Questions about Bestway Wärmepumpe Air Energy Poolheizung 920W

The Bestway Wärmepumpe Air Energy Poolheizung 920W has a noise level of approximately 50 dB.

We use it for a 26,000 litre swimming pool, where the water temperature drops every night and it takes a few hours to reach the desired temperature (the appliance switches off when the outside temperature drops below 12 degrees).

We were surprised by the low level of noise - we could hardly hear it!