The Proposal to Muffle NASCAR Race Cars

Last week, Adam Stern broke a story that NASCAR is considering 15 to 20 potential changes that would help increase the fan base. They’ve already implemented race segments and we’ve heard talk about shortening race weekends from three to two days.

Stern’s article says that one of the ideas on the table is making race cars quieter so that fans can talk to each other and socialize more during races. He notes that many stick-and-ball sports now offer places where people can stand around and congregate during games instead of (as he puts it) “Being restricted to a standard seat”.

Stern notes that, if this went ahead, the change would be done gradually and in a way that allowed NASCAR to evaluate the impacts on the racing and the fans. In other words, a way to tune the sound so that it’s “just right”. Not too loud for the sensitive millennials unable and not too soft for the existing, aging fan base.

Why Are Race Cars So Loud?

Race cars don’t have mufflers.

The reason to eschew mufflers is not so the cars will be loud. It’s because the way mufflers work slows down the airflow out of the engine. You can’t put air into the engine until the air from the last cycle is exhausted. If you slow down the exhaust, you slow down the combustion. There’s a real correlation between sound and speed. Historically, racers realized that mufflers made their cars slower. Therefore, mufflers have no place on race cars.

How Loud Are They?

Research indicates that the maximum noise level a person should experience for an 8-hour shift is 85 dB. Noise exposure is always reported in terms of a sound intensity level and a time you’re exposed to it.

The louder the sound, the shorter the time you should be hearing it. You use the graph below by identifying the sound level you’re going to be experiencing on the bottom axis, then follow it up to the line and read the maximum time you should be hearing it off the left axis. You can hear a sound of 95 dB for four hours safely, a sound of 100 dB for two hours and 105 dB for 1 hour.

Note that this graph only goes up to 115 dB because you shouldn’t be exposed to noises louder than this! That’s why you should always wear earplugs at the track.

The Data

We all know tracks are noisy, but there are people who study noise and they’ve actually measured how noisy tracks are in a way that goes far beyond pulling out a sound meter at the start of a race. NIOSH (the National Institutes for Occupational Safety and Health) is the government organization charged with researching and developing safety standards for workplaces. (Disclosure: I have collaborated with NIOSH researchers, but in nanoparticles, not sound.)

In 2000, NIOSH researchers went into a race shop and to Bristol to measure noise levels. The report and paper were followed up in 2010, where they measured noise levels at three tracks: Kentucky, Indy and Bristol. It is worth looking at the papers, if only to read how they describe a race weekend in the highly technical, specialized language of scientific journals.

The figure below the average readings over an entire race – including cautions and crashes and such – in front. The back bars are the maximum readings. They measured in the stands, the infield and the pit area. Bristol is always included in studies like this because it represents the worst case in terms of sound: It’s entirely enclosed and small. Even so, the average measurements are about the same. Note that peak measurements can be higher. Noises at 150dB have been measured at Bristol, but those are for really short times.

The next graph shows the average numbers for the first 100 minutes of three races, measured in the infield/pit area. I include that to give you an idea of how much the volume changes over the course of a race. Bristol is, indeed, louder when at the loudest and only drops to 100 dB in the quietest times during the race.

The NIOSH researchers found that, at the track, the noise reaches an unsafe level (meaning permanent hearing loss is likely) during a race:

  • In less than a minute in the car
  • In less than two minutes in the pits and infield
  • In 7 to 10 minutes in the stands .

This is why it is so important to wear ear protection at the track — and if you have kids, it’s especially important. Most drivers’ kids on pit road before the race are wearing over-the-ear headphone. Their parents know.

How Much Quieter Are We Talking?

Dale Earnhardt, Jr. (on Episode 164 of his Dirty Mo podcast) states that NASCAR is looking at decreasing the sound level of the cars from 120 dB to 90-100 dB. To understand what that magnitude of a decrease would mean requires understanding dBs.

dB stands for decibel, the unit that measures sound intensity level. The dB was adapted in the 1920s to quantify signal loss in long-distance telephone transmissions. The Bel was named in honor of Alexander Graham, but it turns out that the Bel is too large a unit for everyday use, so we use the deciBel – which is 1/10 of a Bel.

dBs are strange units. I’ve mentioned before that they are logarithmic — not linear. When you go from 10 dB to 20 dB, you’re not increasing the sound intensity by 10: you’re multiplying the sound intensity by 10.

