Bez: “The Sounds of Science”

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We published a review of some earphones yesterday, and it’s sparked rather a polarised discussion on our Facebook page. So we thought this would be a good time to publish the musings on music of our Singletrack Columnist Bez, who’s already examined the topic – and the research – in depth…

AdobePhotoshopExpress_d349f173d1be4a6c8a5c988e0e5c71d9The use of headphones is just one of many aspects of cycling behaviour which generates lively debate.

But it’s debate which rarely braves the cold world of data and quantitative study, preferring to inhabit the opinion columns of newspapers and the soundbites of politicians.

Let’s try and move it on a little.

Signal-to-noise ratio

Much of the discussion of headphones is, sadly, noise. This reached its deafening peak in November 2013, in the wake of a spate of cycling deaths in London. Most notably Boris Johnson publicly decried the use of headphones, even though there was no evidence that they were even in use by any of the deceased, let alone that they had contributed to the collisions.

On the one hand this sparked keen defence of headphones by those who use them, while on the other, the tabloids wheeled out the “zombies” invective, which the Guardian questioned.

So, who’s talking sense?

Is riding with headphones safe?

Often, there’s a simple question we need to answer. But it’s extremely rare that the real world to which it pertains is anything like so simple, even when it might initially appear to be.

Do the strategies adopted by headphone users actually improve safety?

So, I think it’s reasonable to translate “is riding with headphones safe?” (and that should really be the subtly but importantly different “does riding with headphones introduce an unacceptable level of danger?”) into the following questions:

  1. Is the rider’s ability to hear external sounds diminished by the presence of headphones and/or the addition of music, speech etc?
  2. Is the resulting loss of ability to hear external sounds of a degree and nature which diminishes their ability to build a dynamic mental picture of the environment and traffic around them?
  3. Is the rider’s concentration diminished by the additional sounds of music, speech etc?
  4. Is the rider’s loss of concentration of a degree and nature which diminishes their ability to concentrate on the environment and traffic around them, and/or their ability to control their own cycle?
  5. Are there any strategies the rider can readily adopt which can sufficiently mitigate any additional risk that may arise from above?
  6. Does familiarity with the use of headphones reduce some or all negative effects that might be experienced at initial use?
Some headphones, yesterday.
Some headphones, yesterday.

Logical consistency

Before we start actually answering those questions, let’s take a quick look at them in terms of their logical implications.

Firstly, one has to consider deaf and partially deaf people. Logically, if one was to argue that the loss of ability to hear sounds was in itself sufficient reason to prohibit cycling with headphones, one would also have to argue that deaf and partially deaf people would have to be banned from cycling.

Consider deaf and partially deaf people…

Secondly, one has to consider cars. Cars have stereos in, and therefore, logically, if one was to argue that loss of concentration through listening to music or speech was in itself sufficient reason to prohibit cycling with headphones, one would also have to argue that car stereos would have to be banned.

So, while the questions above are well worth asking, if the answers to them are to be used as arguments in favour of prohibiting the use of headphones there are some pretty hefty logical implications if that argument is to avoid hypocrisy.

But let’s take a pop at answering them anyway.

Experimental data

So, why does the discussion rarely include data and research? Well, it’s partly because there’s not much of it about. But there is some.

Testing ability to hear

Let’s kick off with a paper by de Waard et al, which studied cyclists’ response to an auditory ‘stop’ signal whilst using headphones or mobile phones. It was a small study, of 25 participants, and it found that:

Cycle speed was not affected by listening to music, but was reduced in the telephone conditions. In general the response to auditory signals worsened when participants listened to music, in particular when listening with in-earbuds loud auditory stop signals were missed in 68% of the cases. However, when listening with only one standard earbud performance was not affected.

This is hardly surprising: listening to music does reduce the rider’s ability to hear other sounds, and in-ear headphones markedly increase this effect.

Listening to music does reduce the rider’s ability to hear other sounds

Of course, this begs the question: When does one hear an auditory stop signal in real-world road use? I think the use of “a stop signal” carries unfortunate connotations of an on-carriageway directive, and therefore assumptions that there is an inability to respond to “a stop signal”, rather than “an auditory command”. Stop signals are not auditory. They are red lights, white lines, and so on. All visual.

Sadly, this is the most-cited piece of research around, and it’s very often misinterpreted in that exact way.

Comparisons with driving

Some Australians also did a pertinent experiment. It’s not a peer-reviewed paper in a scientific journal, but it is a fairly conscientious test that makes quantitative and qualitative measurements. It found that:

A bike rider with ear-bud earphones playing music at a reasonable volume hears much more outside noise than a car driver, even when that driver has no music playing.

