Noise Optimization: Safety & Legislation
Automotive IQ spoke with Colin Peachey, Group Chief Engineer Controls and Electrical, Lotus Engineering, UK in a three part interview series. The conclusion of our interview series with Colin focuses on the safety and legislative aspects of noise optimization.
"The beauty of the speaker generated system is that all the sound is going to
the front in the area it needs to be to provide a warning and there's not so
much sound coming out from the sides or upwards from the bonnet."
In terms of driver and pedestrian safety how does the active noise technology help?
C.P.: The safety aspect from the driver's point of view; quite often you get into one of these cars when its stationary, but is it on or is it off? You don't really know. Most drivers change gear or know how fast the car is going from the sound of the engine, so they know if they're slowing down or speeding up without having to look at the instrument panel. From the exterior point of view, this gets quite interesting. For example on the early Prius, a number of drivers remarked particularly in town at junctions or traffic lights that pedestrians just walk out in front of the car because they don't hear it and think it is parked! The fact that it is different does, for some drivers, create a level of anxiety, particularly if they've had a near accident at some point.
A significant amount of sound is radiated directly off the bonnet. If you consider driving down a quiet street at night, much of the noise radiated off the bonnet can travel upwards to an open bedroom window. The beauty of the speaker generated system is that all the sound is going to the front in the area it needs to be to provide a warning and there's not so much sound coming out from the sides or upwards from the bonnet. If we picture this sound as coming out in a tunnel of sound rather than wasting a lot of energy projecting unwanted sound upwards.
We've done quite a lot of work with the Guide Dogs for the Blind Association in the UK. We've had some people who were blind or visually impaired come in with their guide dogs to assist us in this technology. We've done various experiments to look at how we have to adjust the levels of the noise and what sort of sounds the dogs actually respond to. We've had this on national TV a couple of times so it has been quite well received. The overall thing that blind and visually impaired people like about our system is it has one point source of noise that's quite clear to identify.
Versus traditional vehicles which end up having more of a Doppler effect?
C.P.: Yes, that's right. When there are multiple sources coming from different directions it is harder to localize the sounds, especially when there are multiple reflections off buildings, whereas this is a point source of noise. One of the things we talked about quite a lot with them was what the sounds should actually be. If you generate some sort of futuristic spaceship noise, you can explain that this is the sound of an EV vehicle, but it is a harder conversation to have with their dog, to say: "Listen to this, boy, because this is what an electric car sounds like."
From a pedestrian safety point of view, sounding like a conventional car is the ideal. There are interesting things about the sound character of an ordinary engine noise because it has got a mix of high frequency sounds and low frequency sounds. The benefit of the low frequency sounds is that they tend to travel further. Whales can talk to other whales on the other side of the world in low frequency underwater whale song. The negative thing about low frequency noise is that you can't spatially locate it as well.
With high frequency noise there is a much better chance of picking out where it's coming from. On your home audio system it's quite important for your tweeters to go in the right place to create the right sound impression but your sub-woofer can go anywhere because that low frequency noise just fills the room and it's not so directional. So a very conventional engine noise naturally contains low frequency noise that warns there's something coming, and then as it gets closer the high frequency element helps locate the exact position of the sound. So the balance of low and high frequencies is quite an important part of providing a good level of pedestrian warning.
Given that the European Commission is considering some sort of a minimum sound standard for EVs and quiet operation vehicles, what are some strategies that you think would be effective toward creating a safe operating environment?
C.P.: The way the regulations seem to be at the moment is that everyone is still making it largely voluntary to put in sound generation. From our discussions so far, and we've spoken to quite a lot of people who make EV and hybrids, there are two questions: The first is will your system meet the legislation when it arrives? Second, could we put it in the car now in advance of legislation?
Our analogy for the adoption strategy is a lot like airbags; by the time it was a legal requirement that every car had an airbag, every car already had an airbag, because the market was driven by product liability and competition. If you could buy a car with airbags, why would you want a car without airbags? It was a safety factor and well-proven that an airbag system made such a difference to injury and death rates that if manufacturers decided not to put one in and someone had an accident, there could be a legal argument questioning as to why they weren’t fitted to the car as a standard? Perhaps it's a little bit frustrating that it is taking quite a long time to reach the point of legislation but there is quite a clear move for people to start adopting these things. For instance the Nissan Leaf has a sound generation system fitted to it. You can buy it for the Prius and quite a few of the other cars. Although people are waiting for it to become a legal requirement and we know that people are also now looking at perhaps the next generation of smart systems for sound generation.
Do you see the regulations as potentially regulating not only the level of sound but also the actual type of sound?
C.P.: Yes. It's interesting that Japan was the first place where there was a voluntary requirement to bring these sounds in. They said they had to be engine-like. It couldn't sound like birds singing or rivers flowing. It had to be a recognizable sound. We did speak to some of the authorities in Japan about this before it came out and at that point they thought they might have a requirement to make all electric cars make the same noise. But the manufacturers resisted this because that didn't give them any maneuverability for sound branding.
Their brand DNA goes out the door with a standard sound.
C.P.: Yes. So I think based upon what Japan produced that's where everyone is largely going. I know there was the movement in the States around the Pedestrians Safety Enhancement Act in 2010 which went into doing an investigation to work out what the sound had to be.
There is the UN world regulation harmonization which seems to be trying to drive towards a single resolution that most territories will actually try to adhere to so manufacturers don't need have to have totally different systems for different markets, which largely seems to be based upon the Japanese requirements. It's interesting that if you look at the requirements for these vehicles, the manufacturers almost didn't want to embrace this concept because they were also making refined cars with conventional engines that were just as quiet. If a pedestrian is hurt in an accident it makes little difference whether it was an EV or a very expensive conventional car. If there is a minimal noise requirement a lot of the high-end luxury conventional cars won't actually meet that. There doesn't appear to be a discussion as to whether it is for all vehicles or only for the so-called quiet vehicles with EV and hybrids. That remains to be had, I think.
It will be interesting to see the first car that has been designed literally from the ground up with this.
C.P.: Yes, definitely. Manufacturers are no longer asking the question, "Does this technology work?" It's more like, "How can I use it? How can I best use it?" All the problems with EVs, around the cost of their batteries and the cost of buying the vehicle, are making it difficult at the current technology level to prove an economic case for them. The industry is saying that over the next five years there needs to be a major breakthrough in battery technology to lower the cost and lower the weight of the batteries for these vehicles for it to really take off. It's the same sort of thing that we've been struggling through on the active noise. It has to work but it has to work in an affordable way that makes business sense.
Do you have a prediction for the first car designed from the ground up?
C.P.: Well, we are doing some development projects with some customers, effectively feeding that into their next cycle of development. We've done a development car with somebody and proven the concept and now they're looking at how to put that in from the ground up. From our point of view, based upon a two to three year development cycle, we should start to see cars that are really exploiting this.
That must be gratifying.
C.P.: It is. The frustrating thing is that we nearly developed this technology too early. We invented it before the problem that really needed it existed. It’s only now that the technology offers significant benefits to manufacturers to justify the development and implementation costs.
Thank you very much for such an informative interview.