Apple today released iOS 4.0.1 for both the iPhone and iPod Touch, and as expected, the update includes a change to the way in which Apple calculates the number of bars to display on the iPhone relative to signal strength. Anandtech was quick to download the update and explain the changes, though the chart below is quite self explanatory.
As you can tell, Apple recalibrated the signal strength to signal bar mapping formula quite substantially.
As you can see the old way (top) put far too much weight into the 5th bar of signal. Apple’s new approach not only splits it up more reasonably between the 4th and 5th bar (still non-linearly keeping you in the 5th bar if possible) but also extends the range of the lower bars.