some MTK phone speech sound noisy interference

[KLiFFF]

if the anntenna is top of the phone, and the microphone is in the bottom, the voice sounds quality is good.
if the antenna and the microphone at the bottom of the phone is bad and noisy speech, and cut off the end of words.
if I remove the microphone from his seat, and 1-2 centimeter will remove from the antenna, then the sound quality is good, no noise and interference.
anybody know why wrong the sound quality in some phone? is it a chipset problem? and what is the solution?
example phone: E56 dual sim, V903 dual sim tv wifi, E66 dual sim

[AVATOR~BOX]

We can edit the mobile audio with super doctor box