title: Experimental validation of the tuneable diaphragm effect in modern acoustic stethoscopes.
abstract: OBJECTIVE
  The force with which the diaphragm chestpiece of a stethoscope is pressed against the body of a patient during an auscultation examination introduces the initial stress and deformation to the diaphragm and the underlying tissues, thus altering the acoustic parameters of the sound transmission path. If the examination is performed by an experienced physician, he will intuitively adjust the amount of the force in order to achieve the optimal sound quality. However, in case of becoming increasingly popular auto-diagnosis and telemedicine auscultation devices with no such feedback mechanisms, the question arises regarding the influence of the possible force mismatch on the parameters of the recorded signal.
  
  
  METHODS
  The present study describes the results of the experimental investigations on the relation between pressure applied to the chestpiece of a stethoscope and parameters of the transmitted bioacoustic signals. The experiments were carried out using various stethoscopes connected to a force measurement system, which allowed to maintain fixed pressure during auscultation examinations. The signals were recorded during examinations of different volunteers, at various auscultation sites.
  
  
  RESULTS
  The obtained results reveal strong individual and auscultation-site variability.
  
  
  CONCLUSIONS
  It is concluded that the underlying tissue deformation is the primary factor that alters the parameters of the recorded signals.
authors.affiliation: Department of Endocrinology, Centre of Postgraduate Medical Education, Warsaw, Poland.|Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Karolina M
authors.identifier: http://orcid.org/0000-0003-1394-728X
authors.initials: KM
authors.lastname: Nowak
authors.affiliation: Institute of Fundamental Technological Research, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Lukasz J
authors.identifier: http://orcid.org/0000-0003-1155-3447
authors.initials: LJ
authors.lastname: Nowak
mesh_terms: D000162:Acoustics; D000328:Adult; D000669:Amplifiers, Electronic; D001314:Auscultation; D002648:Child; D003936:Diagnosis, Computer-Assisted; D004867:Equipment Design; D005246:Feedback; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D011312:Pressure; D012815:Signal Processing, Computer-Assisted; D019023:Stethoscopes; D059015:Wireless Technology
keywords: auscultation; chestpiece; stethoscope; tunable diaphragm