Standards and guidelines concerning noise at the workplace

Owing to the Noise and Vibrations Occupational Safety and Health Ordinance and the action values specified in it for preventive measures, many companies consider themselves obliged to perform supplementary noise measurements at their work premises. The parameter to be determined in this case for assessment of the noise situation is the noise exposure level according to DIN EN ISO 9612:2009-09.

The performance of measurements to DIN EN ISO 9612 is described more precisely in the noise protection worksheet IFA-LSA 01-400 on evaluation of noise exposure in accordance with the Noise and Vibrations Occupational Safety and Health Ordinance. This includes a comparison between the different measurement strategies:

• Task-based measurements (Strategy 1)
• Job-based measurements (Strategy 2)
• Full-day measurements (Strategy 3)

In order for performance of the measurements to be simplified and potential errors avoided, model reports in the form of checklists can be worked through step by step.

The IFA noise exposure calculator is available in the form of a web application for calculation of the noise exposure level from the L_Aeq measurements for individual tasks (time fractions) within a representative working day or week.

The German Institute for Standardization (DIN) provides users of DIN EN ISO 9612 with a spreadsheet program developed in conjunction with the revised version of ISO 9612. The program enables the noise exposure levels to be determined according to the three strategies described in the standard, and the associated measurement uncertainties to be calculated at the same time. Correct application of this program requires knowledge of the provisions of DIN EN ISO 9612:2009-09.

Whereas the technical rules under the German Noise and Vibrations Occupational Safety and Health Ordinance (TRLV technical rules governing noise) and DIN EN ISO 9612 refer to the daily noise exposure level, the ASR A3.7 technical rules for workplaces governing noise and DIN 45645-2:2012-09 take the non-energy-equivalent variable of the rating level as the assessment criterion. The rating level is intended to describe the annoyance and disturbance effect of noise at the workplace, since extra-aural effects of noise can also occur below the levels posing a risk to hearing – even at levels as low as 30 dB(A) ( refer to the German DGUV information leaflet on noise stress at the workplace (PDF, 382 kB, non-accessible) ). These effects are taken into account in ASR A3.7.

One suitable method by which the annoyance and disturbance effect of noise at the workplace can be quantified involves determining the rating level L_r in accordance with DIN 45645-2:2012-09. This involves a workplace analysis, performance of measurement, determining the penalties and dealing with measurement uncertainties. The rating level is formed from the equivalent A-weighted sound pressure level with the addition of penalties for the impulse component K_I and the tonality and information content K_T. The sum of the two penalties must not exceed 6 dB.

The binding provisions of the TRLV technical rules governing noise and of ASR A3.7 constitute the essential criteria for good room acoustics in consideration of the type of use of the workplace. Further consideration of room acoustics may however be beneficial to both workers and employers. If the sound propagation in a room is appropriate for its type of use, the stress on the workers can also be reduced and their satisfaction and productivity increased.

The state of the art described in DIN 18041:2016-03 enables rooms to be divided into two forms of application:

• Group A rooms: acoustic quality over medium and large distances
• Group B rooms: acoustic quality over small distances

The acoustic quality of a room describes its suitability for certain acoustic scenarios. Group A rooms can be modelled with the aid of the IFA room acoustics calculator (German version only). Such rooms include classrooms in schools and group rooms in children's day-care centres, and also seminar rooms, lecture halls, sports halls and swimming pools. Examples of Group B rooms are offices, refectories and canteens.

ASR A3.7, the DIN EN ISO 3382-3 measurement standard and the VDI 2569 assessment guideline place special requirements on shared offices, call centres and open-plan offices.

Where a workplace involves exposure to airborne ultrasound, the TRLV technical rules governing noise can no longer be used to determine the workplace noise exposure: the scope of the TRLV is limited to frequencies between 16 Hz and 16 kHz. Should higher frequencies also be present at the workplace, the procedure described in VDI 3766 should be used to measure and assess the sound exposure.

This adapted measuring method takes account of the particular aspects of high-frequency sound. To prevent an uncontrolled influence of the ultrasound on the measuring instrument, the "U" frequency weighting, which sharply excises the ultrasound component from the signal, is used in addition to the A-weighting for evaluation of the auditory sound component. The VDI 3766 standard specifies three guideline values to be observed at the workplace: one each for the AU-weighted daily noise exposure level, the Z-weighted peak sound pressure level and the maximum one-third octave level of the 20 kHz one-third octave band. The AU-weighting includes both the A-weighting adjusted to human auditory sensation and the U-weighting described above, which eliminates the ultrasound component from the signal under measurement. The characteristic of the Z-weighting (Z = zero) is linear.

VDI 2058 Part 2 addresses the hazard to hearing presented by various forms of short and long-term exposure to noise. In addition to sound in the audible frequency range, it also addresses infrasound and ultrasound. Besides providing information on the risk of hearing impairment as such, it considers aspects for the prevention of hearing impairment and harm caused by noise.