Ear plugs and fish to preserve hearing

[Peter Parts]

Getting your Omega-3s?

Fish story here.

 

Ben

[Shaman97]

Getting your Omega-3s?

 

You will if you buy 'wild caught'.

 

Farm raised? Not so much.

Link HERE

 

[Danny caddyshack Noonan]

Hmmm. So, if you use Omega-3 capsules as ear plugs you get the best of both?

[malcolmblalock]

+1 Great idea! Now I know how to stop the crickets in my ears. Saturate them with fish oil pills! ;-)

[Haynes]

"Despite being much fattier, farmed fish provide less usable beneficial omega 3 fats than wild fish."

As a result, I just eat larger portions.

[Peter Parts]

For a long time, I've been skeptical of the frantic bike hearing-loss research.

 

Has anybody ever collected longitudinal data, like do bikers with longer and/or louder noise exposure have more loss? Or do bikers who deep-sea fish have less loss?

 

Or even a simulation of hearing loss called "temporary threshold shift"?

 

That's a whole lot more valid than trying to apply OSHA standards (which by the way, are based on little more than fantasies) to a recreational activity.

 

Ben

[elkroeger]

Jeez, I hadn't "heard" that. ha ha ha ha!

 

Sometimes I crack myself up.

[Username]

The OSHA standards are based on a "safe" limit of 85 dB for 8 hours. At that, approximately 10% of the population will suffer noise induced hearing loss (NIHL), which is considered an acceptable amount. There is a lot of good research to back that up. On the other side of that coin, there is a percentage of the general population who will not suffer NIHL even if they are exposed to quite "dangerous' levels of noise. It's not just noise and time, it's also genetic predisposition, general health, medications, stress etc. But, all that aside, the OSHA levels are a good basis. And, noise is noise. So, if the noise at your ears inside your helmet is 85 dB, you are probably safe for 8 hrs in a 24 hr period. Applying the 3 dB exchange rule, if you are exposing your ears to 88 dB, you can do so safely for 4 hours. 91 dB for 2 hours and so on. Some work done in the early 90's (I think) found levels of 90+ dB in a sample of helmets including high end helmets. Again, there are variables such as rider height, windshield style, weather, faring etc, but it's a good bet that most helmets don't give you a lot of noise protection at highway speeds.

[Username]

 

Has anybody ever collected longitudinal data, like do bikers with longer and/or louder noise exposure have more loss? Or do bikers who deep-sea fish have less loss?

 

Or even a simulation of hearing loss called "temporary threshold shift"?

 

Ben

 

It might be hard to do a good longitudinal study just on bikers, as people have varied lifestyles and occupational factors that would affect results. Not to mention bike types, faring styles, number of different types of bikes ridden over time, number of years riding........and so on. But, it is a safe bet that riding on the Interstate all day with no windshield, no helmet and no earplugs ain't gonna help you hear your grandkids.

 

As far as TTS, that occurs after a significant noise exposure. Hearing acuity is affected for a period of time after exposure, and then recovers to pre-exposure levels. Often accompanied by tinnitus (ringing, buzzing etc). TTS is a sign that damage has occurred. The "recovery" to pre-exposure levels is a sign of some actual metabolic recovery. In some studies, it's also reflective of the rather coarse measures used. Example would be someone exposed to noise suffering a temporary hearing loss between 1000 and 8000 Hz, which later recovers. However, the threshold measures are generally taken at 5 dB steps, so can't account for smaller changes in hearing. Also, the upper limit of clinical equipment is generally 8000 Hz, and permanent thresholds shift has been documented following "TTS" at higher frequencies. TTS can be considered a sign that some damage has occurred. Repeated TTS is cumulative and will (read WILL) result in eventual PTS.

[Peter Parts]

The OSHA standards are based on a "safe" limit of 85 dB for 8 hours. At that, approximately 10% of the population will suffer noise induced hearing loss (NIHL), which is considered an acceptable amount. There is a lot of good research to back that up. snip

 

Now that is absolutely clear and unambiguous. But is it true?

 

Can you please direct me to "a lot of good research" or even a tiny bit of good research that shows that 8 hrs of exposure, etc.?

 

I am not unreasonable and I am honestly interested in seeing the evidence. I know that you can't show that 0% of people will have no loss at 84 dB and 100% at 86 dB. Of course not.

