January 30, 2015
Very often patients will ask us why they cannot hear well in noisy places, such as restaurants. Some of these people have normal or near-normal hearing. The situation is puzzling to them, since they don’t present with significant decrease in hearing, yet they are noticing a breakdown when in challenging environments. In quiet they hear fine. In noise they become frustrated. Why does this happen? Is it normal? What are the patterns we notice from those who ask about hearing in noise? What can be done?
What we have noticed is very few people under 40 report this phenomenon. As patients reach their 40s and 50s they tend to notice difficulty in hearing, particularly in background noise. This may be true even when hearing levels are normal. Neuroscience has provided us with evidence of a brain region that acts as a filter for background noise when we are listening to a specific signal, such as speech. Background noise tends to be “static”, or relatively constant. Speech, on the other hand, is more dynamic, and has peaks and valleys we extract meaning from. If a particular region of the brain’s cortex loses function, the ability to listen accurately in the din of a restaurant suffers greatly.
This filtering region appears to gradually lose effectiveness over time, particularly with hearing loss. Additionally, degradations in the hearing nerve’s ability to send well-coordinated signals to the brain affect the quality of the signals we hear. Research has found loud noises can affect the synchrony of auditory nerve firing, even before they damage hearing levels. The ear becomes easily “overloaded”. This is partly why it is better to talk slowly and clearly to a hearing impaired person than to shout loudly. Often we will notice a large family gathered at a restaurant, and the grandparents appear to miss most of the conversations. They are feeling the effects of these issues, as well as possible hearing loss, where the high-frequency “clarity” sounds in speech are not heard.
In an upcoming blog we’ll explore some strategies that can help with hearing more effectively in the presence of background noise. Stay tuned, and let us keep you on a clear path.