Measuring sound levels! :D

1. MEASURING SOUND LEVELS
And Determining If Its Harmful To Our Hearing
Physics 101
What is a sound wave?
1. A sound wave is a longitudinal wave.
a. Note: Molecules in a medium for a longitudinal wave move parallel to
the direction of the wave.
2. In a sound wave, it has compressions and rarefactions, which are areas of
high pressure and low pressure when it is propagating.
Shaded= Compressions Rarefactions= Spaces in between
3. Sounds waves are calculated in decibels (dB)
a. Decibels are a commonly used unit for logarithmic comparisons of
power or intensity.
How do you calculate Decibels (dB)?
Key Formula: β(I) = 0 dB +10 log10 (I/Io)
Where: I stands for sound intensity in W/m2
Io stands for the sound intensity level (10-12 W/m2) at 0 dB
β stands for sound intensity level in dB

2. Problem!
At a nightclub with your friends, it is determined that the sound intensity measures
2.50 W/m2. According to 85 dB is considered harmful, would the sound intensity at
the nightclub be harmful?

3. Solution!
Using the sound intensity given in W/m2, it is possible to determine the dB using the
formula:
β(I) = 0 dB +10 log10 (I/Io)
β= 0 dB + 10 log ( 2.5 W / m2 / 10-12 W / m2 )
β= 113.98 dB
If the nightclub is playing music at 113.98 dB, then it is considered harmful
to your hearing!