I suffered the same problem (iPhone randomly muting my voice) and ended up fixing it with this far less technical solution involving a bit of card:

http://www.youtube.com/watch?v=0jhWxYTVx...

It's a bit of a bodge, but it works perfectly.

the problem is in the ic 100 hun percent i make this several times.

I don't really buy the noise cancelation mic issue here, I am a iphone tech at the ifix repair shop, and I have replaced the bottom mic(contained on the click and charge jack) and the top mic, and in most of the cases it fixes the problem for a short period of time before it just comes back and the mic no worky!! Sounds just like whats happening here, turn a screw here and there and the problem seems to be fixed, but then returns, all false positives. That audio IC has to be removed and re-balled and resoldered back onto the board for this problem to go away, so far I have only done 1 wich was successfull. keeping in mind I was re-balling by hand 0.2mm solder balls with a needle, hotair station and a magnifying glass. very intense work, takes about 2-3 hours.

So to what I know this is really the only fix, keeping in mind that sometimes when you "reset all settings" on the phone it can also make the problem go away for a little while, so it's no surprise that turning some screws here and there will also yield such an effect or even replacing the one of the mic's, but the real and only culprit here is the audio codec people!!!

took it to a repair guy and he said it's a software issue which makes sense considering voice memo etc... all work.

There seems to be a fix in iOS 5 that if you go to Setting --> General -->Accessibility --> Hearing and turn on Hearing Aid Mode the problem seems to disappear. At least it did for me and it saved me a ton of money in the process.

On my iPhone, the mic could be re-enabled during a call by pinching the iPhone tightly at about the same point as the noise cancelling mic (next to the headphone jack). This would cause the mic to kick back in for a few seconds after you stopped pinching the device.

Tellingly, directly under the metal shield in that exact location are three press fit connectors for various IC's. I folded a small piece of paper and laid it across the backs of those three connectors. I then re-attached the shield and replaced the back cover. Mic problems seem to be gone for now (crossing fingers). I'm thinking that in some cases, the connector for the noise cancelling mic works a bit loose (or perhaps the sponge used to keep pressure on the connectors compresses somewhat). Time will tell, but right now, it seems to be working again.

My fix was much more low tech...my iPhone apparently had acquired a righteous among of belly button lint in the screen for the mic. I used an old dry toothbrush and gently cleaned out the area and it looks and more importantly, works like new. Sometimes you gotta go low tech first...

Anyway, here the picture showing the location. Basically the standoff is a screw that holds the board to the frame and has a head with an opening to screw into, in this case the cover over all the ribbon connectors has a screw holding it down received by the standoff.

http://cl.ly/3g1Z401o0M3G3l2o3a3V

I also had this issue, and the microphone didn't worked, on receiving and placing calls. Buth using Viber/Voice Notes/Skype/etc worked flawlessly.

What i did,

I cleaned both microphones mesh holes, bottom and the top small hole besides headphone jack (this one was obstructed by grease or dirt, i used a brush and cleaned gentle inside it).

I already had changed the Dock/Microphone flex before this (which didn't fixed the issue).

I unscrew and screw again the top screws, leaving them not so tight, also cleaned the flex connector of the dock, with a soft brush and isopropylic alcohol. (i gave it a full brush all around the iPhone, removing dirt around it.)

After all this and a couple of test call, the issue was gone! :D

Let me know if it worked for you!

Try all the above (clean the small hole and the card trick), and if none of those work, resort to this:

http://www.beijingiphonerepair.com/fix/d...

worked for me. Requires a pretty good open heart surgery of your phone, if your comfortable with that. Use the dissecting guide found on this website to get to that chip. Once you get to it, you have to carefully pry off the EMI shield, one little by little, one side at time and go around a few times.

The tell all symptom for me was when using a hands free headphones, (the mic is in the button part of the headphones and not phone itself) and it still cut out during a call. Sometimes i hear static as well.

Try Going And Reporting It At http://apple.com/feedback And See What We Get, So Dont Forget To Post Your Serial Number On Your Device And Explain Your Issue As Best As Possible

I tried to clean the upper mic as shown in one youtube video and it did not work for me. Then I just went ahead and bought a tiny size 3.5mm Microphone Speaker that is usually used to enhance the voice quality of video recording. This works like a charm and it was just $10 buck at amazon.