  • When you go from 60 to 70, you increase the sound intensity by ten times.
  • When you go from 70 dB to 80 dB you make the sound intensity another ten times more. 80 dB is a hundred times more than 60 dB.
  • 90dB is a thousand times more than 60dB.

Decibels Don’t Measure Loudness

Sound intensity measures the power of the sound wave. But you are not a sound meter. Your ears are incredibly complex things. Your brain is even more complex. How loud a sound appears to you is dependent on many things.

  • Frequency. We hear some frequencies better than others. Our ears are optimized for frequencies around 2000 – 4000 Hz. A noise in that frequency range will appear louder than a noise with the same sound intensity that is outside the range.
  • How many frequencies are in the sound and how closely they are spaced.
  • Duration. We perceive noises as becoming louder with time up to about 1 second. The longer you listen to a sound, the more your ears adjust to it. This is why racing headphone companies tell you to start with the volume at zero and gradually raise the volume to the lowest level you can hear.
  • Dissonance.  Think of how you perceive a crash vs. a concert. How much we ‘like’ a noise affects how loud we perceive it to be,
  • Your mood. There’s a psychological component to loudness.

So the problem is that you can’t really convert ‘dB’ to loudness. Loudness is a psychoacoustical term, meaning that it is dependent on physical parameters we can measure (sound intensity, frequency and duration) — but it is also dependent on psychological things inside your head that we cannot measure.

You’ll see people cite a rule of thumb that so many dB = half the loudness. The problem is that not everyone agrees what this number is. You’ll find people saying an increase of 3dB or 6dB or 10dB means that the loudness doubles. Here’s the way I understand it, based largely on arguments made on this website.

  • If you double the power, you increase the sound intensity level by 3dB
  • If you double the sound pressure, the sound intensity level increases by 6dB
  • If you double the loudness, the sound intensity level increases by 10dB.

The first two of these are things you can actually measure. The last of these is not measured. It is something psychoacousticians have told us.

BUT…

Psychoacousticians don’t all agree. Because they can’t measure the number directly, they infer it from the measurements they can make.

If I brought you a cake and told you the ingredients that went into it, you could probably describe what the cake tastes like without tasting it. You’ve inferred something about the cake’s taste without actually tasting it.

Since we can’t open up your brain and see what’s going on, we have to infer thing. How many dB equals an increase in loudness is inferred. So some psychoacousticians claim that an increase of 6dB doubles the loudness. Others claim the number is 10dB.  There is no consensus.

And if a group of people who have spent their lives studying this phenomenon can’t come to an agreement, I’m certainly not going to answer it. So let’s try something else.

What Would It Sound Like?

Since dB is not an intuitive quantity, we often use examples of things to communicate an idea of what each decibel level means. The graph below pulls together data between 60 dB (ordinary conversation) and 160 dB (a stun grenade: It’s very hard to find everyday examples of 160dB). I’ve colored the NASCAR-related sounds in orange.

 

To get an idea, therefore, of what the proposed sound changes would be like, just look at what’s down the scale.

A reduction of 10 dB

  • If they took the sound down by 10 db, then a race in the stands would go from 96dB to 86dB, somewhere between a very busy restaurant and a garbage disposal.
  • The driver’s sound intensity level would go down to 104 dB, which is between a siren at 30 years and someone shouting and inch from your ear.

A reduction of 20 dB

  • A NASCAR race in the stands that was 96 dB would be 76 dB – about the sound of a vacuum cleaner when you’re using it.
  • The sound level for the driver (inside the car) would go from 114 dB to 94 dB, which is about the sound level for the subway.

A reduction of 30 dB

  • A NASCAR race in the stands that is about 96 dB would be 66 dB – quieter than the sound of a vacuum cleaner when you’re using it and slightly louder than normal conversation.
  • The driver’s sound intensity level would go from 114 dB to 104 dB.

Would it Work?

