Locally resonant metamaterial wall targeting tonal problems arising from heat pumps in residential buildings

Abstract

Arguments over heat pumps' noise problems and benefits in advancing the net zero target are going strong. It is undeniable that the fan and compressor of the heat pump cause pure tones and harmonics. The annoyance of these tonal noises becomes a possible obstacle to the large-scale promotion of heat pumps, especially in residential areas where every household may be equipped with one. Here we propose a feasible heat pump noise solution from the perspective of wall retrofitting by applying a locally resonant metamaterial to the wall. The solution enhances sound transmission loss around its fundamental frequency and its most salient harmonic component from a heat pump. Finite element analysis was used to characterize the acoustic behavior of a membrane-based metamaterial unit cell, and preliminary simulations were carried out.