The structure that introducing mechanical impedance plate and
Helmholtz resonators into the traditional MPP is proposed to
enhance sound absorption performance at low frequencies. The
two methods of acoustic electric analogy and impedance transfer
method are adopted to derive the acoustic impedance and the
sound absorption coefficient of the whole composite structure is
calculated. The sound absorption mechanism is the interaction
result of mechanical resonance and cavity resonance. The
mechanical resonant frequency and Helmholtz resonant frequency
are set in low frequencies. Low frequency sound penetrates the
micro perforated plate and energy is absorbed effectively.
The experimental results exhibit good agreement with the theoretical