The sound we know as voice is created by vibration,
... and voice can only be produced by vibrating structures.
In the larynx, the source of vibration is almost always the true vocal cords.
Hoarseness is produced in two different ways: by air leak or by asymmetric vibrations. Air leak causes a husky hoarseness. Asymmetric vibrations cause a rough hoarseness. Numerous disorders have both air leak and asymmetric vibra-tions and perhaps even more than one type of asymmetry. Asymmetries between the vocal cords, whether in tension, in mass, in length, in stiffness or in combination, will tend to cause the vocal cords to go out of sync with each other during vibration. When out of sync, we have two sound sources and we will hear two pitches simultaneously, a double sound or diplophonia. We perceive diplophonia as a rough quality to the voice.
Air may leak from the front, middle or back of the vocal cords. The vocal cords may be asymmetric in several different ways: mass, tension, length, stiffness or timing.
Two personality traits strongly influence vocal cord disorders. Talkativeness is an innate personality trait that puts a person at risk for mucosal lesions. With more vibrations comes an increasing risk of calluses and swellings, which typically leads to a mixed rough and husky hoarseness. A lack of talkativeness puts a person at risk for muscle atrophy and typically husky hoarseness and discomfort from muscle compensation.
In diagnosis, the most important part of the question, “Why am I hoarse?” is the why. Shouldn’t that be obvious? It should be, but it isn’t. There is an implicit assumption often made that since voice comes from the larynx, all the examiner has to do is look in the vicinity of the vocal cords and whatever appears on the larynx is likely causing the hoarseness. But, mere presence is not sufficient justification for cause. The examiner needs to take this one important step further. The examiner must identify specifically what about the vocal cords is causing air leak and what is causing asymmetry. Looking for invisible, leaking air is not necessarily intuitive.
- Hoarseness is air leaking between two vocal cords that are not closed (white noise) or
- Hoarseness is two different sound sources – cords that are asymmetric in some sense (mass, length, tension or stiffness) and vibrating at different pitches, hence diplophonia.
- Husky hoarseness is a term that could be substituted for air leak.
- Rough hoarseness is a term that could be substituted for diplophonia.
Looking at the vocal cords during endoscopy
- a persistent gap signifies air leak and explains huskiness,
- the vocal cords should vibrate as mirror images and deviation from this symmetry can explain roughness,
- disorders may have components of both types of hoarseness.
- Hoarseness is a general term that includes huskiness and roughness.