Final answer:
Correct option C. The TONAR was the first device developed to measure the balance of nasal and oral acoustic energy in speech, paving the way for future advancements in speech assessment instruments.
Step-by-step explanation:
The TONAR, or The Oral-Nasal Acoustic Ratio, was the first instrument designed specifically to measure the relative amount of nasal and oral acoustic energy for a speech sample. Before the advent of instruments like the nasometer, scientists and clinicians lacked precise methods for quantifying nasal resonance in speech.
The TONAR was a pioneering device, leading the way for the subsequent development of more advanced instruments, such as the Nasometer, OroNasal System, NasalView, and various aerodynamic instruments for assessing speech production and nasal airflow. The Nasometer consists of a microphone located near the speaker's mouth and two nasal prongs that are inserted into the nostrils to measure nasal airflow.