 

But 85 dB and 8 hours are pretty definite regulatory lines drawn in the sand. Therefore, I wouldn't be too impressed by loosely inspirational research that starts with, "Once upon a time there was a boiler making plant with a lot of hard of hearing millwrights...."

 

But let's see just a bit of that "a lot of good research" which is the foundation for the OSHA standards that you identify (besides just some committee's collective opinion based on no hard evidence).

 

As for dismissing a longitudinal study of bikers, nothing could be simpler unless you adhere to old-fashioned notions of "proof" that practical researchers scoff at today. As an example of something inconceivably simple yet informative, how many 70 yr old former bikers have hearing aids compared to non-former-bikers? In 15 seconds, you can think of a dozen ways to turn that crude idea into a pretty helpful study, eh. Wouldn't testing the hearing of a dozen 30-yr biking veterans be helpful? Piece of cake to create that research and just about as bullet-proof as most journal publications. (Yes, I can think of 100 ways it is less than PERFECT as research.)

 

Thanks.

 

Ben

[Username]

The OSHA standards are based on a "safe" limit of 85 dB for 8 hours. At that, approximately 10% of the population will suffer noise induced hearing loss (NIHL), which is considered an acceptable amount. There is a lot of good research to back that up. snip

 

Now that is absolutely clear and unambiguous. But is it true?

 

Can you please direct me to "a lot of good research" or even a tiny bit of good research that shows that 8 hrs of exposure, etc.?

 

I am not unreasonable and I am honestly interested in seeing the evidence. I know that you can't show that 0% of people will have no loss at 84 dB and 100% at 86 dB. Of course not.

 

But 85 dB and 8 hours are pretty definite regulatory lines drawn in the sand. Therefore, I wouldn't be too impressed by loosely inspirational research that starts with, "Once upon a time there was a boiler making plant with a lot of hard of hearing millwrights...."

 

But let's see just a bit of that "a lot of good research" which is the foundation for the OSHA standards that you identify (besides just some committee's collective opinion based on no hard evidence).

 

As for dismissing a longitudinal study of bikers, nothing could be simpler unless you adhere to old-fashioned notions of "proof" that practical researchers scoff at today. As an example of something inconceivably simple yet informative, how many 70 yr old former bikers have hearing aids compared to non-former-bikers? In 15 seconds, you can think of a dozen ways to turn that crude idea into a pretty helpful study, eh. Wouldn't testing the hearing of a dozen 30-yr biking veterans be helpful? Piece of cake to create that research and just about as bullet-proof as most journal publications. (Yes, I can think of 100 ways it is less than PERFECT as research.)

 

Thanks.

 

Ben

 

Well, the OSHA regulations have changed a bit over the years. It used to be 90 dB as the limit before hearing protection had to be worn. You're right, there is no line. 84 dB is not that much different than 85 dB in terms of risk. But, you gotta draw a line somewhere. The OSHA limit is based on "acceptable risk". Which is to say, a balance between causing undue harm to workers and causing undue expense to employers and insurers. If you make the "safe" limit higher, it's cheaper and easier for employers and insurers and workers comp agencies get a break. But, more people would likely get hearing loss.

The 85 dB limit is based on the effect on a large number of people, the general population. Take a few thousand people and expose them to 85 dB for 8 hours a day for 30 years, and 10% of that group will likely get NIHL. That's what studies of large numbers of workers exposed to noise over long periods of time have suggested anyway. With controls for variables other than noise that might also contribute to hearing loss. This linky is as good a study as any, and would have references for many, many others. Since compensation to workers is involved, this has been studied to death.

As to doing a study of bikers, Google "risk of noise induced hearing loss to motorcyclists" and you will get a number of good studies. Some on the general public and some with an occupational slant (police and others who ride for a living).

You are quite right in commenting that setting an arbitrary "safe" point has flaws. Especially if you are not looking at a large group of people, but rather at individuals. Where one person might have a number of factors that increase risk (smoker, genetic predisposition, occupational noise exposure), another might not. One person might suffer a significant hearing loss from much less exposure than would be expected and another might ride an open pipe Harley for 40 years with no adverse effects. That's statistics!

