Patient is asked to speak a word, usually '99' to produce resonance.

NORMAL: As a vocal sound is transmitted from the larynx down through the trachea, the bronchi, the alveoli and then to the chest wall, the sound becomes less distinct and much softer than when heard directly.

If bronchophony is present, the sound is very clear and very loud.

Bronchophony occurs over areas of the lung in which the alveoli are filled with fluid or replaced by solid tissue. It can be heard in consolidation due to pneumonia, collapse, or tumours.