How does the decibel change when you double the sound?

How does the decibel change when you double the sound?

• A. Increases by 6 dB
• B. Decreases by 6 dB
• C. Increases by 3 dB
• D. Decreases by 3 dB

Answer: (C)

Sound level in decibels uses a logarithmic scale based on the ratio of two intensities. If you double the intensity, the ratio is 2, and the change in decibels is 10 log10(2) ≈ 3.01 dB. So the level increases by about 3 dB. (Note: if you were doubling the sound pressure instead of intensity, the change would be about 6 dB, since SPL uses 20 log10 for pressure rather than 10 log10 for intensity.)

Sound level in decibels uses a logarithmic scale based on the ratio of two intensities. If you double the intensity, the ratio is 2, and the change in decibels is 10 log10(2) ≈ 3.01 dB. So the level increases by about 3 dB. (Note: if you were doubling the sound pressure instead of intensity, the change would be about 6 dB, since SPL uses 20 log10 for pressure rather than 10 log10 for intensity.)