Engineered audio in cars

Funny…back in the mid 1970’s turn signal relays were switched over from the really loud “Nack Nock” sound to much quieter ones. When I started driving in the 1980’s I would go to junkyards and pull all the relays out of the old cars. Maybe 1 in 5 still had the old loud ones. I still have a bunch in a drawer and still use them in my 1970 Cutlass. Old cars to me just don’t sound right without them.


You can, but some models are more of a hassle. Some VW/Audi models disable the entire car if the radio is changed, for instance. It’s part of it’s anti-thief system. You need some pin.

Compared to my cheap Toyota Yaris, I just swap the unit and it’s done.

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Curious choice of picture for this post. Can someone explain why this picture was thought to be appropriate?

I believe a lot more sound design (everything design) is coming. It’s what we humans do. Tinker, adjust, change (often driven my a desire to improve). Big underlying issues here, I think, revolving around our sense of “authenticity” and “real.” I suspect that many of the things we consider to be authentic, real, baseline are things our ancestors “contrived” that we inherited as “how things are.”


You can’t always be so sure. The previous generation of the BMW MINI (designed in the 90’s, and which is, I think still being manufactured in some models) has a physical relay in the instrument pack for the indicator. The kicker? The output side’s not electrically connected to anything. It’s soldered down so it stays put. They used a physical relay just to make the sound of a relay. I wouldn’t be at all surprised if that was a common trick, the instrument packs are made by a third party who supply other car manufacturers as well.


Relays really don’t need much current to engage. Even if the alternator’s not generating power, the car just wouldn’t notice the load. No, cars use electronic flashers because it’s cheaper and has become acceptable to customers. Turn signal relays were being disconnected from the signal cluster power supply before LEDs were practical.

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If that’s right it sucks. My last new car was a long time ago, but I’ve always bought them sans radio and installed my own. I’m not a raging audiophile, just a cheap bastard, and every manufacturer charges a fortune for a crap radio.

It’s second declension? I always thought it was fourth.

Could they replace the turn signal sound with a voice saying “Your turn signal is still on” every 10 clicks or so? Would do wonders on the highway.

BB had a weird choice of image for this story btw.

A coworker here is a certified auto mechanic. I forwarded him this, and he laughed his ass off. He said that even the new GM cars, which he works plenty on, use mostly mechanical turn signals. That these “speakers” and “noise cancellation” systems wouldn’t work if you simply switched out car stereos, and people do that on a very regular basis in GM vehicles because it’s so easy to switch them out. Even changing the speakers in the car (also commonly done) would upset the balance and would require some reprogramming, which isn’t done by your standard “radio shop”, and yet, there are zero reports of people thinking their cars are broken after getting a new speaker set and radio put in.

He told me that I need to stop being so gullible and reading sites that fall for easily verifiable bunk.

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On a new episode of Top Gear that aired a week or two ago, they spent some time driving an all-electric Mercedes. The car is so quiet that they included options on the in-car computer to play engine noises over the stereo… there was a bank of a dozen or so different Mercedes models you could pick from.

I find it horribly stupid, but unfortunately no one asked my opinion.

(I think the law mandating that electric cars make more noise is ridiculous too)

my rusted out 1997 subaru certainly did not have active noise cancellation, or mp3 based turnsignal audio. I doubt that my 2005 subaru does either.

I was talking about the traditional generic mechanical turn signal flashers you can still buy at auto parts stores. They don’t work with LED turn signals because they rely on the heat of current flowing to cause the bimetal strip to heat up and “click” to the next position. I know that for a fact, the hard way, by putting LED turn signals on an old-school motorcycle that had one of those in an attempt to get brighter turn signals that used less power (the magnetos on those old motorcycles were so lame that the headlight actually dimmed slightly in time with the turn signal coming on!). I had to swap the bimetal mechanical turn signal flasher out for an electronic one instead.