A bike rider with in-ear earphones playing music at a reasonable volume hears about the same outside noise as a car driver with no music playing, but more than a car driver playing music.

This reinforces the point made earlier, that if one is to argue for prohibiting cyclists from using headphones, one has to also argue for prohibiting drivers from using stereos and even windows in order to be logically consistent.

It's not black and white...
It’s not quite this black and white…

Research overview

The Netherlands’ Institute for Road Safety Research (SWOV) mentioned the de Waard et al paper in a summary of research activities. In it (see p8) they make a notable inference from the experiment:

An experiment in which the participants had to cycle while they were listening to music and using their phones, and were told to stop when they were given an audio signal, indicated that their cycling became less safe than when they did not listen to music.

This is a little disturbing from a research institute, in assuming that some loss of hearing ability (which, crucially, is what de Waard et al tested) is inherently less safe. It’s one of those things that seems obvious, but may or may not be true.

And it’s also the exact type of unfounded inference that I believe de Waard’s “stop signal” test encourages.

On the same page, the authors note that

The use of these types of devices while cycling appears to increase the risk of being involved in a crash.

It’s one of those things that seems obvious, but may or may not be true.

Where they use the phrase “these types of devices”, they are making a common mistake, which is to gather mobile phones and music players into the same category. They are markedly different: the former require interaction and are widely shown to introduce significant cognitive distraction.

The mistake can be highlighted by the data they cite:

15% of the Dutch cyclists said they listened to music during (almost) every trip.

More than 3% of the cyclists report making or receiving a phone call during (almost) every trip.

Approximately 9% [of] bicycle crashes with injury are preceded by the cyclist using devices.

These data are wholly consistent with the hypothesis that phones cause significant added risk and music players do not. Without being able to separate these two groups, however, it actually seems quite possible that music listeners may be under-represented in the crash figures: are they actually less likely to be involved in a collision?

The statistics relating to collisions are murky.

Is there even a worthwhile hypothesis that music listeners are safer? Just as there is a hypothesis that non-helmeted cyclists may be safer because they are less inclined to risk compensation, is there also one that aurally-restricted cyclists are safer because they do not rely on sound signals (which are unreliable) and instead increase their reliance on visual checks (which are highly reliable)? This takes question 5 above and changes it: Do the strategies adopted by headphone users actually improve safety?

Deaf, or possessed of super powers?
Deafened, or possessed of super powers?

Some soundbites

When we break the problem down into testable questions, we find some interesting things, both in terms of the logic and the statistics. Two conclusions stand out:

  • Given sound measurement data and the sameness of the auditory content, it seems impossible to argue a case for banning headphones without that argument being wholly inconsistent with the use of roads by deaf people and/or people in enclosed vehicles.
  • The statistics relating to collisions are murky. There seems to be no compelling evidence that safety is compromised, despite there being clear evidence for loss of hearing. Moreover, the data may even show an improvement in safety and one might hypothesise that this is because loss of hearing increases reliance on the more reliable sense of sight.

However, whatever the data show, like any discussion about restricting cyclists’ behaviour on the basis of things that seem obvious to others, I’m sure this will rumble on.

And, like all those discussions, all this noise achieves is distraction from the real way to solve the problem.

Hit play, hit repeat.

Beyond The Kerb.

Comments (14)

  1. First class reasoning again Bez, but as you realise this is wasted on the type of people who make these claims.

    Let’s just leave the phone issue out, as that’s more cognitive than audio related. If they wanted to stop cyclists using headphones of any description, on grounds of awareness of environmental audio sources, they’s have a hard time justifying not just car stereos, but also the trend for more noise insulation in cars over the past 40yrs and as you point out the roof & windows would have to go too.

    This whole debate has always been fatuous and based on narrow minded and stupid assumptions.

    Having said all that, I never use headphones on the road cos I’m the soft, squidgy target for the morons in tin boxes with their stereos at 140dB and their eyes on their phones, so I prefer to hear them coming.



  2. I’ve hardly ever used headphones in the outdoors, whether walking, biking or anything else. I just don’t see the attraction.
    On the other hand when driving I nearly always have the radio on, whether it’s music or Radio 4. This possibly suggests I’m less attuned to my surroundings when driving – and surely that’s a bigger public safety concern than cyclists with headphones?
    Like cybernaut in previous comment, I feel safer cycling on the roads without headphones, but the calls for a ban are just another example of victim-blaming.

