Thank you for your question.
I am Dr. Su S. and I will try my best to help you.
There can be inflammation of larynx.
This can cause change in sound.
This is associated with with upper respiratory tract infection.
However, I would advise to get an examination by doctor again.
Doctor can assess whether there is any difficulty in breathing.
Please keep the room humidified.
I hope this information will be helpful.
If you have any query, please feel free to ask.
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Wish his healthy life.