In listening to speech, cares should be made to detect whether the speech is strong or weak, whether the words are coherent and whether the expression is clear and fluent. The speech of normal people is natural in pronunciation, smooth in tone, clear in expression and consistent in words. Since the viscera, constitution and physical building are different from person to person, the voice either is high or low, loud or small and clear or full. For example, male voice is low and full, female voice is high and clear, children’s voice is sharp and melodious, and voice of the aged is low and deep. Generally speaking, high and sonorous voice in healthy people is a manifestation of sufficiency of primordial qi and pulmonary qi.

There is close relation between speech and emotions. For example, the voice in joy is lively and cheerful, the voice in rage is stern and quick, and the voice in sorrow is sad and disjointed. These are the normal changes of voice. The abnormal changes of voice are either strong or weak, heavy or deep, hoarseness or aphonia.

Strong and weak voice:
Generally speaking, the loud and sonorous, dysphoric and raving voice pertains to sthenia syndrome and heat syndrome. While the feeble, repeated, silent with few words voice pertains to asthenia syndrome and cold syndrome.

Deep and heavy voice:
Deep and heavy voice is usually caused by failure of pulmonary qi to disperse and obstruction of the nose due to exogenous pathogenic wind, cold and dampness, or by obstruction of the airway due to stagnation of dampness.

Hoarseness and aphonia:
Hoarseness means harsh voice, while aphonia means complete loss of voice. Hoarseness is similar to aphonia in pathogenesis. If hoarseness is very serious, it will develop into aphonia. Hoarseness or aphonia in new disease pertains to sthenia syndrome due to exogenous pathogenic factors attacking on the lung or due to failure of the pulmonary qi to disperse resulting from stagnation of phlegm. Such a pathological condition is known as "a solid bell cannot ring (dysphonia or hoarseness due to sthenia syndrome of the lung)".

Hoarseness or aphonia in a chronic disease pertains to asthenia syndrome due to exhaustion of fluid and impairment of the lung caused by asthenia of lung and kidney yin and asthenia-fire scorching metal (lung). Such a pathological condition is known as "a broken bell cannot ring (hoarseness due to impaired function of the lung)". Hoarseness or aphonia may be caused by prolonged speaking or singing or shouting with rage, which impairs both qi and yin and deprives the throat of moisture. Hoarseness at the advanced stage of pregnancy is due to pressure of the fetus on the uterine collaterals which obstructs the kidney meridian and prevents kidney essence to be transported to the upper. It will heal automatically after delivery.