Hi, I'm having a problem where I'm doing a full duplex voice communication. Both the mic & spk are placed in a same chasis (stainless steel casing for industrial application). Once they are fixed into the casing it has feedback noise. I have already put a layer of fibre wool in the casing & also behind the speaker. The feedback noise is still there. I've also tried putting a 0.1uF cap across the speaker. It still doesn't help. What can be done? I've attached my schematic.Thanks.