Ear defenders are one piece of Personal Protection Equipment (PPE) which are used for your hearing protection. These are mainly used on sites where there is a lot of noise which you need to be protected from.
Ear defenders work by reducing the sound waves entering your ears, making the noisy environment much quieter. The shape of the ear defenders, as well as the material they are made from, is what allows this to happen. With both the thermoplastic and foam working together to reduce the noise.
You should wear ear defenders if you are going to be exposed to a lot of loud noises ranging over 85 and 87 decibels. If this is the case, your employer should supply you with ear defenders for your own personal safety.
It is common for you to need to wear ear defenders if you are working in a factory or on a construction site. Due to you being exposed to tools which produce high sound for long periods of time.