How to improve poor audio with SIM900?

Official Hardware Retired GSM Shield
1

hi,
my SIM900 board works fine but the audio quality is bad, i.e. during phone calls there is a loud background noise of some kHz.
What is the source of this noise and how can it be suppressed?

SupArdu

2

Hello,
I have had similar experience with SIM900. I use a shielded cable to connect microphone, about 1 meter long. If I move it around in different positions, the noise may go away.

I presently use a SIM5215E 3G shield and the audio quality is much better.