Noise Optimization Technology with Colin Peachey of Lotus Engineering

Colin Peachey

Will Hornick, Managing Editor of Automotive IQ, spoke with Colin Peachey, Group Chief Engineer Controls and Electrical, Lotus Engineering, UK in a series of interviews focused on Noise Optimisation for EVs/HEVs.

This is Part 1 of a 3 part interview.

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"You get in a car, you drive it, you flick a switch and all of a sudden it takes themajority of the noise away. That's quite something to hear and most people,the first time they hear it, find it really impressive. The problem was we almost developed the technology too early."

What lead to you working on noise optimization for Lotus?

Colin Peachey: I graduated with an engineering degree back in the early eighties. I went to work for Rover Group as a Junior NVH Engineer from about 1984 so I was involved with NVH, weight reduction, general things like that, but basically working as an NVH engineer. Then when the situation with Rover and BMW came to a head, a former colleague who worked at Lotus invited me to come for an interview and I joined Lotus in 2000. I initially worked on a range of different projects in a general development role but then got back into doing NVH work running the NVH Team.

Lotus developed the active noise technologies as a spin off from the work that they did in the 1980s on active suspension for Formula 1. It was developed and reached the point where we could demonstrate that it worked but it largely didn't go anywhere other than interesting demonstration cars. When I got involved back in the early 2000s, it was a background technology that existed but one that we had not utilized or exploited. At the time, responsibility for it was split between the NVH Group, who had an obvious interest in it, and also the Controls Team who were managing it. The manager running the controls team left so they gave me the NVH and the control side all in one. I became responsible for looking after all of the active technology.

But for the most part this was for traditional ICE vehicles?

C.P.: Yes it was. Fundamentally we started off and developed engine noise control, effectively using an opposing sound field from the loudspeakers to actually cancel the noise that the engine is making. As the engine speed is constantly changing, the noise frequencies are changing and we are cancelling multiple harmonics of the engine noise which is tracked to engine speed. You sit inside the car, switch it on and off and you dramatically reduce the level of engine noise. Having spent years using conventional NVH to knock off the odd dB here and there suddenly taking 10dB off the dominant engine harmonic right across the speed range is pretty mindblowing.

The Formula 1 approach was really about using active control and active feedback on the suspension systems. The idea is that you have a feed forward signal for a fast system response and a feedback signal error signal to constantly adapt the accuracy of the feedforward performance. Once you actually crack that you then think: "What else can I do with this?" I can use it to minimize the vibrations coming through a suspension system into the car to actually control the ride and handling performance. We can also use this to work on noise or any engine vibration and a whole range of things. So once you've delivered the basic system there are a whole lot of things you can do with it. Noise was quite an obvious thing to go for because generally there are loudspeakers already in the car, because you have an audio system, so you're using hardware that's already there. If you can then use that system to cancel noise then you get a cost effective benefit. So we developed the active noise control for engines. Then, slightly more complex, we developed the active roadnoise. If you imagine you're driving along the road surface, quite often there is a lot of low frequency broadband road rumble that comes through. Engine noise has a specific operating speed so an engine has perhaps four or five clear, distinct frequencies that the engine is generating at any point in time. Road noises have a much more broadband effect. Rather than with discreet frequencies you almost end up with a whole spectrum of noise with broader noise peaks that coincide with body cavity modes, Internal tyre cavity modes and resonances or modes of the suspension, chassis or body.

Controlling road noise is far greater challenge than engine noise. Whereas other people have cracked engine noise cancellation as well, we like to feel that Lotus is at the forefront of road noise - broadband noise cancellation. We've put these systems together and the result is quite interesting, particularly working in the sports car world. The objective is not to make a silent car because a sports car is very much about the whole experience of driving it and the sound is a very, very important part of the brand and the product identity.

With the system we can output frequencies to cancel engine noise, but we can also put the additional sound in to create noise. We can use the noise cancellation system to take away the low quality unappealing engine noise of a small 3 or 4 cylinder engine and can actually then make it sound like a V6 or V8. This application is termed engine sound synthesis.

This idea is now being picked up by way of enhancing conventional engines. For example, it's quite widely known that the latest BMW M5 has got electronic sound enhancement. When they brought it out there was a bit of an outcry from the press saying this is fake and is deceiving the customer. Actually when you drive it, the whole driving experience and the fantastic sound quality means it really doesn't matter.

