Noise is irritating and pervasive. At best it is a mere annoyance; at worst it can reduce your quality of life. Noisy plumbing from adjacent flats and buildings can keep people awake. This can result in insomnia, depression and anxiety. The stress can become overwhelming when you're sleep deprived as well.
Molded ear plugs are the best earplugs. For a few pounds you can get yourself a super-comfortable pair of ear plugs which will last for years. ZenPlugs are ideal because they don't protrude from your ears so are comfortable when you lie on your side in bed. They are even antibacterial making them great at preventing ear infections. They last for far longer than foam, wax or soft silicon ear plugs, making them cheaper to use in the long-run.
Insomnia can cause serious life-issues and it is worth avoiding chronic insomnia at all costs. The problem can lead to relationship breakdown, under-performance at work and reduced quality of life. Sometimes the source of the noise can be found and sorted out but sometimes this proves to be impossible. A neighbor's boiler firing during the night is an example of this. The neighbor may be unavailable, not care or not be able to do anything about the problem. Get yourself a pair of molded ear plugs from http://zenplugs.com/molded-earplugs/ and sleep peacefully.