By on June 7, 2016

2013 Ford C-MAX Energi Plug-In Hybrid, Exterior, Charging Plug, Picture Courtesy of Alex L. Dykes

Because we’ll all be travelling around in autonomous electric pods any day now, more and more people want to know whether they’ll be able to hear a pin drop on the sidewalk once those nasty internal combustion vehicles are extinct.

Well, if it’s serene, pastoral bliss you’re looking forward to, don’t expect to find it anywhere near a freeway. The folks at Clean Technica looked at the best studies available on the issue, and the results are bad news for those who think “EV” is another word for “whisper.”

No longer as rare and exciting as when the first models hit the market, electric vehicles still make up only a tiny sliver of overall market share. But the day might come when we’re all dependent on ions for propulsion, instead of evil hydrocarbons.

In order to prevent the crushing of small children and other bipedal creatures in urban environments, EVs emit a a high-pitched whine that doesn’t travel very far. They’re infinitely quieter than revving gas engines, booming diesels and the symphony of stressed exhaust systems.

So, yes — at low speeds, EVs are quiet as hell. But there’s so much else to the picture.

First, think of what you hear right now. Traffic has always been this noisy, right? Wrong. Advancements in engine and tire technology means today’s vehicles are far quieter than those produced even a few decades ago. You’re already hearing less noise than you used to.

But back to EVs. While EVs emit next to no engine noise, that’s their only saving grace. As speeds rise, a gas-powered vehicle’s engine noise falls as a percentage of overall noise, and tire noise picks up. Two highway traffic noise studies published by researchers in the U.S. and Netherlands show an insignificant gap between tire noise and overall noise at highway speeds.

EV tires aren’t magical — they’re made of the same stuff as every other tire. And that abrasive rubber is rolling along an imperfect surface made of asphalt.

The U.S. study found that aerodynamic noise — the sound made by a vehicle pushing air out of its way — outweighs engine noise in internal combustion vehicles at speeds above 110 kilometers per hour (68 mph). Even at low speeds, tire noise outweighs engine noise by a factor of 2:1.

In fact, tire noise and overall noise were so closely tied, the difference between the two wouldn’t be noticeable to the human ear (less than three decibels).

The Dutch study, which used different methodologies, backs up most of the U.S. findings. At 25 miles per hour, engine noise is slightly higher than tire noise, but both are outweighed by overall “road noise.” Once speeds hit 43 mph (70 km/h) engine noise was nearly half of the noise emitted by tires. At 60 mph, engine noise has little significance.

So, while there’ll be less “sharp” sounds in our electric future — tire chirping, revving, and obnoxious mufflers — overall highway noise will continue with little change. Your emissions-free Tesla, Bolt, Leaf or whatever comes next will keep oil in the ground, but it won’t stop noise pollution.

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58 Comments on “Electric Cars = Quiet Roadways? Not so Fast…...”


  • avatar
    JimZ

    while true, it’s specifically for low-speed operation that EVs and HEVs are including sounders. A few years ago, the company I worked for had a couple of Escape Hybrids as pool vehicles. I drove one home overnight, and as I was driving down a street in the neighborhood, it dropped into EV propulsion. just ahead were a couple of kids riding their bikes down the street, and I was rolling along behind them (still in EV.) They had no idea I was behind them, and I didn’t want to hit the horn and scare the p*ss out of them. eventually one of the kids glanced back and saw me, and they moved out of the way.

    • 0 avatar
      dal20402

      This happens often in my C-Max Energi. People in parking lots just don’t realize I’m there. They’re often startled once they see me.

      It’s not a big deal, though, and certainly not enough to justify annoying beepers. Just be aware as a driver.

      • 0 avatar
        redmondjp

        At one of my former employers that makes lift equipment, we had several types of beepers for motion – some of them are very annoying, but you can get pleasant-sounding ones that have more of a chime sound that are not as loud (and loudness is easily controlled by careful application of duct or electrical tape).

        Maybe installing a horn speaker connected to the vehicle’s stereo would work. People would get out of the way if they heard AC/DC blaring behind them.

    • 0 avatar
      PeriSoft

      There should be an ‘aux horn’ button, that makes the sound of a revving LS6.

    • 0 avatar
      TDIGuy

      I drove my employer’s Volt for about a week a couple of years ago. After two days of surprising cyclists and pedestrians, I discovered a button on the end of the turn signal stalk that give a quiet but rapid beep of the horn. Enough to let people know you are there, but not enough to startle someone.

