The Herald yesterday ran a story on just how quiet the new electric trains are. In a polar opposite there was a lot of noise on twitter about how the article was initially presented but after getting past that it provided some really useful information on just how good these trains are. Here’s the useful bit:

Informal noise sampling by the Herald measured the highest level inside electric multiple unit (EMU) number 129 at 72.9 decibels, compared with 83.6dB reached inside a locomotive-hauled train and 92dB in a diesel multiple unit between Puhinui and Homai stations on Auckland’s southern railway line.

With just the air-con switched on before the electric motors kicked in, the top level was 69dB.

A rule of thumb is that every increase of 10 decibels represents a doubling of noise, meaning a jet aircraft taking off at 100dB is roughly eight times as loud as a passenger car clocking 70dB at 105km/h.

Differences were even more pronounced outside the various trains, where the electric was at least four times quieter than diesels accelerating out of stations.

It reached a top count of 77dB when pulling out of its Wiri depot, compared with a high of 99.6dB for the DMU and 101.6dB for a loco-hauled train thundering away from Puhinui Station.

But being far quieter than the trains they will be replacing in a line-by-line rollout to mid-2015 presents a serious new challenge for the electrics, as they will be harder for pedestrians to hear coming.

That means rail operator Transdev is asking its drivers to take extra care to sound warning alarms when approaching level-crossings.

The differences in noise levels are substantial and it’s something I’ve noticed on the few times I’ve been lucky enough to have a trip on one of the EMUs. It’s quite telling also as I still remember a conversation with a one of the senior engineers involved in the project over a year ago. He told me that while they knew these trains would be quieter, they weren’t sure just how they would compare to a carriage in an SA set (the loco hauled ones) which are noisy if you’re in a carriage near the locomotive but can be quite as you move away from it. I’ve graphed the results the Herald recorded.

Note: This chart has been updated to represent perceived loudness rather than simple decibels.

The vast improvement in the exterior noise is impressive and something that is bound to be a welcome relief for those that live, work or play alongside a rail line. In fact if the figures are right then the new trains are quieter on the outside than the existing trains are on the inside. I think it will hugely improve the viability of increased densities along the rail corridor. You can get a sense for how quiet they are from this video

Another good example is this video from TVNZ during the testing.

What caused attention on twitter though was the attention on the noise of the air-conditioning. Basically the trains are so quite that when first turned on the air-con is slightly audible. To me it’s actually a good sign as it shows the rest of the train is of such a high quality that the only issue able to be picked up was air-con noise. What’s more it appears that the engineers are working hard to improve it further.

Acoustic engineers have been trying to soften the air-conditioning noise on Auckland’s new electric trains with a week to go before they are rolled out for commuter use.

A constant air-conditioning hum overlaid the gentle whirring of electric motors and clickety-clack of rail tracks as the Herald joined trainee drivers on a test run of one of five trains being readied to carry passengers between Onehunga and Britomart next week.

Auckland Transport, which is importing 57 three-car trains from Spain for about $540 million in a cost-sharing purchase and maintenance deal with the Government, insists their air-con units already meet noise and efficiency specification limits for both heating and cooling.

That follows considerable design work and the installation of noise-reducing material, said a spokesman for the council body.

But he acknowledged engineers were still fine-tuning the systems to maximise passenger comfort.

He suggested it would be unfair to represent the air-conditioning noise of an empty train heading out of its depot into humid outside conditions as typical of what passengers should expect from next Monday.

“The air-con would have been working very fast until the train reached normal temperature.”

He also believed it would have been more noticeable in an empty carriage with little background noise.

I like the fact that the engineers are working to improve the customer experience further where they can. I just hope that AT manage to start paying this much attention to the customer experience across all of their operations because if they do then there will be a bright future ahead.

Only 5 days to go till these trains start carrying fare paying passengers for the first time

Photo by Patrick Reynolds
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  1. They’ve got one important part wrong: decibels are a logarithmic scale, with 10 decibels representing an increase of 10 times. These trains are literally over 100 times quieter than their equivalents.

    That’s a huge increase in a quality metric. I’m very glad to see the commitment to improvement in service being applied to this project. Trainspotters will be able to tell me: does the click-clack comes from NZ having bolted track rather than continuous welding?