 

[racer7]

The 85 number is a time weighted average based on a specific method.

 

"Impact" and other short duration sounds can be very brief and have siginificant negative effects. Some of us no doubt have friends with hearing damage from firearms, for example. There are plenty of spikes in helmet noise.

 

Back in the days when that std first appeared I created and ran a monitoring program at my place of work, using digital gear worn to get actual employee data rather than the simple sound meters the OSHA guys had at the time. One thing I learned is you will get a whole of employee noise complaints even in mfg plant long before you get anywhere near 85 dB 8 hr weighted. dB is not a linear scale, BTW.

 

At another time I was periodically around old style. unenclosed foudriners (paper making machinery). Dryer stacks especially were very loud- jet engine type levels. You couldn't be understood by anyone without cupping your hands around his ears and screaming. You should have heard the fire alarm in the place!! Ah- the good old days.....

[Peter Parts]

snip

The 85 dB limit is based on the effect on a large number of people, the general population. Take a few thousand people and expose them to 85 dB for 8 hours a day for 30 years, and 10% of that group will likely get NIHL. That's what studies of large numbers of workers exposed to noise over long periods of time have suggested anyway. With controls for variables other than noise that might also contribute to hearing loss. This linky is as good a study as any, and would have references for many, many others. Since compensation to workers is involved, this has been studied to death.

As to doing a study of bikers, Google "risk of noise induced hearing loss to motorcyclists" and you will get a number of good studies. Some on the general public and some with an occupational slant (police and others who ride for a living).

You are quite right in commenting that setting an arbitrary "safe" point has flaws. Especially if you are not looking at a large group of people, but rather at individuals. Where one person might have a number of factors that increase risk (smoker, genetic predisposition, occupational noise exposure), another might not. One person might suffer a significant hearing loss from much less exposure than would be expected and another might ride an open pipe Harley for 40 years with no adverse effects. That's statistics!

 

OK, just to review. I said the OHSA standards are kind of cooked up by committees and don't really have much hard evidence behind them. Username said, that's baloney. When challenged, Username came up with a study to document the 85 dB and 8 hr standard. A big study, nearly 800 workers in 11 trades!

 

The summary of that study says, "Workers exposed for more than 20 years to an exposure level above 85 dB(A) had a three-fold increased risk."

 

Username, is that what you previously called "a lot of good research" nailing down 85 dB, etc. as a standard? In light of your link, do you still say "So, if the noise at your ears inside your helmet is 85 dB, you are probably safe for 8 hrs in a 24 hr period." A bit of a difference between 8hr and 20 yrs (actually a factor of 150,000 or so... and for a possible 3x risk?

 

Based on that, should a biker exposed to 85 dB on an afternoon trip fret? Would he or she be wiser to use 35 dB attenuation ear plugs or to be able to hear traffic noises?

 

Yes, be careful about preserving your hearing. I have and I use several kinds of molded* and foam ear plugs. I believe OSHA standards are pretty sound and support their work.

 

But, unlike Username, I don't believe their standards have a solid research basis or that they remotely apply to my scoot this afternoon.

 

...and that is all I am saying.

 

Ben

 

*Good when I swim lengths in pools.

[Peter Parts]

'been Googling for studies of hearing loss in bikers. A few abstracts that look promising (read: depressing) have shown up but no details.

 

Can anybody get a hold of the full text of articles in British journals by McCombe or the one on Gran Prix racers or other good stuff?

 

Here's stuff I look for in reading academic publications:

 

1. Were the differences found large enough or frequent enough to be of practical significance? Or were the academics just saying the results seem unlikely to arise from chance numbers?

 

2. Was there a relevant control group? For example, if you are testing Gran Prix racers, are they wild risk takers (61% wear no ear plugs... idiots), do they listen to loud music, drink, smoke, swear, and stay up late more than national average?

 

Thanks.

 

Ben

 

[Username]

NIOSH

OSHA

JOEM

 

Wikki

 

To name just a few. Grab one article and look at the references and follow the chain. Noise induced hearing loss is one of those things that's been studied to death, and is so firmly entrenched that no one even cites articles anymore.

