Podcast: How To Make a Honda As Quiet As a Rolls Royce

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Podcast: How To Make a Honda As Quiet As a Rolls Royce

In this episode, we discuss how active noise canceling technology works, what makes it so complex yet so useful, and why it is the unsung and underappreciated hero in your car.

In this episode, we discuss how active noise canceling technology works, what makes it so complex yet so useful, and why it is the unsung and underappreciated hero in your car.

This podcast is sponsored by SAE International


(4:19) - Active Noise Cancellation in Electric and Autonomous Vehicles

This episode was brought to you by SAE International! They're THE go-to spot for automotive lovers and engineers—keeping you ahead of the game and hyped about the future of the automotive world! 🚗✨ 

Click HERE to check out the interview with Elktrobit’s CEO and learn more about the drive behind software defined vehicles!


Hey folks, in today's episode, we're talking about how the future of vehicles, the future of cars, isn't necessarily in the hardware, it's actually in the software. And specifically, we're talking about active noise cancellation. So, taking the awesome magical technology that exists in your AirPod Pros and bringing it into your cars to play the opposite sound, cancel out the noise from the outside, and make the cars inside more quiet and more serene. Let's buckle up and take a quiet, peaceful ride into this one.

I'm Daniel, and I'm Farbod. And this is the NextByte Podcast. Every week, we explore interesting and impactful tech and engineering content from Wevolver.com and deliver it to you in bite sized episodes that are easy to understand, regardless of your background. 

Daniel: What's up folks? Like we said, today's episode is all about the future of mobility, including electric and autonomous vehicles. But before we jump into that, who better to help sponsor this episode than SAE? They've got more than 120,000 members, including both Farbod and myself. And their whole goal is to advance the future of mobility and benefit humanity. So, the future of mobility includes electric vehicles and autonomous vehicles like we're talking about today. And don't just talk the talk, they also walk the walk, folks. As a part of this, they've got a vast amount of technical resources, and one of which we've linked in the show notes today as a part of that mission to spread mobility knowledge. And the technical resource we chose for you today is an interview with the CEO of Elektrobit. They're a leading automotive software development company, and they talk all about the future of software-defined vehicles. So, in the past, your vehicle was largely defined by the hardware that went into it, and now, and moving into the future, it's gonna become increasingly defined that the features that you experience the way that the vehicle drives, et cetera, the future of mobility is software defined. So, it's a really interesting interview. Again, we'll link it in the show notes so you can check out more about it.

Farbod: And what was interesting to me is the CEO of this company put out the statistic that reports from McKinsey indicate that 60 to 70% of the software that's actually operating that vehicle is completely unexperienced by the driver, that means it's not the driver assist, it's not the pretty visuals on the touch screens, none of that, it's all the magic behind the scenes that's happening, it's making your car do its thing that you don't even, you're not consciously aware of. Right?

Daniel: Yeah, I mean, it's true that cars today are very, very powerful, very, very expensive computers on wheels. Yeah. Braking, acceleration, shifting, climate control, thermal regulation of the engine itself, all of this is completely software defined today. And like you're saying, 60 to 75% of it is beneath the surface. It's not the infotainment buttons that you're pushing on the screen. That's where software first entered into vehicles. You know, now we've gotten to a point where the software aspect is controlling almost every single part of how that vehicle lives, drives, breathes, et cetera. And your experience with it as well.

Farbod: And to just tell you how embedded that is in the automotive industry. The CEO again mentioned that automotive manufacturers when they talk about their vehicle OS, they're not just talking about the Android operating system that's on the touch screen. When they say OS they're talking about the entire stack, which is from the most basic embedded software that is running on this chip to get the heat. The temperature off of your engine to the most complex AI algorithm that's doing the self-driving. That entire stack is referred to as the vehicle OS because that's how they see it. It's ingrained into the car itself. It's in the soul of it. So, this is the future of automotive. Software-defined vehicles are kind of already seeing this popular, this insane demand when we see it, when we look at it with Tesla. It's a brave new world, man. It's software-defined. Us, Mech E’s, we're getting outdated.

Daniel: Yeah, maybe, but what I will say it's just a testament to how SAE, they're the leader in connecting and educating mobility professionals like you and I to enable a safe and clean mobility future. Check that out. And then we'll jump right now into our topic for today, which links pretty well into this whole topic, which is using software to define the future of vehicles, including with active noise cancellation. Active noise cancellation is a term that some folks, if you're an audiophile or you buy really nice expensive headphones or…

Farbod: You have an air pod.

