Hearing above the noise – a challenge for everyone
Recent surveys indicate that 5% of children and adults under 60 with “clinically normal” audiograms have difficulties understanding speech in noisy settings. We speculate, however, that this number is much bigger, since many people don’t seek medical advice until their hearing loss is much more pronounced.
In our previous post, we talked about the “Cocktail Party Problem” and explained why it is so difficult to understand speech in noisy environments. Today we will discuss why this holds true for people with “normal hearing” too.
Hearing loss in the ultra-high frequencies
First of all, let’s define normal hearing. In a clinical sense, normal hearing means that you can pick up on sounds of 20dB or less within the tested frequency range.
Since basic hearing tests only cover sounds ranging from 250 to 8kHz, there still might be hearing loss in the ultra-high frequency range of 9 to 20kHz. Ultra-high frequency ranges are more sensitive to background noise and studies have shown a direct correlation between these frequencies and difficulties understanding speech above all the noise. Unfortunately, extended audiometry, which includes ultra-high frequency ranges, is still not used in routine hearing evaluations.
Hidden hearing loss
Hidden hearing loss is a fairly new term, referring to hearing loss that is undetectable even when testing ultra-high frequencies. Preliminary reports indicate that even exposure to temporary noise can permanently destroy synapses between the ear and the brain without affecting hearing sensitivity. In other words, even though there may be no problem identifying tones in a sound-proof room, there can still be neuronal loss that affects our ability to understand speech in noisy environments. The auditory nerve can lose up to 80% of its fibers yet still be capable of hearing tones in a quiet setting!
Other possible causes for hearing difficulties in noisy situations are not related to physical damage to the ear at all. These include Central Auditory Processing Disorder (which will be discussed in a future post), problems with language comprehension or even cognitive deficiencies related to attention or working memory.
As you can see, there are so many reasons why people find it difficult to hear above the noise. Scientists are still trying to figure out ways to differentiate between the possible causes in order to properly diagnosis and treat them. In the meantime, we do our best by keeping abreast of the latest amplification devices, communication strategies and new discoveries! For example, one promising new technology, “Focused Hearing”, claims to help solve the Cocktail Party Problem. More on that in future blogs…