  3. Before I wrote this article, I had a go at riding with headphones on my normal commute. I did so conscious of the fact that there is a significant acclimatisation issue, getting out of one’s comfort zone if you like, where initially it’s going to feel a bit weird and scary, but over time it’s quite possible that you adapt your behaviour and come to be no less comfortable or safe than without. (In fact, it’s quite possible that those behaviour adaptations could result in actually being more safe. Equally, of course, it may turn out that it is—or feels—less safe after all.)

    Some assorted notes from my experience:

    — I used two types of headphones: some behind-head buds (the ones shown in the black and white picture above) and some in-ear buds. The former had only a marginal effect on my ability to hear my surroundings; the latter a significant one (they have rubber parts which effectively seal the ear; to be honest I don’t like this “underwater” effect even if I’m just sitting at a desk).

    — Content makes a difference. I don’t perceive listening to music to be a significant cognitive distraction; however, I recall once trying to learn Spanish from a CD in the car, and I persisted only a couple of minutes before deciding that it was too distracting to be safe.

    — Noise is an unreliable mechanism for evaluating position or speed. Distinguishing the source is particularly difficult when there are many sources. At speeds above 10-15mph, noise also arises from airflow around the ears, glasses, helmet, clothing and so on; there have been occasions in the past when I have looked behind expecting to see a car that I’d heard, only to realise it was just the noise of turbulent air passing over my shoulders.

    — Manoeuvres demand visual checks in order to be confident. I do wonder whether sound can offer a false sense of security and whether one is more likely to use sight if sound is diminished.

    — I felt slightly self-conscious using headphones, knowing that they were visible and that there is a common opinion that using them is irresponsible. But that’s not really a safety issue.

    — Overall, I felt at no significant additional risk using either type of headphones. I certainly felt uncomfortable (mentally, not physically) with the in-ear buds, but it’s very hard to say whether this might affect my safety. I found the open-ear buds (shown above) to be absolutely fine, other than that they generated a lot of wind noise above jogging/running speeds. I’m inclined to test them under my winter cap, which has fabric covering the ears and would eliminate the noise from the airflow.

    — Crucially, I haven’t encountered—and nor can I immediately think of—a scenario where my cycling behaviour would be significantly influenced by a loss of hearing. If I have to make a manoeuvre myself, I check visually; whether that’s moving across the lane or tackling a junction. In the potential collision of a driver hitting me from behind, I would be able to do nothing even if I heard the car, because a car which is about to pass safely sounds exactly like a car which is about to drive into the back of you. To me, sight is what is required; hearing is at best only marginally useful and at worst misleading. To lose it feels unnatural, but not necessarily unsafe.

    Will I become “a user”? Not generally, no. I don’t feel the need, and frankly the wires are a faff. But I do sometimes ride through the night on rural roads, where there is little to see or to occupy the mind, and I may see if listening to music helps me through the long hours of darkness.

  4. i use a bluetooth hands free ear piece. I can play music through it and i wear it in my left ear so that my right is clear being nearer to the traffic… i used to use headphones but prefer this now… i only use it on a commute as it takes away the monotonous of commuting. on ‘normal’ rides i’m too busy chatting to my mates!

  5. I used a single earbud when road riding. It’s a pro-level vacuum seal type in-ear monitor and with a pair of them in I can’t hear a thing (which is great on planes and trains). However, with just one in, the seal is so good that I can have music on at a very moderate level in my left ear, leaving my right ear free to hear traffic. I reckon that the lower quality your headphones, the louder you need to play them to hear and the more distracting they are. I can hear things that are not much more than a whisper in my left ear, meaning I’m not distracted from traffic sounds.

  6. I think we (as vulnerable road users) will probably all agree that although we shouldn’t have to pay particular attention to what people behind us on the road are up to, in reality we ignore them at our (mortal) peril.

    Personally I have, in the past and probably will have again, owned powerful and expensive in car sound systems. I tend to turn them down in town and up on main roads. I am unquestionably less aware of the audible surroundings in a car anyway and with the sounds turned up I might as well be in the house.

    The real issue is, does this matter? The answer is a qualified yes as a car driver. Certainly the emergency services are well aware of the issues of drivers who can’t hear them and don’t see them because they don’t use mirrors.

    Personally one of the reasons I don’t use headphones on the road is because I when I tried it I didn’t like the effect of being even more startled by the usual close-pass situation and felt the effect might cause a heart attack eventually.

