Apple has issued an official statement about the iPhone 4 antenna issue, attributing the problem to a mistake in the formula that calculates the number of bars to display. Apple says that a software update will be available "within a few weeks" that will correct the issue, not only for the iPhone 4, but also the 3GS and 3G.

"To start with, gripping almost any mobile phone in certain ways will reduce its reception by 1 or more bars. This is true of iPhone 4, iPhone 3GS, as well as many Droid, Nokia and RIM phones. But some users have reported that iPhone 4 can drop 4 or 5 bars when tightly held in a way which covers the black strip in the lower left corner of the metal band," wrote Apple. "This is a far bigger drop than normal, and as a result some have accused the iPhone 4 of having a faulty antenna design."

Simultaneously, Apple says it has gotten hundreds of e-mails saying that the iPhone 4 reception is better than the 3GS—this proved to be true in many cases for us during our testing of the iPhone 4, even though we could reliably reproduce the signal dropping problem.

Apple's explanation is that the iPhone—including 3G and 3GS—has always displayed too many bars given a certain level of signal strength. The company plans to adopt AT&T's recommended formula instead as part of its software update and has gone back to re-test everything.

"Upon investigation, we were stunned to find that the formula we use to calculate how many bars of signal strength to display is totally wrong. Our formula, in many instances, mistakenly displays 2 more bars than it should for a given signal strength," wrote Apple. "Users observing a drop of several bars when they grip their iPhone in a certain way are most likely in an area with very weak signal strength, but they don't know it because we are erroneously displaying 4 or 5 bars. Their big drop in bars is because their high bars were never real in the first place."

The bar issue can be a complicated one—we wrote a feature on the disconnect between bars and cell signal back in 2008 that still applies today—but it's important to note that there is no industry standard for how signal translates into the bar display. Manufacturers generally make up their own scale and assign signal values to each bar, taking into consideration noise or interference that may be occurring in your environment.

Apple's explanation that it always used too many bars—especially for users in low signal areas—sounds like the company wasn't doing enough to account for interference or the other variables that come with overall signal strength, resident Ars programmer and former GSM/RF Engineer Clint Ecker told us. At the same time, the explanation gives us some pause—why has this problem in bar calculation only come up now and not previously if it has been in practice for two years already? Furthermore, Apple's statement doesn't address the very real issue of handsets losing up to 24dB of signal strength from simple bridging two of the phone's antennas—which is either a serious hardware flaw or another error in how the phone detunes its antennas.

Apple didn't give enough information to really know what's going on, but we cautiously await this software update that will claim to fix everything.

Update: Readers have reminded us that Apple actually bumped up its bar display as part of the release of iPhone OS 2.1, casting further doubt on Apple's apparent stunned-ness at the situation. "Improved accuracy of the 3G signal strength display" was one of the main listed features when 2.1 came out in September of 2008.