    • 0 avatar
      brandloyalty

      Like the first comment, my Escape Hybrid sneaks up on people in ev mode, but makes pretty well as much noise as any other car the rest of the time.

  • avatar
    05lgt

    This is so timely. Over the weekend I went for a walk that included crossing over a highway, and wished I had a forum to point out that all I heard was the long continuous slap of tire on road. A few (fart can, diesel, or tuned exhaust accelerating quickly) broke through the perceptibility limit, but it was pretty much all tire noise.

  • avatar
    Felix Hoenikker

    I discovered the effect of wind noise during a glider ride a few years back. I thought that the lack of an engine would make the flight dreamily quiet. Wrong, the noise generated by wind on the wings and fuselage was hard to talk over.
    Blimps are another case. I won a ride in one once. They are almost silent when the propulsion motors are cut, but annoyingly noisy in the gondola when the engines are up and running which is most of the time.
    Not being a noise junky, I still look forward to an EV for driving quietly at low speeds.

    • 0 avatar

      I’ve experienced a ride in a glider as well. Like you said, it is far from quiet, and you can hear every creak and moan from the flexing metal.

      • 0 avatar
        FormerFF

        Try getting a tandem in a hang glider. They fly at bicycle speeds and are quieter.

      • 0 avatar
        bunkie

        Back when the first jetliners appeared, it took crews a while to get used to hearing all the hydraulics noises that had been masked by the noise from the props and radial piston engines.

        Me, I’m waiting for electric Harleys. Or, at least, confiscation for the bozos who run open pipes.

        Finally, I want my glider rating! No go-arounds for you!

        • 0 avatar
          "scarey"

          Loud pipes save lives. Most drivers will actually LOOK at you if they hear you, and run over you if your bike is too quiet.

          • 0 avatar
            30-mile fetch

            I’m mildly tempted to LOOK at the bike I hear and THEN run it over. The only person within a half mile that would be sorry is the biker himself. If biking is too risky for you, become a cager and spare us the hearing damage.

          • 0 avatar
            HotPotato

            Trouble is, it’s drivers behind you who hear your loud pipes, not those in front. Damn Doppler effect.

          • 0 avatar
            RHD

            “Loud pipes save lives” translated into English:
            “I like my bike loud and annoying. If you don’t like it, $%&@ you!”

      • 0 avatar
        JMII

        Same occurs on a sail boat. Without the engine sounds of a normal boat you hear all that creaking and moaning. And I’m not talking about just old boats either, even modern hulls do it.

    • 0 avatar
      Kyree S. Williams

      Absolutely. Every time I drive my best friend’s Fusion Energi and it’s in EV mode, I can hear all sorts of annoying noises, like the slapping sound that occurs when I let my foot off of the brake pedal.

    • 0 avatar
      wumpus

      I’ve had a blimp go over me and it was louder than any plane (possibly because it was so slow. It took forever to leave).

      Hot air balloons are said to be the opposite: since they blow with the wind, there is essentially zero “wind in your face” and no wind noise. And then there are motorcyclists who are encouraged to wear earplugs under their helmets.

  • avatar
    Carlson Fan

    ICE cars suck! I’ve actually laughed at them straining as they accerlerate, making all kinds of nosies when they shift gears with the RPMs rising and falling. Meanwhile the Volt effortlessly wisks by them without making a sound other what’s coming from the tires as they pick up speed. Like I’ve said before, I drive the Volt mainly because of the way it drives. The efficiency is just icing on the cake. Around town electric cars are so much nicer to drive than any ICE. Vastly superior IMHO.

    • 0 avatar
      JimZ

      you sound like you’re very much in love with yourself.

    • 0 avatar
      accord1999

      Sounds like you love to beat cars who don’t know they’re in a race.

    • 0 avatar
      orenwolf

      I think you missed the point of the article.

      ICE cars may “suck” in your mind, but they aren’t significantly louder than EVs at speed.

      Besides, what about when your volt has its ICE running? I mean, you know it has one, right? :)

      • 0 avatar
        Carlson Fan

        Agreed they aren’t louder at speed but they sure are when accelerating. The Volt sucks like any other ICE car when the generator is running, thankfully than isn’t very often with my driving habits. 2050 of my first 2200 miles were done on electricity.

