The murmur of breathing is mainly caused by diseases of the respiratory tract, including lung infections and bronchial inflammation, bronchospasm, which can manifest as blistering sounds and croup. Croup is more common in bronchial asthma and wheezing bronchitis, and cardiogenic asthma can also easily cause it, mainly because it affects the diastole of the smooth muscles of the airways, resulting in narrowing of the airways. Bronchial and pulmonary infections can cause alveolar sounds in the lungs, and pulmonary edema caused by pulmonary fibrosis and cardiac insufficiency can also be easily caused, mainly due to secretions or exudate in the airways, which can form a rupture of the alveoli and make sounds when airflow passes through.