When a room is perfectly soundproofed, outside noises such as footsteps, highway traffic, and air conditioners stay outside of the soundproofed area, and inside noises, like those coming from your instrument or voice, remain inside.
Part of getting this right is also about choosing the appropriate sample. Some are super long. If you have an active kick pattern, choose a shorter 808. If your kick is less active, you can probably get away with a longer sample, but those aren’t good for complex bass lines.