        • 0 avatar
          JimZ

          do you also bend over and sniff your own farts?

          • 0 avatar
            Luke42

            “do you also bend over and sniff your own farts?”

            I’ve seen that South Park. He might be that smug, for all I know.

            But, having driven the Volt and the Leaf, the NVH and the smoothness of an electric motor is really hard to beat.

            Every time the 5AT in my van is just a little rough, I ask myself why I haven’t bought an EV yet. Then I remember that nobody’s selling an electric minivan, yet.

          • 0 avatar
            dal20402

            Love electric cars’ smoothness and linearity under acceleration. When I step into my LS460 from my C-Max, it always feels rough and unpredictable because of the shifts, even though the LS460 8-speed is about as smooth as conventional autos get.

    • 0 avatar
      White Shadow

      This is so sad. I recently drove a Volt and I had a hard timing staying awake due to extreme boredom. Then again, I normally drive a turbocharged car with a 6MT. A car like the Volt is an extreme snooze fest.

  • avatar
    Tandoor

    I sneak up on people all the time in my Leaf, despite the annoying whistle/Darth Vader noise it makes. When I was a kid playing ball in the street you could hear a car more than a block away. My old Roadmaster had more wind/tire noise than engine unless you were being a hooligan. But the dog could hear it and would be at the door waiting. Now I get barked at until I get the door open.

  • avatar
    SCE to AUX

    Comparison of two very similar cars:

    2011 Nissan Leaf:
    http://www.edmunds.com/nissan/leaf/2011/road-test-specs3.html

    2012 Nissan Versa:
    http://www.edmunds.com/nissan/versa/2012/road-test-specs/

    Idle
    Leaf = 36.7 dB
    Versa = 43.5 dB

    Full throttle
    Leaf = 67.7 dB
    Versa = 75.0 dB

    @ 70 mph
    Leaf = 67.7
    Versa = 68.4

    So yes, the Leaf is always quieter, but the difference closes to near parity at highway speeds.

    However, I found that my former Leaf was much more pleasant to drive on the highway than an ICE car, probably due to having a different distribution of frequencies in the sound spectrum.

  • avatar
    SCE to AUX

    The first time carrying passengers in an EV is amusingly awkward. The total silence while stopped at a red light is unsettling. Our hybrid is like this, too.

    Without an idling engine providing cover noise, people actually have to talk with each other. Personally, I never operate the radio with passengers in the car, so things can get weird pretty quickly.

  • avatar
    Blackcloud_9

    “Advancements in engine and tire technology means today’s vehicles are far quieter than those produced even a few decades ago. You’re already hearing less noise than you used to.”

    Unless you’re in a HELLCAT (CAPS required when writing this word), then everything is louder – as it should be.

    While find the statement I quoted mostly true, there seems to be a greater abundance of cars out there roaring off the line at traffic signals/stop signs. This obviously ties into the greater number of high performance engines available today.

    This also leads to the thought “What an idiot!” popping into my head with greater and greater frequency

  • avatar
    mcs

    As a cyclist, the quietest thing I usually encounter on the road are Honda Goldwings. In my Leaf, there are many newly paved 35 to 25 mph country roads in my area an at the lower speeds, from a rider/driver perspective, the leaf is quieter than my bicycle. Wind rushing past my helmet on the bike at 20+ mph is pretty loud.

    At higher highway speeds (80 to 90+ mph), the Leaf still seems quieter than an ICE revving up during acceleration. You do get that nice gas turbine whine out of it. Today, I had a tall jersey barrier to my left and you could really hear the motor on acceleration. I’ve owned plenty of beautiful sounding ice cars and this is every bit as nice.

  • avatar
    mcs

    If you want to hear a loud EV, check out this one:

    http://www.youtube.com/watch?v=ZvXmPJStWyY

    • 0 avatar
      PeriSoft

      I think a large component of the noise in that video is a result of a terribly confused audio compression algorithm operating at crushingly-low bitrates.

      • 0 avatar
        mcs

        @perisoft You’re right. Lots of issues with that audio.

      • 0 avatar
        JimZ

        I imagine there are some straight-cut spur gears involved. Those are *noisy*. The Harley-Davidson LiveWire (concept) electric motorcycle has straight bevel gears in its drive and whines like that.

