A decibel (dB) describes what aspect of sound?

• A. Sum of two sound intensities
• B. Ratio of two sound intensities
• C. Amount of scattering
• D. Velocity of sound wave

Answer: (B)

The correct answer relates to the nature of the decibel as a unit of measurement. Specifically, a decibel is defined as a logarithmic unit used to express the ratio of two quantities, typically the intensity of sound. In this context, a decibel quantifies how much one sound intensity is compared to a reference sound intensity.

This logarithmic relationship means that a change of 10 dB represents a tenfold difference in intensity. Therefore, decibels provide a way to easily express large ranges of sound intensities without needing to use very large or small numbers.

The other options do not align with what decibels represent. The sum of two sound intensities is not accurately described in terms of a decibel, nor does it reflect the logarithmic nature of how we measure sound. Scattering refers to how sound waves may change direction after encountering particles or obstacles, and the velocity of sound pertains to the speed at which sound waves travel through a medium, neither of which are relevant to the definition or function of decibels in measuring sound intensity.