oh.. i think its the power supply and the amplifier... if your amp is a cheap one, you must change to a better branded one.. and also a voltage stabilizer..
i wouldnt recommend d sound supressor if u reli wan a quality sound... look for the reason why the aeroplane sound exist....it might be ur cable are too near to ur alternator... or it can be as simple as not enough grounding... u can try loop a small wire to ur both RC output at ur HU and ground it anywhere at ur car body and u might be surprise tat it was gone...any cable near fuel pumps also can be d reason
I tried posting the pictures here, but to no vail, cant do it....so if you do want to look at the pictures let me know, will send to your email address...please offer your price to me...