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Clinicians often auscultate the lungs, using a stethoscope or other listening device, to hear the sounds the body is making on its own accord. When sound carries perhaps too well through the lungs, this phenomenon is called pectoriloquy. These sounds are broken into several categories, with a certain dynamic called bronchophony. This occurs when normal vocal volume carries without muffling through the lungs, often due to conditions like pneumonia or even cancer.
With the stethoscope on either side of the chest, the seated patient is asked to slowly say the number "99" several times in a row. With normal bronchophony, the words will sound muffled and unable to discern. If the words carry clearly enough to hear audibly, an abnormal bronchophony may be diagnosed.
When the lungs are operating normally, its tissue typically filters out clear noises made by the voice box. These acoustics are diminished when bronchophony has been compromised. This allows the sound to be heard more clearly in lungs. A doctor will rule out this phenomenon if the sound is not distinct enough to make out the number.
Bronchophony is just one of several voice transmission examinations that doctors may use to determine if a patient is having respiratory problems. Another similar test is called the whispered pectoriloquy test. This involves the patient lightly whispering the number "99" several times slowly. If the doctor can clearly hear the number through the stethoscope, the test will come back positive. Otherwise, the number will be inaudible or, at the least, completely indecipherable. Yet another test, called tactile fremitus, has the patient saying "99" while feeling for excessive vibrations over the lungs.
Another test similar to bronchophony tests the lungs for egophony, during which an "EEE" sound translates to an "AAA" sound. Listening over each lung with a stethoscope, the doctor will tell the patient to hold an "EEE" sound in a clear, audible voice. If the sound that is transmitted through auscultation is closer to "AAA," the doctor will suspect egophony.
These tests can provide at least a tentative diagnosis of lung consolidation in which the lungs fill with fluid. This could be caused by pneumonia, but other conditions, such as asthma and even cancer, can cause it. To confirm the diagnosis, an x-ray of the lungs will be able to identify the location and severity of the consolidation.