Buzzing in the left ear when sleeping and lying down may be due to ear plugging effect, or it may be due to high jugular vein ball, mastoid conduction vein malformation, secretory otitis media and other diseases. 1. Ear plugging effect: when the head is placed sideways on the pillow and the arteries in the temporal region or ear region are partially blocked due to pressure, pulsatile tinnitus may occur. The above situation is due to the “ear plugging effect”, i.e., the effect of blocking the ear and the reduction of environmental noise. Most of the patients can disappear on their own after changing their position. 2. Elevated jugular venous bulb, mastoid conduit venous malformation: in a quiet environment, the cranial blood return load increases, the venous blood pressure rises after lying down compared with the vertical position, and this symptom can be seen when the local vascular bone wall is thin or missing. The most common etiology is the simultaneous presence of hypertension, atherosclerosis or vascular distortion caused by arterial eddy current phenomenon. 3. Secretory otitis media: patients with this disease have a small amount of middle ear effusion in the left ear, the vertical position of the Eustachian tube is not closed, ventilation and drainage is still possible. Sleeping down after the fluid flooded the Eustachian tube tympanic ventricle mouth can cause negative pressure in the middle ear, resulting in the phenomenon of buzzing in the left ear. It is recommended that patients who experience buzzing in the left ear while lying down should adjust their position in a timely manner, and if the symptoms persist, it is necessary to consult a doctor for systematic examination to clarify the diagnosis.