But, to answer some of your points, the 85 dB for 8 hours has no reference if you are going to be exposed to 85 dB for one day and never again. It's only meaningful in reference to long term exposure. The OSHA standard assumes that a person working in noise is going to work in noise for a whole career and therefore is at risk for NIHL much much later in life. A difficult task in audiology is to separate a noise induced hearing loss from presbycusis. If a 75 year old man who worked 35 years in a mine has a significant high frequency hearing loss, did it come from the noise for from aging? But, if you look at hundreds of 75 year old men, those who worked 35 years in a mine will have poorer hearing than the group that didn't.

So, what does the 85 dB standard mean when you are going to go for a ride. Nothing, unless you are going to ride 8 hours a day for 25-30 years (I wish). It's a good rule of thumb, but nothing more. IF you are not exposed to noise at work and for most recreational activities, then the standard doesn't realistically apply. But, damage from noise is cumulative, make no mistake. And it's time and intensity that combine to do the damage. And, you do pay for it in the end.

I think I see what you are getting at. The OSHA standard when applied to a non-work situation isn't helpful. To say that you should wear ear plugs just because you might be exposed to 85 dB or more for 3-4 days on a bike trip doesn't make sense. I agree with that. The research that exists applies to workplace or long term exposure situations.

For a more practical situation, it's hard to say what anyone's "safe" limit would be. Certainly high intensity impulse sounds are immediately dangerous to hearing. Anything else depends on time, exposure and any number of personal variables.

Me, I wear earplugs anytime I'm doing more than the 3-4 miles to work. That's because at 51 with some high frequency loss and tinnitus due to a history of noise exposure (before I went back to school for audiology), I know what's at stake.

 

 

[Peter Parts]

The fog is lifting. Yes, OSHA means nothing for bikers out for a ride, as you are now saying.

 

Maybe now you should also re-think generalizations like "damage from noise is cumulative"... without mentioning TTS and rest periods.

 

I haven't seen anybody discuss noise content. Wind noise is pretty "white" although some helmets have 500 Hz resonance peaks. That's vastly less damaging for the same SPL loudness as a forging hammer which bangs the same peak frequency or band of frequencies all day, 5 days in a row.

 

Nor have I seen anybody discuss Marshal Chasin's conjecture that noise you like is less damaging.

 

And about ear plugs, if you've been reading recent research, you'd be more concerned about bone conduction from tight fitting helmets than air-borne.

 

Everybody should take care with their hearing. But I am allergic to knee-jerk adherence to industrial standards applied to biking in the absence of meaningful evidence.

 

Ben

 

IMPORTANT FOOTNOTE: even if you don't live in a country with a civilized medical system, you should pay for a hearing check. At the least, you'll get a baseline for comparison to later results (insist they let you have a take-home copy of the results). In Canada, you can get high-class testing at the Can. Hearing Society or hospitals, and it is free; commercial dispensing audiologists vary in reputability but I am sure some are similarly capable if not equipped. With all the old folks on this forum, good to track how your presbycusis is coming along.

[Boffin]

I always wear ear plugs with my Caberg Justisimo, and on longer journeys with my Schuberth C2 (a nice quiet helmet). The reason has more to do with comfort than noise protection. I find that the noise for long periods becomes tiresome - I feel more fatigued after a trip without earplugs than one with earplugs. Possibly subjective, but real for me.

 

I also find the louder noise triggers my tinnitus.

 

Andy

[Peter Parts]

All good thoughts from Andy, again.

 

But the MC community has been all too complacent about fixing "hearing ergos." The story that is emerging now with tiny microphones doing measurements is looking different than just plugs-in or plugs-out. First, there is a quite linear relationship been speed and dB at your ears.

 

I don't know enough to put factors in a Letterman list, but roughly comparable effects arise from:

 

1. keeping the ragged edge of wind from your windscreen over ear height by getting the rider and windscreen coordinated right,*

 

2. choice of helmet and visor and how you use the visor (3/4 helmets seem to make less noise, my first impression),

 

3. ear plugs or "active" noise suppression (you've seen the Bose and Sony ads?) (seems promising to me but sometimes it is a cure that is louder than the disease)

 

After those, there are matters such as noise coming up the bottom of the helmet and fit.

 

Funny, I can't recall measurements done with no helmet (and can't think of why anyone would bother anyway).