    What I don’t see is why anyone, cyclist or driver would consider this a safety issue. If the cyclist needs to hear you coming, you need to think about your driving.

    It’s a bit like insisting that HGV’s are equipped with radar so they don’t roll over people in their blind spots when turning left at junctions. The solutions to this problem are installing advance boxes at the junctions and making sure they are kept free of vehicles other than bikes (and that that includes coppers who should know better,) educating cyclists that like any vehicle they should only overtake on the right, stop painting stupid 18″ wide facilities down the gutters and finally making sure that the drivers are in no doubt that they will be held genuinely accountable if they take a life (with sentencing which is more appropriate and jury direction which makes jurors take offences seriously.)

    I remain fully in favour of presumed liability as a driver, cyclist and pedestrian. I worked in Holland and it just works.


  7. “If the cyclist needs to hear you coming, you need to think about your driving.”—QFT.

  8. I’ve used various ear buds for 15odd years when riding, and probably the entire time I was a courier.

    Never had a problem with that setup.

    However, they’re not canal* type isolating ones, so you can still hear. Cars are really loud!

    Also, I think it really is important to hear. Changes in engine note signal a manoeuvre before I see the car around half the time.

    *sigh. Not that canal! I wasn’t wearing headphones then!

  9. Flicking back to the headphone review, this makes me think…. It’s the wind noise that forces me to increase the volume. Perhaps a set of ‘phones designed* to minimise the house would lead to people riding with lower volume, therefore giving the best of both worlds.

    Like a bypass turbofan engine.

    *oh if only we knew a local designer for a set of Singletrack bike headphones 😉

  10. Fascinating article with some well thought out points, especially the thoughts about the deaf/partially deaf cyclist. I think that as long as you can ride a bike without passing a Government exam then they’d have a hard time banning anything cyclists do that could be classed as dangerous whether it’s earbuds or simply taking your hands off the bars to stretch/remove clothing/hydrate.

  11. Good article again Bez.

    As a regular user of headphones on both my road and mtb setups, i thought i’d add my thoughts.

    I bought some nice new headphones, with the rubber grommet type ear piece, and they are terrifying to use on the bike, even after years of music on the go. As your experiment shows, I was mentally uncomfortable with the lack of outside sound.

    I have some cheap in-ear buds with the foam pads, and they allow plenty of sound through, which i think is the ideal situation.

    As with everything, a little moderation and compromise is required, yes listen to music, but don’t worry about the sound quality, make sure you can hear the world. I find a good volume guide is you should be able to hear the TDI sat behind you at the lights.

    And irrespective of who does what, whether they are right and wrong, the cyclist is the spongy part, look out for yourself and do what feels safe to you.

  12. I’ve tried this on bike and motorbike. Hearing is already muffled with a motorcycle crash helmet but I didn’t like the sense of detachment headphones gave. Tried it on a road commute in town and was similarly shocked by proximal unexpected passes by cars. Even when doing a lifesaver to pull out to overtake parked cars it wasn’t enough to see cars going that wee bit quicker.

    Interesting science but as a motorcyclist you learn defensive riding techniques that carry over to the cycling world. Banning anything is nannyism gone mad, yet so too is to voluntarily remove another defensive sense. With the best will in the world, cyclists can miss seeing cars too.

    Personally buds are great for the 12 mile part on unlit cycle path when I can be bothered commuting, but i feel much more in touch with the trail and the gnar otherwise!

  13. The car argument is a bit silly. You don’t need to be quite as aware of other cars behind you when driving in traffic because they aren’t constantly streaming past you in your own lane.

    I can think of one situation where being able to hear the car behind me was very useful. A car approached me from behind, drew level, then turned left. Because I heard the car I knew it was there, and because I heard it slow down I instinctively knew it was turning. I looked over my shoulder and was able to take evasive action by turning left myself – accident avoided. The fact that the approaching car did not sound right alerted me.

    I have ridden with headphones before they created enough wind noise that the music had to be turned up to the point it drowned out traffic. That was scary. If you can hear music without losing the sound of cars then it would seem not to be a.problem.

  14. “In the potential collision of a driver hitting me from behind, I would be able to do nothing even if I heard the car, because a car which is about to pass safely sounds exactly like a car which is about to drive into the back of you. ”

    Not to me. I can tell a lot about what’s going on behind me by the sound. Wide road, car approaching to my right, no worries. Narrow road with a lorry approaching directly behind, uh oh. Better bunnyhop that drain cover instead of going around it because I am about to get grazed…

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