Daniel: Yeah, you have AirPods Pro, right? These are things that, you know, whether you know it or not, it actively impacts your life because of the silence that you're able to experience with AirPods Pro or with your noise canceling headphones. That's thanks to the magic of active noise cancellation. What we're trying to do now is bridge that technology that's been used in headphones. Now to try and drive a similar level of serenity peace and quiet, et cetera, in electric and autonomous vehicles as well.

Farbod: Yeah. So, do you want to talk about how active noise cancelling actually happens?

Daniel: Yeah, let's do that. And actually, before we do that, I want to talk about the context here. We know why noise canceling is great and perfect for when you're sitting on an airplane and you hear that awful humming noise and you want to be able to sleep and take a nap, that's the reason why, that's why I first bought noise canceling headphones so I could sleep on a plane. Let's talk about the context of why you might want this in an electric and autonomous vehicle. Obviously, the quieter the ride, the better. And it feels more luxurious, et cetera. But why is it so pertinent now for EVs and AVs? Unlike traditional combustion engine cars, EVs don't have these loud engines.

Farbod: So, that's like, I remember the office, right? There's an episode where one of the characters has a Prius and an EV only mode, like the skit is that they can creep up on someone because it's totally quiet. So, the selling point of EVs has been like they're significantly more quiet than these combustion engine vehicles, right? Not exactly. Like to an extent that's true, but apparently as you start traveling down the road higher and higher speeds, the sound of the combustion engine actually becomes more and more negligible. And the ambient noise of your surroundings is what becomes overwhelming louder and louder.

Daniel: Well, and that's what I was gonna say is, when I'm driving my diesel hatchback, I actually like hearing the engine noise to some extent, right? It's, it's a little comforting, but if you were to take that away, which is what EVs do, right, the sound of the motor is pretty much negligible. What you're left with is road noise, which is not pleasant. It's a lot more like this airplane awful, constant hum, rumbling noise that I hate when I was on an airplane. So, reducing these noises is important for driver and passenger comfort. This is where active noise cancellation technology comes into place. What we've been using to reduce unwanted sound in headphones, we're now trying to use to negate awful road noise, et cetera, inside the cabin of a car. Which again, if you think about the 3D space that you're trying to do noise cancellation, and it's a lot more complex to do it for the entire inside cabin of a car, versus the couple cubic inches of air near your ears.

Farbod: Yeah, for sure. And like before we get into, I guess, active noise canceling, let's talk about the traditional noise canceling approach, which has been passive noise canceling.

Daniel: Yeah, exactly.

Farbod: That's when you embed things like foams within the door or like on the roof or the floor to absorb some of those sound waves that are coming through so the passengers inside don't feel it.

Daniel: It's really, really complex. It's more challenging than you might think to be able to achieve that with physical noise canceling. And it's also pretty expensive. You can spend a lot of money and then it impacts the overall mass of the vehicle trying to add foams to reduce noise and reduce rattles and reduce squeaks and et cetera.

Farbod: And that's dead weight. You're always gonna carry it around, right?

Daniel: Yeah, exactly.

Farbod: It's not adding anything to the structure. Like it's not, your car isn't stronger because of it. It's only there to make your cabin more quiet, right?

Daniel: And where margins of error are so thin on other systems, right, you don't want of piece of foam you're adding to try and reduce road noise to impact something like airbag deployment, right?

Farbod: Exactly.

Daniel: Cars are very, very complex, very, very delicate beings. And you don't want to do anything to tip the scale one way or the other. Right? So, the advantage here, the potential advantage of using active noise canceling technology, using speakers, using sound, using software, right? To go back to software defined vehicles using software rather than physical pieces of foam, that benefit comes about to make a cabin that's quieter than any vehicle we've ever done and do it with less cost, do it with less parts than we've ever done it before either. And now it's even more pertinent when there's no engine noise to drown out the rest of the annoying road noise that you're experiencing in the car.

Farbod: Yeah. So how does active noise canceling work? The general high level idea is whatever noise you're experiencing, it has a frequency and an amplitude. Like the amplitude is how loud it is and the frequency is the pitch of it. So, if you can create a noise that is the same amplitude, but it's the opposite in terms of frequencies, like if you have a perfect sine wave that's up-down, and then you can create a cosine wave, which is down-up, the same magnitude, they should cancel each other out, and you should hear nothing in an ideal scenario.