    Which is wonderful, but I’ve just realised this has a downside. Once they are in regular service on all lines they will make freight hauling seem extremely noisy in comparison, potentially causing other problems.

    1. Don’t think thats true. I’m not sure about the actual power level but in terms of the perception of loudness a 10dB increase is a doubling of volume, more or less.

      Nonetheless even 10dB less is a massive difference in perceived volume, let a alone 20dB less.

      1. from wiki:

        The decibel (dB) is a logarithmic unit used to express the ratio between two values of a physical quantity, often power or intensity. One of these quantities is often a reference value, and in this case the decibel can be used to express the absolute level of the physical quantity. The decibel is also commonly used as a measure of gain or attenuation, the ratio of input and output powers of a system, or of individual factors that contribute to such ratios. The number of decibels is ten times the logarithm to base 10 of the ratio of the two power quantities.[1]

        So does that mean the difference between 80 dB of the EMU and 100 of the SA sets expressed as a power ratio is not 20, but x 10^3. 10x10x10 = 1000x louder? Really?

      2. yes it’s something like 10dB is twice as loud. But of course twice as loud is subjective. Then it depends on weighting, is it dBA or dBC or whatever? For some people could be much quieter, for others not as much. Also, frequencies around 2khz are the ones that appear louder to us at that kind of level but it changes at different levels. So Yes, Patrick, it takes ten times more power to increase a sound 10 dB but to a human ear that only sounds as twice as loud, not ten times.

        1. The real concern is actually that sounds above 85Db start to cause permanent injury, so until now these trains have quite literally been giving the people living next door to them and using hearing loss. Long term investments such as these EMUs have very real quality of life improvements and savings to the public health system. IMO those sorts of benefits should also be included in the BCRs, the whole point of a government is to look at things holistically and generate synergy across different areas rather than the silo mentality that currently exists.

          1. It’s not quite that simple as it is a dose-damage response. Sound above 85dBA for eight hours a day is the usual threshold for significant risk of occupational noise induced hearing loss. Sound power (note not loudness) doubles every 3dB basically. So 88dBA the daily dose is hit in four hours, at 91dBA it’s two hours. So someone working in a loco unit is getting their daily noise dose in under two hours.

            Sound under 85 can contribute to permanent hearing loss too, if your exposed to it long enough.

            But yes on the flip side the new EMUs are so quiet they basically remove all risk of contributing to long term hearing loss.

            FYI those of you that use your iPod to drown out other noise are almost certainly doing permanent damage.

          2. Just as well the EMU’s are quieter as there will be lots more of them whooshing around. Generally rail irritates people less that other noise sources, but the success of the electric trains and POAL’s grand plans is likely to lead to greater frequency of night freight trains that are currently diesel. This may offset the lifestyle benefits of electrification to people living close to the railway.

            The World Health Organisation recommends and most developed countries adopt lower dB levels at night as the health effects of sleep deprivation are significant. NZ is behind the times and out of step on addressing this issue in relation to transport in general, whether rail, road or air.


  2. George beat me to it but in my experience many people don’t fully grasp that a decibel range is not linear. Just out of curiosity what would the bar chart look like if it was displayed with a linear sound-level scale?

    I wonder if that would have more visual impact.

  3. that article is exemplary of the Herald. Title against the CRL (wtf?), then an article that talks about something completely different.
    Also, a comparison with a Bus would be very interesting.

    1. It’s intentional, much as National’s announcement last year that they’d fund the CRL in 10 years time, these sorts of articles are put out to confuse people into thinking the CRL is currently progressing and hence National is investing in Auckland. I’ve spoken to several people who said they were voting for National because of its investment in PT such as the CRL, and NZ Herald is to a large extent to blame for that.

      1. What a load of cobblers, take off your green and red tinted glasses and look at the real world. As if the Herald would print an article because the government said so. The Herald is mainly left leaning as with most media outlets so I don’t think your conspiracy theory holds water,

        1. I disagree. The Herald is tilted towards what sells papers (actual paper) to ageing baby boomer suburbanites. They pander to National voting folk who love a good read about ‘scandalous’ train failures or what not, because that’s their only remaining market.

