Wearing time of hearing protection: why short breaks cost so much

The rule: for the whole exposure

According to DGUV Rule 112-194 (section 7.6), hearing protection must be worn for the whole time a person is in noise that is hazardous to hearing. The rule explains this with a calculation: because sound energy is averaged, the breaks essentially determine the protection, not the attenuation of the product. In a noise area, use is mandatory from the upper action values of 85 dB(A) and 137 dB(C) in any case (section 7.4, requirements at a glance).

The worked example in the rule

With a continuous level of 105 dB(A) over eight hours and hearing protection with 30 dB attenuation, 75 dB(A) reaches the ear when it is worn all day. If it is left off for 30 minutes, the level is 93 dB(A). The risk to hearing then remains. The rule also quotes the rule of thumb from DIN EN 458: if hearing protection is worn for only four hours of an eight-hour day, the effective protection is at most 3 dB.

How to calculate the effect

Effective reduction over the day = −10 · lg [ x + (1 − x) · 10^(−D/10) ] dB. Here x is the share of time without hearing protection in the duration of the noise exposure and D is the effective attenuation at the ear in dB, that is the M or L value after the real-world deduction.

The table shows why attenuation alone says little: with 30 dB attenuation, 15 minutes without protection halve the effect over the day. Hearing protection with 20 dB that is always worn protects far better over the day, with 20.0 dB, than a 30 dB protector that stays in the pocket for an hour a day and achieves only 9.0 dB. For the daily value itself see Calculating the daily noise exposure level.

What helps against breaks

Section 7.2 of DGUV Rule 112-194 lists measures that increase the willingness to wear hearing protection. According to it, warnings are only the last resort.

• Wearing trials and choice: employees try several models, and disposable earplugs in several sizes. Criteria are in Earplugs or earmuffs?.
• Custom-moulded earplugs: individually fitted hearing protection is often motivating.
• Music during monotonous work: hearing protectors with radio or music playback can help, provided safety reasons do not rule them out.
• Training with listening examples: practical training at least once a year; listening examples can simulate hearing loss (hearing protection training).
• Example and follow-up: managers wear hearing protection themselves, even for short visits, and address non-use at once to clarify the reasons.
• Keep hearing protection within reach: issue points at the entrance to the noise area, for example dispensers.

When too much attenuation is the reason

Anyone who only wants to speak to a colleague briefly or hear a signal is more likely to take hearing protection off when it isolates strongly. A residual level below 70 dB(A) can encourage that. More is in Overprotection and Warning signals and speech with hearing protection.