Re: [Phys-L] exploring explosions

[Bill Norwood <bnorwood111@gmail.com>]

Hi David,
- If you will search online for sound level charts, safe hearing levels,
safe sound levels you will encounter such data as the maximum safe
listening time for music at 100 decibels is 15 minutes, and after this a
small amount of permanent hearing damage will occur. For 130 decibels some
permanent damage can be instantaneous.
- Anyway, perhaps a locus of safe listening points could be plotted for
particular explosions. One might need to use an array of cheap sound level
meters. For one of our student labs we purchased about 15 of these, for
example.
- The main reason this is worth doing is because you are working with young
people, and they are some of the very ones who are part of an early partial
permanent hearing loss epidemic caused by earbuds, loud bands etc.
- One good website for starters would be DangerousDecibels.org
- I have done significant work on the problem of loud bands and would share
any of my lengthy reports with you if you wish. And this does include some
treatment of the explosions issue as it relates to veterans.
Bill Norwood
Manger, Elementary Labs
Physics Dept
U of MD at College Park

On Mon, Dec 5, 2016 at 4:01 PM, David Strasburger <dstrasburger0f@nobles.edu
> wrote:

> Dear Phys-L-ers
>
> Exploration question:
>
> What are some simple interesting ways to measure an explosion?
>
> My school is building a new library next to the science building, and the
> site prep includes several weeks of blasting to break up the granite ledge
> under the site. Twice a day there is a significant explosion outside my lab
> window. The blasting mats jump and the ground shakes.
> (video from turkey day: https://www.instagram.com/p/BNIGIhuhn5V/)
>
> My students love this. When the two minute warning horn sounds we all get
> up and go to the window to watch.
>
> My AP physics class is particularly interested. And now I find that
> contractor is open to doing an "educational" shot sometime in the coming
> week. I am looking for suggestions of things to measure. The only thing we
> have planned right now is pretty simple: put something high contrast on top
> of the blasting mats then use video capture to measure ∆h of the mats. We
> would estimate how much mechanical energy is getting delivered to the mats
> based on mat mass and mean height of jump.
>
> The blasting company has portable seismographs that they place by all
> nearby buildings (insurance, I think - your foundation cracked? not our
> problem) and I hope to get access to that data. No idea what I would see,
> but I'm curious. (Wave speed through the local rock?)
>
> We have lots of vernier probes (including, now that I think of it, a
> temperature probe on a very very very long cord, but I suspect the
> temperature change would be small in any location where the probe had a
> shot at survival)
>
> I'd love to hear suggestions for measurements that high school students
> might do to extract a little science from what is otherwise a routine
> disruption.
>
> thanks
>
> david
>
> ___________________
> David Strasburger
> Physics & Astronomy teacher
> Dean of New Faculty
> Noble & Greenough School
> 10 Campus Drive • Dedham MA• 02026
> (781) 320-7167
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