help block out noise. There are specific noise reduction curtains as well. You can get these types of curtains in the colors and designs that you want for your nursery, and you can easily shit them when you want to block out lawn mowers and noisy kids.
You can put pads around the door that absorb the noise that is trying to get into their room, or even put them around the room. These may be ideal around the exterior window as well. If there are a lot of noises that come by the door of the nursery, put them on the exterior door, even if it makes the door look a little odd.
After your baby grows out of being sensitive to sound, you won't have to worry so much about keeping all of the sound out. There are a lot of different ways that you can try to reduce the amount of sound that bothers your infant, and you can even get functioning shutters that close over their window while they sleep. Look at different models and sizes of these different options to see what is best for your infant's room, without having to spend a ton of money or make a lot of changes.