IEA HPT Annex 51: Acoustic Signatures of Heat Pumps

The project aims at enhancing the acceptance of heat pumps and removing market barriers by reducing acoustic noise emissions and vibrations. The project involves: innovative experimental laboratory work, various numerical approaches and preliminary work in context of uniform legal and normative boundary conditions. In addition, new assessment schemes are developed and perceptual tests are carried out.

Short Description

Initial situation, Challenge, Motivation

Heat pumps are a versatile energy efficiency and renewable energy technology with vast potential in contributing substantially to the required changes in the energy system. Especially air-based heat pump systems can play an important role in densely populated, urban areas due to their multiple advantages such as low space requirement or simple installation. The compressor and fans of air-sourced heat pumps often emit acoustic emissions which are reinforced in the transition period as a result of the icing of the compressor. The operating noise of heat pumps can cause conflicts in neighborhoods leading to problems concerning health, psyche and finance. This may become a serious disadvantage for the heat pump technology and may hamper its broad market penetration.


This project primarily aims at enhancing the acceptance of heat pumps and removing market barriers by reducing acoustic noise emissions and vibrations.

Innovative content, results and findings

For that purpose, preliminary work for elaborating uniform legal and normative boundary conditions is carried out. The development of acoustic emissions in the operation of heat pumps will be analyzed in detail on both, a component and a unit level by means of innovative methods and test infrastructure. Novel approaches in reducing acoustic emissions of heat pumps such as noise suppression, various installation options, sound and vibration absorption measures are pursued and assessed regarding their impact.

In addition, realistic noise propagation simulations are carried out to identify ideal installation scenarios and orientations especially in smaller settlement areas. Furthermore, innovative concepts for an optimum mounting and insulation sheathing are developed. Perceptual tests are used to elaborate the impact of various operative and acoustic noise absorbing measures on the annoyance. The assessment of the annoyance will be related to acoustic and psychoacoustic parameters to develop an assessment scheme.

The know how gained within this project, and the results and findings from former research projects, will be disseminated in both, the framework of international expert meetings and on a national level to various target groups comprising especially manufacturers of heat pumps and their components, acoustic consultants, installers and planers of heat pumps, and national decision makers. National research activities and international transfer of know-how and findings relating to the reduction of acoustic noise emissions of heat pumps as envisaged in this project, is of vital importance for strengthening the competitiveness of the national heat pump sector. Possibly arising problems of acceptance due to acoustic noise emissions are seen as one of the greatest challenges in developing the heat pump market to a mass market.

Project Images

Terms of use: The pictures listed underneath the header “Project Pictures” originate from the projects in the frame of the programmes City of Tomorrow, Building of Tomorrow and the IEA Research Cooperation. They may be used credited for non-commercial purposes under the Creative Commons License Attribution-NonCommercial (CC BY-NC).


Austria, France, Sweden (Germany and Italy if national funding is provided)

Contact Address

AIT Austrian Institute of Technology GmbH
Center for Energy
Project manager, Operating Agent: Dr. Christoph Reichl
Project staff: Dr. Johann Emhofer
Giefinggasse 2, 1210 Wien,
Tel: +43 (0) 50550-6605

Vienna University of Technology Institute of Building Construction and Technology
Project manager: Univ. Prof. Dipl-Ing. Dr. techn. Thomas Bednar
Project staff: Univ.Ass. Dipl.-Ing. Maximilian Neusser
Karlsplatz 13/206, 1040 Wien
Tel.: (+43 1) 58801-20101

Graz University of Technology
Institute of Thermal Engineering
Inffeldgasse 25/B, 8010 Graz,
Project manager: Ao. Univ.-Prof. Dr. René Rieberer
Project staff: Dipl.-Ing. Philipp Wagner
Tel.: +43 (0)316 873-7302

Austrian Academy of Science
Acoustics Research Institute
Wohllebengasse 12-14, 1040 Wien,
Project manager: apl. Prof. DI Dr.-Ing. Holger Waubke
Project staff: Dr. Christian Kaseß
Tel.: (+43 1) 515810