It sounds like wheezing. Do you hear sneezing or coughing? I would look inside his throat with a flashlight for anything unusual (yellow or white material, mucus) inside his mouth and throat. Look for bubbles/foam in either eye, swelling of eyes or face, and for any discharge from nostrils. Have you added any new birds recently? Where did he come from?
He could have a respiratory disease, and symptoms may point out which one it is. Testing is the best way. MG (mycoplasma gallisepticum,) coryza, infectious bronchitis, ILT, and a few others are common ones. Antibiotics such as Tylan or Tylosin may treat symptoms of MG. Most diseases can leave survivors carriers for life. Here is a good link that has those and other diseases:
https://edis.ifas.ufl.edu/publication/ps044