When I stream audio from my iPhone 4 into my Ford Sync audio system over bluetooth, the audio quality is excellent. However, if I plug in a USB cable to get access to the hands-free features, then the audio quality degrades almost immediately. Sound comes out with "hissing" sounds, pops and cracks. This is even more noticeable when listening to spoken word or podcasts.

I have tried different USB cables and have verified that the same audio files do not play with the same defects thru the iPhone's speakers when using headphones. Also, the same files played over my Mac sound just fine. Any pointers would be appreciated. If you are experiencing this same problem with your Ford Sync system, please add a comment to know that at least I am not the only one experiencing this issue. Thanks.

  • 4
    Regardless of the resolution, you should certainly report the issue to Ford's customer service. They need to be aware that their customers are having this problem.
    – user9290
    Sep 27, 2011 at 12:41
  • Tweet them @FordCustService
    – EmmEff
    Sep 28, 2011 at 1:52

3 Answers 3


I read a post about this before on the apple discussions board. The upshot of it is there doesn't seem to be a permanent fix. However, people have provided several workarounds of which some work for some people but none seem to work for everyone. Here's a few things to try.

  • Leave iPhone in Airplane mode while connected
  • Turn off WiFi on the iPhone
  • Turn off 3G on the iPhone
  • Connect the cable while the device and stereo are off, then turn both on
  • Rebooting the iPhone

I can't say from personal experience whether any of these actually work but anecdotal evidence from peoples experience in the thread linked to above would suggest they may. I think it may be a hardware design issue that is probably due to interference from the USB cable when it's connected but many people on that thread say that it only started when they updated their iPhone 4 to iOS 4.1. If you're on that version you could try updating to the latest version of the iOS software. You could also wait until Apple release iOS 5 which is likely to be October 4th 2011 as they may have fixed it.

  • I followed your suggestion of connecting the cable when the iPhone and car stereo were off, then turning both of them on. I tried it only once and it actually worked. I would like to try this a few more times to see if it works every time. Sep 27, 2011 at 18:16
  • 1
    I repeated the process of turning the car stereo off before connecting the iPhone and it seems to be working consistently now. Before doing this, I would keep the car stereo on at all times; now all I do is turn it off before leaving the car. Not perfect, but it seems to be working. Not sure about the other suggestions on your list, but at least this one works so far. I will mark your answer as correct. Thanks for referring me to the Apple discussion. It's good to know I am not the only one! Sep 30, 2011 at 17:53

I found a solution.

When you connect to your car using USB it sends the music files to your car stereo and the car system processing them. It's not like AUX connection when the sound just goes to your stereo and plays through the speakers.

If you changed the options for individual tracks in your iTunes library, the car stereo receives the files with different settings such as "volume adjustments" and "equalizers". This causes your stereo to process all the files incorrectly and messes up the sound quality, corrupts the bass, and creates cracks or hiss when it plays.

Go to your iTunes library, list all your tracks and highlight them all by pressing "Command+A" on Mac or "Ctrl+A" on PC. Then right click and select "Get Info". In the pop-up go to Options and adjust the volume to "none". Then, in the "equalizer", pick "None". It will bring all the songs to the original settings but your car stereo won't have any problems when you connect through USB. The sound becomes clear and even better than AUX connection.



Those symptoms sound like the result of over-amplification of the audio signal. I get the same result on my iPhone 4 when I have my car audio turned up, but the iPhone's internal volume not maxed. If I reverse that and max the internal volume (turning the car audio volume down to compensate), the amount of cracking/popping/hissing goes down substantially.

My experience is with using the headphone jack, though, not USB. I'm not sure if you would see the same effect there.

  • I do not use the headphone jack at all (since both my car and iPhone have both Bluetooth and USB). When using Ford Sync, the iPhone automatically raises the iPod app's volume all the way up to its maximum value. So I am in fact using the car/iPhone volume levels as you suggest and I still get the hisses, cracks and pops. It is noticeable regardless of volume. Sep 27, 2011 at 18:22

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