 

Sorry if I say it again, but there's a big gap between measuring noise in a helmet and knowing, even crudely, the relationship of that exposure to harm. No one should err on the side of damage, of course.

 

Ben

 

*if you have a throttle counter-force spring, you can just take your glove(s) off and feel around your helmet and you'll immediately know where the turbulence runs.

[Paul Mihalka]

After reading this I hate to think what my lousy hearing would be if my wife didn't feed me fish twice a week. She loves fish, specially salmon, much more than I do. No Omega3 in a good steak?

[Username]

The fog is lifting. Yes, OSHA means nothing for bikers out for a ride, as you are now saying.

 

Maybe now you should also re-think generalizations like "damage from noise is cumulative"... without mentioning TTS and rest periods.

 

I haven't seen anybody discuss noise content. Wind noise is pretty "white" although some helmets have 500 Hz resonance peaks. That's vastly less damaging for the same SPL loudness as a forging hammer which bangs the same peak frequency or band of frequencies all day, 5 days in a row.

 

Nor have I seen anybody discuss Marshal Chasin's conjecture that noise you like is less damaging.

 

And about ear plugs, if you've been reading recent research, you'd be more concerned about bone conduction from tight fitting helmets than air-borne.

 

Everybody should take care with their hearing. But I am allergic to knee-jerk adherence to industrial standards applied to biking in the absence of meaningful evidence.

 

Ben

 

IMPORTANT FOOTNOTE: even if you don't live in a country with a civilized medical system, you should pay for a hearing check. At the least, you'll get a baseline for comparison to later results (insist they let you have a take-home copy of the results). In Canada, you can get high-class testing at the Can. Hearing Society or hospitals, and it is free; commercial dispensing audiologists vary in reputability but I am sure some are similarly capable if not equipped. With all the old folks on this forum, good to track how your presbycusis is coming along.

 

Yes, OSHA does in fact, have little to do with a recreational rider's decision to wear hearing protection, but it does give at least a place to start. You have to draw the line somewhere.

 

In terms of cumulative effects of noise, that's not debatable. For the same reason that antioxidants have a regenerative effect, noise has a degenerative effect. Noise has two effects, mechanical damage in the case of high intensity sounds (like gunshots, standing next to aircraft engines, things like that) and more subtle physiological effects. Mainly in the loss of efficiency of support mechanisms in the stria vascularis that support the outer and inner hair cells in the cochlea. TTS is a sign of cochlear damage and while it is "temporary" and hearing recovers after a rest period, that threshold recovery is not complete physiological recovery. If you're not a smoker and treat yourself well and have lots of fish oil and things, the recovery will be better, but never complete.

 

Noise content in regards to motorcycles is mostly white noise, like you say. Depending on helmet type, windscreen, motorcycle speed, ear canal characteristics and a host of other factors, there will be peaks at specific frequencies. The ear canal and middle ear tend to boost frequencies at around 2600 Hz. Low or high frequencies though, don't matter. A narrow band noise is potentially as damaging as wide band white noise. White noise at 100 dB carries the same risk of damage as a 90 dB narrow band noise. Intensity is not loudness. It's intensity, not perceived loudness that is the greatest contributor to noise induced hearing loss.

 

One of the potential pitfalls to ear plugs is the occlusion effect, where low frequency energy resonates in the space between the eardrum and the ear plug and depending on the type and level of noise, can be at damaging levels. You have an approximately 60 dB threshold to bone conduction of ambient noise (much less to sound transmitted by direct contact bone conduction though). Noise levels have to be pretty darn high to to reach damaging levels by bone conduction, but plugging the ear can definitely add risk with some people, and some ear plugs and the insertion depth.

 

Marshal's statement reflects the complex physiological processes at work in NIHL. It also reflects the large number of contributing factors, including health, stress, fatigue etc.

 

Addressing the footnote. I've been an audiologist for 10 years. Yes, a hearing check can be a good idea. At least getting a baseline. On the other hand, using regular audiograms to decide whether to protect your hearing is like using regular lung x-rays to decide when to stop smoking. While all audiologists are well equipped to do monitoring, yes, there are some who just want to sell you a hearing aid. Don't think for a second though, that hearing aids are much help. Yes, we go on a preach about NIHL and the damage that you can do. Most likely though, NIHL over time will result in a mild to moderate high frequency hearing loss. The problems you will experience will be difficulty understanding speech in noise. Despite the manufacturer's claims, hearing aids are not going to magically solve this.

