Qualified use of hearing protection: from 110 dB(A)

What qualified use means

With qualified use it is assumed that the hearing protection achieves the attenuation from the type-examination at work too (DGUV Rule 112-194, section 6.2.5). The condition is practical training, repeated and documented at least four times a year. The manager ensures use as the manufacturer states and training according to annex 5. This makes adequate protection possible even at extremely high levels.

From when it is required

At a daily noise exposure level of LEX,8h = 110 dB(A) and above, the German TRLV Lärm calls for special protective measures. They include qualified training and use (section 9.3). Below that, qualified use is voluntary; but it allows the selection to be calculated without a real-world deduction.

Ordinary training and qualified use

	Training under DGUV Regulation 1	Qualified use
Frequency	before first use, when needed and at least once a year	at least four times a year
Practical exercises	mandatory, because hearing protection is category III PPE	yes, under annex 5
Check of the protection achieved	recommended for foam earplugs	at least once a year, for earplugs, custom-moulded earplugs and combinations with earmuffs
Real-world deduction Ks	9, 5 or 3 dB depending on the type	0 dB
Documentation	yes	yes

What changes in the calculation

Residual level with the EP1227 foam earplug (M 35 dB, Ks 9 dB without qualified use) for mid- to high-frequency noise. A worked example, not a suitability check.
Noise level LEX,8h	Without qualified use	With qualified use
105 dB(A)	105 − (35 − 9) = 79 dB(A)	105 − 35 = 70 dB(A)
110 dB(A)	110 − (35 − 9) = 84 dB(A), not recommended	110 − 35 = 75 dB(A)
115 dB(A)	115 − (35 − 9) = 89 dB(A), not permitted	115 − 35 = 80 dB(A)

The full calculation is in Calculating the residual level at the ear. At even higher levels a combination of earplugs and earmuffs may also be needed.

Checking the individual protection

The selection rests on the values of the type-examination less the real-world deductions. In practice the attenuation varies more between people, so flat-rate deductions are only a stopgap; an individual measurement is better (section 7.12). The rule names these methods:

f-MIRE
audiometric and audiometry-like methods
loudness comparison
acoustic leak test
pressure test (custom-moulded earplugs only)

Details are in DGUV Information 212-003. Custom-moulded earplugs are checked by the manufacturer before first use; the company’s functional check is made at least every three years. If the measurement shows leaks that cannot be fixed, the exercises are repeated or another type of hearing protection is chosen; the real-world deductions only fall away if no leaks occur.

What is practised

Annex 5 of the rule describes typical errors that training can avoid:

Foam earplugs: not rolling or squeezing enough before insertion, inserting too shallowly, not holding long enough after insertion (at least 30 seconds, better one to two minutes or as the manufacturer states), the wrong size (How to insert earplugs correctly).
Custom-moulded earplugs: practise insertion before first use; the marking is usually red for the right and blue for the left ear.
Earmuffs: seal, hair, glasses, respirator, swapped earmuffs, headband worn wrongly (combination with other PPE).

Frequently asked questions

What is qualified use of hearing protection?

Use with practical training at least four times a year, documented. It is then assumed that the attenuation from the type-examination is achieved at work (DGUV Rule 112-194, section 6.2.5).

From what noise level is it required?

From a daily noise exposure level of 110 dB(A) under the German TRLV Lärm.

How often must the protection be checked?

At least once a year; the rule recommends the check at every training session (section 9.3 and annex 5).

What changes in the residual level calculation?

The real-world deduction Ks falls away: L'EX,8h = LEX,8h − M (or − L) instead of − (M − Ks).

How is the individual protection measured?

For example with f-MIRE, audiometric methods, loudness comparison, an acoustic leak test; for custom-moulded earplugs also a pressure test (section 7.12; details in DGUV Information 212-003).