Hi there. This is Dr Satya Kiran ENT Surgeon from Hyderabad. This condition is called DYSPHONIA. it is related to vocal cords.
U did not mention ur father's profession, his voice usage / overuse etc, any addictions like smoking etc. The history given followed by examination of vocal cords by videolaryngoscopy will clinch the diagnosis. Confirmation by biopsy in certain diagnoses.
Next Steps
voice rest, hydration, abstinence from smoking if applicable
Health Tips
rule out carcinoma (cancer) if a known smoker