Final answer:
The word pronounced as 'onomatopoeia' is onomatopoeia. It describes words that imitate the sound they represent. The loudness of sound is described by the intensity level or decibel, not to be confused with pitch or timbre.
Step-by-step explanation:
The word pronounced as "onomatopoeia" is onomatopoeia itself (option a). Onomatopoeia are words that phonetically imitate, resemble, or suggest the sound that they describe. Common examples of onomatopoeia include words like 'bang', 'thud', and 'hiss', each mirroring the sound of the action or object they represent.
To address the second part of the question, the term that is used to describe the loudness of sound is intensity level or decibel (option b). Decibels measure the intensity of sound, and the higher the decibel, the louder the sound will be perceived. This is different from other sound characteristics such as frequency, which relates to the pitch of the sound; timbre, which is the quality or color of the sound; and oscillation, which has to do with the repetitive variations in amplitude over time.