Noise assessment for Heat Pumps: Development of psychoacoustic metric incorporated in fan development [15]

Today, using renewable energies is absolutely essential for climate protection. That is why air/water Heat Pumps enjoy a high level of acceptance in heating technology. Demand for them is rising and, with heat outputs from 3 to 30 kW, they are a useful solution for detached homes and apartment blocks. However, air/water Heat Pumps do not work completely silently and the more dense the buildings are, the more the neighbours can get disturbed by noise pollution. It is by no means just the measurable sound pressure level that is crucial, but human noise perception, which is where psychoacoustics and its examination methods come into play.

When air starts to vibrate, a noise is generated. For example, air/water Heat Pumps do not operate silently either. The motor and fan specialist ebm-papst has therefore developed a metric that relates physical parameters and psychoacoustics with their investigation methods to the human acceptance of a noise. A special psychoacoustics laboratory for test subjects was set up to demonstrate the operating noise of Heat Pumps and the fans installed in it in various configurations. Assessments by the test subjects are analyzed using statistical and psychological methods. The developed is now used for psychoacoustic evaluation in the end device. 

The results are incorporated into in-house fan development, and also provide information about the tested air/water Heat Pumps and which fans are best suited to the individual installation scenario. Running through an aero dynamical improvement process, in- and outflow conditions of our fans are optimized to reduce losses inside the impeller including the mechanical periphery. Intelligent and self-diagnostic motor technologies lead to an increase of operating safety and improve the service capability. The fans AxiTone and AxiEco Plug-in operate economically at optimum efficiency with very low noise levels and can also be intelligently networked. As the noise and power consumption of the speed-controlled compressor drive also have to be factored in, there is a need for inverter electronics that reduce operating noise through optimum commutation and, thus, also increase the energy efficiency of the Heat Pump.