It takes just a split second for a car accident to completely change a person’s life. Mercedes-Benz PRE-SAFE® can help to minimize the damage. Once the vehicle’s sensors have detected that a collision is unavoidable, a comprehensive system of safety features are activated within the short time that remains before the impact occurs. It takes just 150 milliseconds to deploy the reversible seat belt tensioners, for example. To put that into context, the duration of a human blink is 100 milliseconds. 
 
 “PRE-SAFE® was first introduced at Mercedes-Benz in 2002,” says Rodolfo Schöneburg, Head of Vehicle Safety, Durability and Corrosion Protection at Mercedes-Benz Cars. “It kicks in before the collision occurs, preparing the vehicle and its occupants. PRE-SAFE® is therefore one of our systems that is based on what actually happens in real-life accidents and helps to save people’s lives.” 
 
 Harnessing the stapedius muscle reflex in the ear 
 
 Mercedes-Benz is now extending its PRE-SAFE® technology with PRE-SAFE® Sound. It will be debuted in the new E-Class, model series 213, available from 2016. The system is the first to harness a natural reflex to condition the ear – when a collision is imminent – for the loud noise that is anticipated from the impact. If an impending collision is detected, the vehicle’s sound system plays a short interference signal, which can trigger a reflex, whereby the stapedius muscle in the ears contracts, which alters the link between the eardrum and the inner ear for a split second and better protects the inner ear against high acoustic pressures, which can result from a loud crash. Most importantly, the stress on the ear can be reduced. ||||| Crash safety technology has come a long way in the past decade or so, with cars that now sense an impending crash and can prepare the driver for impact or even attempt to avoid a collision entirely. Mercedes’ current crop of E Class sedans take pre-crash preparation to an entirely new level, even going so far as to provide your ears with an extra layer of audio protection. It’s called “pink noise” and it’s designed to keep your hearing intact after being bombarded by the extremely loud sounds typically associated with a vehicle crash. 
 
 As IEEE Spectrum points out, the noise of a crash — from crunching metal, breaking glass, and the explosive deployments of airbags — can hit 165 decibels or higher, and has the potential to permanently damage a passenger’s hearing. To counteract that, Mercedes has built a system that, when a crash is imminent, produces a blast of pink noise, measured at around 80 decibels. Mercedes describes the sound thusly: 
 
 A frequency spectrum known in physics as pink noise is ideally suited for this purpose. It sounds like a bit like diffuse traffic noise, the breaking of waves or a waterfall. 
 
 Pink noise — which Mercedes calls “Pre-Safe Sound” in its marketing — is unique in that its power is inversely proportional to the signal. When it hits the ear, it triggers muscles in the ear to contract by reflex, automatically bracing the inner ear and eardrum for the extremely loud noise of the crash by reflecting some of the sound before it reaches the point where it could cause problems. 
 
 Mercedes says that the system reduces the possibility of hearing damage after a crash, and it’s been working on perfecting the technology for a while now. We’ll have to wait for the company to compile whatever crash data it can from the E Class, and the subsequent hearing health of passengers, before we’ll know if it’s actually working as well as the company wants it to. ||||| Mercedes-Benz is trying to cut down on hearing damage caused by the deafening crunch of a car crash, and it's doing so by blasting pink noise through the stereo when you're about to hit something, to trigger a fascinating physical response. 
 
 Mercedes-Benz has done a lot to push automotive safety forward over its long history. In 1978, the S-class offered the first (or one of the first, depending on who you ask) 4-wheel ABS systems on a production car. In 1987, along with BMW and Toyota, Mercedes put the first traction control systems into production cars. 
 
 More recently, in 2003, the company introduced its Pre-Safe system, a series of measures that kick in when the vehicle detects what it decides is an inevitable crash. Seat belts quickly tension to an optimum point, windows and sunroofs close, the seats puff up to stabilize the bodies in them, and in some cases they even move slightly toward the center of the car before impact. 
 
 And for 2016, proving these guys really do think of everything, a system to protect your ears from hearing damage that could be caused by the sudden, deafening crunch of a car crash has been introduced. 
 
 The Mercedes-Benz team decided to protect against this by triggering a reflex in the body known as the acoustic reflex, or stapedius reflex – an involuntary muscle contraction in the middle ear that effectively dampens the vibrational energy that's transferred to the cochlea. 
 
 When the stapedius muscle flexes, it pulls on the stirrup bone in the middle ear, weakening the connection between the eardrum and the inner ear, so that some proportion of the sound is reflected back out through the eardrum without reaching the inner ear. It takes about a tenth of a second to kick in, so it wouldn't normally protect you from a loud, sudden sound like the impact of a car crash. 
 