I'd rather use the OSHA standard as a benchmark and protect what I have left. I'm already having significant difficulty understanding speech in noise and some pretty wicked tinnitus which is a result of both my years as a mechanic (in my previous life) and stress.

 

[Username]

All good thoughts from Andy, again.

 

But the MC community has been all too complacent about fixing "hearing ergos." The story that is emerging now with tiny microphones doing measurements is looking different than just plugs-in or plugs-out. First, there is a quite linear relationship been speed and dB at your ears.

 

I don't know enough to put factors in a Letterman list, but roughly comparable effects arise from:

 

1. keeping the ragged edge of wind from your windscreen over ear height by getting the rider and windscreen coordinated right,*

 

2. choice of helmet and visor and how you use the visor (3/4 helmets seem to make less noise, my first impression),

 

3. ear plugs or "active" noise suppression (you've seen the Bose and Sony ads?) (seems promising to me but sometimes it is a cure that is louder than the disease)

 

After those, there are matters such as noise coming up the bottom of the helmet and fit.

 

Funny, I can't recall measurements done with no helmet (and can't think of why anyone would bother anyway).

 

Sorry if I say it again, but there's a big gap between measuring noise in a helmet and knowing, even crudely, the relationship of that exposure to harm. No one should err on the side of damage, of course.

 

Ben

 

*if you have a throttle counter-force spring, you can just take your glove(s) off and feel around your helmet and you'll immediately know where the turbulence runs.

 

I know there was some research done with probe mics and helmets, but it was done in the 90's, I think. Not sure if there has been any work done with more modern helmets or with no helmets. Probe mic measuring equipment is readily available now, and if one rigs a power supply it would be fairly simple to take the equipment that I have in my clinic and put it in a top box, doing some measuring while riding. It would be nice to do dosimeter measures, but my dosimeter doesn't have the ability to measure with a probe mic. They're available though, and that's what they use to measure NRR. I should try to get my hands on one, it would be very interesting to measure TM SPL's with various helmets, with and without earplugs. I'd also like to see the spectral differences with earplugs, as I know some on this forum (and other bike forums) have mentioned occlusion effects.

Active noise suppression in a helmet would be interesting. Active noise suppression is just the introduction (electrically) of a 180 degrees out of phase waveform representation of ambient noise. It's the same technology that hearing aids use to almost eliminate feedback. Lexus (I think) has it in a car and the Q400 aircraft that Porter flies out of Toronto uses noise suppression. Since it's electronic, there's no increase in intensity of noise. There have been speculations that noise suppression in personal headphones is dangerous because it takes out too much of the ambient noise, leaving the wearer vulnerable to being run over by cars or crushed by falling helicopters. I won't make any assumption there.

 

Choice of helmet, for sure. I have an old X-Vent AGV full face that is still a very quiet helmet. I have an AGV Open GL modular that I didn't realize how loud it was until I bought a newer HJC. Like you say, windshield type and height are big factors, along with helmet type.

 

Again, I can't say where to draw the line in terms of potential harm to the casual rider. But, I do recommend that you pick a point and stay with it. I don't usually wear plugs on my 8k, 50 kph ride to work, but I probably should.

[Peter Parts]

A treat to read such comprehensive posts as those from Username.

 

The point about white noise at 100 dB (which is really loud for white noise and very noxious) being kind of comparable to most noises in the world with big peaks at certain repeating frequencies - but adding up to "only" 90 dB. 10 dB is a solid difference. So my point is that sometimes really loud white wind noise is not as damaging as softer peaky noises and biking is not as hazardous to your hearing as some people suppose.

 

If I have any minor point to add, it is that getting a chest X-ray from time time really is like "locking the gate after the horse is gone." But hearing decline is more gradual and not a "disease process", so not quite the same. Also, hearing tests can give you a bit of insight into whether it is "occupational" damage or age frailty.

 

The concern for active noise control (which has been used in powerhouses forever) is that it sometimes it has to pump a loud mirror-image into your ear to counteract a large noise and sometimes 1 plus -1 does not equal zero.

