A newly installed heat pump domestic central heating system immediately generated noise complaints from a neighbour. The owner contact us and subsequently provided the requested smartphone videos of the noise at the neighbour, close to the units and inside the adjacent garage. This allowed us to rule out structure-borne noise (a common noise issue for A/C and pump installations) and to diagnose that the cause was primarily sound reflections that created an amplified 93Hz pumping frequency standing wave.
From the photos provided, we devised a simple solution involving low-cost components available in DIY stores (plywood and loft insulation). Once installed, they reduced the tone at the neighbour by about 30dB (as shown in this noise signature), eliminating the problem. This was a fast, low-cost project completed remotely (no site visits) via smartphone data from start to finish.