Hi there, I am an audiologist ( hearing specialist) and speech language pathologist
I would strongly recommend getting his hearing checked with a qualified audiologist and then meeting a qualified speech and language therapist in your area to assess whether your child's language level is age appropriate
Next Steps
Meet an ent doctor to rule out any ear infections and then meet a qualified audiologist ( with a bachelors or masters degree in audiology) to assess the hearing level of the child. He /She may refer you to a speech language therapist or if qualified, will do a speech and language assessment also.
Health Tips
Sometimes the child maybe responding to very loud sounds or hearing well when it is very quiet surroundings so we may think the child is hearing fine but the hearing level required for speech is much more finer. Also this is the prime age for normal speech and language development so it is necessary to rule out any hindrances in development.
Hope you found the response helpful. Feel free to contact me for further recommendations