Saving our Bacon

Pigs can't fly, and right now they are responsible for quite a lot of humans failing to fly too! Why? To try and stop the spread of pig flu. Recent audio research to help keep pigs healthy may soon catch sick people who do try to fly despite having flu. They could well be hauled out of departure lounges by the flu police working on tip-offs from computers.

What does flu have to do with sound research, though? Well, people (and pigs) with flu cough, so spot the coughers and you can spot the flu. Trouble is healthy people also clear their throats in a cough-like way and cough after choking on a sandwich that goes down the wrong way. If you can find a way to tell the different kinds of cough apart though, maybe a computer system could be designed to automatically recognise flu carriers.

Back in 1998 a team from Nippon Medical School in Tokyo showed that different kinds of cough sounds might be automatically recognised. They recorded a series of ill people coughing and compared them with a series of healthy participants who coughed voluntarily. They found that by using sound analysis techniques they could tell the difference between different coughs. The telltale signature was in the high frequency sounds in the middle part of the cough.

Sounding Perky

Move on 10 years to 2008 and a joint team from the Faculty of Veterinary Medicine in Milan and the Department of Biosystems from Katholieke Universiteit Leuven in Belgium showed that a similar thing could be done with the coughs of pigs. It is vital that ill pigs are identified quickly before the illness spreads through the herd. Coughs are one of the main way farmers can do this. So could a computer system be programmed to tell the difference between a cough caused by a lung infection and one from a healthy animal? The team recorded pigs with pneumonia out in the field as well as healthy ones made to cough in a lab.

Rather than looking at just one feature of the sound, they looked at lots of different properties and found a series of clear differences between sick and healthy coughs. Healthy coughs last a few tenths of a second longer than infectious ones on average, for example. Similarly, healthy coughs come further apart than sick ones. The frequency of the sound differs too: infectious coughs peak at a much lower frequency to healthy ones. Put all the different properties where there is a clear difference together and you have the signature of a bad pig cough: an ill pig.

Once the scientists have done their classification experiments, it's time for the audio engineers to step in. Their job is to turn this into a practical system, work that is still in progress. The aim is to create a classification program that constantly monitors the sounds from a pig house and can automatically hear when a pig is unhealthy, allowing it to be quickly treated.

Not to be sneezed at

Farmers may worry about their pigs, but the rest of us are probably more worried about the human form of pig flu. Right now it is invisibly spreading across the world as people move around. One holiday flight and a flu bug can now travel from one side of the world to the other inside a day.

Some airports are trialing ways to stop ill travellers boarding flights. One method that has been partially successful is to use infra-red scanners to spot when a passenger leaving a plane has a fever. Engineers at BioRICS, a spin-off company from Katholieke Universiteit Leuven where the pig research was done, think the pig approach could work in airports too. It wouldn't be looking for coughing pigs of course (a coughing pig wandering through departures wouldn't be hard to spot, after all) but coughing humans. If they can make it work their system will use microphones scattered around airport lounges that sound an alarm if they detect someone coughing in the wrong way.

So the coughing pigs may well save our bacon yet, and as long as the audio engineers get it right you won't be hauled off by the flu police just for clearing your throat.