Precious Hearing: Shouting from the Roof Tops

March 10, 2015

As International Ear Care Day 2015 just passed,  I’d like to discuss some of the strange ways we treat our precious hearing.

Why do we call our hearing ‘precious’ (is there a better word than precious?).

Dr. Barry Blesser of MIT in a speech to The National Hearing Conservation Association in 20121, pointed out the our ears are different from most other senses. They are fully functional at birth. They remain ON 24 hours a day, 7 days a week, until we cease to exist. As Dr. Blesser put it, we have no ear lids. With them being so valuable and unique, why do we abuse them in a way we don’t abuse any other sense. As children, we cover our eyes to protect them from bright light, cover our ears for loud noise, and shy away from hot or sharp objects (for the most part). At some point in our development, we maintain our protective actions for everything but our ears. As teenagers the lure of the power of music overcomes our sense of preservation. This sense of oto­invincibility (that our ears can take anything) caries on through adulthood for many of us. We go to concerts and revel at the power of the music. Some of that power comes from shear acoustic power of the performance.

Recently, I went to a Keith Urban concert. The opening act was moderately loud at 93 decibels. The next act, a bit louder at 98 dB and the Keith came on and the sound levels peaked at 110 dB (only someone in the hearing conservation business wearing two hearing aids would spend time measuring this in a concert ­ with an app on my phone. Notice I use the term sound, not noise).

While these were peak values, it is interesting to note that all three acts are using the same sound system for the concert. How loud is that?

Let me use an industrial context to illustrate my point.

Hearing Conservation

There are hearing conservation regulations in many countries defining how loud the sound can that a worker is exposed to. In some countries, once a level of between 80 and 85 decibels is reached, a worker will need to wear hearing protection regardless of the amount of time they were exposed to the sound. Their hearing will be consider safe if they remained in the noise up to 8 hours as long as they wore something to block the sound in their ears. Eventually what will happen is the sound level will rise above that level (the level at which they need to wear a hearing protector). There’s a calculation of the amount of sound energy to which the ear can be exposed as the sound rises. In many jurisdictions if the sound rises 3 decibels, the amount of time you can be exposed to that sound is just in half. For example, if the sound rises from 85 to 88 decibels, the safe exposure time drops from 8 hours to 4 hours. If it rises to 91 decibels, the safe exposure time is 2 hours. (In this I am referring to the sound level underneath anything being worn to protect your ears from sound).

For this example, let’s assume the protector being worn is only providing 1 decibel of protection. That’s not realistic but it simplifies the illustration because many people don’t use hearing protection at all). For those of you reading this who were of the understanding there would be no math, I apologize.

What’s the point. Let me go back to Keith’s concert.keith urban

If it wasn’t a concert casino but was an industrial workplace, the 90 minutes Keith played at sound levels would be unsafe. Actually, using the method of calculating how long we could safely be exposed to those levels of sound above, if we assumed an average sound level 100 decibels for Keith’s 90 minute concert, we’d have to either leave of protect our ears with earplugs after 15 minutes. What happens after 15 minutes? It’s complicated but the risk of hearing damage rises dramatically.

Why am I picking on Mr. Urban? I’m not. I’m using his concert as an illustration of the problem. WE, the audience, are demanding our entertainment and our
entertainers gives us this kind of energy. In Europe, especially Sweden, earplugs are commonly worn in loud venues. NFL football games last 2 1/2 to 3 hours and sound levels recorded at the 50 yard line have been record at exceeding 110 dB. Using the same math as above, the stands should be emptied after 3 3/4 minutes or have all the fans wear earplugs or muffs. Hockey game noise levels have been measured at 104 dB. At that level we should have fans wear earplugs or limit the game to one

7 1/2 minute period. Not realistic? Sure it is. The obvious choice is for the people, we fans, to get our energy from the play, the performance, the action and not the sound level. Stevie Wonder concerts have fans movin’ and groovin’ at safe hearing levels. Leonard Cohen concerts are exceptional events with moderate sound levels. Showing my age? Possibly. The point is, it is possible to enjoy sports and entertainment without loosing your hearing.

Producers of these events must make protection available and give guidance to the audience about the need to wear it. To not do so is to conscious hurt people and I doubt that’s their intent. Either than, or enjoy Keith’s 15 minute concerts.

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