Helen Keller explains that her teacher Anne Sullivan tried to talk to her with common conversational methods, but the problem was that a non-hearing child cannot really have a conversation the same way as a hearing child can. This is especially true when the child is also blind. A non-hearing child can’t pick up tone of voice, and a non-seeing child can’t pick up body language.
The deaf and the blind find it very difficult to acquire the amenities of conversation. … They cannot distinguish the tone of the voice or, without assistance, go up and down the gamut of tones that give significance to words; nor can they watch the expression of the speaker's face …. (Ch. 6)
This makes perfect sense. While Anne Sullivan did her best to teach Helen Keller how to communicate, and young Helen was very intelligent and able to learn many words, conversing with her would still be impossible for most people. To converse with Helen, you would need to know the signs to spell into her hand. Most people do not know them. Helen’s parents learned them, of course.
Helen Keller explains that even after she started college, communicating with others was difficult. She had teachers who had never had a blind or deaf student before.
Of course my instructors had had no experience in teaching any but normal pupils, and my only means of conversing with them was reading their lips. (Ch. 18)
Helen Keller read lips with her fingers. It was a method of communicating, but I imagine it was not an easy one and I can see how it would be awkward. Yes, I think it would be difficult for hearing impaired children to converse with others, especially if the others were not trying to make accommodations. It just demonstrates how much Helen Keller had to overcome.