 

Thanks much, Username.

 

Ben

[Username]

True. A difference of about 10 dB is a doubling in physical intensity and is indeed a solid difference. And, as loudness is a subjective measure, "loud" white noise can seem louder and be perceived as potentially damaging when it may not be.

 

On the noise suppression thing, I guess it depends on how it's done. When actual 180 degrees out of phase noise is added to an environment (inside a car, plane etc) the potential for peaks that are not cancelled is a potential threat. When done electronically, such as in hearing aids and some earbuds, the threat is lessened. That is, if the out of phase signal is added electronically in a digital processor before it is generated as actual output.

I confess though that while I know the theory of suppression systems, I am not up on the actual mechanics in systems other than hearing aids.

It's been an interesting discussion though, Ben. Thanks

Bill

[EddyQ]

Hey Bill (username),

 

Thanks for all the info relating sound. I somehow missed this interesting thread. PeterParts pointed me to in on THIS thread.

 

This spring I measured sound levels at my ear using a pocket sound recorder (zoom H2) and a cheap computer microphone. The recording of wind noise was then analyzed with some math (MATLAB) that I had to do myself, because I could not find any free software that does what needs to be done.

 

To plot noise levels, I broke roughly a 30 seconds to a minute of sound into 4096 sample chunks (44KHz sample rate). I time weighted the chucks and did an FFT. Each resulting FFT chuck was then averaged with the next. Over a minute, there are hundreds of FFT's averaged. So, the resulting noise level is essentually a long moving average of the measured sound. Sharp noises due to passing cars, trucks ect are attenuated due to the averaging. The plot of noise level was quite repeatable and smooth.

 

My cheap setup was not calibrated vs frequency or level, but I did run some test tones through my computer speakers and found the frequency response was not that bad to 10KHz. Past 10KHz, my system suffered losses. The wind noise I measured did not appear white. More pink than white. Past 10KHz the noise level is greatly attenuated. The majority of the wind noise is between 100 and 500Hz. I wear a Arai Profile (full face) helmet. Maybe it is related to helmet and maybe not.

 

Based on my data, I concluded that levels of roughly 90-100dBSPL are at my ear at 80mph with the shield of my RT down. With ear plugs, this level might be safe for long term exposure. But as Peter and yourself say, it isn't a certain thing.

 

I began this testing because my ears were not comfortable after a few all day rides WITH ear plugs. It might be just a earplug fit problem, but your info about higher sound WITH earplugs is very interesting. Something I might consider in the future. How would you reduce this resonance? Change the earplug to one that "leaks" a little and dampens the resonance??

 

Ed -

 

BTW, electronic noise canceling isn't something to get very excited about. For cancelation to happen, you need to add a signal 180 degree out of phase AND exactly the same level as the unwanted signal. Think of how hard it is to keep your audio system flat across all frequencies to within 1dB. It is likely even harder to keep your system flat for phase. For you to get 20dB cancelation (same as a poor ear plug), you need your cancelation signal to match within 0.9dB and better than 6 degrees phase. 30dB would require levels match within 0.25dB and better than 1.5 degrees. Factory calibration of the "system" helps, but only works if the system never changes. The only real way to do it is a real-time calibration which sends out test tones periodically to update the calibration. If the system is complex and works, it might be nice to add another microphone somewhere away from your helmet wind noise which brings in clearly all the sounds around your bike as you ride. Another system architecture is to put a microphone inside your ear and simply use a feedback amplifier to cancel the measured signal. This would be very simple and require isolating earbuds which attenuate the earbug output from becoming an input signal causing the system to oscillate (similar to a stage microphone feeding back and screaching). But if you already have isolating earbuds, why would you need cancelation? Perhaps it would achieve even better dB attenuation. Donno . . .

[Peter Parts]

Ed -

Yeah, some dangers with noise cancellation. Works pretty good ordinarily but I am skeptical if possible inside a helmet. I say this as a very frustrated and worn-out person who has been measuring loudspeaker/room output.

 

All credit to you for your measurements but there are terrible obstacles to getting the right numbers. You are absolutely right in talking about relative loudness and your numbers are solid for that.

 

Likewise, great stuff doing your own FFT. I've been watching all kinds of music (like big organs) on my real-time freeware Mac spectrum analyzer. Way to go.

