The ability to hear a sound – and the ability to understand what that sound is – are two vastly different things for all of us, but especially for someone who is deaf.
Think about this: you go into a noisy restaurant, people are talking, plates are clattering, perhaps music is playing. You can hear it all, but there are too many sounds and it is all indistinct. Now try having a conversation with someone sitting at the table with you. Again, you may be able to catch bits of what is said, you can hear it, but you cannot understand all of what it being said.
Whilst deafness is not the same, the experience of hearing sounds or hearing speech but not understanding it is the same for many.
It is important that you are aware of this in relation to your deaf student. S/he may be able to hear and understand some of the time, but not others or s/he may only have the most basic awareness of sound. And by this, we mean s/he hears enough of a noise to know that s/he should scan the environment for something.
For someone with significant deafness, hearing aids will only provide bits of sound and it is important to understand that their sole purpose is to amplify sound to assist the deaf person in his or her perception of sound. For some but not all, hearing aids also assist in the perception of speech.
The word “perception” is very important because, unlike glasses, hearing aids do not and cannot correct how sound is heard. They only amplify sound and speech.
Talk to your deaf student to gain a better understanding of what, if anything, s/he hears. This is particularly important to do in learning environments such as labs and workshops where safety alarms may be in use. Adaptations may be required to ensure the safety of your deaf student and others. See information on this site about flashing lights and other warning signals for deaf people.