This is obnoxious

 I keep my headphones as quiet as possible, both for my hearing and for those around me, but I'd find this really annoying:

Amid growing fears that listeners could cause irreversible damage to their hearing - the highest setting is as loud as a chainsaw - Apple is developing an automatic volume control.

A new patent reveals that the next iPods and iPhones could automatically calculate how long a person has been listening and at what volume, before gradually reducing the sound level.

The device will also calculate the amount of "quiet time" between when the iPod is turned off and when it is restarted, allowing the volume to be increased again to a safe level.

I suppose this could get them out of lawsuits, though. If an iPod goes that loud, listening to it at that volume might constitute using the product as it was intended, making Apple liable. Different recordings are mastered to different volumes, so to work properly the device will have to measure the output volume, not just the position of the volume knob.

I'd like a CD player or iPod that has a different kind of automatic volume control: One that matches the headphone output to the surrounding noise; it would need a microphone. That way, it would turn itself up when subway noise got ridiculous, but it wouldn't inflict unnecessary noise on your eardrums once everything quieted down. It would also act as a compressor, bringing up the quiet parts of songs so you can hear them without making the loud parts even louder.*

I'd like a computer to substitute for me fiddling with the volume my whole trip home. I don't need a computer to tell me it's loud.

*On a total side note, another thing I'd like to see is separate masters for home stereos vs. headphones (it's Christmas time, so I'm all gimme-gimme-gimme). iPod listeners want the crap compressed out of their music (I'm talking audio compression, not computer file compression) for this very purpose -- a wide dynamic range means that in order to hear quiet parts through the din, you have to turn the volume up, which in turn kills your ears when everything gets loud again. By contrast, a home stereo has little else to compete with, so there's no need to sacrifice dynamic range for an all-the-time loud recording. This would be a nice ceasefire to the loudness wars.