On Alternator Whine, A Noise That Messes Up In-Car AUX Ports | iLounge Backstage


On Alternator Whine, A Noise That Messes Up In-Car AUX Ports

A couple of weeks ago, we reviewed Griffin’s Noise-Reducing Audio Cable, a special auxiliary audio cable designed to fight “alternator whine,” a high-pitched sound that appears when certain iPod or iPhone accessories are connected to the auxiliary (AUX) input ports in certain cars. Since AUX ports should deliver optimal sound quality when properly connected to Apple’s devices—unlike comparatively noisy FM transmitters and cassette tape adapters—users should expect to have clean a connection as possible between iPod or iPhone and the car, without interference. Yet that’s not the case, at least with some accessories, and thus this particular sound joined an increasing list of potential in-car audio issues users have experienced, including:

* Perceptible hard drive whirring sounds in the headphone ports of certain, older iPods.
* Perceptible but quiet signaling beeps and bloops in the headphone and Dock Connector ports of certain iPods, apparently related to changing menus and perhaps the “clicker” features of some models.
* Loud screeching noises (known as TDMA interference) emitted wirelessly by original iPhones and iPhone 3Gs operating in EDGE mode, correlated with any use of the cell phone, EDGE data, or occasional status checks between the phones and nearby cell towers.
* Quieter, higher, pitched noises emitted wirelessly by iPhone 3Gs operating in 3G mode, correlated with cell phone and data use.
* A high-pitched “alternator whine” related to an electrical ground loop, which starts as a perceptible but quiet whistle and appears to change pitch when the vehicle accelerates.

In our review, we temporarily put aside the question of whether car makers or accessory makers were to blame for this noise. After testing our vehicle’s AUX port with a custom-built dual 47 k ohm, impedance-matched loading resistor cable, the answer turns out to be “accessory makers.” By using filters to remove the high sound frequencies the whine falls within, the Griffin cable solves a problem that various accessory makers appear to have created themselves with engineering that—depending on one’s perspective, and the specific company in question—is either sloppy, deliberately bad, or deliberately good. In any case, the cost to affected users is $20, and the need to use a long, bulky cable with a big filtering box in the center.

Viewed most charitably, or under the “deliberately good engineering” theory, in-car accessory makers should make engineering decisions that optimize an iPod’s sound output for the maximum number of cars, thereby enabling most users to avoid additional costs and suffering from noticeably reduced audio quality for the sake of insuring compatibility with a small fraction of problem vehicles. A company might argue that a minority of users will hear alternator whine because the accessory has been built to produce clean sound in the majority of cars; the solution for the minority is an additional cable. Assuming that the cost of making the main accessory work better with all cars is relatively high, or the cost of increasing compatibility for all is to decrease the sound quality for the majority, this might just be acceptable.

Less charitably, alternator whine from a ground loop could signal sloppy engineering—something that could be fixed very easily by a small change to the accessory—or worse yet, that the manufacturer is deliberately creating a sound problem that its own parts are required to solve. It’s bad enough having to pay through the nose for iPod and iPhone accessories as is; a Monster Cable-like system of separately-sold magical “noise-cleaning” cables and chargers for specific cars would be a complete nightmare.

Our belief is that alternator whine isn’t being created intentionally by accessory makers, any more than Apple wanted to create the TDMA noises that have made iPhones less than fun to use in many cars. But as we’ve suggested to accessory companies who design these in-car products, it’s time to do testing and engineering for the most popular car makes out there, with a focus on making the best possible sound for the largest group of users. We were told by one company that it had for years been experiencing ground loop issues with Toyota vehicles, a reason why our Toyota Highlander test vehicle exhibited the alternator noise that Griffin’s cable can remove. But Toyota is the world’s largest seller of cars, and currently commands 16% of U.S. market share—a huge percentage for a single company. If something doesn’t sound right in this vehicle, there are a lot of others out there that it won’t sound right in, either.

In any case, the alternator whine isn’t an earth-shattering issue; your car might not be affected by the noise, and even if it is, you may never have noticed it, or even thought to consider buying something to remove it. But going forward, we are inclined to make it one of a few types of noises that our reviews will expect makers of iPod and iPhone accessories to be avoiding in their auxiliary audio devices—after all, can an accessory truly claim to properly “work with iPhones” or be “made for iPods” if it adds distortion to their audio signals? And should users be pushed to spend an additional $20 to correct what could be fixed by a manufacturer at the source?

