Learning Object-Measuring Sound

A powerpoint summary about measuring sound, specifically about sound intensity levels and it's unit, equation and manipulating the equation to calculate specific values in two separate questions.

1. Measuring Sound

2. Introduction Everyone is familiar with sound, we have ears to detect it after all! But what is sound? Sound is a mechanical wave which is created by a vibrating object. But how do we measure it?

3. Instrument Sound Level Meter

4. Common Sound Intensity Levels http:// windchimes.co.za /photos/ sound_intensity_levels.gif

5. Unit of measuring sound Unit: Decibel (dB) Reference sound intensity level of 0 dB is an intensity of: I =10 -12 W/m 2 (the quietest sound a human ear can detect) All other sound intensities are measured in reference to this threshold hearing intensity.

6. Sound Intensity Level When comparing a specific sound intensity to the reference intensity (I o ), it’s known as sound intensity level. Equation: Where B= “ bel ” I= specific sound intensity I reference intensity (I =10 -12 W/m 2 )

7. Question #1 : You are at the Mariners soccer game where you are told the sound intensity is 10^-20 W/m 2. What is the sound intensity level? *Hint*: What are you trying to find?*

8. Solution #1: Since you know sound intensity level corresponds to “B”, you would use the equation below and simply plug in the values you know. I= reference intensity= 10^-12 W/m 2 I = 10^-20 W/m 2 B= what you are trying to find. Calculate! Answer: 80 dB

9. Question #2 You are at the Thunderbird Stadium watching a basketball game, where you find out the sound intensity level is 100 dB. What is the sound intensity in W/m 2?

10. Solution #2 You will need to rearrange the sound intensity level equation, to find sound intensity (I) inside the Thunderbird stadium.

11. Solution continued... Plug in known values: Divide by 10:

12. Solution continued… Since it’s log base 10, everything can be written in base 10: Isolate for I = Final Answer: 10 -22 W /m 2 *To check*: Just plug back into original equation

13. Thank You! 