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The vocal fremitus is a palpatory examination method in which the examiner places both hands on the patient's chest at the level of the 8th - 10th rib between the posterior axillary line and the scapular line, while the patient repeats the number 99 several times in a deep voice (corresponding to the natural frequency of the thorax). This results in oscillations of the thoracic wall, which is diagnostically directional by side comparison.

Source of error: Women and children sometimes have a too high pitch, which is why the natural frequency of the thorax cannot be made to vibrate.

Air-containing alveoli reduce low frequencies at:

• Pleural effusion (until cancelled)
• Pneumothorax (until cancelled)
• Emphysema
• Atelectasis
• Pleural rind (reinforcement is also possible for very thick pleural rind)
• Tumor (if applicable)

The vocal fremitus is aggravated by compressed lung tissue such as in:

• pneumonia
• Fibrosis (possibly)
• Pulmonary edema (possibly)

Error source:

Women and children sometimes have a too high voice pitch, which is why the natural frequency of the thorax cannot be made to vibrate.

1. Herold G et al (2018) Internal Medicine S 376
2. Anschütz F (1978) The physical examination S 87-89