Sound Intensity Intensity definition Changes with distance Intensity scale - decibels.

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Presentation transcript:

Sound Intensity Intensity definition Changes with distance Intensity scale - decibels

Which wave is has higher energy? a) b)

Sound Intensity Higher energy = higher amplitude. In terms of sound, this means it is louder! Higher amplitude = Higher volume

Intensity Changes with Distance Peanut butter on bread, as you spread it out, the thickness of the peanut butter decreases, but the total amount of peanut butter does not.

Intensity Changes with Distance The total energy of the sound wave does not change, it just spreads out.

Geometric Proof r R 2r = R Set up a ratio Area of small circle Area of large circle 4r24R24r24R2 r2R2r2R2 = r 2 (2r) 2 = r 2 4r 2 = 1414

Main Point Double the distance Intensity decreases by 4 times Inverse Square Law! Intensity = volume

Create your own analogy…

Intensity Source 10,000,000,000,000 Jackhammer, gun 1,000,000,000,000 Siren, rock concert 100,000,000,000 10,000,000,000 Subway, lawn mower 1,000,000, ,000,000 Busy traffic 10,000,000 Vacuum cleaner 1,000, ,000 Normal Conversation 10,000 Mosquito buzzing 1,000 Whisper Rustling leaves 1 Threshold of hearing The human ear is AMAZING This is a huge range of intensities. Also, it is an inconvenient scale.

Intensity Source dB 10,000,000,000,000 Jackhammer, gun 130 1,000,000,000,000 Siren, rock concert ,000,000, ,000,000,000 Subway, lawn mower 100 1,000,000, ,000,000 Busy traffic 80 10,000,000 Vacuum cleaner 70 1,000, ,000 Normal Conversation 50 10,000 Mosquito buzzing 40 1,000 Whisper Rustling leaves 10 1 Threshold of hearing 0

Source dB Jackhammer, gun 130 Siren, rock concert Subway, lawn mower Busy traffic 80 Vacuum cleaner Normal Conversation 50 Mosquito buzzing 40 Whisper Rustling leaves 10 Threshold of hearing 0 Main Point Decibel scale is used to measure sound intensity (volume) +10 dB = 10 times the volume +20 dB = 100 times the volume USA Today – ipod article

Extra Credit assignment Write a 500 word report (NO COPY PASTE!) On hearing loss and ear bud use. Use sources USA Today article OSHA Other? Must cite your sources ( )

The Threshold of hearing is strongly dependent on frequency Which is the easiest frequency to hear? ~ 3300 Hz When the sound is loud (top curve, threshold of pain) all frequencies can be heard equally well. Frequency Response Curves