I am hearing impaired (deaf, hard of hearing, whatever you will) from childhood. I'd like to offer some explanations and suggestions. Forgive the numbering - it's easier for me to think of a lot of information this way.
1. Learning to compensate for hearing loss by lipreading and observing facial expressions and body language is like any skill, it can be a lot harder if you're not a child, and even harder if you've got any condition (such as dementia) that impairs your ability to learn new skills. Even if you are a very accomplished lipreader, you will probably be able to read less than 50% of the words said and less if they're out of context.
2. When someone loses hearing with age, it is often because the little hairs (called cilia) in their inner ears break off. These cannot be replaced and even if you increase volume (e.g. turning the television up, shouting, hearing aids), you may not increase clarity as much as you'd like.
3. English is a language that relies heavily on its consonants for understanding. (Try writing a couple of sentences with just the consonants and the same with just the vowels. Then get someone to read them. The odds are they'll understand the former not the latter.) However, consonants tend to be higher pitched and it is the higher pitched sounds that typically go most with age-related loss.
4. However, conditions such as glue ear (from infections) may affect lower pitch hearing more and so the balance between what people hear may be different. The difference can help you to tell the cause of the hearing loss.
5. People with sensineural loss (nerve damage) typically speak louder and people with conductive loss (something wrong with the bones or eardrum) typically speak quieter. Again whether someone speaks louder or quieter can give you a clue to the type of hearing loss.
6. You may have heard the stereotypical conversation that goes like this..."speak up, I can't hear you...there's no need to shout!" That's because if you lose hearing, what usually happens is that there's a cut-off, say 40dB (which is a volume). Below 40dB, the person doesn't hear and above 40dB, they hear as loudly as if they had no loss. (Ditto other volumes.) That means that it's annoying for them and for others. You may need to practise just how loudly to speak to be helpful but not annoying.
7. Hearing aids can take a lot of getting used to. If you have age-related higher-pitch loss and get hearing aids adjusted for standard hearing it will probably come across as a shock when you hear the loo flush ('Niagara falls') or the doorbell ('fire alarm test'). Sometimes getting the audiologist to adjust the sound balance to be halfway between how it was and 'normal' can be better than correcting fully.
8. Beware in-ear hearing aids - they can be very fiddly. On the other hand, it's easy to take a behind the ear hearing aid ('beha') off and to pull it apart. One option is to get the sort of aid that was more usual many many years ago with an earpiece leading to a cable down to a box worn on the chest or on a belt. This can be good because it may be more robust and also because the wearer may find it more familiar if they've been used to listening to personal stereos/radios over the years.
9. If you have 'normal' hearing, you will be able to pick out a voice against quite a lot of background noise (up to 30dB louder than the voice) and you probably won't be aware of this. A deaf person will typically not be able to do this, so if you want to communicate with a deaf person, try to be aware of background noise.
10. The environment will make a lot of difference. The balance between hard surfaces will make a difference and whether hard or soft surfaces are better will depend on the balance of hearing loss (high/low). Thus you may find important conversations better held in, say, the kitchen or bathroom rather than the living room or bedroom.
Hope some of this helps.
