During the 2022-05-23 call between Hyfe and the FDA, Dr. Eger asked about the half-second time-frame for detecting coughs. Specifically, he inquired as to whether a half-second was sufficient time to determine whether a sound was cough or not (ie, if the lack of acoustic context would make it prohibitively hard to determine whether such a short sound was a cough).
We consider that a half second is long enough to unambiguously differentiate between a cough and non-cough sound.
We validated this position as follows: Hyfe labelers have reviewed approximately 100 hours of continuous audio, labeling cough events from beginning to end (include the explosive and voiced phases). The below shows the distribution of total cough lengths for 7,044 coughs.
The median total length of a cough is 0.418 seconds. Though some coughs extend for greater than 0.5 seconds (if you include all phases), the explosive phase of the cough is sufficient for differentiating between a cough and non-cough sound, even in the case of the tail end of the (post-explosive phase of the) cough being cut off.
What follows are some sound examples to show this.
Examples of sounds classified by Hyfe’s algorithms as “cough”.