Pre-Safe Sound: Playing ‘pink noise’ in the split second before impact (2015)

https://www.mercedes-benz.com/en/mercedes-benz/next/connectivity/pre-safe-sound-playing-pink-noise-in-the-split-second-before-impact/

by rosstex • 10 years ago

345 156 10 years ago

mercedes-benz.com

codeulike• 10 years ago

The interesting bit:

If an impending collision is detected that would be expected to produce a loud crash, the vehicle’s sound system plays a short interference signal. This causes the stapedius muscle in the ears to contract, which for a split second changes the link between the eardrum and the inner ear and so better protects it against high acoustic pressures. Most importantly, the reflex reduces the damage to hearing.

xorgar831• 10 years ago

Here's the sound: https://www.youtube.com/watch?v=bCOw5lisrIU&t=25s

Swizec2• 10 years ago

I might be imagining this, but I could swear I felt my ears becoming "full". Sort of like tired of the noise and numbing down? It's hard to describe but it felt similar to being on an airplane for a long time where sound becomes kind of dull because of all the engine noise.

Angostura5• 10 years ago

I wonder if it as cool hypothesis that they decided to implement as a cheap bit of marketing, or whether the protective factor is actually evidence-based.

oblio• 10 years ago

That's a bit cynical of you, isn't it?

Also, would you say the same thing if it was another car company that did this?

pja3• 10 years ago

Did you actually read the article, or are you just here to snark on HN?

Here, let me do your research for you. First link on a search for "stapedius reflex" is https://en.wikipedia.org/wiki/Acoustic_reflex

A quick search on Google Scholar for "acoustic reflex noise" turns up this paper from 1962 which states in the abstract that the acoustic reflex is more easily triggered by wide bandwidth noise than a single sinusoidal tone. http://scitation.aip.org/content/asa/journal/jasa/34/9B/10.1...

I think we can safely say that this work is pretty evidence based.

yorwba• 10 years ago

From https://en.wikipedia.org/wiki/Acoustic_reflex#Protection_rol... :

  According to the article Significance of the stapedius
  reflex for the understanding of speech, the latency of
  contraction is only about 10ms, but maximum tension may
  not be reached for 100 ms or more.[6] According to the
  article Le traumatisme acoustique, the latency of
  contraction is 150 ms with noise stimulus which SPL is
  at the threshold (ATR), and 25-35 ms at high sound
  pressure levels. Indeed, the amplitude of the
  contraction grows with the sound pressure level stimulus. 10]


  Because of this latency, the acoustic reflex cannot
  protect against sudden intense noises.[10][6] However,
  when several sudden intense noises are presented at a
  pace higher than 2–3 seconds of interval, the acoustic
  reflex is able to play a role against auditory fatigue.[10]

I did not bother to check more than the abstracts of the references, but it does seem like evidence exists.

mannykannot2• 10 years ago

I have read somewhere of a click being played through tanks' crews headphones when the main gun is fired, for this reason. This was wrt 70s-era Soviet tanks.

lordelph• 10 years ago

Mildly interesting: when I played the sample pink noise in the article, my dog went mental.

buserror• 10 years ago

Of course he did. Poor thing, he realized you were going to be involved in a car crash in the next 100ms.

(sorry couldn't resist :-))

obitoo• 10 years ago

Mine didnt - she continued to gaze at me wondering if I had any food.

rrmm• 10 years ago

I wonder if that noise is going to be a major ptsd trigger for people involved in an accident afterwards. (Of course probably any loud noise would be). It will be interesting to see any data they can collect out of this on the benefit in practice.

smegel• 10 years ago

Sounds more like white noise to me. What makes it pink??

wingerlang• 10 years ago

I don't know really know what this means tbh, but here's an explanation: http://www.acousticfields.com/white-noise-definition-vs-pink...

jrockway• 10 years ago

It's white noise with a different power distribution; low frequencies are louder:

http://i.stack.imgur.com/MMr0a.png

eyuelt• 10 years ago

Redshift

leblancfg• 10 years ago

The sound is distinctly crisper on BigQuery, though. Of course, cables can make a difference but not always -- use CAT-8.2 if possible.

timpattinson• 10 years ago

Because humans hear frequency in log scale, pink noise has more "even" distribution of amplitude to our ears. Pink noise -> 100-200hz has the same power as 10k-20k ie each octave has equal power AFAIK.

wrigby2• 10 years ago

White noise is defined as having equal energy per frequency; that is, a 10hz wide slice of spectrum centered on 100hz will have as much energy in it as a 10hz wide slice of spectrum centered on 1khz.