Daniel: And that's called perfect destructive interference. So, we talk a lot about interference, and you probably hear it a lot in terms of like “Oh, I'm getting like some static, some radio interference or my phone call, there must be interference. You're not being able to hear me.” That's like partially destructive interference, meaning that another signal is partially disrupting the signal that you're trying to receive on your phone or on your radio or on your TV, et cetera. Perfectly destructive interference is like what you're saying. The exact opposite of the wave that's trying to enter your ear, for example, producing a wave that's the exact opposite of that in terms of frequency and the exact same magnitude completely cancels it out. The analogy I like to think of is like you're at the playground and there's a kid about to shoot you with a water gun. The stream of water is coming out and it's headed towards you. This is like the noise that's outside of your car. If you were to sit there with your water gun and you had a magic water gun that shoots a special water stream that exactly matches the first stream and stops it right in its tracks before it hits you and you stay completely dry. That's the goal of active noise cancellation here is to basically create a shield fighting sound with sound, so to speak, in a way that you don't experience any of the counter sound that's being produced by these speakers to protect you. They're actually perfectly destroying, you know, perfectly destructively interfering with the sound waves that are coming in, just like that stream of water that's trying to get you wet in the first place.

Farbod: Yeah. And now that we have the principle of it down, let's talk about why it's challenging. In order for you to have that perfect destructive interference, your timing needs to be impeccable. That means that the wave that you're generating cannot have any sort of phase shift. Because if it is, then it completely destroys the purpose. Not completely, but to a great extent, it destroys the purpose of what you're trying to do with noise cancellation. The reason that's challenging in the automotive world is because the environment that you have is not consistent enough. There's a lot of variations in geometry and that impacts the resonance frequency, it impacts the time for you as the passenger to hear a certain noise and the frequencies that are going to be the most relevant to you. There's also the issue of where the noise is being generated. So, let's say if like, I don't know, your suspension is going over something that's really rocky and that's the main source of the noise, that mechanical area, maybe from the moment that you hit a rock to the moment that that noise reaches you, you have, let's say, what? A couple of milliseconds. That means whatever active noise canceling that is meant to counter this is in place needs to be able to pick up that noise, analyze it, and then generate the counter noise in like literally a millisecond or less.

Daniel: Yeah, I mean, it's really, really, really challenging. It's already a very challenging task for headphones, right? But there were, when I was reading this, I thought of around five key factors that make it even more complex to do it in a car versus in headphones.

Farbod: Please do tell.

Daniel: One is coverage, right? Car active noise cancellation has to cover the entire cabin, whereas headphones are focusing on just the air volume just around your ears, or in the case of AirPod Pro, only the air volume like right inside your ear. Noise types, cars deal with a lot of different types of noises, like road noise, engine noise, and even honking, which is something that you want the driver to be able to hear. Whereas I feel like headphones are really good at targeting steady low-frequency noise, like the humming of an airplane. Complexity, these active noise cancellation systems in cars have to be more complex because you're using multiple microphones, multiple speakers for different types of sound noises. Adaptability is like what I was saying, there's a lot of different driving conditions and then there's also noise that you want to be able to hear which brings me to my last one is safety. Car active noise cancellation has to balance noise reduction with maintaining the driver's awareness of what's going on outside. It completely defeats the purpose if you're driving inside your car and it's like a completely sound sealed chamber and you can't hear when the person behind you is honking. You can't hear when someone outside the car is yelling at you. You can't get extra signals that there's a car passing you on the left or right side before you open your door and it gets smashed off, right? You don't want a completely noiseless cabin. You want an active noise cancellation system that's adaptive enough to get rid of the annoying noise and leave the ones that you need for safety. All of these are really, really intensely, I don't even know if this is a word, but complexifying factors, right? It makes it increasingly complex versus the headphone problem, which leads into why we need such strong horsepower, firepower, let's say, from the software engineering perspective to be able to achieve this challenge. The hardware is there. It's the software that helps balance all these different complexities that helps understand the nuance of what's required in an active noise cancellation system for cars, which started getting rolled out as early as last year. I think the Honda Accord 2023 model year had some pretty impressive active noise cancellation system. And that's due to these really, really intense software engineering teams solving this really, really complex problem.