We think not. But perhaps you, readers, have another take on this subject?

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Interesting article, but I’m confused. What are you labeling “accessories”? I put a Sony CDX-GTX 330 radio/cd player with an auxiliary input in my car and run my touch through it without any problems. Is the radio/cd the accessory or the cable I got to connect the two?

Posted by Larry Steudle on March 4, 2009 at 6:10 PM (CST)


I believe it’s mostly the fault of the auto manufacturer.

In my own personal example.  We had a 2005 Nissan Sentra.  The standard stereo unit had an AUX input (3.5mm stereo jack).

Multiple iPods, and multiple cables never ever caused a problem.
We recently got a Kia Spectra and the problem exists.

After taking it to the dealer,  they compared with many other Kias in the showroom and every single one of them had the problem.  Regardless of trying various iPods and cables.

The problem is usually only evident when using a charger plugged into the 12v adaptor.

A ground loop is created, most likely due to in-proper earthing of the stereo unit,  or the 12v adaptor.

Ground the vehicle and it’s powered accessories properly,  and the problem will be gone.  Auto manufacturers,  make your cars properly !!

Posted by Matt on September 30, 2009 at 7:16 PM (CDT)


Totally agree! Accessory manufacturers are to blame.
My iPhone 3GS worked perfectly with a cheap AUX cable - on or off charge. There was no noise. I recently bought the (over priced) TomTom iPhone Car Kit. It has a charger but no AUX cable so I used the same one I had only to get an incredible amount of alternator whine. It’s horrible and it’s completely the fault of the TomTom accessory. When I unplug the TomTom power source, it’s gone. Problem is, the TomTom Car Kit needs power to run it’s included GPS enhancement. The kit cost me AU$160. ...A $20 (probably AU$30) cable on top? I might ask for a refund.

Posted by Nashstar on January 9, 2010 at 1:51 AM (CST)


The problem originates in the car. Only if I plug in a (Belkin) car charger and the AUX cable at the same time do I get the alternator whine. It would be nice if the TomTom car kit fixed the problem, but that would add to its cost any perhaps they were unaware of the problem when they designed it.

Posted by Davomate on February 24, 2010 at 6:39 PM (CST)


I agree with Nashstar’s post.
It is the Accessory manufacturers.

I too just purchased the TOMTOM car kit.

I have to plug the aux jack direct into the iphone because if I plug into the car kit I get all kinds of noise.

If I have the phone in the car kit but use the factory iphone headset jack the sound works the same but no noise.

120 bucks and poor filtering….doesnt surprise me these days.

Posted by Greg Nauman on May 13, 2010 at 2:13 PM (CDT)


I recently had this problem on my 2000 Honda Accord; connecting the audio ground and power ground in my iPod cable reduced the problem slightly but did not eliminate it. Last night I cracked open the center console and grounded the 12v cigarette plug directly to a bolt on the chassis; this all but eliminated any alternator noise.

Now I can’t hear the whine unless I pause the music and crank up my amplifier past the point of even the least comfortable listening level. However, circuit activity in the iPod itself still generates noise. This is to be expected when so much electronics is crammed into one pocket-sized package.

However, the point is that this is not a product of poor accessory design. Alternator whine is the improper grounding of car components. If the alternator is properly isolated from the electrical system, how could an accessory, no matter how improperly wired, somehow bring the alternator into the circuit?

Posted by Ben on March 12, 2011 at 10:28 PM (CST)


I am a licensed amatuer radio operator and I’m NOT the first “HAM” to point the finger for ignition and alternator noise right at the auto manufacturers.  CHEAP is how they make electrical systems in cars % trucks to keep their costs down.  KNOWING that police and fire vehicles come from the factory built as communication platforms—- it should be done for all American vehicles leaving the factories. “Bonding”, filtering, and isolating a new vehicle takes the consumer many many hours and is a royal pain.

Posted by Ron on October 22, 2011 at 8:38 PM (CDT)

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