New research shows that for certain individuals with hearing loss, the problem could be the brain having difficulty processing sounds. This differs from the natural inability to discern vocal sounds from other surrounding noise.
The Journal of the Association for Research in Otolaryngology recently published research on the Cocktail Party Effect. The scientists, from the Oregon Health and Science University (OHSU) and the Portland Health Care System, found that people with hearing loss experience the Cocktail Party Effect differently than people with normal hearing.
“People with normal hearing can separate and understand the multiple voices, but they just get confused about which voice is saying what,” said Lina Reiss, Ph.D., associate professor of otolaryngology/head and neck surgery at OHSU in a press release.
Reiss, who has hearing loss herself, co-wrote a research paper on broad binaural pitch fusion in hearing loss three years ago. This, combined with another paper, suggested that speech sounds could also become fused and blended in a similar way.
The new study used 21 test subjects, 11 with normal hearing and 10 with hearing loss. They were brought together at the OHSU’s Hatfield Research facility. They were placed in a double-walled booth. During this experiment, two vowel sounds were played simultaneously through participants’ headphones. A different vowel sound played in each ear. The vocal pitch was different, as male and female voices were used. Each test subject had a touch screen on which to record recognizable vowel sounds.
At the end of the tests, it was clear that those with hearing loss experienced an abnormal fusing of speech across both ears. This was not dependent on pitch differences. Different vowels sounds when fused were heard as new and completely different vowel sounds.
This new discovery of abnormal binaural fusion could explain why those with hearing loss often consider crowd settings confusing and hard to follow. Reiss suggested that this could lead to new therapeutic measures to improve speech perception and understanding on a global scale.