How is sound pressure level expressed?

Sound pressure level is expressed in decibels (dB), which is a logarithmic unit used to measure the intensity of sound. This unit is particularly useful in acoustics because it allows for easier comparison of sound levels that can span a wide range of intensities. By using a logarithmic scale, small changes in sound intensity can be represented in a more manageable way, making it easier to understand variations in perceived loudness.

In measuring sound pressure levels, a reference value is used (commonly the threshold of hearing, which is 20 micropascals), and the formula for calculating sound pressure level in decibels is:

SPL (dB) = 20 * log10(P / P0)

where P is the sound pressure in pascals, and P0 is the reference sound pressure.

The other options, while related to pressure, are not appropriate for expressing sound pressure levels directly. Pounds per square inch and kiloPascals are units of pressure but do not convey the logarithmic nature of sound perception. Pascals is a unit of pressure in the International System of Units, but again, it lacks the scale that decibels provide for measuring sound levels.