What is wheezing?

Physical sign: A symptom is what a patient describes. A sign is what a doctor finds. Sometimes they can be the same thing. A wheeze is a sign that indicates spasm or tightening of airways. This makes it hard to breathe out. So the patient has to force the air out. The velocity increases and causes a musical tone that can be heard with a stethoscope. It happens with asthma, emphysema, and other copd.

Muscle spasm: Contraction of the muscle around the terminal bronchioles, this narrowing makes a wheeze when air flows be. Can also occure if the vocal cords close as if talking when taking a breath, paradoxical vocal cord movement.

Breathing noise: Wheezing typically refers to the high-pitched noise heard when air is forced through narrowed lower airways during asthma. Pprimarily on exhale when mild, then also on inspiration when airways are tighter. At its worst, air hardly moves: thus no wheezing at all, an ominous sign, and is an emergency. Wheezing is not stridor (upper airway) nor sonorous rhonchi (larger airways). Experts can sort out.