        • 0 avatar
          mcs

          @jimz Good point. That might be what I’m actually hearing. I’ve had whines from other types of transmissions as well and the motor is liquid cooled, so there should be some sound insulation from that. I did find a book that discusses all of the aspects. It seems to me to be thorough:

          https://goo.gl/1Lwsbw

  • avatar
    rehposolihp

    “In fact, tire noise and overall noise were so closely tied, the difference between the two wouldn’t be noticeable to the human ear (less than three decibels).”

    Although one study (Dimmick and Olson 1941) found the minimum detectable SPL change to be 1.5-3 dB nearly every other study finds the minimum change to be 1 dB or less.

    dB is a logarithmic scale – which is important here. 3 dB represents a doubling of loudness – not just ‘a little louder’.

    That said I have nothing else to contribute….I just felt like that bit needed fixing.

  • avatar
    Russycle

    I’m not sure I should care. Cars traveling at highway speeds aren’t really a big deal. I used to live next to the Santa Monica freeway, after a couple days I didn’t even notice the sound of thousands of cars rushing by 50 yards away. I find the start/stop noises of city traffic much more annoying, and EVs will significantly reduce that.

    • 0 avatar
      mcs

      @russycle I agree that the stop/start noises are the worst. I was noticing that while stuck in traffic today after reading this post. It depended on the speed traffic and the particular car. At one point in a slow moving tunnel, my EV was the most obnoxious car in the pack. Usually, the pedestrian warning doesn’t bother me, but for some reason, it was getting to me today. Some of the loudest noises I heard were brake related with a couple of cars definitely in need of new pads. Another thing I noticed was the noise from cooling fans.

      Still, once I hit the country roads near my home and their fresh pavement at 35 mph, I could hear the birds chirping and the crickets doing their thing. I’ve passed runners on 25mph roads and could hear the sound of their sneakers hitting the pavement.

  • avatar
    Robbie

    This article says nothing more than:

    Total car noise = Tire noise + Engine noise

    and for EVs, Engine noise=0 but Tire noise >0. Was this rally worth a TTAC entry?

  • avatar
    brn

    I’ve been saying this for years. I live next to a freeway and, expect for the occasional douchenozzle with a straight-pipe, I don’t hear the engines. Not at all. I hear tires.

    • 0 avatar
      JimZ

      agreed. my place is about 1,100 ft. from I-94. the vast majority of noise is, as you say, tires. occasionally I’ll hear the “hum” of someone hitting the rumble strips. the only discrete “vehicle” sounds I hear most often are either a loud-ass Harley, or a handful of douchebag squids winding out their sportbikes.

  • avatar
    "scarey"

    I remember reading several years ago that the Prius/Insight/Leaf were so quiet that they are
    dangerous to blind people crossing the street, because they won’t be heard. This was hyped
    so much that laws were going to be proposed that hybrids and electric vehicles have
    noisemakers attached to simulate the sounds of internal combustion engine cars.
    Am I the only one who remembers this ?
    http://www.slate.com/articles/business/
    gearbox/2012/05/hybrid_and_electric_cars_too_quiet_why_they_re_
    dangerous_to_pedestrians_.html

    • 0 avatar
      JimZ

      no, you’re not the only one who remembers this, since hybrids and EVs *are* adding external sounders.

      • 0 avatar
        mcs

        Mine has that noise. It was annoying me today, so I’m thinking about changing it. At first, I thought maybe synthesizing a V12, then again, maybe a better sound would be a gas turbine. Then, it hit me. Ice Cream Truck sounds! I’d drive every kid in my town crazy.

        Actually, the sound isn’t that loud. In the underground garage where I probably need it the most, it approximates the sound of the ventilation fans and blends in, so it’s effectively silent. Almost hit someone that bombed out of an elevator while focused on texting. I stopped and they almost walked right into the car. The look on their face was priceless.

  • avatar
    raph

    I figured it would be tire noise. That’s what I mostly hear from the majority of vehicles on the road. Especially people who neglect to rotate their tires or do not rotate them correctly (looking at the buffoons that rotate only front to back and the tires end up cupping as a result – because you know like changing out that winter and summer air you should never cross-rotate radial tires!)

  • avatar
    Joss

    Sirens – when we do go fully self driving let’s convert them back to bells..

    Well done Japan keeping your fire truck bells for gentler occasions.

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