Methods of Recording and Analysing Cough Sounds

doi:10.1006/pulp.1996.0035

Pulmonary Pharmacology

Volume 9, Issues 5–6, October 1996, Pages 269-279

https://doi.org/10.1006/pulp.1996.0035 Get rights and content

Abstract

Efforts have been directed to evolve a computerized system for acquisition and multi-dimensional analysis of the cough sound. The system consists of a PC – AT486 computer with an ADC board having 12 bit resolution. The audio cough sound is acquired using a sensitive miniature microphone at a sampling rate of 8 kHz in the computer and simultaneously recorded in real time using a digital audio tape recorder which also serves as a back up. Analysis of the cough sound is done in time and frequency domains using the digitized data which provide numerical values for key parameters like cough counts, bouts, their intensity and latency. In addition, the duration of each event and cough patterns provide a unique tool which allows objective evaluation of antitussive and expectorant drugs. Both on-line and off-line checks ensure error-free performance over long periods of time. The entire system has been evaluated for sensitivity, accuracy, precision and reliability. Successful use of this system in clinical studies has established what perhaps is the first integrated approach for the objective evaluation of cough.

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Cited by (50)

Analysis of COVID-19 Resulting Cough Using Formants and Automatic Speech Recognition System
2023, Journal of Voice
Citation Excerpt :
This assessment of cough intensity so far has mainly relied on subjective measures, such as cough reflex sensitivity, and on the patient's symptom perception, which was assessed through visual analog scores for cough, various cough symptoms, and quality of life questionnaires.2 The authors in3 have described their system uses audio signals sampled at 8 kHz. Data reduction is achieved by selecting 1-s segments that contain signals above an energy threshold.
As part of our contributions to researches on the ongoing COVID-19 pandemic worldwide, we have studied the cough changes to the infected people based on the Hidden Markov Model (HMM) speech recognition classification, formants frequency and pitch analysis. In this paper, An HMM-based cough recognition system was implemented with 5 HMM states, 8 Gaussian Mixture Distributions (GMMs) and 13 dimensions of the basic Mel-Frequency Cepstral Coefficients (MFCC) with 39 dimensions of the overall feature vector. A comparison between formants frequency and pitch extracted values is realized based on the cough of COVID-19 infected people and healthy ones to confirm our cough recognition system results. The experimental results present that the difference between the recognition rates of infected and non-infected people is 6.7%. Whereas, the formant analysis variation based on the cough of infected and non-infected people is clearly observed with F1, F3, and F4 and lower for F0 and F2.
Discrimination between respiratory and non-respiratory sound waveforms in dogs using acoustic wave recordings: An objective metric of cough
2019, Veterinary Journal
Citation Excerpt :
In people, cough generates high velocity, non-laminar airflow producing a characteristic auditory signal (Korpas et al., 1996; Martinek et al., 2013). The resulting acoustic waveform can be detected and objectively evaluated (Korpas et al., 1996; Subburaj et al., 1996; Knocikova et al., 2008; Abaza et al., 2009; Martinek et al., 2013). Audio-based cough monitoring in human medicine is capable of providing reliable data on the number of coughs by examining acoustic waveforms with sensitivity and specificity of 85% and 91%, respectively (Korpas et al., 1996; Knocikova et al., 2008; Abaza et al., 2009; Martinek et al., 2013).
Cough is an important respiratory protective mechanism, which when persistent also contributes to disease pathology. It is therefore both a marker for and a target of therapeutic intervention. In dogs, assessment of cough is subjective, generally based on owner’s perceptions of clinical signs. In humans, acoustic cough monitoring provides objective data on cough frequency by examining acoustic waveforms. We hypothesized that healthy mesocephalic dogs would demonstrate characteristic cough waveforms which could be distinguished from other acoustic behaviors (AB); whine, bark, growl, lick, drink, chew and throat-clear. Data were obtained from 10 healthy employee-owned dogs. Acoustic behaviors were recorded using a CTA-laryngeal-microphone and analyzed using RavenPro bioacoustics software for nine objective acoustic parameters (AP). Similarity between AB were assessed using a one-way analysis of similarity (ANOSIM) with a P < 0.001 significance level. Inter- and intra-group statistical analysis was performed using a one-way ANOVA on ranks with P < 0.05 significance level.
With the exception of throat-clear, cough was dissimilar to every other evaluated AB (P < 0.0001), with significant differences in one or more of the analyzed waveform parameters (P < 0.001 for each). No between-subject differences were identified between cough and throat-clear groups for any parameter. All other behaviors showed statistically significant within-group variation (P < 0.001). Cough and throat-clear (a clinically similar mechanism to protect the airways) have repeatable acoustic features that are distinguishable from other common AB and are consistent between dogs. Acoustic monitoring may provide an objective means for evaluating cough frequency and intensity in dogs with respiratory disease and assessing response to therapeutic intervention.
Muscle activation and sound during voluntary single coughs and cough peals in healthy volunteers: Insights into cough intensity
2018, Respiratory Physiology and Neurobiology
Citation Excerpt :
A few authors have also investigated cough sound intensity which, as expected, is correlated with the flow responsible for generating the sound (Lee et al., 2015; Lee et al., 2017). Cough effort has also been shown to influence cough sounds (Pavesi et al., 2001; Subburaj et al., 1996) but again the impact of cough operating volume was not taken into account in these studies and low operating volume coughs, where flow is severely restricted, were not included. Studies exploring the relationships between cough sounds and measures of EMG are lacking.