If your goal is to allow people to talk with each other during races, 10 dB isn’t going to do it. I’ve plotted the sound intensity as a function of frequency for a male human voice (male because that was what I could find data for) and for a NASCAR race car. Remember that every 10 dB is another factor of 100. There’s a pretty big gap between car and voice. It would take a 30 dB reduction to even approach the point where you could have a conversation.

The most likely way NASCAR would accomplish decreasing the sound would be a muffler. Any regular reader of this blog knows that change is never as simple as bolting on a part. A muffler would require re-routing the exhaust. Since teams have different configurations for some tracks, it’s not one change, it’s three or four across the cars. Stern cites an estimate of a couple thousand dollars in parts per change.

But it’s not just the muffler. Mufflers restrict the engine’s airflow, so everything involving the engine would have to be re-examined. The Computational Fluid Dynamics calculations of the motion of air in and out of the cylinders will have to be re-done. When you’re dealing with something as complicated as a car, every change propagates down the line both ways. It is never as simple as changing out a part.

To me, one of the biggest reasons to watch a race at the track instead of on the television is the visceral experience. I wear earplugs from the moment I get to the track until I’m in the car to leave. I can still hear the cars, but I can also feel the sound waves in my bones and that is a feeling unparalleled. You don’t get that going to a baseball game. People and beer are the other two big reasons for me.

Is Quieter The Best Solution?

I can think of a number of good reasons why you might want to consider making race cars quieter.

  • Dealing with increasing political pressure to eliminate race tracks as sound nuisances (something tracks in Europe already face). Some tracks are being swallowed by development. Okay. We can compromise. We’ll bring the sound down a little, you stop trying to get rid of us.
  • Increasing safety by ensuring that people can hear each other and communicate effectively: Watch out! There’s a tire cart behind you!
  • Protecting the hearing of fans or — more critically — of the people who work at race tracks and are repeatedly exposed to loud noises. The average fan may attend a few races per year. A crew member does 36-39 (Duels in Daytona, all-star races). They are exposed to high noise levels for 8-16 hours a day for 2-3 days a weekend.

BUT: Making a change so that millennials can talk amongst themselves during a race is definitely not one of them. There’s a fine line between recognizing that younger people have different habits and endorsing those habits.

I went to see a production of Long Day’s Journey into Night last year on Broadway. They ran it in stages. (No flags and we call the breaks “Intermission”.) Even so, it was about three hours. There were millennials there. They were mostly quiet and attentive during the play. It’s not like they’re incapable of doing it — if they really want to.

And the fact that they don’t want to is the reason why stick-and-ball sports are giving them places to congregate where the game isn’t the main attraction. If you want to spend a couple hundred dollars on a sporting event and then treat the event as though it was on television in your living room, have at it. It’s a good change for me because it removes them from where I am. I can focus on the game — which is why I came.

The change NASCAR is considering goes beyond this: It changes the sport for everyone. That’s why it’s raised so much ruckus.

Perhaps NASCAR is overthinking this.

Perhaps a simpler solution is to make the change at the track level. Convert a couple of suites to social media havens. Put in super-fast wifi. Have free snacks. Instead of renting out the suites to organizations, sell tickets.

Then, if you want to watch the race without hearing it, you can do so with like-minded people who wish to communicate on Topics of Great Importance during the race. And the rest of us aren’t affected.

Update: A Possible Solution to Hearing Loss?

The question of permanent hearing damage related to racecars comes up once or twice a year on this blog. Last year, I explored whether an iPod was worse for your hearing than going to a NASCAR race. (It is.)

The reason people lose their hearing from going to races and not wearing ear protection is that the noise kills their hair cells. Hair cells (which are named because they look like hairs on a microscopic scale, not because they have anything to do with hair) are responsible for changing the incoming pressure waves of sound into electrical signals so your brain can process them.

Chickens and sharks can re-generate hair cells, but humans (and other mammals) cannot. The death of hair cells accounts for 90 percent of hearing loss according to the Centers for Disease Control and Prevention.

A team of scientists published a paper in Cell Reports on February 21st of this year. Here’s part of their abstract:

…using a small-molecule approach, we show significant expansion (>2,000-fold) of cochlear supporting cells expressing and maintaining Lgr5, an epithelial stem cell marker, in response to stimulation of Wnt signaling by a GSK3β inhibitor and transcriptional activation by a histone deacetylase inhibitor. The Lgr5-expressing cells differentiate into hair cells in high yield.

