An Effective Noise Attenuation System for Mid-range Frequency.

Purpose: Development a new combined material, nanomembrane and melamine foam, for noise attenuation at mid-range frequency to reduce noise inside an airplane cabin. Methods: To be able to investigate how acoustic properties of acoustic foams are affected by nanomaterials, a new type of Helmholtz resonator based on a combination melamine foam and nanomembranes is proposed. Its performance was evaluated experimentally based on ASTM C384 and ASTM C522. Results: The Helmholtz resonator based on an association of nanomembranes doped with carbon nanotubes and melamine foams provided an effective sound absorption coefficient peak (α), ranging from 0.94 to 0.99, in the range of 1200–1600 Hz, a drastic shift from the high frequency range (5500–6000 Hz) commonly detected for melamine foam. The new system sound absorption peak performance at mid-range frequencies (1200–1600 Hz) was obtained with an increase in thickness between 0.05 and 0.09%, a virtual no weight addition to the soundproof material. Moreover, the analytical model based on Langmuir air flow resistivity and the Delany–Bazley equations captured the experimental trend with accuracy. Conclusion: The new material proposed is a valuable option for noise attenuation inside airplane cabin, in special, regional jets. [ABSTRACT FROM AUTHOR]