Slightly Off-Topic on acoustics, help needed!

Hello
I am currently reading "Musical Acoustics" by Donald E. Hall, and I stumbled
on an exercise which seems simple but I can't solve..
Here it is:

If you attend a rock concert wearing earplugs that provide reduction of 13 dB,
what is the ratio of the sound intensity reaching your eardrums to that
just outside the plugs?
What percentage of the sound energy is getting through?
What percentage is being blocked out?
In order to achieve 23dB reduction, what percentage would have to be blocked out?

--- In tuning@yahoogroups.com, Alex Pi <alexpi@...> wrote:

> If you attend a rock concert wearing earplugs that provide reduction
> of 13 dB,
> what is the ratio of the sound intensity reaching your eardrums to
that
> just outside the plugs?

10^(-13/10) = 10^(-1.3), about 5%.

> In order to achieve 23dB reduction, what percentage would have to be
> blocked out?

10^(-2.3) , about 0.5%. It is exactly 10% of the 13 decibel figure,
since they differ by ten decibels.

Sorry to insist in such an elementary matter, but I need some clarification.
This book is a little light on math, and my math knowledge is not very good but I am working on it.
Can you explain the solution in terms of intensity ratios and SIL differences?

On Mar 4, 2007, at 9:00 PM, Gene Ward Smith wrote:

> --- In tuning@yahoogroups.com, Alex Pi <alexpi@...> wrote:
>
> > If you attend a rock concert wearing earplugs that provide reduction
> > of 13 dB,
> > what is the ratio of the sound intensity reaching your eardrums to
> that
> > just outside the plugs?
>
> 10^(-13/10) = 10^(-1.3), about 5%.
>
> > In order to achieve 23dB reduction, what percentage would have to be
> > blocked out?
>
> 10^(-2.3) , about 0.5%. It is exactly 10% of the 13 decibel figure,
> since they differ by ten decibels.
>
>
>