(I don’t expect you to understand that, just to appreciate how much work I have to do to figure out this stuff myself so I can explain it!)

Back in 2012, this research group discovered a type of stem cell in the ears that is also found in the lining of human intestines. (The cells are the Lgr5 mentioned in the abstract.) These cells regenerate once every eight days. These scientists found a way to convince these stem cells to regenerate into hair cells instead of intestinal cells.

The problem is that this process took a very long time and had a very low yield. The paper reports a new type of growth method in which they add a few chemicals and get way, way more cells (11,500 vs. 200). Note that it took them five years to figure out how to make this fairly small step. Scientific research is slow, even when done by really brilliant people.

CAVEAT

When you read a popular report of a scientific paper, the headline is usually misleading. This story was advertised as “Scientists Regrow Sound-Sensing Cells” and “A New Breakthrough in Lab-Grown Cells Could Restore Hearing“. But if you actually read the paper…

  • The work was done in mice. Anyone who’s worked with mice knows that there are many, many cases in which something that worked really well in mice fails to work in human beings.
  • This paper reports only that they’ve figured out how to grow the cells – they don’t actually know if the cells actually work yet. That’ll probably take another three to five years. That’s the nature of research. It’s hard, it takes a lot of time and requires a lot of small people and money.

Nonetheless, this is a major advance — and good news for those of us who spent too much time at rock concerts and race tracks in our youths and are now starting to suffer for it.

Related:

Is an iPod more dangerous for your ears than a NASCAR race car?

Anyone who’s ever been to the track knows that racetracks are loud. Quite frankly, it’s one of the things many people (including me) like about actually being at the track as opposed to watching on television. But could that noise be doing your hearing permanent damage? Is it any worse than any of the other sounds we encounter on a daily basis?

Let’s go to the data…

What is Sound?

Think about a guitar string vibrating and the molecules that surround it. When the string moves, it pushes molecules out of the way.  Those molecules bump into other molecules and so on and so on. When the guitar string moves back and forth, the air molecules do, too. When they move back and forth 440 times each second, we call that a note (concert A, to be specific).

We model the waves as compressions and rarefactions — or squishes and non-squishes. When I picture a sound wave, it looks like this:BSPEED_PressureWave

The dark areas are where many air molecules are bunched up together. The light areas are where there aren’t many air molecules. The wave on top has a higher frequency than the wave on the bottom because there are more light and dark areas in the same length than there are in the wave on the bottom.

Vocal cords work the same way. They vibrate and the set the air near them into motion.  The air is alternately compressed and rarefied.  Each molecule bumps into the next until the vibration reach your ear.

To get a louder sound on a guitar, you pluck the string harder. It moves more, so the molecules move more. Similarly, when you shout, your vocal cords vibrate with a larger amplitude and the noise that comes out is louder.

When I speak to you, the sound moves along the air between my mouth and your ear. (Note that the air molecules don’t actually travel between my mouth and your ear. They just move back and forth quickly.)

BSPEED_EarAnatomy

The outside is shaped to collect and focus sound waves so they pass through the ear canal (the external auditory canal in the picture) and hit the eardrum.

The eardrum (called the tympanic membrane in the picture) separates the outer and middle ears.  It is a tightly stretched membrane, much like a drum head. When the vibrating molecules reach it, it vibrates with the same frequency as the air molecules. The eardrum causes the hammer, anvil and stirrup bones to vibrate in the same pattern, which amplifies the sound.

If you ever have a chance to look at one of your speakers without the covering on it, it’s worth doing. Find something with really strong bass. If you look carefully, you can actually see the speaker move. It’s converting electrical signals into motion of air molecules and those sounds travel through your ear.

The video below shows a speaker filmed with a high speed camera. As the video plays, they’re increasing the frequency of the sound being sent to the speaker. This is pretty much what your ear drum does as well.

This is pretty much exactly how your eardrum works. You can think of it as the speaker encodes the sound and your ears decode it. The louder the sound, the further the speaker cone must move.

