Hearing protection for impulse noise: bangs, impacts, peaks

What the peak sound pressure level is

The peak sound pressure level LpC,peak is the highest value of the instantaneous sound pressure level, C-weighted (§ 2(4) LärmVibrationsArbSchV). It has action values of its own: 135 dB(C) as the lower and 137 dB(C) as the upper value. In Germany 137 dB(C) must not be exceeded at the ear (§ 8(2)); EU-wide, the exposure limit value of 140 dB(C) applies with hearing protection taken into account (Directive 2003/10/EC). Typical sources are straightening and hammering work or nail guns (noise level table).

Three cases in DGUV Rule 112-194

Section 6.8 of DGUV Rule 112-194
Case	Hearing protection	Note
Continuous noise with LEX,8h of 85 dB(A) or more and impulsive sounds	ordinary hearing protection, attenuation matched to LEX,8h	check the peak action values; the daily level is usually the stricter criterion
High single impulses at LEX,8h up to 80 dB(A)	level-dependent hearing protection	must attenuate the impulses sufficiently and allow hearing and communication in quieter phases; suitability by the passive M and L values
Extremely high impulses, such as gunshots, explosions or straightening work on large tanks	peak level decisive; if necessary earplugs and earmuffs combined	residual level at the ear at most 137 dB(C); with safety glasses watch for leaks at the arms

Special impulse-filter earplugs, as used in police work, according to the rule only attenuate noticeably from about 150 dB(C) and often do not have approval under the PPE Regulation.

Calculating the peak level at the ear

L'pC,peak = LpC,peak − (M − Ks) for mid- to high-frequency impulses; L'pC,peak = LpC,peak − (L − Ks − 5 dB) for low-frequency ones. At most 137 dB(C) is permitted; protection is rated as well suited up to 135 dB(C).

Worked examples (M 25 dB and L 18 dB of the EP904 earmuffs, Ks 5 dB). They show the calculation; they do not replace a suitability check.
Peak level	Type of impulse	Calculation	At the ear	Assessment
150 dB(C)	mid- to high-frequency	150 − (25 − 5)	130 dB(C)	up to 135: well suited
160 dB(C)	mid- to high-frequency	160 − (25 − 5)	140 dB(C)	above 137: not permitted
150 dB(C)	low-frequency	150 − (18 − 5 − 5)	142 dB(C)	above 137: not permitted

The third example shows that with low-frequency impulses the attenuation is clearly lower, because besides the smaller L value a further 5 dB is subtracted. The method for daily and peak levels is set out in Calculating the residual level at the ear. If one protector is not enough, a combination of earplugs and earmuffs should be considered.

Level-dependent hearing protection

Electronic hearing protection with level-dependent attenuation amplifies quiet signals. The amplification decreases as the outside level rises. The electronic share of the inner level is typically limited to 82 dB(A) at most. Up to about 82 dB(A), perception is mostly better than with other types of hearing protection; at high levels, depending on the passive attenuation, more than 85 dB(A) can reach the ear (section 4.6.1). The passive attenuation values therefore count when assessing the impulses.

Procedure at work

Determine peak and daily levels in the risk assessment.
First reduce the impulses at the source (order of measures).
Determine the case under section 6.8 and select hearing protection with suitable attenuation.
Calculate the peak level and daily value at the ear and compare them with table 5.
Check communication and warning signals (listening tests).

Frequently asked questions

From what level does the peak sound pressure level matter?

The lower action value is 135 dB(C) and the upper one 137 dB(C) (§ 6 LärmVibrationsArbSchV). In Germany 137 dB(C) must not be exceeded at the ear (§ 8(2)).

Which hearing protection helps against bangs?

That depends on the case: for continuous noise with impulses, ordinary hearing protection chosen by the daily level; for high single impulses in an otherwise quiet environment, level-dependent hearing protection; for extremely high impulses, a choice by peak level, if necessary as a combination (DGUV Rule 112-194, section 6.8).

How do you calculate the peak level at the ear?

L'pC,peak = LpC,peak − (M − Ks) for mid- to high-frequency impulses and LpC,peak − (L − Ks − 5 dB) for low-frequency ones. The result must not exceed 137 dB(C).

Are impulse-filter earplugs approved?

According to the rule, special impulse-filter earplugs only attenuate noticeably from about 150 dB(C) and are often not approved under the PPE Regulation. Check the marking and type-examination.

Hearing protection for impulse noise: bangs, impacts, peak levels