Sound Clarity and Understanding Speech

I can hear you, but I can’t understand you.

Healthy hearing is much more than the audibility (loudness) of sound. Sound clarity and intelligibility, or understanding speech and recognizing words, are just as important.

The inner ear is lined with two types of hair cells — inner hair cells and outer hair cells. Outer hair cells are responsible for amplifying, tuning and filtering sounds, while inner hair cells convert sounds into electrical signals carried to the brain. The loss of either cell types lead to a decrease in sound sensitivity, clarity and intelligibility.

What is speech intelligibility?

Try listening to the Words in Noise test, a functional test administered in hearing clinics to assess understanding of speech in noisy backgrounds.

Critical information lost at high frequencies

Today’s treatments for hearing loss – amplifying devices such as hearing aids – are limited in their ability to improve the clarity and intelligibility of sound, as they cannot replace the tuning and filtering of lost hair cells. This often translates into difficulties understanding speech and following conversations – often in noisy backgrounds.

Additionally, most acquired SNHL begins in the high frequencies (2,000 Hz to 8,000 Hz). High frequency hearing loss is associated with problems understanding speech, because a lot of speech sounds – especially “s,” “f” and “th” – are high frequency, soft sounds. When you can’t hear these consonants, it can be very difficult to recognize words.

Add all this together, and millions of people with hearing loss continue to struggle to understand speech, even when using assistive devices.

Source: Monson et al (2014) The perceptual significance of high-frequency energy in the human voice. Frontiers in Psychology, 5, 587

Speech Intelligibility and Quality of Life

Hearing is how we communicate and relate to one another. It’s an important part of our social and emotional well-being.

Any degree of hearing loss can be damaging to relationships – personally and professionally. Friends, coworkers and significant others often do not understand how hearing loss can impact someone’s life, and often do not know what to do to communicate effectively.

To struggle with understanding speech can also be exhausting, emotional and isolating for someone with hearing loss. Many people decide to avoid social situations, especially in environments where there may be background noise.