    2. Especially one of the old dunger buses which are still in regular service. I’ve noted quite a few NZ Bus buses with recent (F-, and G-series plates) registration plates but the style of the bodywork and the clearly geriatric state of the engines gives away their true vintage as belonging more to the W- and X-series plates. Anyone know what’s going on? Have NZ Bus just recycled a bunch of clangers and said that they’re new buses, because just look at these new registrations? I wouldn’t put it past them.
      One thing’s for sure, there are far, far more old buses on Auckland’s roads than should be allowed given NZTA’s position that a commuter bus fleet shouldn’t be more than 10 years old.

      1. NZ Bus’ fleet painted in the Waka branding are probably worst buses running in Auckland, all of them are loud, dirty and very old. I hope AT implement some pretty tough minimum standards when contracting out the new bus routes, as well as minimum sizes and I sure as hell hope they ban NZ Bus from plastering any further routes with ads on the windows. The Link buses are horrid to rid in as well as being too small, furthermore, the Link is actually more expensive than taking a regular bus so in effect passengers pay extra for the privilege of having windows blocked for ads.

        1. I’ve done some noise measurements for events in Aotea Square. The maximum SPL at the boundaries of the square must be no more than 65dBA that is basically a conversation level. Unfortunately traffic in Queen St easily reached 80dBA and buses went around 95dBA.

  4. I took the article as positive as that was all they could come up with. At the end of the day it is just another example of the high quality journalism we have come to expect from the herald, and probably shows why people don’t read papers anymore.

    On another note I went to Wellington yesterday and on the way backnflew over the top of Wiri Depot. A lot of businesses have got logos and advertising messages painted on their roofs, I couldn’t help wonder if Auckland Transport haven’t missed a trick here, and could use the roof space more imaginatively than a giant AT logo.

    It was also impressive seeing allnthe new trains lined up, probably 12 units or so were visible from the air.

      1. You mean the story about increasing security on trains because there have been physical assaults on staff? Come on Patrick, that’s legitimate news and you bloody know it. There’s not a single mention of people being safer staying off public transport; if anything, the additional security should help people feel safer.
        Would you rather they didn’t cover it at all? White-wash a real issue which has seen railways staff off work after being deliberately injured? Now who’s trying to distort reality to fit a particular narrative?

        1. Yes i do mean that crazy beat-up. The implication is that passengers are at risk. This is so not the case, some fare evaders get violent when confronted. You are at no more risk on the trains than anywhere else in the city, and certainly a lot safer than getting in your car. Furthermore, after yesterday’s attempt to spin great news as a problem this is just getting silly. Where is the two page info graphic on the new trains?, like Waterview got? The herald has an agenda, and i’m calling them on it. That’s all. 500 million on a brand new transport kit and no celebration from the herald in the week before the launch?, just snivelling and scuffling around for negative little stories. Why this story now? It’s not the fact of it, which of course they should report, but how they pitch this and everything to do with AKL’s rail revival. Funny really.

          1. This air-con story was an agenda. Reporting on the assaults on train staff resulting in increased security presence is, you know, reporting. It’s a legitimate story, and they covered it without much in the way of breathless hysteria. You had to get nearly to the end of the article to find out that the union says it knows of an average of three assaults on staff a month so far this year.

            Sometimes a story is just a story. Hell, they decorated it with a truly awesome photo of the new trains, rather than some stock photo of a police car or a Maori warden. If they were really pushing an agenda with this one, it’s missing a lot of the usual give-aways like frantic hyperbole and wild speculation.

          2. Matt they ran the same story about train staff about a month ago. This one didn’t provide any new info over what had been reported previously.

  5. To quote Marlo Stanfield: “This is what you call one of them good problems.” If the mild hum of the aircon is your acoustic concern on a train, that’s a quiet train. Herald journos and editors not missing a chance to obfuscate though!

    1. The Herald journos are desperate to spin a tale that something about our new trains is below par, no matter how trivial it really is.

