Some iPods exhibit a "static" noise -- audible through headphones -- when the iPod is accessing its hard drive. (In general, the better the headphones, the more apparent the static.
The issue is clearly not affecting all new iPods, and may in fact only be affecting a very small number of users. However, there have been enough reports that it appears this is more than an isolated issue.
Unfortunately, it's difficult to accurately assess how many iPods actually exhibit this behavior, as it's only observable in specific circumstances: in a quiet environment (or using headphones that isolate external sound), with the iPod hard drive spinning, and using headphones with high efficiency and good reproduction of detail. In noisy environments, the static may be masked by external noise. Similarly, whereas headphones with significant isolation, high efficiency, and detailed resolution -- such as the Shure E2c or E3c or Etymotic ER-6 or ER-4P -- make it very easy to hear such static, many other headphones may not reveal the problem. Finally, even in the "ideal" circumstances, users with less than perfect hearing may have a hard time detecting this noise, which, by all accounts, isn't loud.
The issue appears to be isolated to the iPod's headphone jack; the dock connector, which provides a line-level audio signal, does not exhibit the problem. However, during testing with a user whose iPod has this problem, we've concluded that it's most likely not a feedback issue between the hard drive and the iPod's actual headphone jack: When using the iPod in FireWire disk mode with headphones connected, the static is not present, indicating the noise is somehow contained in the audio signal, not the headphone jack itself.
That being said, some users have speculated that the issue is simply one of grounding: on some iPods, the headphone jack is too "flush" and some headphone plugs are thus coming in contact with the iPod's metal case. We haven't been able to test/verify this, as we don't have any iPods that exhibit the problem.
MacFixIt reader Brent Green confirms the assessment that better headphones make the static noise more apparent, and adds that the noise does not scale with volume -- in other words, the noise is audible even at low volume levels:
"I also have this problem with a new 40GB unit. I did not think I had it at first, but when I got better headphones it was clearly there. Basically the pack-in headphones don't reveal the problem as much.
"Also, I could easily verify that my headphone plug was not coming into contact with the iPods metal case. I could easily see the white plastic around the headphone jack. Some are speculating that the static occurs when the jack touches the metal. Not so in my experience.
"I have noticed that the intensity of the sound does not scale with volume on the iPod. In fact, you can easily turn the volume all the way down and still hear the noise quite easily. It appears to be at a constant level, and independent of the iPods volume."
"I downloaded a little spectrum analyzer program from the Internet and ran the audio output from each iPod into the line-in on my PC's sound card. With this software I could clearly see the bump in noise intensity when the hard drive would cache the iPod's RAM. I could also measure the difference between the two iPods. While playing music with the volume all the way down, I would typically register ~-80dB when the hard drive was inactive. With the first iPod, I would get bumps to -50dB when the hard drive was active. With the second, the sound would only bump to ~-65dB.
"I could also visually see a difference in the frequencies measured. The first unit would get a bump at 2.5kHz when the hard drive first started up. There was a general elevation between 2.5kHz and 8kHz during the entire hard drive access. When the drive shut down, there would be a spike at 8kHz. With the second unit, there was no initial spike of any kind. Overall, sound intensity would still increase between 2.5 and 8kHz, but less so than the other unit. Then at the end of the hard drive access, there would again be a spike at 8kHz.
"All of this really proves nothing new, except that this really isn't a black and white issue. Rather than iPods being either affected or not, it seems that there may be a range in severity of the problem. Due to this nature, it is possible that the problem is common, with some iPods being 'better' and therefore less bothersome."
Make sure your firmware is up to date Several readers have been able to eliminate the unwanted static noise by updating to the latest version of the iPod firmware available for their model.
Check the Apple iPod Updater page for the latest release.
Noise appears sensitive to pressure After as little as two weeks of use some iPods develop heavily distorted sound with extreme sensitivity to touch.
Irakli Loladze thinks he has found the reason behind the problem:
"My silver iPod mini after two weeks of gentle use started to make horrible static noises. Any pressure, as small as thumb pressure anywhere on iPod mini, would make horrific sounds to come back. Resetting iPod did not help.
"I was just curious what caused such unbelievable distortion. I carefully disassembled by iPod. Then I started to play the iPod and disconnected the wheel, then the hard drive, but my iPod was still playing (out of 25 min flash memory) and still distorting sound.
"Eventually, I narrowed the problem to a small little part that contains the headphone jack and the hold switch.
"This small part attaches to the main iPod board only via a small black connector. This is an Apple oversight!
"The small part with the headphone jack attaches via screws to the aluminum case, but does not screw to the main board. Because of this any pressure on iPod case, dock connector, or simply plugging in and out headphones, creates tension between the small part and the main board.
"Since only the black connector sits between these two parts, it wears out. What is even worse is that the black connector is attached to the main board via ten very fragile copper pins that stick out of the main board. With regular use, contacts get loose and slightest pressure on iPod creates nasty squeaky static type noises killing all the joy the iPod brings. [...]
"To rely on ten tiny fragile pins is just plain silly. Using inflexible black connector is puzzling, because in the current design the battery, hard drive, wheal, and screen all use flexible cables.
"Apple needs to change iPod mini's design ASAP and attach 'the headphone jack/hold switch part' to the Main Board via a flexible cable.NOTE: You should never take apart your iPod. Doing so will void the one-year limited warranty.
Plug/unplug less often Some users have found that minimizing the number of times they plug in/out headphones and not pushing harsh pressure on the mini's case reduces the incidence of sound distortion.
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