Pink noise has equal energy per octave; the slice of spectrum from 40hz-80hz has as much energy as the slice from 80hz-160hz and the slice from 1khz to 2khz.

Pink noise can be thought of as white noise with a very low-q (3dB per-octave, specifically) low-pass filter applied.

martin-adams2• 10 years ago

I worked with an audio engineer on real-time video encoding hardware and he said that in audio compression, you can throw away audio data immediately after a loud noise because the ear can't pick it up. This is probably an oversimplification, but sounds like a similar technique in this safety feature. I like it.

chipperyman573• 10 years ago

Interesting! Can you completely discard it (as in, complete silence immediately after) or just compress the immediate bits after a lot more than normal?

pvdebbe• 10 years ago

I'm guessing that the data couldn't completely be silenced because then any heavy dynamic compression at playback would bring out the optimization and break the sound.

martin-adams2• 10 years ago

Sadly I don't know the answer. I was just the GUI engineer fascinated by the cleverness of how to compress audio.

kimburgess4• 10 years ago

This is actually a big part of how MP3 compression works. Rather than using straight up data compression, it uses a psychoacoustic model to simplify different components of the signal that are affected by masking.

There's a nice high-level (human readable) technical overview here if you'd like to learn more: http://arstechnica.com/features/2007/10/the-audiofile-unders...

kimburgess4• 10 years ago

I should add, as another side note / rabbit hole to those new to the art of 'fucking with brains through audio' — masking is also frequently put to use in mixing, particularly EDM and more percussive genres.

To help squeeze every last drop of perceived dynamic range out of a track you can use a technique known as sidechain compression (http://samplesfrommars.com/blogs/tips-tricks/18999227-how-to...) to dynamically compress other components of the mix in response to (usually) a kick drum.

stirner• 10 years ago

Doesn't all lossy compression use models of human sensory processing to determine which information is important?

kevincennis• 10 years ago

Yup! This is called temporal masking [1].

There's also simultaneous or frequency masking. If you've ever wondered why loud noises prevent you from hearing something that would otherwise be perfectly audible (e.g. a loud motorcycle driving by your apartment can temporarily drown out a noisy air conditioner), that's why.

Both of these psychoacoustic concepts are used in perceptual audio encoders like MP3 - the idea being that certain bits can be discarded because the listener wouldn't be able to hear them anyway.

https://en.m.wikipedia.org/wiki/Auditory_masking

logotype• 10 years ago

This is why I only listen to music in PCM 24-bit WAV's instead of compressed audio. The difference is huge due to the missing frequencies in MP3 and similar formats.

hiharryhere• 10 years ago

Forwarded this onto my dad who is an ENT specialist. He responded:

"The Stapedius reflex has been use for artillery gunners for decades but the pink noise use is certainly novel."

arprocter• 10 years ago

I was going to ask if this would work at the gun range

ComputerGuru• 10 years ago

This is a comment from Reddit on the same [0]; though I cannot vouch for its veracity, I found it interesting nonetheless:

Former Benz master tech here.

I've spent a good bit of time diving into the nitty gritty of these systems.

It uses all of the vehicle sensors to determine crash logic.

You want to fire the pretensioners before the airbags if at all possible. This locks the occupants in a much more secure and predictable psition.

Accelerometers can determine if something like a rollover is in progress.

Heavy braking + high speed + sudden activation of the parking sensors indicates a crash before physical contact happens.

It can use the radar on distronic equipped cars to predict a crash.

If the vehicle is in a slide, and a sudden yaw correction happens, this means a collision has occurred, even if the airbag sensors haven't been triggered. This is useful because the airbag sensors are only good at detecting force in one dimension.

It's even possible for the vehicle to determine to fire the pretensioners but no airbags based on occupant size and weight (determined through seat/steering wheel position and capacitive mats in the seats) and impact vectors.

It will even do things like full field the alternator up to 18+ volts to slam the windows shut super fast in the event of a rollover.

The actual detection logic fills a 4" thick book.

It's a big reason those cars are so damn expensive.

Mercedes doesn't fuck around with safety.

If I had to be in a wreck, it would be in an S class. Hands down.

0: http://www.reddit.com/r/todayilearned/comments/59qhaw/til_ne...

LeonM• 10 years ago

If I had to be in a wreck, it would be in an S class. Hands down.

