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Sound: a non-invasive measure of cough intensity
  1. Kai K Lee1,2,
  2. Sergio Matos3,
  3. Katie Ward1,
  4. Gerrard F Rafferty1,
  5. John Moxham1,2,
  6. David H Evans4 and
  7. Surinder S Birring1,2
  1. 1 Division of Asthma, Allergy and Lung Biology, King's College London, London, UK
  2. 2 Department of Respiratory Medicine, King's College Hospital NHS Foundation Trust, London, UK
  3. 3 Institute of Electronics and Telematics Engineering, University of Aveiro, Aveiro, Portugal
  4. 4 Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
  1. Correspondence to Dr Kai K Lee; kai.lee{at}


Introduction Cough intensity is an important determinant of cough severity reported by patients. Cough sound analysis has been widely validated for the measurement of cough frequency but few studies have validated its use in the assessment of cough strength. We investigated the relationship between cough sound and physiological measures of cough strength.

Methods 32 patients with chronic cough and controls underwent contemporaneous measurements of voluntary cough sound, flow and oesophageal pressure. Sound power, peak energy, rise-time, duration, peak-frequency, bandwidth and centroid-frequency were assessed and compared with physiological measures. The relationship between sound and subjective cough strength Visual Analogue Score (VAS), the repeatability of cough sounds and the effect of microphone position were also assessed.

Results Sound power and energy correlated strongly with cough flow (median Spearman’s r=0.87–0.88) and oesophageal pressure (median Spearman’s r=0.89). Sound power and energy correlated strongly with cough strength VAS (median Spearman’s r=0.84–0.86) and were highly repeatable (intraclass correlation coefficient=0.93–0.94) but both were affected by change in microphone position.

Conclusions Cough sound power and energy correlate strongly with physiological measures and subjective perception of cough strength. Power and energy are highly repeatable measures but the microphone position should be standardised. Our findings support the use of cough sound as an index of cough strength.

  • Cough/Mechanisms/Pharmacology
  • Lung Physiology
  • Respiratory Measurement

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:

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  • Acknowledgements We would like to thank the volunteers for their participation in the study, Dr Abdel Douiri for assistance with statistical analysis and King's College Hospital for an unrestricted investigator led research grant.

  • Contributors Study concept and design: KKL, SB; Acquisition of data: KKL, KW; Analysis and interpretation of data: KKL, SM, GFR, JM, DHE, SB; Drafting of the manuscript for important intellectual content: KKL, JM, SB; Revision of manuscript: KKL, SM, KW, GFR, JM, DHE, SB.

  • Competing interests None declared.

  • Ethics approval East London and the City Research Ethics Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement King’s College Hospital NHS Foundation Trust.

  • Data sharing statement No additional data are available

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