How to improve the "Pi-pa" noise when make a call

When two bluetooth devices conncting , for example , phone with bluetooth function and bluetooth earphone. when making a call , there seems a bit "Pi-Pa" background noise from earphone . it seems worse when both devices are a bit away. how to debug it ? Our BT chipset is CSR BC4. thanks

Looking forward to your reply. thanks

I think the noise is related to the bluetooth antenna efficiency , cause the BER is high . I think you can improve the bluetooth antenna performance .

Best Regards !

thanks for your suggestion , i will try on antenna .

but i searched this issue on the web , found some earphones vendors declared their eraphones are with anti-noise feature , i wonder if it's related to the chipset's DSP , maybe others. wish you give some suggestion, thanks