As you might expect, there’s a limit to how far a speaker cone can move and, of course, YouTube is full of videos showing you what happens if you put too much power into a speaker.

Why is that at all relevant aside from the fact that it’s fun to blow things up?

Because the exact same thing can happen to your eardrum. Very loud sounds force the eardrum further than it was designed to bend, and then it breaks.

Anyone who’s had a burst eardrum knows that it is not just inconvenient, it is downright painful. Sometimes it heals, and sometimes it requires surgical intervention. But bursting an eardrum isn’t the most common problem.

As the vibrations travel into the ear, the inner ear coverts the pressure (sound) waves into electrical nerve outputs.  The cochlea contains over 20,000 strands of hair-like receptor cells called hair cells.  Different lengths allow different cells to detect different frequencies.

BSPEED_Sound_HairCells

And if you’d like to actually see a hair cell in action, responding to Bill Haley’s “Rock Around the Clock”, you can.

Here’s the problem. Loud sounds kill hair cells. Sharks and chickens can regenerate hair cells. People cannot. Once they’re gone, they’re gone. Racetracks are loud, so you want to take all the precautions you can to prevent permanent hearing damage. There are two primary considerations: sound intensity and length of exposure.

BSPEED_Sound_Flowchart

You can damage your hearing from one really loud sound, but you can also permanently damage your hearing by repeated exposure to lower volume sounds.

Sound Intensity

The loudness of a sound is proportional to its intensity – how much power per area the sound wave contains. The further you are from a sound source, the more the power has spread out over and the quieter the sound seems.

BSPEED_Sound_Intensity

It’s one of those distance-squared things, so if you move twice as far away, you get four times less intensity. Remember this – it’s going to be really important later.

Ears have an amazing dynamic range. The human ear can hear from 10-12 Watts per square meter (the threshold of hearing) to 1013 Watts per square meter (the threshold of pain). That’s from o.ooooooooooo1 Watts per square meter to 10000000000000 Watts per square meter.

It’s pretty hard to talk about things when they span such a great range, so we use a logarithmic scale and a unit called deciBels (dBs). The original unit was the Bel, which was named after Alexander Graham Bell and was developed as a way to measure the sound level on the brand new concept of telephony. A deciBel is a tenth of a Bel, but no one uses the Bel as a unit anymore.

Logarithmic scales work very differently than straight scales.  To show this, let’s plot sound intensity vs. deciBels to see how they compare.

BSPEED_Sound_dBLogScale

Whoops. That isn’t very helpful, is it? You can see the three biggest values and everything is too small to even show up. Let’s blow the scale up.

BSPEED_Sound_dBLogScale2That isn’t very useful, either. The three highest value are off the chart and I can barely see 130 to 70. The last four are so small they’re about worthless.

This is why deciBels are useful. Let’s look at just 20dB range. I’ve normalized the data relative to 80 dB, so 80 dB is 100% intensity and all the other bars are measured relative to that.

BSPEED_Sound_20dB

Let’s say you change the volume of your radio from 60 dB to 70 dB, then from 70 dB to 80 dB. How does the sound intensity change?

  • When you go from 60 to 70, you increase the sound intensity by ten times.
  • When you go from 70 dB to 80 dB you make the sound intensity another ten times more. 80 dB is a hundred times more than 60 dB.
  • 90dB is a thousand times more than 60dB. Not shown, but you get the idea, right?

Although the logarithmic scale makes things easier to use, its nonlinearity makes you have to think a little harder about how to understand measurements. The size of the change depends on the value you’re looking at.

  • Going from 80dB to 79dB decreases the sound intensity from 100% to 79%.
  • Going from 79dB to 78dB decreases the sound intensity from 79% to 63%.
  • Going from 80dB to 77dB decreases the sound intensity from 100% to 50%.

Note that the loudness you perceive is not the same thing as sound intensity. That’s a whole ‘nother topic.

There’s one more thing we need to consider: how long you subject your ears to a sound. One loud sound for a few minutes might not have any effect, but listening to the same sound for eight hours could start to kill hair cells. So here’s a summary of what we’re worried about when it comes to sound permanently damaging our hearing:

How Loud?

