According to the Linguistic Society of America, there are nearly 7,000 distinct human languages, which include everything from Hopi to British Sign Language. Humankind’s propensity for spoken language, however, would be difficult, if not impossible, without one key skill of the human brain: the ability to control the pitch of our voices.
While this might not seem like a terribly advanced trait, this human ability is actually unique amongst primates and is critical in our ability to express ourselves in complex spoken languages. Melodic control is not just important in singing – the ability to fluctuate pitch throughout a sentence or phrase can is important when we want to express our mood, emphasize words, or indicate whether we are speaking a statement or a question. In fact, melodic control is so important in some languages, like the tonal Mandarin language, that distinct pitches can give a completely different meaning to identical words.
Although speech output and the ability to produce a seamless combination of vowels and consonants is a product of the lips, tongue, and throat muscles, the most important player in melodic control is the larynx. Often colloquially called the ‘voice box’, the larynx is made of folds, also known as vocal cords, which vibrate as we push air through them. In a process much like tuning a guitar string, by tightening and increasing tension on our vocal cords, we can cause our larynx muscles to vibrate more quickly and produce different pitches.
Relatively few species have this degree of control over their larynx, which is a prerequisite in the development of a spoken language. This larynx control, however, has little to do with the larynx itself; rather, research from a lab at the University of California, San Francisco has shown that the activation of neurons in a brain area called the dorsal laryngeal motor cortex can cause the larynx muscles to flex to change pitch. Thanks to this small portion of our brains’ motor cortices, we have the ability to form complex languages and, perhaps better yet, the gift of music in our lives.
High-frequency Hearing Loss
For people with hearing loss, however, this ability to change pitch quickly and easily can cause a whole lot of trouble. Many people with hearing loss do not experience full loss of hearing in either or both ears. Rather, they often find it difficult to hear sounds in specific frequency ranges.
One of the most common types of hearing loss is known as high-frequency (or high pitch) hearing loss. This condition is often defined as an inability to or a difficulty in hearing sounds between 2000 and 8000 Hz. While this may not seem too bad in the grand scheme of things (you can still hear some things, right?) high-frequency hearing loss can make it incredibly challenging for people to understand human speech.
Since spoken human languages often have a wide range of different tones and pitches, many of these sounds at the higher frequencies can be difficult or impossible for someone with high-frequency hearing loss. Fricative sounds such as the S, H, and F in the English language are particularly high in pitch. If you can’t hear someone when they say these letters, you might find that you constantly have to ask people to repeat themselves or you risk missing out on important information. It’s easy to see how this can be extremely frustrating over time.
Luckily, hearing aids are often a very effective treatment for people with high-frequency hearing loss. Since your hearing healthcare professional will be able to give you more individualized and appropriate guidance about what treatment options are best for you, it’s best to reach out for a consultative appointment as soon as possible if you think you might have high-frequency hearing loss so you don’t have to miss out on the joys of music and conversations with your loved ones.