Intensity
Sound intensity: definition and unit.
intensity is power per unit area !
Power divided by the area, this is the area over a wave front. As the wave front travels through space the area over the wave front increases, therefore the further you are from the source the lower the Intensity is at your location.
How does this sound travel ? In what direction does it go ?
Sound will travel in 3 dimensions and so it is the surface are of a 3 dimensional shape that represents the waves motion. A sphere, what is the Surface area of a sphere ?
http://www.5min.com/Video/Intensity-and-Loudness-174070544
Threshold of hearing and frequency response of ear.
Sound intensity level is measured in decibels.
Doubling the sound intensity increases the sound intensity level by 3 dB.
therefore the scale is NOT linear, (you should not think that 100dB is twice as powerful as 50dB it would be about 70,000 times more powerful (at the distance you are at)))
The dB(A) scale is used because it is adapted for the ear’s frequency response.
Use of sound-level meter.
Examples of sound intensity level.
Hearing impairment.
Ear protection in industry, etc.