Remember that how loud something is (i.e how it will affect your ears) depends both on how loud the source is and how close you are to it.  Here are some representative sounds.

BSPEED_Sound_Levels

The NASCAR values in orange come from peer-reviewed scientific articles and my own measurements. The yellow is the maximum volume I measured for my iPod (Gen 5, I believe).  These are average values. It makes a difference if a car is idling or if the driver is gunning the engine. It makes a difference if you’re sitting in the front row or high in the stands or standing on pit road.

The upper line on the graph is the threshold of pain. This is the point at which sound starts to hurt. It is significantly higher than the sound levels that can cause permanent hearing damage.

The second line comes from the Occupational Safety and Health Administration (OSHA) recommendations for occupational noise exposure. As the sound intensity increases, the time you should experience that sound decreases.

BSPEED_Sound_OSHATimeIntensity

The louder the sound, the shorter time you want to hear it.

  • OSHA doesn’t recommend listening to a 90dB sound for longer than eight hours.
  • When you get to a 105 dB sound (like a single Sprint Cup car), you should limit exposure to less than an hour.
  • A 110 dB sound shouldn’t be listened to for more than half hour
  • A 115 dB sound shouldn’t be experienced for more than fifteen minutes

The noise you experience at a NASCAR race averages around 96-100dB and it’s usually only for three or four hours. The actually noise you hear will vary – when the cars are further from your seat, they’re not as loud.

Peak measurements of 140 dB were found at Bristol. Those measurements were spikes and didn’t last very long. Bristol is a small track that is ringed all the way around and filled with people. At tracks like Daytona or Atlanta, the stands don’t go all the way around the track and the track is much larger. The sound isn’t going to get as loud at a track like that.

Now if you’re the driver, you’re spending four or five hours sitting right next to the source of the noise. Drivers are much more careful now about protecting their ears than they were back in the day. If you visit the track and spot any of the older drivers, you’ll notice most of them wear hearing aids.

Even the recently retired Jeff Burton has noted that he wishes he would have paid more attention to protecting his hearing earlier in  his career because he’s noticing hearing loss now. (Some of that, unfortunately, is just part of getting older, but if you compare a race car driver with someone the same age who worked in an office, you’ll find a significant difference in their hearing levels.

The same thing goes for folks who work in the garage, which means not only the crews, but the reporters, the track personnel, etc. who spend just as much time there as the crews. One estimate I read suggested that, at worst case, you can get permanent hearing damage in just six minutes on pit road without ear protection.

Smack dab in the range of NASCAR noises is the iPod. You might be surprised that a little iPod can be louder than a NASCAR race car, but remember the importance of proximity (its one of those distance squared things, so twice as close is four times louder). When you’re using an iPod, the sound source as close as you can get it to your eardrums, whereas you are not (I hope) putting your ear right next to the exhaust of a NASCAR race car.

But audiologists are increasingly seeing iPod (and similar device)-induced hearing loss so significant that the people needed hearing aids. And these are very young people, mind you!

An expert noted that, although older devices (Walkman, anyone?) posed the same problems, those ran on batteries, so you could only use those for a few hours before the batteries gave out. I can listen to my iPod for eight to ten hours straight without it wearing down.

How to Keep Your Ears Safe

Earplugs and headphones. Seriously. You’ve noticed during the National Anthem that most of the drivers’ kids on pit road are wearing over-the-ear headphones. Kids’ hearing is much more fragile than adults. Kudos to the Kenseths and the Gordons, especially, for always making sure their kids ears are covered.

You’re thinking – I’m good. I have my scanner and those are over-the-ear headphones. Yes, but if you’re blasting the volume, you’ve got the same issue as an iPod. The experts recommend turning the volume all the way down, then turning it up until you can just hear it. Your ears acclimate to sounds.

If you’re at the track and there are car noises, you need to be wearing earplugs. Those squishy disposable foam earplugs work amazingly well, provided they fit right (some people have bigger ear canals than others!) and provided you use them.

Remember: a dead hair cell never comes back. You’ve lost part of your hearing that science has no way of restoring yet, save for hearing aids (which have their own issues). Save those hair cells. Earplugs. Always.