Why do I have trouble understanding speech in background noise?

One of the most challenging listening tasks for people with hearing loss, especially in old age, is following a conversation in the presence of background noise.

Unfortunately, this is true even when using hearing aids to compensate for the elevated hearing thresholds and hearing speech louder than before.

But why?!

The simple answer to this is that speech perception in noise is very complex and involves our auditory system and other areas of our brain. 
In other words, this ability is affected by auditory factors and other cognitive factors unrelated to hearing, such as working memory, selective attention, and linguistic knowledge. 
It is well known that natural aging entails a decline in some or all of these cognitive functions. Therefore, many older adults, even with relatively good hearing thresholds, show significant difficulties understanding speech in noise. 

Your hearing aids include advanced technology for improving the signal-to-noise ratio (i.e., the level of speech relative to the noise level) to help you hear better in noisy situations. But still, hearing aids cannot replace your natural hearing system and cannot compensate for cognitive declines. Therefore, your expectations from your hearing aids need to be realistic. 

We recommend you try the second program ("Meeting" setting) in your hearing aid when conversing in a noisy environment.
You may find this hearing program more beneficial in noisy situations because it provides you with the best signal-to-noise ratio compared to other programs.