Final answer:
The root word 'phon' means sound, which is associated with various words related to audible sensations. The loudness of sound is described using intensity level or decibels, and phons are used to express loudness perception numerically.
Step-by-step explanation:
The root word "phon" means sound. This can be seen in various English words where 'phon' is used as a prefix or suffix indicating an association with sound, such as 'telephone' (a device for transmitting sound), 'phonetics' (the study of speech sounds), and 'symphony' (a harmonious arrangement of sounds).
When considering the properties of sound waves, the word or phrase used to describe the loudness of sound is b. intensity level or decibel. Loudness can be expressed numerically using a unit called phon, which relates to the perception of sound loudness. This differs from decibels, which measure the physical intensity of sound.