To be honest, I'd rather be in a Tesla, since no amount of smart sensors can replace a crumple zone. The S class in particular has a big engine (usually a V8), which won't play nice during a front end collision.

3chelon6• 10 years ago

Crumple zones assume a nice, controlled, head-on crunch. Not so useful against getting whacked in the side by a truck. But then, probably not much is.

SolarNet• 10 years ago

Also, they use the same materials engineering from SpaceX designed for collisions in space. One of the reason their safety rating was so high.

semi-extrinsic4• 10 years ago

I see this claim tossed around a lot, but is there really a documented significant effect on safety from not having an engine up front? I mean, with a car having that huge front, is there not so much space for crumple zones that engine or not is insignificant?

Now I know the Model S claims "best in class NHTSA rating", but no comparable luxury sedan has been crash tested by either US NHTSA or Euro NCAP.

That's right, neither the BMW 7-series, the Audi A8 nor the Mercedes S-class have been tested. So we just don't know.

Edit: Update: I've checked various other cars, and the only one I could find where both an EV and a non-EV version have been crash tested in the same year is the 2014 Kia Soul (a small MPV) Euro NCAP tests. For that car, the diesel one did worse than the EV on driver protection, specifically of the feet, which was caused by spot welds (presumably in the torpedo wall) breaking and sharp edges protruding near the driver's feet. But for child safety, which is more focused on just acceleration and thus a better proxy for crumple zones, the cars were equal. So this seems more indicative of a design fault with the Soul than a lack of crumple zones.

3chelon6• 10 years ago

This is all fascinating stuff, thanks.

Of course, in the future when all cars are connected (even if they're not self-driving), combining all this sensor data and sending it to the vehicles behind you would save countless lives. The number of times you hear about pile-ups in fog and heavy rain - that could all be avoided by cars talking to each other.

But I'll bet there's still no open (or even closed) standard on inter-manufacturer comms yet?

spydum• 10 years ago

and all the script kiddies will find it great fun to send out those "collision" signals on a busy roadway just to screw with people. the futures gonna be great!

arethuza2• 10 years ago

That does raise interesting security problems though - my car receives a message saying to stop as quickly as possible, how does it decide whether this is a valid message or someone hacking cars for fun?

JustSomeNobody2• 10 years ago

... when all cars are connected ...

You're so funny. This is a world of proprietary technology.

mseebach2• 10 years ago

You could mostly prevent pile-ups, but pile-ups generally don't kill people. Also, you don't need connected cars to avoid pile-ups, you just need to keep your distance and your eyes (sensors) on the car in front of you. Both of which works pretty well with current (unconnected/unilateral) technology.

None of the causes in listed in this article require interconnection to avoid: http://uk.businessinsider.com/the-cause-of-the-most-fatal-ca...

JshWright• 10 years ago

Assuming the occupant didn't see it coming, the car will have made all its decisions and initiated all active safety measures before a human being inside the car would even notice a collision is taking place.

The car is effectively 'done' progressing the event before the human even starts.

supermatt• 10 years ago

It actually seems a lot slower than I would have expected, to be honest. The seatbelt tensioners take 150ms to activate, during which time I would have travelled 2m at 30mph (1). That effectively makes them useless, no?

1) https://www.wolframalpha.com/input/?i=distance+traveled+in+1...

giarc• 10 years ago

It will even do things like full field the alternator up to 18+ volts to slam the windows shut super fast in the event of a rollover.

I imagine this breaks the window mechanisms. However, you've been in a rollover, probably doesn't matter anymore.

tome• 10 years ago

How is this of benefit? All I can see it doing is chopping off my arm if I've got it hanging outside the window.

tlb• 10 years ago

Motor & gear mechanisms usually have a lifetime that decreases at something like voltage^3. So you can double the voltage and get 1/8 the life. Since they have to be rated for thousands of cycles normally, you can overpower them a lot for a single cycle.

nom• 10 years ago

It sounds like it also may cause damage to other electronic components. They essentially switch the alternator into different mode that doesn't limit the output voltage in order to generate as much energy as possible.

I can't imagine them running a separate wire in the harness only for this one feature. It makes more sense to simply increase the voltage of the 'mains' 12V power inside the car, dump as much energy into it as possible, and design all critical components to handle the event gracefully. Sacrificing the less important electronics sounds like a viable option during a rollover event.

