These go to eleven...

April 24, 2007 11:13 PM

Does listening to an MP3 player at a higher volume significantly increase the rate at which its battery drains?

I suppose there are two (elementary) ways of thinking about this: A basic volume dial is a potentiometer—the signal is at full strength from its source, and you're merely adding resistance when you "turn it down."

But, I have no idea how the volume controls on either say, an ipod or my Creative Zen Vision work, given that it is accessed digitally. For these players, is it altering the strength of the output signal at the point where it is being generated? Or is it a digital control to an analog potentiometer? (I also know little about the nature of a simple stereo signal itself...)

Even if it were, would the difference in battery life be at all significant? (Would I be able to eek another 20 minutes out of my player by turning it on its lowest volume and using my car's amp to push it out at a "reasonable volume"?)

Much obliged!

posted by disillusioned to technology (8 comments total)

Hell, *are* you still spending the energy if the pot has limited the output further downstream by resisting?

I really don't know anything about electrical engineering stuffs...
posted by disillusioned at 11:17 PM on April 24, 2007

Well, at the very least, you're probably kicking the device out of some sort of sleep mode. Most MP3 players go into a power conservation mode when they're not being interacted with through their interfaces. When you change the volume digitally, you're probably "waking it up." If, on the other hand, the volume is a real analog pot, you're right in assuming that the power consumption remains constant.
posted by fvox13 at 11:20 PM on April 24, 2007

Well, relatively constant...
posted by fvox13 at 11:20 PM on April 24, 2007

It doesn't matter how the volume control works; louder sound means more electricity, and more electricity means faster battery drain. The energy has to come from somewhere. The device can't pull it out of its ass.

The only way that differing volumes would not increase the battery drain is if the volume was controlled by a resistor after the amplifier. In this case, some of the current would get converted to heat if the volume was anywhere but all the way up. However, no portable audio player works this way because it would be stupid.

Now, the effect on battery life will not be exactly proportional because many other parts of the device also consume power, and do so at a rate unaffected by the volume setting. That is, doubling the volume will not halve battery life.
posted by kindall at 11:21 PM on April 24, 2007

Yes, you will get longer life by turning down the volume. Lower volume = moving the speaker cones less distance = less energy output.

However how much longer depends on the nature of your MP3 player. Hard drive based players spend a small amount of their available power moving speaker cones and more spinning hard drives, so you'll notice very little difference.

solid state players like a nano use less power to access the music, but still have a fair amount to light and display the screen. However you will get noticeable results.

In something like a Shuffle a significant portion of its power budget is sent down the headphone jack (no display to power) so you'll get the most bang for your volt from something along those lines.

That said, if you sit your volume out to an amp at 1% you will get horribly distorted audio and it probably won't be worth the extra listening time.

As an aside, tests have shown that even the codec you use (MP3, AAC, WMA, etc) can have a noticeable effect on battery life since some take more horsepower to decode than others,.
posted by Ookseer at 11:30 PM on April 24, 2007

If you're really curious, it'd be pretty simple to set up an experiment. Charge the iPod up and then let it play until it's dead. Repeat with different volume settings.

If you're inclined to believe us without manufacturing your own proof, though, the answer is yes. Greater volume = more power consumption.
posted by chrisamiller at 12:00 AM on April 25, 2007

I have some anecdotal experience, since I've usually got one of two pairs of 'phones plugged into my iPod. I haven't witnessed noticeable difference in battery life whether I've got the inefficient (requiring more power to reach a given volume) headphones or very efficient earphones.

The display light and high bit rate audio files (which requires more frequent disk accesses) do a lot more to shorten battery life than the volume control does (On a solid-state unit like the iPod Nano, the power consumed of data access is comparatively negligible). Nothing whacks the battery like playing videos, which means continuous backlight, continuous disk read and high CPU consumption. Apple's published specs for the iPod Video 30GB tell you to expect 14 hours of continuous audio playback and 3.5 hours of continuous video. Amplifier output levels aren't considered significant enough to be calculated as variable.
posted by ardgedee at 3:27 AM on April 25, 2007

Since you're talking about using it in your car, it makes sense to offload as much of the work as possible. Put it out at a low volume, and let your car stereo amp deal with any changes. Soft to loud in earphones is a difference, but not that big of one.
posted by Mr. Gunn at 5:37 AM on April 25, 2007