The typical feature of interstitial lung disease is

Rales are abnormal lung sounds characterized by discontinuous clicking or rattling sounds. They can sound like salt dropped onto a hot pan or like cellophane being crumpled. Crackles are the clicking, rattling, or crackling noises that may be made by one or both lungs of a human with a respiratory disease during inhalation. They are usually heard only with a stethoscope ("on auscultation"). Bilateral crackles refers to the presence of crackles in both lungs. Basal crackles are crackles apparently originating in or near the base of the lung. Bibasal crackles refer to crackles at the bases of both the left and right lungs. Bilateral basal crackles also refers to the presence of basal crackles in both lungs. Crackles are caused by the "popping open" of small airways and alveoli collapsed by fluid, exudate, or lack of aeration during expiration. Crackles can be heard in patients with pneumonia, atelectasis, pulmonary fibrosis, acute bronchitis, bronchiectasis, acute respiratory distress syndrome (ARDS), interstitial lung disease or post thoracotomy or metastasis ablation. Pulmonary edema secondary to left-sided congestive hea failure can also cause crackles. Ref Davidson 23rd edition pg 579