Serial space-folded acoustic metamaterials for hairdryer noise reduction

Existing noise control methods for hairdryers typically require modifications to the internal structure or impeller, whereas conventional silencers may increase device volume and reduce ventilation efficiency. To address these limitations, we propose a serial space-folded acoustic metamaterial (SSFAM) for noise control in hairdryers. The acoustic performance of the SSFAM was analyzed using the finite element method (FEM). The results show that the proposed structure achieves broadband sound insulation exceeding 5 dB over the frequency range of 1353 Hz − 2027 Hz. The predicted resonance frequencies and overall STL trends were compared with impedance-tube measurements, showing similar resonance frequencies and overall spectral trends. An indirect aeroacoustic solution method was adopted, in which the computational fluid dynamics results were mapped onto the acoustic mesh to analyze the sound field characteristics of the hairdryer with and without the SSFAM. After the SSFAM was installed, the pronounced first shaft-order component near 1574 Hz was effectively suppressed, and the 1400–2000 Hz band sound pressure level was markedly reduced. In the prototype test, the mean A-weighted equivalent continuous sound level ( L Aeq ) of the hairdryer, obtained from three repeated measurements, decreased from 83.3 dBA to 79.2 dBA after the SSFAM was installed. These results indicate that the proposed method can effectively attenuate noise within the 1353–2027 Hz frequency range, providing a viable solution for noise control in small-scale aerodynamic devices.