(1997 c): ‘Asymmetry of respiratory sounds and thoracic transmission’, Med. Pasterkamp, H., Patel, S., and Wodicka, G. (1997 b): ‘Chest surface mapping of lung sounds during methacholine challenge’, Pediatr. ![]() Pasterkamp, H., Consunji-Araneta, R., Oh, Y., and Holbrow, J. (1997 a): ‘State of the art: respiratory sounds-advances beyond the stethoscope’, Am. (1996 b): ‘Posture-dependent change of tracheal sounds at standardized flows in patients with obstructive sleep apnea’, Chest, 110, pp. Pasterkamp, H., Schäfer, J., and Wodicka, G. (1996 a): ‘Characteristics of lung sounds at standardized air flow in normal infants, children and adults’, Am. (1996): ‘Effect of gas density on respiratory sounds’, Am. (1993): ‘Measurement of respiratory acoustical signals. (1982): ‘Vesicular lung sound amplitude mapping by automated flow-gated phonopneumography’, J. (1981): ‘Pneumotachograph calibration for inspiratory and expiratory flows during HeO 2 breathing’, J. (1973): ‘The mechanism of bronchial breathing’, Chest, 63, pp. (1995): ‘Significant differences in flow standardised breath sound spectra in patients with chronic obstructive pulmonary disease, stable asthma, and healthy lungs’, Thorax, 50, pp. (1994): ‘Frequency distribution of breath sounds as an indicator of broncho-constriction during histamine challenge test in asthmatic children’, Pediatr. (1972): ‘The cocktail party effect’, Audiology, 11, pp. (1995): ‘Measurement of respiratory acoustic signals: Effect of microphone air cavity width, shape and venting’, Chest, 108, pp. (1983): ‘Comparison of lung sound and transmitted sound amplitude in normal men’, Am. (1980): ‘Determination of the site of production of respiratory sounds by subtraction phonopneumography’, Am. (1997): ‘Higher-order statistics: a robust vehicle for diagnostic assessment and characterisation of lung sounds’, Tech. ![]() (1996): ‘Airflow effects on amplitude and spectral content of normal breath sounds’, J. (1981): ‘Spectral characteristics of normal breath sounds’, J. Resonance peaks in the spectra of expiratory tracheal sounds are also apparent in the spectra of expiratory lung sounds at the anterior chest.įorgacs, P. Ambient respiratory noise explains some, but not all, peaks in the spectra of expiratory lung sounds. HeO 2 causes an upward shift in tracheal resonances that is also seen in the anterior chest recordings. ![]() a maximum reduction of 3 dB, during modifications of ambient respiratory noise. ![]() Another prominent spectral peak, around 700 Hz in adults and 880 Hz in children, shows insignificant change, i.e. Ambient noise reduction decreases the amplitude of this peak by 20±4 dB in the room and by 6☓.6 dB over the chest. A prominent spectral peak around 960 Hz appears in ambient noise and over the chest and neck during expiration in all subjects. Flow-gated average sound spectra are compared statistically. Spectral analysis is applied to ambient noise and to respiratory sounds measured on the chest and neck. gas (HeO 2=80% helium, 20% oxygen) is used to modify airway resonances.Ambient respiratory noise levels are modified by directing expiratory flow outside the recording chamber. Five healthy male non-smokers, aged from 11 to 51 years, are seated in a sound-proof acoustic chamber. 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.
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