Reprogramming of the process for calculating the audibility of alarm signals when wearing hearing protection according to Zwicker/Lazarus

Project No. FF-FP 0392


completed 12/2016


The software used for the assessment of new hearing protectors at the Institute for Occupational Health and Safety of the DGUV (IFA) for the calculation of warning signal audibility while wearing hearing protection is based on the BAuA Research Report FB 340 dating from the year 1983 and, as Visual Basic program, can only be locally used. The program cannot host external users as the IFA also maintains the associated signal and background noise spectra.

The program is used to calculate three defined labels of warning signal audibility while wearing hearing protection: S (rail construction), V (vehicle driver in public road traffic) and Ex (railcar drivers and drivers/shunters in railway operation, x = 1 to 3). These labels are then marked in IFA’s "positive list" of hearing protection.

The until now used program is uneasy in handling and no longer according to the state-of-the-art.


The program has been transferred into a C# code within the scope of the present project, and an offline version for use within the IFA as well as an online version with restricted functionality for external users, in particular producers of hearing protection, has been developed. Here, the psychoacoustic models, the basic calculation methods and the decision criteria have been maintained so that the results are still compatible with those of BAuA FB 340. This has been ensured by the fact that the calculation core of the previous Visual Basic program has been maintained by converting it into a code which can be called up as a DLL (dynamic link library) in a C# environment.


As a result of the research project, three applications are available:

  • offline application Zwicker.UI for use by IFA,
  • browser interface Zwicker.Web for the online application,
  • calculation unit Zwicker.Service for the online application.

These applications have been described and documented in the installation and operating instructions Zwicker Apps. Apart from the labels S, V and E1 to E3, the complete offline version also comprises the calculation of the labels W and X. After having defined a freely configurable label "Test", the associated calculation result is also given. Apart from the calculation of single hearing protectors via an input mask, also a batch processing of an arbitrary number of hearing protectors can be carried out by uploading the respective input file. With the routine "Zwicker.UI.config.exe" all relevant program parameters can be adjusted. For the results output, the user can select between a detailed format showing all intermediate results or a short report.

With the input mask of the online version, the same data input as for the offline version is possible, except for the freely configurable label. Only individual calculations of hearing protectors can be carried out, a batch processing is not possible. The results are given in a one-page downloadable report which, apart from the attenuation curve of the hearing protector, only gives a summary of the results for the labels W, X, S, V, and Ex.

Last Update:

14 Sep 2017


Financed by:
  • Deutsche Gesetzliche Unfallversicherung e. V. (DGUV)
Research institution(s):
  • Müller BBM GmbH

-cross sectoral-

Type of hazard:



personal protective equipment

Description, key words:

PPE, Ear Protection, Signal audibility