Understanding human responses to air source heat pump noise: examining tonal changes and operating cycles

Air Source Heat Pumps are pivotal in the Government of the United Kingdom's target of achieving net zero carbon emissions by 2050. However, their widespread adoption faces challenges, with noise being among the main barriers to entry and a restricting factor at the planning stages. This study addresses concerns regarding noise propagation from outdoor units to indoor environments through a two-part experiment, aiming to capture human responses to Air Source Heat Pump noise based on the changes in the characteristics of noise emissions at various operating conditions, background noise levels, and source distances. The first part evaluates peoples' responses under static operating conditions to 20-second recordings, using the Self-Assessment Manikin scale and an annoyance scale. Following each recording, they used the Self-Assessment Manikin pictorial scale and an annoyance scale to report their response. In the second part, responses to transient Air Source Heat Pump operation cycles are assessed using 60-second recordings. Participants evaluated each recording at two points: after a transition in the operating cycle and at the end of the recording. The findings of the study provide insights into the human response to heat pump noise, essential for developing strategies to facilitate wider Air Source Heat Pump adoption.