Well I have been suffering with low in-call volume for a while now. This problem seemed to exist for me since the last ICS update. I was hoping JB may have fixed it but it didn't. I tried volume + and many of the other potential fixes. Nothing seemed to help. I was thinking of getting rode of the One X. Then I recalled reading a post on here or over on XDA, can't remember, about cleaning the tiny speaker grill holes with a soft tooth brush. At the time thought, nah! My phone is really clean, if those holes where clogged I would be able to see it. So I dismissed that idea out right. So here I was weeks later and the volume is no better. If I'm in a quiet room its manageable but any ambient noise at all and hearing the caller was a real struggle. Last night I was browsing the forums to see if there had been any fixes for the low volume lately. Nothing, so I thought I had nothing to lose and got a soft toothbrush and gently scrubbed over the speaker holes. I wasn't expecting any difference because they looked perfectly clean to me. WoW! What a difference. I can't believe how much difference that has really made. I have now uninstalled the volume + and have had to turn down the volume. So to the guy who first suggested this fix, I apologise for dismissing the idea all those weeks ago and thanks to you I'm no longer thinking of getting rid of my trusty One X.