Data reduction for cough studies using distribution of audio frequency contentReport as inadecuate

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, 8:12

First Online: 12 December 2012Received: 15 March 2012Accepted: 29 October 2012


BackgroundRecent studies suggest that objectively quantifying coughing in audio recordings offers a novel means to understand coughing and assess treatments. Currently, manual cough counting is the most accurate method for quantifying coughing. However, the demand of manually counting cough records is substantial, demonstrating a need to reduce record lengths prior to counting whilst preserving the coughs within them. This study tested the performance of an algorithm developed for this purpose.

Methods20 subjects were recruited 5 healthy smokers and non-smokers, 5 chronic cough, 5 chronic obstructive pulmonary disease and 5 asthma, fitted with an ambulatory recording system and recorded for 24 hours. The recordings produced were divided into 15 min segments and counted. Periods of inactive audio in each segment were removed using the median frequency and power of the audio signal and the resulting files re-counted.

ResultsThe median resultant segment length was 13.9 s IQR 56.4 s and median 24 hr recording length 62.4 min IQR 100.4. A median of 0.0 coughs-h IQR 0.0-0.2 were erroneously removed and the variability in the resultant cough counts was comparable to that between manual cough counts. The largest error was seen in asthmatic patients, but still only 1.0% coughs-h were missed.

ConclusionsThese data show that a system which measures signal activity using the median audio frequency can substantially reduce record lengths without significantly compromising the coughs contained within them.

KeywordsAacoustics Cough sounds Monitoring AbbreviationsFFTFast Fourier Transform

AbsxThe absolute value of x i.e. always positive.

Electronic supplementary materialThe online version of this article doi:10.1186-1745-9974-8-12 contains supplementary material, which is available to authorized users.

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Author: Antony Barton - Patrick Gaydecki - Kimberley Holt - Jaclyn A Smith


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