Final answer:
The conversion between phons and decibels (dB) for a sound of 50 phons at 9000 Hz would typically be approximately 50 dB. However, the exact conversion may vary based on the human ear's response to high-frequency sounds.
Step-by-step explanation:
The student's question involves the conversion of phon levels to decibels (dB) for a certain frequency, which is a topic in acoustics, a branch of physics. A sound that is 50 phons at 9000 Hz corresponds to a certain sound intensity level in decibels. Using standard phon to decibel conversion charts or the equal-loudness contours of the Fletcher-Munson curves, we can find that a sound of approximately 50 phons typically equates to a sound intensity level of 50 dB, especially at frequencies where the human ear is most sensitive (approximately 1 kHz to 5 kHz). Since the question doesn't provide a specific conversion chart or curve, and we are dealing with a high-frequency sound (9000 Hz), selecting an exact value from the given options might not reflect the conversion accurately without additional context. However, for the purposes of a standardized test or classroom setting where simplifying assumptions may apply, one could argue that the closest option is likely 50 dB (Option C), aligning with the stated phon level. It is important to note that this approximation is based on a typical conversion and does not account for the specifics of high-frequency hearing response, which can vary.