How can I make a diy anechoic chamber?
26 % Nacl solution has a maximum conductivity of 244000 mS/cm.
The skin depth = sqrt (2/ (mu sigma omega)) = 1cm where attention of E field is 1/2.73
10 dB which implies attentiation of electric field by 1/10^0.25

Thus length required = skin depth * ln(10^0.25)) = 0.6 cm

Thus a saltwater layer which is 3 mm in thickness would provide a reflection isolation of 10 dB for an anechoic chamber.