Experimental investigation of the effect of moisture on the acoustic properties of lightweight substrates used in green envelopes

Substrates are used in green walls and roofs to supply air water the roots of growing plants. These substrates porous with micropores which store macropores facilitate drainage entry. Effect moisture on acoustic absorption is studied for two lightweight substrates: coir dust perlite. Measurement dry moistened conducted evaluate their effective speed sound, attenuation, characteristic impedance, compressibility density between 100 Hz 1000 using an impedance tube three microphone-two load method. these quantities found depend strongly upon interaction substrate particles at microscale. Performance rigid-frame limp frame models evaluated when applied characterization substrates. Finally, sound layers composite plant-substrate samples analyzed different contents.