Theodores2• 10 years ago

If I had to be in a wreck, it would be in an S class. Hands down

I do wonder why rally and track cars have roll cages with mandatory helmets, windows made of plastic and prominent switches for cutting the electrical systems and fuel. This is in the lower racing classes that have otherwise standard road going cars. Rally cars go on dangerous tracks, track cars go fast on safety standards approved tracks. Road cars combine the ability to achieve dangerous speeds and they go on roads as dangerous as the rally cars. At 155 miles an hour you are far from guaranteed to be safe in an S class. I would go for the roll cage, 4 point harness, Hans device, helmet and fireproof suit if I was to thi

Theodores2• 10 years ago

If I had to be in a wreck, it would be in an S class. Hands down

That way of thinking aside, Mercedes are the true pioneers of safety even if the liked of Volvo claim more credit. Fantastic as these innovations are, we need to restrict vehicles to their safety ratings. This then means that the safer cars are quicker, the S Class becomes quickest on the road, Tesla aside...

komali24• 10 years ago

I can't find the article but I read that you're more likely to experience a head injury as a pedestrian in a major city than a cyclist, and yet I always wear my helmet on my bike and never when I'm walking around.

I guess it's about finding that balance between protection and, what, fashion? I don't know.

laacz• 10 years ago

Vehicles with rollover cage are forbidden from driving on public roads in most of EU.

wmeredith• 10 years ago

If I had to be in a wreck, it would be in an S class. Hands down.

Most "car guys" you talk to would say the exact same thing. The luxury flagships are super-interesting from a technology standpoint. You can look at them and see what new features will be coming to Camry's and Taurus's in the next decade or so.

bertil• 10 years ago

All that effort to protect the people inside, and they still won’t try to do anything to prevent them from running people over.

I wish car safety was also based on what happens to people outside the car.

kijin• 10 years ago

People inside a Mercedes are more likely to be Mercedes customers than those outside. They're even more likely to become repeat customers if they just totaled their car and walked away from it without a scratch.

We need to make car manufacturers pay for externalities if we want them to care about people outside the car. They won't do it on their own.

gururise• 10 years ago

Fascinating stuff. Kudos to Mercedes-Benz for pushing the envelope and making driving safer.

cpeterso• 10 years ago

I often listen to pink noise while I work to suppress room noise and mask tinnitus. Ironically, I find it is also good for relieving headaches! :) I have a CD with hour-long tracks of just white noise (sounds like static), pink noise (sounds like waves), and brown noise (sounds like airplane hum).

http://whitenoisemeditation.bandcamp.com/

audeyisaacs• 10 years ago

You can also use SoX!

`[audey@feather ~]$ play -c2 -n synth whitenoise lowpass 400 highpass 40`

Stenzel• 10 years ago

The pink noise in the video has some strange dropouts and is compressed. If you want to listen to real pink noise I suggest this: http://stenzel.waldorfmusic.de/post/pink/ Source Code: https://github.com/Stenzel/newshadeofpink disclaimer: I made this.

JHHuijnen• 10 years ago

Dear everyone,

Mercedes is a good marketeer and with best intentions they included protection of hearing in their campaign. I wouldn't blame them for not knowing and after having spent lot's of money on this it could be dissapointing to hear that in fact, the acoustic reflex arc, otherwise known as the stapedius reflex does not protect hearing against loud sounds. It is simply a myth that even among many professionals is believed.

The facts are that the ear's transparency for sounds is traditionally tested with only a single frequency, around 226 Hz, and around that frequency the sound levels get reduced by the acoustic reflex. Thus it seems as if the ear protects itself for loud sounds and the myth is born although it has only been measured at a single frequency.

Technology to measure the same prinicples for a wider frequency range is currently only available for a selective group of researchers and for the industry developing medical instruments in this direction (for which I work). We know that above 1000 Hz the stapedius reflex is doing the opposite of protection. It will increase the sound levels.

I could explain why the reflex is doing this, why did it evolve like this during the last many thousands of years. It is certainly easy to understand that a couple of hundred years ago (before industrialization) no protection for loud sounds was actually needed and thus hearing protection is not a logical candidate for explaining why we have such acoustic reflex...

Though this is not the point. The point is that Mercedes' feature is not protecting your hearing during a collision impact. They made it with best intentions and for that they deserve a compliment and credits.

A little more info about the acoustic reflex that I consider to be correct can be found here: https://youtu.be/3a3Eeuhkh-c?t=1164

Feel free to try to get in touch with me as well if you want to find out more about this topic.

Cheers Jos

Pre-Safe Sound: Playing ‘pink noise’ in the split second before impact (2015)

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