This past Saturday, I attended Qualifying at the Indianapolis Motor Speedway. I had the opportunity to “take-in” the event with a young man who was a first time attendee. It is always a great treat to experience the excitement of a first time attendee. We first noticed the “roar” when we were on 10th Street and when we were approaching 16th and Georgetown, the excitement of my young friend was palpable.
He asked me, “Is this where they race the Indy 500? How fast do these cars go?Can we get something to eat? I sure would like to get a driver’s autograph.” If you can recall your first experience with racing or the track, I’m sure you can relate.
Besides seeing the historic cars in the museum and explaining some of the traditions, I wanted him to learn about noise, hearing loss, and safety. He assisted me in taking samples from various locations for spectators. Much of the stands was closed and inaccessible, but we did try to see what one’s exposure might be from different vantage points.
I used a TENMA mini sound level meter (Model 72-935) to measure noise levels and a personal noise dosimeter (ER-200) to estimate my noise dose.
We sampled from four different locations. Three were on the outside of the track and one was on the inside of the track. One was in the front row. One was under the penthouse tier. One was in the upstairs seating near the First Turn. One was on the inside of the track behind the pit area.
The samples represent noise from one car on the track at a time traveling at speeds near 230 mph. The noise levels are much higher when multiple cars are on the track at the same time and quiet periods are minimized as the cars are continuously passing the spectator. During qualifying, there is a 10-12 second window of acute noise as the car approaches and passes the spectator. Then there is a quiet period as the car travels around the track. During those quiet periods, the sound level meter would show a range of 68-78dBA in our seating area.
You might think that a 10-12 second exposure window cannot be harmful, but we recorded an estimated noise dose of 50% per hour at that location. That means in two hours, one would reach the limit of permissible exposure for one day.
Our sampling in the front row near Section 32 yielded an estimated 100% dose per hour. We observed “Qualifying” for nearly three hours on Saturday. Had we not used hearing protection we would have easily exceeded the permissible daily allowance.
The peak noise level we measured was 108.9 dBA. This occurred during the qualifying attempt of Rookie James Davison. Right after that we estimated another noise dose of 100% while Ryan Hunter-Reay was running a qualifying attempt. Both were from the upper level Penthouse location near Turn 1.
Interestingly, the safest measurements were taken in the walkway behind the pit area in front of the first row on the Tower Terrace seating area. There, we estimated a 25% noise dose and our peak noise levels were 100.1 dBA. The noise must have hit the equipment in the pits and then reverberated and traveled over our heads. Lots of factors besides the noise source itself contribute to noise levels and noise dose.
A noise dose is a measurement of noise exposure based on time and noise level. A 100% noise dose is the limit of permissible exposure.
When you encounter hazardous noise levels, limit your time exposure, walk away, or use hearing protection. Noise-induced hearing loss is preventable.
DISCLAIMER: This example is for educational purposes. The dosimeter predicts average risk, not individual risk. The ER-200 provides a good estimate of noise dose as a screening device. The mini sound level meter provides a good estimate of noise levels as a screening device.
Speak Your Mind