Integration of commercial microspeakers in an acoustic absorbing liner

In this work, the fabrication of an acoustic sound absorbing surface (i.e. liner) made of commercial Visaton™ K16 microspeakers is presented. The acoustic liner is made of a circular surface composed of a 10 cm diameter fix support with 7 embedded microspeakers covering 8.5% of th overall surface. Different electrical connections of the microspeakers using no added electronic circuit are tested and the obtained absorption coefficient is 0.2 close to the natural resonance frequency of the microspeakers. A Negative Impedance Converter is used to electrically compensate the losses occurring in the acoustic liner. The maximum sound absorption is raised to 0.31 using the NIC again close to the natural resonance frequency of the microspeakers with a 7 microspeakers configuration covering 8.5% of the wall surface. The back cavity of the microspeakers is found to slightly move the maximum absorption peak but not to modify the maximum absorption. The influence of the microspeakers density is measured in open circuit configuration. The surface covered by the microspeakers ranges from 2.85% up to 12.35% of the wall surface. The maximum sound absorption ranges then from 0.1 to 0.34.