Levels and quantities
| Term | Meaning |
|---|---|
| dB (decibel) | Logarithmic measure for the sound pressure level. An increase of 3 dB means roughly double the sound energy; that is why the daily value falls by 3 dB when the exposure time is halved. |
| dB(A), LA | A-weighted sound pressure level, also called sound level. The A-weighting models human hearing and is the basis of the action values for the daily noise exposure level. |
| dB(C), LC | C-weighted level. It attenuates low frequencies less than the A-weighting does. The peak sound pressure level and the SNR method work with it. |
| LAeq | Equivalent continuous sound level, A-weighted: the time-averaged level of a fluctuating noise. |
| LEX,8h | Daily noise exposure level: the time-averaged level referred to an eight-hour shift, covering all sound events at the workplace. See Calculating the daily value. |
| LEX,40h | Weekly noise exposure level: the averaged daily value referred to a 40-hour week. |
| LpC,peak | Peak sound pressure level: the highest value of the instantaneous sound pressure level, C-weighted. See Impulse noise. |
| Octave band, Lf | Level in a frequency band with centre frequency f in hertz. Attenuation values and measurements are given per octave band. |
| Noise (legal) | Any sound that can impair hearing or otherwise directly or indirectly endanger the safety and health of employees (§ 2(1) LärmVibrationsArbSchV). |
| Infrasound, low-frequency sound, ultrasound | Infrasound is at about 1 to 16 Hz, low-frequency audible sound at 16 to 140 Hz, ultrasound starts at 16 kHz (DGUV Rule 112-194, sections 6.9 and 6.10). |
Law and duties
| Term | Meaning |
|---|---|
| Action value | Threshold from which duties apply: lower action values 80 dB(A) and 135 dB(C), upper ones 85 dB(A) and 137 dB(C). The effect of hearing protection is not taken into account. See Hearing protection requirements. |
| Noise area | An area in which an upper action value can be exceeded; it has to be marked. See Marking noise areas. |
| LärmVibrationsArbSchV | The German Noise and Vibration Occupational Safety and Health Ordinance, the legal basis in Germany. |
| TRLV Lärm | Technical rules for the LärmVibrationsArbSchV; they put the ordinance into concrete terms, for example on measurement and assessment. |
| DGUV Rule 112-194 | The rule “Use of hearing protection” of the German Social Accident Insurance. It describes selection, use and training. |
| Risk assessment | Identifying and assessing hazards at the workplace. See Noise risk assessment. |
| Occupational health checks | Advice and examination by the occupational physician. See Occupational health checks for noise. |
| BK 2301 | The occupational disease noise-induced hearing loss in Germany. See Noise-induced hearing loss BK 2301. |
| STOP principle | Order of protective measures: substitution, technical, organisational, personal measures. Hearing protection belongs to the last step. See Order of measures. |
| Competent person | Someone with the specialist knowledge needed for a task, usually through vocational training or work experience and specific further training (§ 2(7) LärmVibrationsArbSchV). |
Hearing protection and attenuation
| Term | Meaning |
|---|---|
| SNR | Single Number Rating: a single value in dB for the mean attenuation of a hearing protector. See SNR and H/M/L. |
| H, M, L | Attenuation values for high, medium and low frequencies. |
| APV | Assumed Protection Value, the assumed protection per octave band: mean minus standard deviation of the laboratory test. |
| PNR | Predicted Noise Level Reduction, the noise reduction value of the HML method (DIN EN 458). |
| Residual level, L' | The level effective at the ear under the hearing protector. The prime on L' marks the level at the ear, for example L'EX,8h or L'pC,peak. See Calculating the residual level. |
| Real-world deduction, Ks | A deduction from the M or L value because hearing protection attenuates less in practice than in the laboratory: 9, 5 or 3 dB depending on the type. |
| HML check | The simplified calculation in DGUV Rule 112-194: residual level = noise level − (M − Ks) or − (L − Ks). |
| Noise class HM, L | Classification of noise: mid- to high-frequency (LC − LA up to 5 dB) or predominantly low-frequency (LC − LA above 5 dB). |
| Overprotection | Too much attenuation: a residual level below 70 dB(A), where communication and the feeling of isolation are to be checked. See Overprotection. |
| Qualified use | Practical training at least four times a year with documentation; the real-world deduction does not apply. See Qualified use. |
| Markings W, X, S, V, E | Additional markings for audibility of signals and special areas of use. See Hearing warning signals. |
| Custom-moulded earplug (otoplastic) | Individually fitted hearing protection. The company’s functional check is made at least every three years. |
| EN 352 | Series of standards for hearing protectors: part 1 earmuffs, part 2 earplugs, part 3 earmuffs attached to industrial safety helmets. See EN 352. |
| PPE category III | The highest risk category of the PPE Regulation (EU) 2016/425; hearing protection belongs to it. See CE marking. |
| Notified body | The testing body that carries out the EU type-examination and supervises production; its four-digit number follows the CE mark. See EU type-examination certificate. |
Frequently asked questions
What is the difference between dB(A) and dB(C)?
Both are frequency-weighted sound pressure levels. dB(A) models human hearing and is the basis of the action values for the daily level; dB(C) attenuates low frequencies less and is used for the peak sound pressure level and the SNR method.
What does LEX,8h mean?
The daily noise exposure level: the time-averaged noise exposure level referred to an eight-hour shift (§ 2(2) LärmVibrationsArbSchV).
What does SNR mean for hearing protection?
Single Number Rating, a single value in decibels that summarises the mean attenuation of a hearing protector.
What are H, M and L?
The attenuation for high, medium and low frequencies. For selection, calculate with the M value for mid- to high-frequency noise and the L value for low-frequency noise.
What does a prime in L'EX,8h mean?
The prime marks the level effective at the ear under the hearing protector, that is the residual level.
Sources
- DGUV Rule 112-194, annex 8 List of abbreviations for acoustic measurement and assessment quantities, in German
- German Noise and Vibration Occupational Safety and Health Ordinance (LärmVibrationsArbSchV), in German
- DGUV Rule 112-194 “Use of hearing protection”, September 2024 edition, in German
- DGUV Rule 112-194, chapter 6 Selection (attenuation, ergonomics, work environment, signal audibility), in German