Swelling tests are perhaps the most detailed vocal task.
The examiner reassesses the upper and lower ends of the pitch range at the very softest volume the patient can produce, for comparison with the previously recorded maximum vocal range.
One of the easiest ways to determine the upper limit of the soft vocal range is to have the patient sing the first four words of the nearly universally known song, “Happy Birthday to You.” When singing the words, “happy birthday to you,” between the words “day” and “to” is a melodic interval of a fourth (5 semitones). If no sound comes out on the word “to,” or if there is a significant onset delay to the start of vocal cord vibration on that word, then there is likely some mechanical vibratory limitation of the vocal cords commencing within this interval of a fourth. This test can be repeated at a lower or higher tone and the tone where the voice cuts out more precisely determined. This denotes the soft cutoff point.
Quite often, this requires some coaching. There are a number of disorders that impair soft voicing and despite the patient’s interest in solving their problem, no one likes to “fail” at a test, not even a patient. This is especially pronounced in professional voice users. Even when an individual’s chief complaint is that they are missing notes, they utilize significant effort to avoid sounding “bad” on these notes during an exam. Coaching the patient to sing softer and softer and emphasizing the importance of hearing on what tone the vocal cords stop vibrating and when the voice sounds bad, can improve patient compliance with the test. Emphasis is placed on hearing and discovering the hoarse or impaired voice.
Another option is to allow the patient to first sing the phrase loudly at a pitch, then sing it a second time at the same pitch, but with very limited volume.
Generally, a healthy larynx should be able to produce similar tones at both soft and loud volumes at both the upper and lower ends of their vocal pitch range. When one cannot reach almost the same note softly that one can reach loudly, there is probably a vibratory impairment. The greater the difference between the soft-volume vocal pitch range and the high-volume vocal pitch range, the more significant the vocal cord vibratory problem.
Robert Bastian has termed this test for the soft, upper vocal ceiling, the “vocal swelling test” and the exam is very sensitive for vocal cord vibratory margin swellings (nodules and polyps). In general, the point at which there is an onset delay or soft sound cutoff point signifies the tension at which a swelling on one vocal cord touches the other vocal cord and stops cord vibration. It is just like putting your finger lightly on a vibrating guitar string, dampening or stopping the vibration and sound.
The same task can produce a pitch break, where the sound suddenly jumps up, often nearly an octave. This jump in pitch represents the sudden shortening of the vibrating segement by the swelling.
It is also possible to learn to hear a central glottic gap with this test. The point at which the patient cannot start the vocal cords vibrating (because all the air leaks out between the cords without entraining them) does not occur at as precise a pitch as when a swelling stops the vibrations. But there will be a general pitch range over which the vocal cords cannot be entrained during low air flow because of the width of the glottic gap.
Occasionally vibratory impairment may be secondary to compression from a mass above the vocal cord. A dilated saccular cyst may dampen the vocal cord’s vibrations at certain pitches if compressed against the true vocal cord. Compression from the saccular cyst may also shorten the effective vibratory length of one vocal cord creating diplophonia.