Then we started to work on electric cars, the very first Tesla vehicles were all based on Lotus architecture and we built them here at the Lotus factory in the UK. We started to drive these vehicles on site and it became quite apparent that at low speed you just couldn't hear them coming. We had a number of near accidents that were had because these cars were quite silent. Then someone came up with a bright idea: we've got this sound generation for the inside of the cabin, let's just turn it round and put it on the outside.

We like to think that with all the upcoming legislation for quiet cars and sound generation, we were among the first people to actually raise this issue and put this to the market. People thought, this is just crazy because having gone to all this effort to make quiet cars why would we put noise back in. We will perhaps talk more about this later but I think the thing that made the risk quite clear was some work done in America by NHTSA looking at real world accident data that reached the conclusion that these quiet cars did pose a real risk to pedestrians.

We developed these technologies and they were very interesting, they were very capable, they were really impressive. You get in a car, you drive it, you flick a switch and all of a sudden it takes the majority of the noise away. That's quite something to hear and most people, the first time they hear it, find it really impressive. The problem was we almost developed the technology too early.

This was a solution that didn't really have a problem because at the time if we wanted to make the engine quieter we could just put a more NVH material on the car or we could redesign the intake or the exhaust system or put balance shafts on the engine. All these approaches that are conventional NVH solutions to make a car quiet were proven and effective. They might have had a penalty in that the engine was perhaps not as efficient or the car was not quite as light but NVH engineers could fix these problems through conventional means. When Active Noise was invented, we were putting the highest end audio speakers into the cabin to get the best sound output and needed state-of-the-art computing power to get the system to run. In the end we had a solution which, although elegant, was much more complex and much more expensive than the basic, totally acceptable means of doing it with passive NVH.

Which I guess is okay at the very high end?

C.P.: Yes, we thought it was unfortunate that the cars that really needed this technology, which were the cars with poor NVH, were the small cheap cars but they couldn't afford it and the cars that could afford it, the high-end Mercedes, BMW, were cars that didn't actually need it because they had a solution already. So for a long time this technology sat on the shelf.

We had one application in production on the Nissan Bluebird for the Japanese market car and they put engine noise cancellation into production in 1992 which was a license of our technology. But apart from that, it looked as if it was a solution to a problem that didn't exist. The thing that really made the difference was probably round about five or six years ago when people started to plan for CO2 reduction and needed solutions to make cars more efficient from both a weight and engine efficiency point of view that didn't have a detrimental effect on CO2. All of a sudden we got phone calls asking: "You know you used to do that active noise, are you still doing that?"

And then a re-purposing began?

C.P.: Yes. We basically had the technology that we developed and the IPR that we owned. We've actually got into a licensing deal with Harman Automotive, who make high-end automotive audio systems. I think what clinched it for them is that they had about five customers in a row and request that their next generation of audio platform needed to be designed to be capable of active noise control. The OEMs were then realizing that ANC provided a solution to keep their CO2 low without having to sacrifice the refinement because the customer wants low CO2 but he wants all the things (including refinement and comfort) that he's already got. He's not interested in a low CO2 car if it is noisier than the conventional car he already has..

Of course, the customer isn't specifically dealing with regulations - it's the car manufacturers.

C.P.: That's right, yes. But legislation can result in taxation penalties and in addition competition is driving you to make your cars efficient and refined. Then as technology developed the processing power needed to run these systems is less than what's on your phone. So within the audio DSP chips Harman were using there was the capacity available, with high-end speakers in the car. In relative terms this can be put into a production solution at a fraction of the cost of what it would have been twenty years ago." And all of a sudden there is a reason for doing it.

Yes, it's a perfect meeting of all the necessary factors.

C.P.: That’s right. Some factors are specific to internal combustion engines and then some are quite specific to EV and hybrids and then there’s the potential for taking weight out of the car, that’s equally applicable to both types of vehicles. We have a business need driven by both legislation and competition , an affordable and effective solution and interested customers. That’s why I believe the time for this technology is now.

Part 2 of our interview series with Colin Peachey focuses on the possibilities made available with active noise control…

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