Farbod: Well, what was interesting to me is I'm not as familiar as you are with the design of a cabin or automotive world in general. But when I was reading this article, they were like, we are aware of what a complex problem this is. So, the way that we've gone about addressing it is by picking our battles. At least that's how I like interpreted it. So, you were mentioning like when you think about a headphone, you got someone's head and that's the only thing you care about. When you have a car, you have an entire cabin to be aware of for noise cancellation. Well, they were like, what if we just limited the scope of the noise cancellation to the person's head? So, the speakers that they have essentially try to create what they call a bubble around each passenger's head and that's where the area that they wanna keep the noise out of. Then there's the issue of, well, what kind of noises can we get rid of? Like you have the very high frequency of a honk, but then you have the lower frequency of the rumbles that you hear from the suspension system. Well, they pick their battles on that front by saying, let's just limit it to everything that's under 1000 Hertz because all the major, like let's say 90% of the car noises that people find annoying, those are happening at under 1000 Hertz. And then that kind of plays into the safety thing that you were talking about, because if you're worried about honks or other emergency noises, those are all above 1000 Hertz. Or someone speaking, it's usually operating at over 1000 Hertz. So, I don't know, for me it was interesting to see like these workarounds, these subtle workarounds that the automotive world has found to still address the problem, but keep this nice balance of safety and feasibility in mind.

Daniel: No, I agree. And this super complex problem, it seems almost like an insurmountable challenge, but by making a couple of those key assumptions, you're able to turn this into a solvable problem with software. And so far, active noise cancellation has been known to meaningfully improve the in-cabin experience, specifically in EVs, right? Making the ride quieter, making it more comfortable, almost completely removing things like tire noise from the road and wind noise when you're driving at fast speeds on the highway. Those are things that, and I don't know if you've ever driven an EV, but I guess we rode in a Tesla together. Was that your first time?

Farbod: It was my first time.

Daniel: You tend to notice road noise, wind noise a lot more when there's no humming engine noise to take that out. And in addition to that, we alluded to it before, in addition to creating a better in-cabin experience, we're also able to reduce our reliance on these noise dampening materials, like adding foam everywhere, et cetera, that we're traditionally used to try and passively filter some of this noise out by reducing the use of those foams we're able to reduce the mass of the vehicle, increase range, increase efficiency, which are also huge pain points for people who are using electric vehicles.

Farbod: Lower the environmental impact, that's another one. Yeah. You know, EVs are supposed to be good for the planet, so this is even more aligned with that principle in mind.

Daniel: Oh, I agree.

Farbod: So, I don't know, I didn't expect to care this much about active noise cancelling, to be honest with you, but this was super informative. And it further highlighted that theme that we talked about from the SAE article, which is software is more and more driving the functionality of these vehicles. Like it's not just all about hardware anymore. In fact, in some cases like this, we're seeing how software can completely replace bits of hardware that we thought were just gonna be necessary like through all time. I don't know, it's been informative for me and I hope the audience enjoyed it as much as we did.

Daniel: Yeah, I agree. I'll wrap it up here and then we can close out this episode.

Farbod: Send it.

Daniel: Hey folks, imagine the silence you experience with AirPods Pro, right? I like to travel, so I put my AirPods Pro in and it's like the world goes out and it's just me and my silence or me and my music. That peace, that silence, that serenity, that's the magic of active noise cancellation at work. But now we're trying to bridge that technology from headphones into electric and autonomous vehicles, turning your daily commute from this loud buzzing rattling commute into a serene AirPods Pro like Oasis of calm. This leverages active noise cancellation, like I said, but we're doing it in cars that plays the opposite sound to cancel out the noise that's happening from outside, like road noise, like wind noise, et cetera, making the inside of the car a lot quieter. This is really important for electric and autonomous vehicles because they're becoming more popular and because the engines are quieter, other annoying noises become more and more noticeable. This is already rolling out, companies like Honda are using it starting this year, and it leverages really, really intense software engineering to get it done. I think it's a really complex and really interesting challenge for us to jump into.

Farbod: Honda should hire you for an ad.

Daniel: I don't know about that, man, but...

Farbod: I don't know, I didn't even know they had it in the 2023 model. Now I kind of want a Honda, and I'm a Toyota fanboy, but that's besides the point. Folks, thank you so much for listening. As always, we'll catch you in the next one.

Daniel: Peace.

As always, you can find these and other interesting & impactful engineering articles on Wevolver.com.

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The Next Byte: We're two engineers on a mission to simplify complex science & technology, making it easy to understand. In each episode of our show, we dive into world-changing tech (such as AI, robotics, 3D printing, IoT, & much more), all while keeping it entertaining & engaging along the way.


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