The Truth About Active Sound
Earlier this week, we [linked](https://www.motoringfile.com/2015/01/27/car-purists-vs-active-sound/) to an [article](http://www.washingtonpost.com/business/economy/americas-best-selling-cars-and-trucks-are-built-on-lies-the-rise-of-fake-engine-noise/2015/01/21/6db09a10-a0ba-11e4-b146-577832eafcb4_story.html?tid=pm_pop) from the [Washington Post](www.washingtonpost.com) describing how car enthusiasts feel about technology-generated engine sounds. Our takeaway was that Active Sound is a necessary evil given the advances made in fuel efficiency (e.g. displacement on demand) and safety. Since I have not had the chance to exchange with an engineer from MINI about this technology, I’m the first to admit that my knowledge on the topic is very limited. With that in mind, and thanks to a detailed anonymous tip from a [SME](http://en.wikipedia.org/wiki/Subject-matter_expert), we’ve decided to demystify the inner workings of Active Sound. In short, it is not evil and has nothing to do with fake engine noise.
Very often and across various industries, observers, enthusiasts or mis-informed journalists (kind of paradoxical if you ask me) consider new technologies such as Active Sound as black sorcery. It’s change for the sake of change and tends to ruin the driving experience, or as some of MotoringFile commenters like to say, “it ruins the brand.” But from what we gather, it appears that the notion that car manufacturers are using engine recordings and pumping them into the cabin is quite misguided.
To make a vehicle sound “sporty,” car companies have historically employed a variety of design and engineering techniques that can lead to undesirable cabin noises. Traditional methods to solve this problem involve [balance shafts](http://en.wikipedia.org/wiki/Balance_shaft), active exhaust and induction tubing. Since this process consumes significant engineering and financial resources, does it really matter if the ideal sound is electronically achieved rather than mechanically? We think not.
Manufacturers of car audio products such as [Harman Kardon](http://www.harmankardon.com/estore/hk/us/index.jsp) dedicate massive R&D efforts into noise management (e.g. cancellation, enhancement). In fact, they partner with car companies early in the development cycle of a new vehicle to create the best cabin experience possible. It involves analyzing the engine sound at all RPMs and looking for specific frequencies (harmonics) that are deficient. Engineers then adjust these frequencies in very subtle amounts to achieve a smooth sound across the RPM band.
Thousands of measurements are recorded in each seat of the car. In cases where a frequency is deficient, an amplifier generates a waveform that is similar to a [sine wave](http://en.wikipedia.org/wiki/Sine_wave) (as opposed to a rumored engine recording) at the specific frequency where the drivetrain harmonic is missing. If the deficiency is in the exhaust area, a tone from the rear speakers is generated. If it’s engine-related, a tone from the front-end of the car is generated. The end-result is a cabin sound that the car manufacturer wanted to achieve and would have done so mechanically until this technology became available.
Based on what we’ve just described, it seems obvious that this technology is here to stay. Active Sound saves money while achieving the same mechanically engineered sound and driving experience. What’s not to like? Besides, millions of cars already boast the technology. On a side note, our recommendation to car makers would be to better communicate on the subject. Although most drivers don’t care for these details, it would go a long way in the enthusiast community.
<p>Matt Farah made a great point that with more and more engineering dedicated to safety and reducing road noise it is obvious that in cockpit engine noise will also be reduced greatly so they need to “pipe” it in. His recommendation is to move south and open the windows more.</p>
<p>So do we know how it is implemented in the Cooper S? Because my justacooper is painfully quiet, even with a CAI, and I’d love to get some engine noises into the cabin. The Cooper S implementation sounds interesting but I know virtually nothing about it.</p>
<p>What happened to the exhaust burble and pop? Is it gone on this generation? I remember MINI killed it after getting some negative owner feedback.</p>
<p>Only available in Sport Mode but sounds a bit better than on the last generation. Then again, I would recommend getting the pro JCW exhaust. A must-have option in my opinion.</p>
<p>Also not available on the Cooper.</p>
<p>Why? I think its a waste all around. Did the first cool sounding car sound cool or was the sound cool because the car was fast or handled well. To me, and I know I’m in the minority, a Tesla sounds cool as it makes no sound at all because it’s a genuine sound. The real sound a car makes is the only sound I want to hear. I blew off lots of loud Mustangs in my MINI over the years because being louder didn’t make them faster. If the guy driving it felt cooler with the louder sound more power to him….you should get the car you want not the one I want but when I have to sit next to the extra loud car at a light I’m gonna think the Tesla sounds better than ever.</p>
<p>Agreed</p>
<p>Agreed x2. Cosmetic enhancements are neither required nor desired.</p>
<p>My request is that this be a feature that the driver can turn on or off with a toggle switch. I prefer a quiet cabin and natural vehicle sounds – but sure maybe from time to time I’d be in the mood for some digitally delivered engine noise and flip goes the switch!</p>
<p>Would hope that in 15 years time our automated-self-driving electric vehicles aren’t pumping thermal engine noise to enhance our driving experience. Or if they are – an on-off switch would really be appreciated.</p>
