Can employees sign away mandatory obligations?

This question arose today:
If we have a mandatory hearing protection zone, can employees who do not wish to wear hearing protection sign some declaration that they accept the risk to their hearing and will make no claim on the company should they suffer hearing loss?

The answer is NO.

Where a noise assessment has identified that the noise exposure (combination of noise level and exposure time) is above the second action point (85 dBA) of the Control of Noise at Work Regulations 2005, then the employee must wear the protection provided.

What the employer must do is to take reasonably practical steps to prevent the noise exposure in the first place, either by choice and maintenance of machinery or by the control of transmission methods by devices such as acoustic enclosures.  SSS also strongly recommend that employees be given a choice of hearing protection; some prefer insert-type protectors and other prefer ear muffs.

Although Reg.7 of the Control of Noise at Works Regs., states that the employer "shall ensure so far as is reasonably practicable that no employee enters that area unless that employee is wearing personal hearing protectors", in some cases it may be a lower risk to allow certain people not to wear hearing protection. For example, forklift truck drivers who pass through a mandatory hearing protection area are not at risk because their exposure time is low, but the wearing of hearing protection would increase other risks, such as the potential for collision with a pedestrian.  Where a company has made this decision, then it must clearly publish the rules,

Supporting Regs:
Control of Noise at Work Regulations 2005 Reg 8(2)(a) Every employee shall make full and proper use of personal hearing protectors provided to him by his employer in compliance with regulation 7(2) and of any other control measures provided by his employer in compliance with his duties under these Regulations.

Health and Safety at Work, etc Act 1974 Reg 7(b). 
It shall be the duty of every employee while at work, as regards any duty or requirement imposed on his employer or any other person by or under any of the relevant statutory provisions, to co-operate with him so far as is necessary to enable that duty or requirement 
to be performed or complied with.