 

Several recent studies of helmet noise some done in situ at different speeds. Dunno how they got past the Ethics Committee on that one.

 

Great disappointment to see how many people are clueless about setting up a windscreen.

 

Ben

 

 

[EddyQ]

Thanks Peter.

Likewise, great stuff doing your own FFT. I've been watching all kinds of music (like big organs) on my real-time freeware Mac spectrum analyzer. Way to go.

 

I have a few shareware programs that do FFT's on sound files. But they are useless at measuring levels of noise. You see, an FFT of noise is more noise. But the noise spectrum is centered around the correct noise level. To accurately obtain that center, you simply average the heck out of it. I've done this before when measuring performance of RF circuits (my other job).

 

Great disappointment to see how many people are clueless about setting up a windscreen.

I'm probably one of those clueless people. As far as I know, if wind hits the mic, then noise is generated and nothing can stop that.

[Peter Parts]

Ed -

I see, "Q" as in electronics.

 

Different meanings to the word "noise." Wind noise is fairly random, I suppose, but there may be some peaks there that a spectrum analyzer might show, dunno.

 

Not that I believe your modest disclaimer about not knowing about windshields, but I recall some "universal truth" about windscreens that 48 degrees is "correct"*. Aside from being close and having a windscreen a touch below sight-line, I use Saeng Edging. It blasts the wind 2 inches higher (but not bugs and stones). Turbulence hits over my ear level. Good for ears and good for neck.

 

Even though I don't share the hearing damage panic, I sure value quiet and touring comfort.

 

Ben

 

*Sorry, I never did learn what baseline 48 degrees is from. My guess is it means slightly upright from 45 degrees.

 

 

[EddyQ]

When you said windscreen, I thought you was talking about some fuzzy or foam thingy that audio folks put over their microphone. You really mean what I refer to as a windshield.

 

I see, "Q" as in electronics.

Nope, "Q" as in the Q branch of the british secret service. A fictional term used in Bond Films (James Bond). The Q branch develop of all James Bond's wonderful "toys". The name EddyQ came from my engineering office mates. I think they think I am an advanced tinkerer . . . I cannot argue with that !

 

I use Saeng Edging. It blasts the wind 2 inches higher (but not bugs and stones). Turbulence hits over my ear level. Good for ears and good for neck.

That edging looks like a good idea. It may solve another minor issue with my windshield. In the rain, it spits drops of rain into my lap. This thing looks like it may "gutter" the water to the sides.

 

Ever read up on the uses of turbulance?? The dimples on golf balls cause turbulence which make the ball fly farther. Seems breaking up the laminar flow across a smooth surface does good things to prevent "lifting" of the laminar flow of air. If air lifts, then all sorts of bad turbulents and wind noise is generated at the surface. I'm certain that is what is happening at the forhead and sides of my helmet. There is no simple solution other than lifting the air as you say. Trial and error is the only way to fix it.

 

BTW, I made some "turbulence generators" similar to those used on aircraft wings and taped them on the rear edge of my stock windshield. They do not force the wind up, but add a spin to it and produce a vortex. My first try helped (sorry no hard data) and I may get back to it someday this fall. I think I need to try much smaller and tighter vortexes.

 

I also found the flow of air across my helmet shield is very unstable. It flows up and then down with the slightest nod of the head. This tells me the air off the windshield hits the forhead at a 90 degree angle. That likely causes turbulents in every direction. I almost want to try a small sun visor on the helmet so the air will hit at more of an angle. I've seen folks make shields out of bicycle helmet shields. My fear is these would chatter and make more noise than the wind.

[Peter Parts]

snip I almost want to try a small sun visor on the helmet so the air will hit at more of an angle. I've seen folks make shields out of bicycle helmet shields. My fear is these would chatter and make more noise than the wind.

 

I can't imagine riding without my Ventor peak, a 3-4 inch peak with air vents that can block the sky and the sun right down to the horizon. No kidding. Doesn't seem to make noise or catch the air. Pity they are out of business.

 

Saeng Edging is nice stuff. Nice company too but into new management now. World's greatest fairing for Airheads. Yes, Saunders was an aeronautical engineer.

 

Sorry about the "windscreen" old chap.

 

Ben