I tried all the above and nothing worked. I even sent it to a repair firm who changed the mic and the power button bizzarly - they then said the phone was unrepairable! I rang a guy I found on google - Mike on 01924 262112 and he sorted it within an hour. I cant remember what he said cured it but it wasn't software. I think his company is called iphone repairs direct - really helpful and I can ring my friends again - happy girl :)

I found Mikes site so thought I would share it with you - there is also a landline & mobile number on the site for him www.iphonerepairsdirect.co.uk

Debbie

I have figured it out!

Its caused by a bad simcard connection.

Do this, open the back of the phone. Make call to another phone and put that speaker on. While calling , press down on the back of the circuit board where the sim card lay, right where the clear plastic tab (to remove the battery is) and press down on that. You'll notice that the mic then will work. So put the cardboard precisely there, adjust thickness to get it to work. Good luck!

The method described by Tyler Leeds works for me. My iphone4 microphone problem resolved after I added a few layers of paper between the metal shield and the three connectors undernealth it.

I see alot of these. I fixed two today with this problem. Both were fixed by replacing the dock connector mic assembly. When the mic works on apps and voice memos it is using the top mic. The bottom mic works on calls.

Hi All,

I agree totally with Noel Br - there are loads of 'I've fixed it' and 'totally worked for me' shouts from folks who've had a quick results from the bit of paper od cardboard or paper 'fix', but isn't a fix at all, just a temporary solution to what is essentially a manufacturing defect. The audio IC, as Noel says, is a BGA device, and not really repairable by man-in-the-street, as it requires some specialised kit to achieve. I'm also well hacked off at Apple for their failure to warranty against this kind of issue - it's a result of poor quality control at manufacture. sorry guys, but it has to be said!

Cheers,

Mel

@Craig, are you sure of that because when you open Voice Memos if you blow gently into the bottom mic it registered volume but the top mic doesn't register at all. I've tested that on a number of phones including the one I think is faulty.

I solved mine just today. I had to open up the phone to get to the audio codec chip. Used a small paper tape to glue it down firmly. Now it works perfectly. Follow the link provided above http://www.beijingiphonerepair.com/fix/d... For a clearer understanding

My problem was solved by just resetting the iPhone: push on/off button & home button simultaneously, and microphone was working again. It was as simple as that. - Special thanx to the lady of the Apple store (the guys there didn't know that aparently)..

hey guys,

a great fix that i found out worked way better than paper or cardboard (on the back near the mic cancellation) is blu tac! just put a small amount and it will mould around the area that need to have pressure on it! good luck guys!

Paper didn't work for me:( I'm wondering if they fix it in 6.1 as it is strange it works with other apps but not with gsm calls. And it is too bad that there is no workaround with headset or bluetooth..

In my experience it is due to the cable the connect the dock connector to the logic board. So I have seen a method where people put a piece of cardboard inside on top of the flex cable, but also replacing the dock connector for about $10-15 has always worked for me! You can find a tutorial on how to do it on this website.

Hope This Helped!!

~Nico Plyley

The only way of repairing this is to reball the audio complier IC or replace it we can do this go here

Somebody says:

Okay I did some research and I figure it all out no it's not a hardware or issue or a software issue it's actually kind of simple

There's a new mic and that would be at the tip next to the headphone jack the little hole if there's something covering that hole no sound goes through I have slick wraps so it was being covered I took it off and did a video record test and the audio went through try it for your self when recording a video just tape that hole or put ur figure just to test it out and you will see. Hope this was some useful information.

Update

BUT I SAY:

THE PROBLEM IS THE BASIC (DOWN NEAR TO THE CHARGING JACK) MICROPHONE, OPEN THE BACK COVER OF THE IPHONE AND TAKE OUT THE MICROPHONE CAREFULLY, AND CLEAN THE MICROPHONE COVER FROM THE OUTSIDE AND INSIDE AND CAREFULLY CLEAN UP THE SMALL HOLE OF THE MICROPHONE ITSELF. THIS IS THE ONLY SOLUTION. USE A WOODEN TOOTH CLEANER STICK.