🔊 Sound power level of machinery and equipment — engineering method (accuracy grade 2) — PN-EN ISO 3744

Environment PN-EN ISO 3744

Overview

THE STANDARD CHANGED THREE WEEKS BEFORE THIS ENTRY. The PKN card of PN-EN ISO 3744:2011 (Polish-language version) has the header "Wycofana i zastąpiona przez PN-EN ISO 3744:2026-09 - wersja angielska" [Withdrawn and replaced by … — English-language version] and the withdrawal date 03-09-2026. The English-language version of 2011 has the same date and the same successor. The new edition (publication 03-09-2026, 78 pages, KT 157 Physical Hazards in the Working Environment) implements EN ISO 3744:2026 and ISO 3744:2025. Both cards of the 2011 edition still have the row "Aktualna w ocenie zgodności: 30-09-2026 — Patrz Komunikat Prezesa PKN" [current for conformity assessment: … — see the Communication of the President of PKN] and the row "Dyrektywa 2006/42/EC" [Dyrektywa = Directive] (machinery) — the standard was a harmonised standard, and the old edition serves conformity assessment until the end of September 2026. We have not read the content of the Communication of the President of PKN.

WHAT THE NEW EDITION CHANGES — ACCORDING TO THE FOREWORD OF ISO 3744:2025 (extract made available by the publisher): • the determination of the SOUND ENERGY LEVEL was removed — because of its rare use and the repetition of other text of the method; it also disappeared from the title. Scope on the card of the new edition: methods suitable for all types of noise (steady, non-steady, fluctuating) "z wyjątkiem krótkotrwałych zdarzeń impulsowych" [except short-duration impulsive events], whereas the 2011 edition also covered "pojedyncze impulsy energii dźwiękowej" [single bursts of sound energy]; • the absolute background noise criteria were removed and replaced by new criteria for compliance with the requirements for background noise; • the estimation of the environmental correction K2 from an estimate of the equivalent sound absorption area was removed; methods of qualifying the test environment other than the absolute comparison test were moved to ISO 26101-2; • many special cases were moved to annexes; a new Annex I describes how a laboratory can reduce uncertainty; the requirements for instrumentation and for the cylindrical surface were updated (consistency with ISO 7779). THE SENTENCE THAT SAVES THE CONTINUITY OF RESULTS: the foreword states that the revision does NOT change the basic procedure for determining the sound power level, and the reproducibility standard deviation remains as in the 2010 edition. Results according to both editions are considered equivalent — EXCEPT for measurements in an environment qualified by K2 calculated from the estimated equivalent sound absorption area, because this route was removed. HISTORY FROM THE INTRODUCTION: the method was published as ISO 4872 in 1978, and as ISO 3744 in 1994 (environment with K2f ≤ 2 dB in each band, A-weighted levels only from bands). ISO 3744:2010 relaxed the requirement to K2A ≤ 4 dB and permitted the A-weighted level to be measured directly with an A filter — to make determination in the field easier when assessing compliance with regulations.

METHOD (edition ISO 3744:2010, clauses 1–4 — extract made available by the publisher): the sound power level (in the 2010 edition also the sound energy level) is determined from sound pressure levels measured on a measurement surface enveloping the source, in frequency bands or A-weighted. Environment: a laboratory room or a flat outdoor area, with one or more reflecting planes; ideally — an open space, e.g. a qualified hemi-anechoic room; in a poorer environment corrections are applied within the given limits. The uncertainty corresponds to ISO 12001, accuracy grade 2 (engineering). Frequency range: octave bands 125–8000 Hz (one-third-octave bands 100–10 000 Hz). BACKGROUND NOISE CRITERION (4.2.1.1 of the 2010 edition): the averaged background noise level over the measurement surface is to be at least 6 dB, and preferably more than 15 dB, below the level of the source measured together with the background — in each band of the range. If neither the relative nor the absolute criteria are met, the report must state this and must not suggest a measurement "in full conformity" with the standard (4.2.3). With a difference smaller than 6 dB the standard points to ISO 9614-1 or 9614-2 (sound intensity) as the route to grade 2 results.

A REGULATION THAT CHANGED EARLIER THAN THE STANDARD. Two entries in the scopes cite "PN-EN ISO 3744:2011" together with "Załącznikiem nr 4 do Rozporządzenia Ministra Gospodarki z dnia 21 grudnia 2005" [Annex No. 4 to the Regulation of the Minister of Economy of 21 December 2005] (Journal of Laws No. 263, item 2202 — equipment for use outdoors, noise emission). The regulation is in force, but the amendment of 9 May 2025 (Journal of Laws 2025 item 654, in force since 22-05-2025) REPEALED Annex No. 4: noise measurement methods are henceforth specified by the annex to Commission Delegated Regulation (EU) 2024/1208. The original Annex No. 4 cited EN ISO 3744:1995.