Very few studies have addressed how coughing varies in intensity. We assessed the influence of cough effort and operating volume on the mechanics of coughing using respiratory muscle surface electromyography (EMG), oesophageal/gastric pressures and cough sounds recorded from 15 healthy subjects [8 female, median age 30 (IQR 30–50)years] performing 120 voluntary coughs from controlled operating volume/effort and three cough peals. For single coughs, low operating volumes and high efforts were associated with the highest EMG activity (p < 0.001); the resultant pressures increased with effort but volume had little influence. In contrast, cough sounds increased with both volume and effort. During cough peals, EMG fell initially, increasing towards the end of peals, pressures remained stable and sound parameters fell steadily to the end of the peal.
In conclusion, effort and operating volume have important influences on cough mechanics but modulate muscle activation, pressure and cough sound amplitude and energy differently. Consequently, these cough sound parameters poorly represent voluntary cough mechanics and have limited potential as a surrogate intensity measure.
Validation of a digital audio recording method for the objective assessment of cough in the horse
2010, Research in Veterinary Science
To validate the use of digital audio recording and analysis for quantification of coughing in horses.
Part A: Nine simultaneous digital audio and video recordings were collected individually from seven stabled horses over a 1 h period using a digital audio recorder attached to the halter. Audio files were analysed using audio analysis software. Video and audio recordings were analysed for cough count and timing by two blinded operators on two occasions using a randomised study design for determination of intra-operator and inter-operator agreement. Part B: Seventy-eight hours of audio recordings obtained from nine horses were analysed once by two blinded operators to assess inter-operator repeatability on a larger sample.
Part A: There was complete agreement between audio and video analyses and inter- and intra-operator analyses. Part B: There was >97% agreement between operators on number and timing of 727 coughs recorded over 78 h. The results of this study suggest that the cough monitor methodology used has excellent sensitivity and specificity for the objective assessment of cough in horses and intra- and inter-operator variability of recorded coughs is minimal.
Cough sound description in relation to respiratory diseases in dairy calves
2010, Preventive Veterinary Medicine
Cough can be a biomarker in case of respiratory diseases. By monitoring and analyzing cough sounds through automatic devices, the farmer can obtain an early warning about a developing outbreak of respiratory infections. Cough sounds can be characterized by particular acoustic features (amplitude, frequency and duration) that are obtained by sound recording, labeling and analytic procedures. Based on these features, it might be possible to develop an automated cough recognition system. The aim of the study described in this paper is to investigate whether it is possible to discriminate cough sounds from other frequently occurring sounds in youngstock stables. Nasal swabs and blood were taken to identify the microbiological agents responsible for the respiratory problems. The collected cough sounds were compared to metal rack sounds, which are very common sounds in cattle farming, to identify acoustic differences between them. Results show that the length of cough sounds was significantly different from metal rack sounds (0.34 versus 0.37 s, P < 0.05). Also, the analysis of amplitude and fundamental frequency showed significant differences between both types of sounds (resp. 0.21 and 0.18; 1326 and 3868 HZ). This indicates that it is possible discriminate cough sounds from other sounds and that cough sound can be used as a non-invasively diagnostic tool for respiratory diseases in youngstock groups.
Cough sound analysis to identify respiratory infection in pigs
2008, Computers and Electronics in Agriculture
Cough sound detection is a central element to diagnose common respiratory diseases like pneumonia in intensive pig farming. The aim of this work is the description of acoustic features of cough sounds originating from a lung infection and the comparison between these kind of cough sounds with those provoked by inhalation of citric acid.
Coughs have been recorded from infected animals in field conditions (pneumonia) and from healthy animals in laboratory (induced). After having completed the classification, the investigation on infectious and non-infectious cough sounds has involved the main differences among acoustic parameters, like the Root Mean Square (RMS), the peak frequency (Hz), the duration and the time occurring between successive coughs in a cough attack.
The results show a significant difference among the RMS, peak frequency and duration in cough sounds from healthy and infected animals. RMS was 0.215 for healthy animals and 0.124 for infected ones (P = 0). Non-infectious coughs have an average peak frequency of 1600 Hz, while infectious coughs stand around 600 Hz. Also the length of sounds is significantly lower (P < 0.001) for non-infectious coughs (average 0.43 s) than for infectious ones (average 0.67 s). The space of time between each sick cough in a cough sequence seems shorter than the interval occurring between healthy coughs (0.37 s versus 0.52 s).
The above mentioned findings could be surely helpful to develop a real-time cough classification algorithm, based on sound feature analysis, in order to acquire a monitoring system for automatic and continuous infection in pig houses.

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Regular ArticleMethods of Recording and Analysing Cough Sounds

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Regular Article
Methods of Recording and Analysing Cough Sounds