Final reports for download:


IEA HPT Annex 51 – Executive Summary and Document GuideIEA HPT Annex 51 Executive Summary and Documents Guide

IEA HPT Annex 51 – 2-page Summary – Acoustic Signatures of Heat Pumps – 2-page_summary_Annex 51_2022

IEA HPT Annex 51 – Umbrella ReportIEA HPT Annex 51 Umbrella Report

Deliverable 1.0 – Introduction IEA HPT Annex 51 D1.0

Deliverable 1.1 – Measurement Techniques IEA HPT Annex 51 D1.1

Deliverable 1.2 – Regulations – Countries overview IEA HPT Annex 51 D1.2

Deliverable 1.3 – Regulations – SynthesisIEA HPT Annex 51 D1.3

Deliverable 2.1 – Selection of Heat Pumps for Round Robin Tests – Market figures – IEA HPT Annex 51 D2.1

Deliverable 2.2 – Round Robin Tests – Air-to-Water Heat Pump – Heat Pump Water Heater – IEA HPT Annex 51 D2.2

Deliverable 2.3 – Seasonal Sound Power Level – Air-to-Water Heat Pump – IEA HPT Annex 51 D2.3

Deliverable 3 – Overview on Heat Pump Component Noise and Noise Control TechniquesIEA HPT Annex 51 D3

Deliverable 4 – Analysis of the Effect of Operating Conditions of Heat Pumps on Acoustic BehaviourIEA HPT Annex 51 D4

Deliverable 5 – Report on heat pump installation with special focus on acoustic impact IEA HPT Annex 51 D5

Deliverable 6 – Annoyance rating and psychoacoustical analysis of heat pump soundIEA HPT Annex 51 D6

Deliverable 7.1 – Educational material on acoustics of heat pumps  – IEA HPT Annex 51 D7.1

Deliverable 7.2 – Workshop material and conference contributionsIEA HPT Annex 51 D7.2

Webinar presentations download

Introduction Annex 51 webinar – Caroline Haglund Stignor (Heat Pump Centre)
Annex 51 overview – Christoph Reichl (AIT, Austria)
• European Standards and Legislation – Roberto Fumagalli (Polimi, Italy)
• Noise and seasonal variations based on interlaboratory results – Francois Bessac (CETIAT, France), Thomas Gindre (ISE, Germany)
Effect of different heat sinks and operation modes on acoustic emissions – Kamal Arumugam (DTI, Denmark)
• (Transient) Noise of Heat Pumps – Thore Oltersdorf (Fraunhofer ISE, Germany)
• Heat pump installation and effects on surrounding environment – Christoph Reichl (AIT, Austria)
Annoyance rating and psychoacoustical analysis of heat pump sound – Henrik Hellgren (RI.SE, Sweden) (8’)
• Panel Q&A of the presentations (20’) – lead by Caroline Haglund Stignor (Heat Pump Centre)



The primary aim with Annex 51 is to further increase the acceptance of heat pumps (as air-to-water, water-to-air, air-to-air and brine-to-water units) for comfort purpose with respect to the noise and vibration emissions.

A second focus is placed on increasing knowledge at different levels (manufacturers, acoustic consultants, installers, legislators). To reach this goal, first different reasons to reduce sound emissions depending on countries (legislation), locations and applications have to be gathered and understood. The main influencing factors to the acoustic signature of these units will be identified. Collecting and combining research results in these fields on the different implementation levels (component, unit and application) will finally lead to directions for improved components, units and control strategies including guidelines, as well as training and inputs to future standards. The aim is to gather the knowledge and expertise of the participants on the different levels in order to forward this knowledge and establish recommendations and advices.

All presentations given at the workshop in the framework of the ICR2019  by Annex 51 members are now online and ready for download:


Annex 51 Acoustic Signatures of Heat Pumps in the framework of the International Energy Agency Technology Collaboration Programme on Heat Pumping Technologies

Acoustic Regulations of Heat Pumps

1D Modelling of Heat Pumps including Acoustics

Simultaneous energy efficiency and acoustic evaluation of heat pump systems using dynamic simulation models

Acoustic Emissions and Noise Abatement of Air to Water Heat Pumps – part1

Acoustic Emissions and Noise Abatement of Air to Water Heat Pumps – part2

Testing campaign on the energetical and acoustical behaviour – part1

Testing campaign on the energetical and acoustical behaviour – part2

Heat pump noise – Operation dependence and seasonal averaging


Final report of the national Austrian Project “SilentAirHP” (in english and german language)



Bachelor work “Sound field simulations of air-water heat pumps in a terraced housing estate”



Additional documents for deliverable 7.1 in original language





Austrian National Deliverables