Physics · University
Intensity-level difference
The ratio is an intensity ratio. Pressure-amplitude ratios use 20 log₁₀ under matched impedance conditions.
Method and conditions
The ratio is an intensity ratio. Pressure-amplitude ratios use 20 log₁₀ under matched impedance conditions.
ΔL = 10 log₁₀(I₂/I₁)
Worked examples
Two sound intensities satisfy I₂/I₁ = 117. Calculate L₂ − L₁ in decibels. Round the final result to 4 decimal places if needed. Answer in dB.
Apply 10 log₁₀(117); the reference intensity cancels in the difference.
20.6819 dB
Two sound intensities satisfy I₂/I₁ = 230. Calculate L₂ − L₁ in decibels. Round the final result to 4 decimal places if needed. Answer in dB.
Apply 10 log₁₀(230); the reference intensity cancels in the difference.
23.6173 dB
Try it
Two sound intensities satisfy I₂/I₁ = 77. Calculate L₂ − L₁ in decibels. Round the final result to 4 decimal places if needed. Answer in dB.
Two sound intensities satisfy I₂/I₁ = 243. Calculate L₂ − L₁ in decibels. Round the final result to 4 decimal places if needed. Answer in dB.
Check your work
Answers and marking notes
- 18.8649 dB
Apply 10 log₁₀(77); the reference intensity cancels in the difference.
- 23.8561 dB
Apply 10 log₁₀(243); the reference intensity cancels in the difference.
Further reading and review references
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