The DPOAE screening calculator gives the frequencies of the stimulus and of the distortion product, the signal-to-noise ratio at four frequencies and the number of passed frequencies for a pass or refer result.
How the calculation works
- Enter the stimulus ratio f2 / f1.
- Enter the emission level and the noise floor at 2, 3, 4 and 5 kHz.
- Read the signal-to-noise ratios and the result.
Example
For f2 = 2000 Hz and a ratio of 1.22, the tone f1 is 2000 / 1.22 = 1,639 Hz and the distortion product 2f1 − f2 is 1,279 Hz. The levels give signal-to-noise ratios of 16, 16, 10 and 3 dB. Three frequencies reach 6 dB, so the screening result is a pass: 3 of 4.
Why it matters
The calculator helps students and technicians in audiology and neonatal screening, school nurses and parents who want to understand a report that says pass or refer after a hearing screening.
Good to know
A refer result does not mean that the person has a hearing loss. In newborns, fluid or vernix in the ear canal and the middle ear in the first days of life can block the emission, noise in the room or movement of the baby raises the noise floor, and a probe that is not well sealed reduces the stimulus. For this reason, babies who do not pass are retested before a full diagnostic assessment, usually with auditory brainstem response testing. The emission is a test of the outer hair cells and not of hearing as such, so a baby with a problem of the auditory nerve can have normal emissions, which is why programs often combine the emissions with another test for babies who were in intensive care. The signal-to-noise criterion and the number of frequencies vary between programs, and some use also a minimum emission level. Early detection and intervention before the age of six months give children a much better outcome for speech and language.
Related tools
The tympanometry calculator checks the middle ear before the test, the air-bone gap calculator separates types of hearing loss, the critical band calculator treats frequency analysis and the Greenwood calculator maps frequency to place in the cochlea.