Final answer:
John's voice sounds different due to a head cold, which causes the nasal passages and pharynx to become congested, changing the resonance of his voice. Not getting a flu vaccine could have contributed to his illness. A physician's diagnosis is essential in understanding the extent of his respiratory condition.
Step-by-step explanation:
When John caught a head cold, the infection caused by the virus led to inflammation and a buildup of mucus within the upper respiratory tract, which includes the nasal passages, oral cavity, and pharynx. In a healthy individual, these structures work together to facilitate clear breathing and voice production. However, when congested, they can resonate differently, resulting in a voice that sounds nasal or hoarse. The nasal passages can swell and produce excess mucus, blocking the normal airflow and altering the resonance characteristics of the sinuses and vocal tract. The oral cavity and pharynx can also be affected if they too are swollen or have increased mucus production, which can further change the quality of one's voice.
John's illness was likely exacerbated by not receiving the flu vaccine on time. Additionally, the immune response to the viral infection, with symptoms including coughing, sore throat, and runny nose, can also modify the sound of the voice. A visit to a physician for diagnostic tests like chest radiography and collection of various samples is a prudent step in understanding the full extent of John's respiratory condition.