 Normally, this reflex is triggered by loud sounds or vocalization, but researchers have found that presenting more than one tone at once can trigger the effect at a lower sound volume. 
 
 To this effect, Mercedes-Benz engineers decided to use a short blast of pink noise – which basically combines all possible tones – in the seconds before impact, at 80 decibels, through the car stereo system. That 80 decibel level isn't even an uncomfortable volume, but it's enough to trigger the desired acoustic reflex just before the crunch of impact. 
 
 Hearing loss is far from the worst damage a person can suffer from a car accident, but this is a cheap and simple way to reduce some of the human impact of road trauma, and a very cool idea. 
 
 Pre-Safe Sound is rolling out as of this year on the E-Class, and will presumably be implemented in other cars with the Pre-Safe system in coming years. 
 
 Source: Mercedes-Benz ||||| Illustration: Mercedes-Benz 
 
 Advertisement 
 
 Dumb cars shield against crashes. Smart cars avoid them. Shrewd cars prepare you for them. 
 
 This year, Mercedes-Benz is introducing what surely is one of the shrewdest precrash features yet: a burst of sound that causes a muscle inside the ear to contract, bracing the eardrum against the potentially deafening noise of the crash itself. 
 
 Tip o’ the hat goes to IEEE Spectrum’s auto maven, Lawrence Ulrich, who pointed out to us the importance of “Pre-Safe Sound,” standard in the 2017 E class. (Ulrich will describe this and other marvels in “Top Ten Tech Cars,” in our April issue.) 
 
 The idea of pre-crash safety has been out there for a while. For instance, a car can instantly tighten the seatbelt to minimize movement and prevent the body from “submarining” forward, under the belt. Or it can inflate a tiny airbag to nudge the driver toward the center, protecting against side impact. Or it can close the sunroof, adding to the rigidity of the cabin. 
 
 But Pre-Safe Sound goes to ear-popping lengths. When the car’s sensors sense an impending crash, the cabin is filled with a burst of “pink” noise, a broad spectrum of frequencies in which the power is inversely proportional to the frequency. That triggers the so-called acoustic reflex, in which the stapedius muscle—the smallest muscle in the body (remember that for Trivial Pursuit)—contracts, bracing it, the bones of the inner ear, and the eardrum. 
 
 The pink noise is around 80 decibels, about equal to that of a dishwasher and completely safe. A crashing car puts out around 145 dB, high enough to damage hearing, at least some of the time. Worse still—and this part is not emphasized by Mercedes-Benz or any other carmaker—is the noise created by the near-instantaneous deployment of the airbag: around 165 dB. It’s estimated that 17 percent of the people who are exposed to airbag deployment suffer some degree of permanent hearing loss. 
 
 That’s why its important to put the various safety features into action in the right order. First comes totally safe features, like emergency braking, seltbelt pretensioning and Pre-Safe Sound. The airbags come only when necessary, during the crash itself. 
 
 Pre-safe noise took a long time to go from a gleam in an inventor’s eye to a commercial offering. A U.S. patent for the idea was filed in 1997 by one Armin Kausch, an employee of a subsidiary of TRW Automotive. That patent application cited earlier work going back as far as 1960. 
 
 It takes time to get the bugs out. Remember that whenever you read that cars without steering wheels will be plying our roads before your kids are old enough to get a driver’s licence. 
 

– A coming safety feature for cars aims to protect drivers and passengers in a novel way: to save their hearing in a crash. The idea is that when a smartcar senses an imminent collision, the sound system sends out a burst of "pink noise" inside the car. That causes a muscle inside the ear to contract and thus protect the eardrum from the louder noise of the crash about to come, explains IEEE Spectrum. Mercedes-Benz is marketing it as "Pre-Safe Sound" in its newest E-class fleet. When a car crashes, the decibel level can easily reach 145, which is enough to damage the human ear. And that doesn't count the noise of the airbag deploying, which is even higher at around 165 decibels. The so-called pink noise is a safe 80 decibels, and it's enough to trigger what's known as the "acoustic reflex" to protect the ear. "Hearing loss is far from the worst damage a person can suffer from a car accident, but this is a cheap and simple way to reduce some of the human impact of road trauma, and a very cool idea," writes a blogger at New Atlas. Normally, the acoustic reflex takes about one-tenth of a second to kick in after a noise, not enough time to protect the ear from an instantaneous loud boom. The idea here is to trigger it early and safely. "A frequency spectrum known in physics as pink noise is ideally suited for this purpose," explains Mercedes in its own post on the feature. "It sounds like a bit like diffuse traffic noise, the breaking of waves or a waterfall." It's promising, but we'll have to wait for crash data to see whether it works as advertised, notes a post at BGR. (See Volvo's bold safety pledge.)