Clinical correlations

Measuring laryngeal function

One way to visualize the larynx is with an instrument called an endoscope. The endoscope may be rigid or flexible. The rigid endoscope may be uncomfortable for the patient, and may elicit the gag reflex. Since the scope is inserted through the mouth, the patient is limited to sustained vowel sounds, rather than speech. The flexible endoscope is inserted through the nasal passage for an unobstructed view of the vocal folds. Since the scope does not interfere with pharyngeal movement, the larynx can be visualized producing a wide variety of speech.

 

The electroglottograph is an inexpensive, simple machine that measures the amount of contact between the vocal folds as they are vibrating. Electroglottography is a non-invasive procedure, and two electrodes are placed on the neck over the thyroid cartilage. The degree of vocal fold approximation and fundamental frequency are two of the measures which can be obtained through electroglottography.

 

The voice can also be measured acoustically, through instruments such as the Computerized Speech Lab (CSL) by Kay-Pentax. The CSLcaptures the voice and can measure sound pressure level, frequency, and time. It will display the voice in a waveform and in a spectogram, and measure jitter, and shimmer, among other parameters. The CSL is probably the gold standard for clinical analysis of speech and for research, but there are some very good downloadable free programs which also perform voice analysis. Two of the more popular ones are CSpeech/TF32 and Praat. The lab for this unit involves making some acoustic measures of voice through a free downloadable program called Praat.

 

The role of the speech-language pathologist in working with laryngeal disorders

Voice disorders may occur through vocal abuse, or may be of an organic nature, for examples tumors or cysts. They may also occur as a part of a neurological disorder, such as Parkinson's disease, or through trauma. Speech-language pathologists assess and treat voice disorders. They may provide therapy and instruction on the proper use of the voice, and/or use instrumentation to diagnose and treat a voice disorder.