Table 2. Types of adventitious sounds and its characteristics.

Types	Continuity	Durationa	Timingb	Pitchc	Qualityd	Causee	Disease Associatedf
Wheeze	Continuous	> 80ms	Inspiratory, Mostly Expiratory, Biphasic	High (> 400Hz)	Sibilant, Musical	Airway narrowing, airflow limitation	Asthma, COPD, Foreign body
Rhonchi	Continuous	> 80ms	Inspiratory, Mostly Expiratory, Biphasic	Low (< 200Hz)	Sibilant, Musical	Secretion in bronchial, muchosal thickening	Bronchitis, COPD
Stridor	Continuous	> 250ms	Mostly Inspiratory, Expiratory, Both	High (> 500Hz)	Sibilant, Musical	Turbulent airflow in larynx or lower bronchial tree (Upper airway obstruction)	Epiglottitis, foreign body, croup, laryngeal oedema
Fine Crackle	Discontinuous	± 5 ms	Inspiratory (late)	High (650 Hz)	Non-musical, Explosive	Explosive opening of small airways	Pneumonia, Congestive heart failure, Lung fibrosis
Coarse Crackle	Discontinuous	± 15 ms	Mostly Inspiratory (early), Expiratory, Both	Low (350 Hz)	Non-musical, Explosive	Air bubble in large bronchi or bronchiectatic segments	Chronic bronchitis, bronchiectasis, COPD
Pleural Rub	Discontinuous	> 15ms	Biphasic	Low (< 350Hz)	Non-Musical, Rhythmic	Pleural membrane rubbing against each other	Inflammation of lung membrane, lung tumour
Squawk	Continuous	± 200 ms	Inspiratory	Low (200—300 Hz)	Short Musical and non-musical	Oscillation of peripheral airways	Hypersensitivity pneumonia, pneumonia
Gasp	Continuous	> 250ms	Inspiratory	High	Whoop	Gasping for breath	Whooping cough

^aInformation from [10, 17, 19, 20, 23]

^bInformation from [8, 10, 20, 21]

^cInformation from [10, 14, 20, 23]

^dInformation from [8, 10, 18–20]

^eInformation from [8, 15, 16, 19–21, 24]

^fInformation from [8, 10, 20, 22]