If the sound pressure level is measured at 55 dBSPL at 10 feet, what would it be at 20 feet from the source?

To understand how the sound pressure level changes with distance from a source, it is important to recognize that sound intensity decreases as the distance from the source increases. This phenomenon can be explained through the principles of the inverse square law, which states that the intensity of sound decreases proportionally to the square of the distance from the source.

In this case, when the sound pressure level is measured at 55 dBSPL at a distance of 10 feet, moving to 20 feet away from the source effectively doubles the distance. Since the intensity drops by a factor of four (since distance is squared) when you double the distance, we can anticipate a decrease of about 6 dB.

Thus, when we subtract this decrease from the original sound pressure level of 55 dBSPL, we arrive at a new sound pressure level of approximately 49 dBSPL. However, since sound pressure levels are typically rounded to the nearest whole number, this aligns closely with the value of 50 dBSPL.

This understanding of how distance affects sound levels is crucial in audio and acoustics, as it helps in designing sound systems and understanding how sound propagates in different environments.