Many of the newer cars are like my Jeep Wrangler, that uses a CAN bus for all the steering-wheel switch gear that just sends messages to a control computer under the hood to actually turn power on and off to things. Any relays, whether mechanical or electronic, are under the hood (note that it depends on how much current is being pulled as to whether a mechanical relay is cheaper than an electronic relay… for 15 amps to the headlights a mechanical relay is cheaper, but my Jeep uses an electronic one because it modulates the headlights for Canadian daylight running lights via pulse-width modulation and mechanical relays can’t handle that duty cycle). Even the overhead light is controlled by that computer, there’s a widget to plug into the OBDC port that among other things sets parameters in the computer to do different things with the overhead light (like not turn it on when the doors are off, something you do in a Jeep) and if you leave a door open for half an hour or leave the dashboard light switch on for more than that the computer helpfully turns the light out for you to avoid running down the battery. Things like steering wheel radio controls wouldn’t be easy to implement in the cramped confines of a Jeep Wrangler if not for the CAN bus.

Finally: Lion, you’re right that removing the radio won’t cause the car to die (otherwise stereo thieves would be disabling cars left and right when they steal the OEM radios), but most cars since the 2006 model year have had a CAN bus for the dashboard running gear due to a change in the OBD2 requirements that require CAN at the OBD2 port and simply replacing the stereo won’t turn on the amplifiers for the speakers, resulting in a mute car. My Jeep is like that, you have to put in a CAN adapter to tell the Jeep to turn on the rear amp for the subwoofer when using an aftermarket radio, then train the Jeep to recognize that CAN adapter using a strange sequence of switch gear manipulations (basically toggling in binary data like on old-school computers from the 1960’s). The reason why your old school auto mechanic doesn’t know about things like that is because he is like most old school auto mechanics, he is a total electronic ignoramus, and he doesn’t switch out car stereos. He doesn’t see mute cars because car stereo places won’t switch out a radio unless there’s an adapter available for it, or unless it’s an older car that doesn’t need an adapter, and self-install places like Crutchfield publish whether there is an adapter for your car and whether one is needed. Regarding the turn signal flasher, the “click click click” is from a tiny speaker under the dashboard (on my Jeep the same one that goes “ding ding ding!” if you open the door with the key in the ignition) or from a tiny speaker embedded in the “flasher” itself, not from bimetal strips expanding/contracting and causing a relay to flick to the next position. That is true of virtually every modern car, which is why you never hear of people having to change out turn signal flashers anymore – the electronic ones don’t fail the way the old mechanical ones did. Not during the ten-year life of the average car, anyhow. Reducing warranty claims is a goal of all manufacturers now, and with today’s longer warranties, the electronic ones are worth the extra cost to them.

Actually, 1) He does switch out car stereos. And 2) He’s also an EE.

Sure. A relay is a fairly specific component, though - a magnetic coil and a mechanical switch. They’re definitely still in use

My comment above about the MINI instrument pack isn’t guesswork. I was an EE involved in the validation of that part before the cars got built.

I’m sure that electric cars and hybrids will soon be required to produce artificial engine noise as a warning to pedestrians and other drivers. Maybe engine (and other) noises will be easily downloadable and changeable, like ringtones.

I dunno. To me, the former owner of a Series III Jaguar XJ6, that trick sounds exactly like something one would find in a car bearing the legacy of British Leyland and Rover Group.

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I have a 2001 chevy if I forget to turn off the blinker it will beep loudly through the stereo speakers after a few minutes.

This. Emphasis on “other.” I don’t see the need to skeuemorphize the “engine noise” as traditional “vroom-vroom” in the first place. Since we’re all aware it’s just for show, I propose the standard default should be the Jetsons’ noise.


Buddy of mine here at work drives a first-generation Honda Insight (the one with the fender skirts). If ever a car looked like it should make the Jetson noise, it’d be that one.

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My cars tend to be imaginary or broken.