The "Headphones Prohibited" sign ensures health and safety in the workplace by reminding employees and individuals that wearing headphones or listening to music while engaging in the given activity or being in the given area can pose a health and safety risk. If being able to hear is an essential part of the job, then it is imperative that individuals are alert and reading to listen for instructions or information. 

The sign is best displayed around the workplace where inter-employee communication is essential for the functioning of the job and the wellbeing of the individuals. It can also be used in environments where certain machinery is being operated to ensure people are alert of their surroundings.