title: [Pulmonary crackles, what does the clinician hear?].
abstract: BACKGROUND
  The overall duration of a pulmonary crackle is usually less than 20-30 ms but psychoacoustics demonstrates that an acoustical event with a duration of less than 20-40 ms cannot be estimated in terms of pitch and duration. We pose the hypothesis that the main resonant information is contained into the breath sounds following the crackle.
  
  
  METHODS
  Eight patients with COPD, viral pneumonia, bronchiectasis, congestive heart failure, hypoproteinemia and fibrosing alveolitis were recruited for this study. Thirty-six crackles were analyzed in time and frequency domains; 12 in each category of low, medium and high frequencies. The acoustic features of the crackles, their segments (initial deflection width, first cycle duration, two cycles duration, decay segment) and the breath sounds following the crackles were compared.
  
  
  RESULTS
  The study confirms the differences between the three crackles categories in time and frequency domains. No statistical differences were found between the decay segments and breath sounds in each category.
  
  
  CONCLUSIONS
  Breath sounds modified by lung tissue density could be the main resonators determining the fundamental transmission frequencies of crackle signals. Combined acoustic analysis of crackles and breath sounds could replace single analysis of isolated crackles.
authors.affiliation: Service des soins intensifs, grand hôpital de Charleroi, haute école Condorcet et laboratoire d'acoustique médicale appliquée, Charleroi, Belgique. Electronic address: guy.postiaux@gmail.com.
authors.forename: G
authors.initials: G
authors.lastname: Postiaux
authors.affiliation: Facultat Ciències de la Salut Blanquerna, grup de recerca en fisioteràpia (GReFis), universitat Ramon-Llull, Barcelone, Espagne.
authors.forename: J
authors.initials: J
authors.lastname: Vilaro
authors.affiliation: Haute école de Louvain en Hainaut, Montignies-sur-Sambre, Belgique.
authors.forename: J-L
authors.initials: JL
authors.lastname: Charlier
authors.affiliation: Service de pneumologie, hôpital Notre-Dame de Grâce, Gosselies, Belgique.
authors.forename: E
authors.initials: E
authors.lastname: Marchand
authors.affiliation: Service de médecine interne, clinique Reine-Fabiola, 73, avenue du Centenaire, 6061 Montignies-sur-Sambre, Belgique.
authors.forename: E
authors.initials: E
authors.lastname: Lens
mesh_terms: D003937:Diagnosis, Differential; D006309:Hearing / Q000502:physiology*; D006801:Humans; D008168:Lung / Q000502:physiology*; D008171:Lung Diseases / Q000175:diagnosis; D010820:Physicians; D012135:Respiratory Sounds / Q000145:classification / Q000175:diagnosis*; D013016:Sound
keywords: Acoustical analysis; Analyse acoustique; Auscultation; Breath sounds; Bruits respiratoires; Crackles; Craquement; Psychoacoustics; Psychoacoustique