Feelings of loudness are different from person to person. So don't talk of "measuring" the "loudness".
For psycho acoustic values we have units to express loudness:
Sone (loudness N) and Phon (loudness level L).
You can really measure the sound pressure with a sound pressure level meter. That is measured in dB SPL. Loudness is a subjective measure but sound pressure is an objective measure. But that is different. Don't mix it up. Scroll down to related links and look for more on decreasing of sound pressure with distance.
Yes the loudness of a sound is called its intensity.
Intensity
Loudness or sound level is measured in units called decibels (dB).
Loudness increases with increasing amplitude of the sound wave, also called increasing sound pressure.
The human perception of sound intensity is called loudness. Loudness is influenced by the amplitude or energy of the sound wave and is measured in decibels (dB).
The loudness or quietness of a sound is called its volume or intensity.
The loudness of sound is typically measured in units called decibels (dB). This unit quantifies the intensity of sound waves perceived by the human ear. Sound level meters are commonly used to measure the loudness of sound in various environments.
decibels
The measure of the loudness or intensity of sound is called decibels (dB). It quantifies the level of sound pressure that is perceived by the human ear. The higher the decibel level, the louder the sound.
The unit of measuring loudness of sound is called the decibel (dB). The decibel scale is logarithmic and is used to compare the intensity of different sounds.
Just like any other substance in existence, the magnitude of sound or loudness can also be measured. In this case, the standard unit of measurement for loudness is called decibels.
Units used to measure loudness are Sone (loudness N) and Phon (loudness level L). Scroll down to related links and look at "Loudness - Wikipedia" and "Sound level change and the change of the respective factor of volume and loudness"