      1. My impression was slightly more nuanced. I got the feeling that Mathew Dearnaley was trying to write something nice, but that he has been instructed not to. There was a tension in the article that disrupted the normally smooth flow of news writing. Perhaps Patrick might have some thoughts about the aesthetics of it 🙂

        The headline is so obviously wrong that it feels added by a sub-editor, someone who is clearly under instructions to discredit trains in particular and PT in general at every possible opportunity.

        Whatever the cause, the result is just making the Herald look sad, so sad.

        1. We do know that Dearnaley’s work is edited. And it seems the editors aren’t really sure what a train is and what they’re for. But there you go.

          Which will be around longer do you think; trains in AK or the Herald? Or more to the point which is growing and which is declining right now?

          I guess the thought of people taking the train and reading the paper is a bit hard to grasp? No attempt to sell it even at the bigger suburban stations for example….

          1. Orsman is senior staff in the Auckland newsroom. The conflicted output regarding the public transport renaissance in Auckland speaks volumes about just how much influence he has on editorial direction generally.

            I really wish editorials in NZ papers had to carry a by-line, so that we could tell which of the assassinations are Orsman’s work. If it’s good enough for the Economist to by-line all but a very few collaborative editorial pieces, it should be good enough for a rag that’s barely worthy of being wrapped around a quality serving of fish and chips.

          2. I can always spot Roughan’s particular form of deeply suburban old man thinking. The herald is full of wrongness but of slightly different flavours. I agree about by-lines: We always do it. All views come from a point.

            There is likely a high degree of panic at the paper as it declines, leaving the aged suburban rump it’s only substantial readership block, so I guess it is trying to reflect their idea of that group’s prejudices back at them in an attempt to gain approval and subscription renewal. This is a declining market though, surely, by definition. Despite the paper’s attempt to reinforce a tired view.

            Business section best, if lacking sufficient counterfactual views for a real debate. But more info and less cringing spin there.

            Interesting the print version of the train assault story is more nuanced than the online one, it has a quote from AT whereas the online one says they declined to comment. So one is inaccurate at least..?

        2. Yeah, generally the journo writes the article and the editor picks the title/headline. Quite how they’ve managed to spin it negatively and roll it in with the CRL is beyond me.

  6. It’s the same story with the new trains here in Sydney in that the loudest thing (if you can say that) is the aircon. On the rare occasion the system switches off then the train is virtually silent and it’s eerily quiet. I wonder if in a climate like Auckland’s, it’s really necessary to have the aircon switched on non-stop. Even here I think it doesn’t need to be on as much as it is. Aircon overkill.

    1. It’s better to let the air-con control the operation of its motors than leave a person turning the system on and off when they think it’s necessary. Let the environmental monitoring system in the air-con units do their work. Being turned on doesn’t mean it’s always running, and once you get 70 people in a carriage you desperately want air-con running just to keep the air moving.

      1. On something like train AC is needed all year round to keep it feeling dry, a constant temperature and to clear out BO. Worse way to put people off using PT is if they arrive at work or wherever they’re going feeling sweaty and damp from sitting on a crowded train with no air movement.

  7. Do you have to push a button on the side of the door to enter/exit, rather than it opening automatically? If so, perhaps some ‘push to open’ stickers might be required to avoid people just standing there waiting.

    1. Doors are push button as per basically every other train anywhere else with a modern PT system. No need for stickers, I’m sure the vast majority of train users have experienced trains with push buttons, even Wellington has them.

      1. > Doors are push button as per basically every other train anywhere else with a modern PT system

        I haven’t travelled much on trains overseas, except for metro-style systems, like San Francisco’s BART, the Paris Metro, or the London Underground, where automatic doors are the norm. Which seems like the sort of thing Auckland is aiming for in the future with our new trains, what with the CRL, 10 minute headways all day, closely-spaced stations, and so on.

        I’m sure most people will figure it out in about 15 seconds when the doors don’t open, but it’s far from being obvious, especially to people whose main comparison will be Auckland’s previous trains, not some random train they might have used years ago in Winnipeg or Düsseldorf or Wuhan or Perth. Even if you see the button, there’s decent odds one would assume it’s intended for the train manager, not the public.

