Effect of ambient respiratory noise on the measurement of lung sounds



The effect of ambient sounds, generated during breathing, that may reach a sensor at the chest surface by transmission from mouth and nose through air in the room, rather than through the airways, lungs and chest wall, is studied. Five healthy male non-smokers, aged from 11 to 51 years, are seated in a sound-proof acoustic chamber. Ambient respiratory noise levels are modified by directing expiratory flow outside the recording chamber. Low-density · gas (HeO2=80% helium, 20% oxygen) is used to modify airway resonances. Spectral analysis is applied to ambient noise and to respiratory sounds measured on the chest and neck. Flow-gated average sound spectra are compared statistically. A prominent spectral peak around 960 Hz appears in ambient noise and over the chest and neck during expiration in all subjects. Ambient noise reduction decreases the amplitude of this peak by 20±4 dB in the room and by 6±3.6 dB over the chest. Another prominent spectral peak, around 700 Hz in adults and 880 Hz in children, shows insignificant change, i.e. a maximum reduction of 3 dB, during modifications of ambient respiratory noise. HeO2 causes an upward shift in tracheal resonances that is also seen in the anterior chest recordings. Ambient respiratory noise explains some, but not all, peaks in the spectra of expiratory lung sounds. Resonance peaks in the spectra of expiratory tracheal sounds are also apparent in the spectra of expiratory lung sounds at the anterior chest.


Respiratory sounds Computers Respiratory air flow Spectrum analysis 


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  1. Forgacs, P. (1972): ‘Noisy breathing’,Chest,63, pp. Suppl:38S-Suppl:41SGoogle Scholar
  2. Gavriely, N., Palti, Y., andAlroy, G. (1981): ‘Spectral characteristics of normal breath sounds’,J. Appl. Physiol.,50, pp. 307–314Google Scholar
  3. Gavriely, N., andCugell, D. W. (1996): ‘Airflow effects on amplitude and spectral content of normal breath sounds’,J. Appl. Physiol.,80, pp. 5–13Google Scholar
  4. Hadjileontiadis, L. J., andPanas, S. M. (1997): ‘Higher-order statistics: a robust vehicle for diagnostic assessment and characterisation of lung sounds’,Tech. Health Care,5, pp. 359–374Google Scholar
  5. Kraman, S. S. (1980): ‘Determination of the site of production of respiratory sounds by subtraction phonopneumography’,Am. Rev. Respir. Dis.,122, p. 303–309Google Scholar
  6. Kraman, S. S., andAustrheim, O. (1983): ‘Comparison of lung sound and transmitted sound amplitude in normal men’,Am. Rev. Respir. Dis.,128, pp. 451–454Google Scholar
  7. Kraman, S. S., Wodicka, G. R., Oh, Y., andPasterkamp, H. (1995): ‘Measurement of respiratory acoustic signals: Effect of microphone air cavity width, shape and venting’,Chest,108, pp. 1004–1008CrossRefGoogle Scholar
  8. Kuyper, P. (1972): ‘The cocktail party effect’,Audiology,11, pp. 277–282CrossRefGoogle Scholar
  9. Malmberg, L. P., Sorva, R., andSovijärvi, A. R. (1994): ‘Frequency distribution of breath sounds as an indicator of broncho-constriction during histamine challenge test in asthmatic children’,Pediatr. Pulmonol.,18, pp. 170–177CrossRefGoogle Scholar
  10. Malmberg, L. P., Pesu, L., andSovijärvi, A. R. A. (1995): ‘Significant differences in flow standardised breath sound spectra in patients with chronic obstructive pulmonary disease, stable asthma, and healthy lungs’,Thorax,50, pp. 1285–1291CrossRefGoogle Scholar
  11. Mercer, J. L. (1973): ‘The mechanism of bronchial breathing’,Chest,63, pp. 856Google Scholar
  12. Muller, N. L., andZamel, N. (1981): ‘Pneumotachograph calibration for inspiratory and expiratory flows during HeO2 breathing’,J. Appl. Physiol.,51, pp. 1038–1041Google Scholar
  13. O'Donnell, D. M., andKraman, S. S. (1982): ‘Vesicular lung sound amplitude mapping by automated flow-gated phonopneumography’,J. Appl. Physiol., 53, pp. 603–609Google Scholar
  14. Pasterkamp, H., Kraman, S. S., DeFrain, P. D., andWodicka, G. R. (1993): ‘Measurement of respiratory acoustical signals. Comparison of sensors’,Chest 104, pp. 1518–1525CrossRefGoogle Scholar
  15. Pasterkamp, H., andSanchez, I. (1996): ‘Effect of gas density on respiratory sounds’,Am. J. Resp. Crit. Care Med.,153, pp. 1087–1092Google Scholar
  16. Pasterkamp, H., Powell, R. E., andSanchez, I. (1996a): ‘Characteristics of lung sounds at standardized air flow in normal infants, children and adults’,Am. J. Resp. Crit. Care Med.,154, pp. 424–430Google Scholar
  17. Pasterkamp, H., Schäfer, J., andWodicka, G. R. (1996b): ‘Posture-dependent change of tracheal sounds at standardized flows in patients with obstructive sleep apnea’,Chest,110, pp. 1493–1498CrossRefGoogle Scholar
  18. Pasterkamp, H., Kraman, S. S., andWodicka, G. R. (1997a): ‘State of the art: respiratory sounds-advances beyond the stethoscope’,Am. J. Respir. Crit. Care Med.,156, pp. 974–987Google Scholar
  19. Pasterkamp, H., Consunji-Araneta, R., Oh, Y., andHolbrow, J. (1997b): ‘Chest surface mapping of lung sounds during methacholine challenge’,Pediatr. Pulmonol.,23, pp. 21–30CrossRefGoogle Scholar
  20. Pasterkamp, H., Patel, S., andWodicka, G. R. (1997c): ‘Asymmetry of respiratory sounds and thoracic transmission’,Med. Biol. Eng. Comput.,35, pp. 103–106CrossRefGoogle Scholar
  21. Sanchez, I., andPasterkamp, H. (1993): ‘Tracheal sound spectra depend on body height’,Am. Rev. Respir. Dis.,148, pp. 1083–1087Google Scholar
  22. Wodicka, G. R., Kraman, S. S., Zenk, G. M., andPasterkamp, H. (1994): ‘Measurement of respiratory acoustic signals. Effect of microphone air cavity depth’,Chest,106, pp. 1140–1144CrossRefGoogle Scholar

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© IFMBE 1999

Authors and Affiliations

  1. 1.Department of Pediatrics & Child HealthUniversity of ManitobaWinnipegCanada
  2. 2.School of Electrical & Computer Engineering & Department of Biomedical EngineeringPurdue UniversityWest LafayetteIndianaUSA
  3. 3.VA Medical CenterLexingtonUSA

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