The NALS annual report 2025 documents the conclusion of the project: the revision of DIN 45680 was discontinued without consensus; the content developed is being published as a Technical Specification. The technical and procedural consequences are set out below.
Mika Wihanto
February 2026
Since 1997, DIN 45680 has governed how low-frequency noise immissions are measured and assessed. It is the basis of almost every assessment of hums, and it has needed revision for years. A draft was available in 2020.
In the DIN/VDI Standards Committee Acoustics, Noise Control and Vibration Engineering (NALS), the technical work on it was done in working group NA 001-01-02-11. We contribute there.
The NALS annual report 2025 puts it soberly: the work could not be completed due to a lack of consensus. An arbitration procedure followed. Its result: the content developed will not be published as a standard but as Technical Specification DIN/TS 45610-1 “Low-frequency sound – Part 1: Methods for the measurement, evaluation and assessment of low-frequency sound immissions”. It was published in January 2026. The project to revise DIN 45680 was discontinued.
In addition, a Technical Report (DIN/TR 45610-2) is being published that explains the background to the revision. The working group was put on hold at the end of 2025.
A Technical Specification is not a standard. It does not go through the same consensus procedure and does not carry the same presumption of conformity. In practice, this means:
We continue to calculate and assess according to DIN 45680 where the regulations require it, and additionally report the results according to DIN/TS 45610-1 where they lead to a different evaluation. This duplication is unsatisfactory, but it is currently the most honest way of dealing with the situation.
Two further NALS publications are directly relevant to our work: DIN 45687-1 and -2 on quality assurance of software for calculating outdoor sound, both published in December 2025. They specify the requirements that calculation programs must meet and how their conformity is assessed, i.e. a verifiable way of checking whether a propagation calculation corresponds to the state of the art.
Also published: DIN 45669-2 (measurement of vibration immissions, February 2025) and DIN ISO 226 with the updated equal-loudness contours, the hearing threshold curves we describe in our article on the ear as a measuring system.
In 2025, NALS supervised a total of 32 national committees with around 344 experts; 106 meetings took place.
The contribution is voluntary. It has a technical rationale: knowing how a method came about, which alternatives were examined, which specifications were made and which points were deliberately left open determines how reliably its application can be judged in an individual case. For low-frequency sound, this concerns exactly the points where assessments arrive at different results.