        Let’s give a little comparison. I stood the other day at the corner of Victoria Street and Franklin Road, waiting through two full light cycles for the pedestrian crossing light to go green, until I got impatient and started mashing the button in frustration. Turns out some pedestrian lights are now programmed to stay red even when the button hasn’t been pushed. You get a little blue LED next to the button to indicate whether it’s been pushed. Well, that’s a perfectly understandable design, but it flies in the face of decades of habit.

        A sign to tell you about the change doesn’t seem like too much to ask, and it might have saved five minutes of my life that I’d have otherwise spent standing around like a chump. Same for the trains. Would signs save a thousand people from missing one half-hourly train each? Maybe. Seems worth it to me.

        1. Maybe temporary stickers until the public catches on and/or the diesels are out of service. It doesn’t take long for it to become second nature. Sydney is the odd man out in Australia for this as all the other cities have push button doors but we for some reason don’t. Even stranger, the new trams do have push button doors. We’ve got a Warmer and more humid climate than our southern rival, yet still no….

        2. Good grief this is a non issue, there’ll be someone on each carriage who knows or can work it out, then the rest will see and quickly learn. Don’t want the trains to look there’s some anal and small minded flatmate in charge running around putting post-it notes up on everything…..

          1. I agree, I thought it was a non issue too but clearly it’s not to a lot of people around here.

          2. Train arrives, door doesn’t open. Person starts looking around for way to open it. Problem solved. Aucklanders are NOT any stupider than the rest of this world’s tool-using apes.

        3. Yes well traffic lights are an interesting comparison as in most other places you don’t need to push the beg button. So in fact Aucklanders should be very used to pushing buttons and the new trains will be an easy fit.

          1. Well why don’t they just open automatically like the current ones? Seems like a backward step. I first got slightly flustered by this when I was abroad (Italy). Was about to get off an OLDER train and the door didn’t open. Quickly figured out that you had to open it yourself of course. Ever tried catching an unfamiliar train in an unfamiliar place? You have to know which side the platform will be on. You’re standing on the wrong side, pushing the button and nothing happens. When it’s dark outside it’s hard to tell. Funny that some get angry about little things. I thought trainspotters would be interested in the minutest things?

          2. It’s to create a better passenger environment. In the middle of winter the last thing you want is the doors opening and filling the train with cold air if no-ones getting on. Opposite issue in summer. Having push buttons means the doors only open if they’re needed and so can control the air-con better.

        4. The door button lights up green when the door is available to open.
          The ADKs and ADLs initially had them and it worked out fine.
          When I was at Newmarket yesterday, a test EMU pulled up, and a minute later a passenger intending for a West line train came up, looked at the train door for about two seconds, and then pushed the button. Of course as the train was not in passenger service, the door did not open, but my point is the guy found the button, and pretty quickly (even if he missed the “Test train” destination signs).

  8. Just measured the internal sound level in a 3 car DMU and also on a 4 car SA set, DMU was 84 dB, SA set was 63 dB
    Measured it using an app on my Android phone, which admittedly is not a proper sound set up, but app does seem to tally with the ambient noise when I use it, so it probably no worse than the Herald reporters used.

    DMU was noisy, due to the Engine being under the floor but I was away from the engine area not right above it, The SA was measured at the far end – i.e. away from the Loco.

    So given that result I’m expecting the EMU to be pretty quiet inside and out wit h the above comparison numbers.

    All this reminds me of when Qantas flew A320 planes here in NZ domestically (thats a while ago now), they used to specificially mention on the before take off and landing announcements how much noisier the flaps and wheels would sound and that this was due to the interior of the aircraft being much better sound insulated from engine noise so it was generally quieter and did not mean that there was anything wrong with the plane. And compared to the old Boeing 737s Air NZ used to fly to A320s are quieter except for flaps and wheels deployments.

    And maybe this noise thing is just that – a side effect of really quiet trains and as someone else said “its really is a nice problem to have”..

  9. On Paris metro you can push the button, and the door opens slightly before the metro has stopped. This means you can jump out and hit the ground running.

    I suspect Aucklands EMUs can in fact be programmed to open all doors at stops in the future. Which may happen at say Britomart.

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