The sounds heard through the stethoscope when the patient speaks (“ninety-nine”). These are normally just audible but become much louder {bronchophony) if the lung under the stethoscope is consolidated, when they resemble the sounds heard over the trachea and main bronchi. Vocal resonance is lost over pleural fluid except at its upper surface, when it has a bleating quality and is called egophony.
The air carrying the voice, produced in the larynx, passes through the throat, mouth and nose. The shape and size of these structures will influence the timbre of the voice, or vocal resonance. This will vary from person to person and even within an individual; for example, with a cold.
In auscultation, the vibrations of the voice transmitted to the examiner’s ear, normally more marked over the right apex of the lung. These vibrations are abnormally increased in pneumonic consolidation, in lungs infiltrated with tuberculosis, or in cavities that communicate freely with a bronchus.
The reverberations of the spoken voice that pass through the lungs and chest wall, discernible via a stethoscope. These vibrations undergo changes when the lungs are compressed, solidified, or when there is fluid in the chest cavity.