HOW ACCREDITATION SCOPES CITE THE STANDARD. Measurement of 25.09.2026 on the database of PL accreditation scopes (1310 laboratories with entries): 41 entries at 23 laboratories. Almost all notations are the 2011 edition — withdrawn on 03-09-2026; the new edition is not yet in any scope. THE EXCLUSION OF CLAUSE 8.3 recurs in 25 notations ("z wyłączeniem pkt. 8.3" [excluding clause], "excluding section 8.3" and similar) — in the 2010 edition clause 8 is "Determination of sound power levels and sound energy levels"; we do not have the content of 8.3, so we do not know what the laboratories exclude. Two notations exclude clause 9 (measurement uncertainty), one limits the method "do przestrzeni otwartej z pomijalną poprawką środowiskową K2A" [to open space with a negligible environmental correction K2A], two cite the 1999 edition. Object: most often "Maszyny i urządzenia – hałas" [machinery and equipment — noise] (19), also heat pumps and air conditioners, agricultural machinery, cooling towers, turbines. Methodology: "Poziom mocy akustycznej (z obliczeń)" [sound power level (calculated)] (9 and variants), A-weighted sound pressure level, levels in 1/1 and 1/3 octave bands; two entries also have "poziom energii akustycznej" [sound energy level] — a quantity that the new edition no longer determines.

THE KEY OF THE "LABORATORIES" TAB: "PN-EN ISO 3744" — 22 laboratories and 39 entries, without any foreign entries; it will not show one laboratory (AB 1241) with the notation "PN EN ISO 3744" without a hyphen. The survey method from the same series, PN-EN ISO 3746, has a separate entry in the database.

WHAT WE DO NOT GIVE. Of the 2010 edition we had clauses 1–4 (up to 4.2.3), of the 2025 edition — the foreword and the introduction. We do not give the microphone arrays, the dimensions of the measurement surfaces, the corrections K1 and K2, the formulas for the sound power level or the uncertainty values.

Method principle

The noise source is enveloped by a hypothetical measurement surface (hemisphere, parallelepiped or cylinder) over a reflecting plane, and the sound pressure levels are measured on it at many points — in octave or one-third-octave bands or A-weighted. After subtracting the influence of background noise and reflections from the surroundings (corrections), the sound power level of the source is calculated from the averaged pressure level and the area of the measurement surface; unlike the pressure level, it does not depend on the distance or on the room.

Applications

• Declaration and verification of the noise emission of machinery — Machinery Directive 2006/42/EC (the "Directive" row on the card of the 2011 edition)
• Equipment for use outdoors — regulations on noise emission into the environment
• Heat pumps, air conditioners, chillers — acoustic declarations of products
• Agricultural machinery, turbines, cooling towers, industrial equipment in the field

Key parameters

Standard

Standard number

PN-EN ISO 3744:2026-09 (wersja angielska; wprowadza EN ISO 3744:2026 [IDT], ISO 3744:2025 [IDT]); zastąpiła PN-EN ISO 3744:2011 (wprowadzała EN ISO 3744:2010 i ISO 3744:2010)

Title (PL)

Akustyka — Wyznaczanie poziomów mocy akustycznej źródeł hałasu na podstawie pomiarów ciśnienia akustycznego — Metody techniczne stosowane w warunkach zbliżonych do pola swobodnego nad płaszczyzną odbijającą dźwięk

Title (EN)

Acoustics — Determination of sound power levels of noise sources using sound pressure — Engineering methods for an essentially free field over a reflecting plane

Step-by-step procedure

1. Edition of the standard

   From 03-09-2026 PN-EN ISO 3744:2026-09 is in force; for conformity assessment the 2011 edition is current until 30-09-2026 (PKN card). Agree with the client which edition to test to — the new one does not determine the sound energy level.

2. Operating conditions of the source

   From the noise test code for the given machine (ISO 12001) or from the product regulation — mounting, load, operating modes.

3. Test environment

   Checking the reflecting plane and the environmental correction; in the 2025 edition qualification mainly by the absolute comparison test (other methods in ISO 26101-2).

4. Background noise

   In the 2010 edition: background ≥ 6 dB (preferably > 15 dB) below the level of the source in each band; in the 2025 edition the criteria were changed — WE DO NOT GIVE the new values.

5. Measurements on the measurement surface

   Sound pressure levels at the points of the microphone array, in bands or A-weighted (WE DO NOT GIVE the arrays).

6. Calculation and report

   Sound power level with corrections for background and environment; in the report the edition of the standard, the frequency range and — if the background criteria are not met — an explicit statement of this fact.

Required equipment and apparatus

Health and safety (OHS)

• Measurements at machines in motion — guards, danger zones, emergency stops
• High noise levels (ranges up to approx. 137 dB) — hearing protectors for personnel
• Measurements in the field — weather conditions, wind and precipitation also affect the safety of working with the instrumentation

Frequently asked questions