xperia u cracking sound

[Manu1]

whenever u answer a call i get this noise thing it comes like every 10 secs or so is it a problem with my phone or my network?

[Uliwooly]

it could be a network issue, or an old SIM card

[Sam]

Have you noticed if this is happening in just one area or does it not matter where you are when you place the call?

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[Manu1]

old sim indeed

[Manu1]

not just one but many places

[_alexdon_]

Either replace your SIM or take the phone to a sony center for a quick check.