<p>It seems that some commentators don’t read the article…</p>
<p>Very true, Eric. Car companies have been using mechanical methods to tune the interior of the car for decades. They almost never release a car just as it comes from pre-production without tuning it first, because there are always audible problems that can’t be detected in the design stages. body panels can have resonant frequencies that cause droning at certain speeds, all kinds of audible garbage can need tweaking. Turning it off would be like removing a resonator or active exhaust or balance shaft from the car and literally making it sound different than the manufacturer intended. There’s nothing “pure” about introducing undesirable sound problems into the cabin.</p>
<p>I appreciate the historical point of view of the article.</p>
<p>And today it proves to be still a preoccupation of car lovers ;)</p>
<p>Pinesalad, you bring back memories of a company car that I had back in the Mid 70’s, a Chevrolet Impala actually. In 73 the government had a mandate that the bumper had to have a 5 mph cushion. Well, GM evidently didn’t check, well at least my car, but at 60 mph you would get this vibration sound, almost like a bumble bee sound. Very annoying. I, even had a Division Manager, who had heard about my bees, come out to ride with me in my territory. Poor Harry, he couldn’t believe it, and it wasn’t long that he want the airport to get back to Chicago. Before he got out of the car he said, “Bill, I’m putting in for another new car for you, and hopefully you won’t have that annoying sound.” A month later I received another, although not a 4-door, but the Custom coupe 2-door.</p>
<p>We finally figured out what was causing this noise, the last week that I had the car, it was in the plastic overlap seam between the front bumper and the grill. Put some calking in there, wa la a, noise gone.</p>
<p>I feel as though I should be indignant about all of this – but honestly, my smile has taken over my brain.</p>
<p>“In short, it is not evil and has nothing to do with fake engine noise.” It clearly is about faking the engine noise, or am I missing the entire article?</p>
<p>No, in short, mechanical noises are tuned for decades.</p>
<p>It’s just that today, this is also made electronically.</p>
<p>So I want to understand this because I know a customer will ask, the Active Sound IS electronic engine noise that is tuned by HK and supplements the actual motor noises and is necessary due to the customers demands for quieter cabins?</p>
<p>HK only cares of the optionnal hifi system.</p>
<p>Customers always want quieter cabins…+ sportier noise on sports car.
It’s just that today, this is ALSO made electronically</p>
<p>I really appreciate your input, but I still see this in the article: “In short, it is not evil and has nothing to do with fake engine noise.” and clearly this is not written right because every post here is saying it is fake engine noise made electronically. Perhaps the difference is Active Sound means actual engine noise tuning PLUS electronic noise</p>
<p>I think the best answer is to drive a Cooper S in normal mode (=without Active sound) then in sport mode (=Active sound activated).
You can really feel (more than hear…) the difference….
But anyway it is quite subjective.</p>
<p>I will do that with mine in about an hour when I leave the dealership, I was just calling out the fact people keep saying it has nothing to do with fake engine noise when it does have something to do with it.</p>
<p>The term “electronic engine noise” might confuse people into thinking it’s a recording of an engine when it’s actually just certain frequencies being added to match the level of adjacent ones.</p>
<p>A microphone is used for cancellation of unwanted noise for a quieter cabin, enhancement is used to maintain a smooth and sporty drivetrain sound desired by MINI (and others).</p>
<p>This is a fun debate to follow.</p>
<p>Here’s the problem. The Active Sound source file may actually be based on a real engine that’s been tuned for whatever. NVH, exhaust note, whatever, it doesn’t matter. But that note is a reflection of the current operational state of the engine when it is making the sound. With any synthesized sound system that augments the impact of the real sounds and vibrations that do make it to the driver are NOT actual reflections of the current operational state of the engine. This is fundamentally different than the tuning during design or installation into a particular chassis (when the real exhaust tuning happens).</p>
<p>So, in the system you describe, how is a tone found deficient? By comparing it to some table somewhere. And no, one couldn’t actually tune all this out mechanically at all, because the fact is that cabins are to first order metal boxes, and the wavelengths of sound goes from longer than the box (heavy bass) to much shorter than the box (high trebles) this means that no matter what, there is a mess of nodes and antinodes that move around the car no matter what as one changes source locations and frequencies. To make matters worse, this sound profile changes based on occupancy, or what seat your dog just moved to. No amount of active audio will ever change the basic physics.</p>
<p>Synthetic vs derived from current operational state is why people like me view it is a sad state of automotive affairs. Sure I’m stuck with it. But then, fake carbon fiber appliques are here to stay as well. Guess what I think about them!</p>
<p>Sporty cars should either make a noise “naturally” or none at all. I love hearing the whine of my R53’s Dinan CAI or the burble and pop of its Milltek exhaust. Piping it in it the automotive equivalent of fake boobs.</p>