Sound simulator
Play a real heat pump recording where the unit would go, then walk around and measure how loud it is from your windows and garden.
What you need
A speaker or a second phone to play the recording, and a phone whose microphone the tool can use to measure. Your browser will ask for permission.
What it can't tell you
Phone microphones aren't calibrated sound meters, so treat the readings as approximate. Real units vary with model, size and how hard they are working.
What next
See how big a unit is with the AR visualiser, and read about noise and where the unit goes.