The app, developed by Justin Chan at the University of Seattle and colleagues, plays a continuous 150-millisecond sound through the paper funnel, which is placed near the ear canal.
Both acute and chronic middle ear infections cause fluid to build up behind the eardrum, and sounds that would normally have vibrated the eardrum are reflected back along the ear canal.
Tested on 53 children between the ages of 18 months and 17 years, the app determined the likelihood of fluid present with an accuracy of 85 per cent.
This accuracy is comparable to medical tools such as a tympanogram, which is only available in specialist clinics. The tympanogram is inserted into the ear canal to make an airtight seal. It sends a low-frequency tone and a puff of air, determining whether there is fluid behind the eardrum based on how it moves.
The app provides an easy way for parents to determine whether their child might have a middle ear infection, says Chan.
Ear infections are common in childhood and can be hard to diagnose in young children – they may tug on their ears or have only vague symptoms such as fevers.
“One of the challenges is just knowing when you need to go in to see the doctor,” says team member Randall Bly.
The team found no difference in accuracy between trained doctors and parents who were asked to use the app.
The app includes a stencil of a funnel that can be traced onto paper from the smartphone’s screen.