Question
I feel some of my patients with bone-anchored processors face different feedback challenges than my patients with traditional hearing aid technology. What is the current feedback technology for some of the newer processors?
Answer
The Oticon Medical Ponto Plus has a new strategy for feedback management. It used to be merely a checkmark on the digital phase canceler (DFC); it was either on or off. On meant that you had a phase inverter, and off meant you did not have one. The downside of a phase inverter is that you can get entrainment, which is where the microwave goes ‘ding,’ and the Ponto goes ‘ding, ding,’ and that is because the feedback canceler thought that the microwave was feedback. It sent an out-of-phase signal to cancel it. It really was not feedback, and now that tone is audible.
Oticon’s new feedback canceler employs frequency shift. The frequency shift happens right when the device thinks it is about to go into feedback, and it shifts the whole signal by about 9 Hz. This avoids a potential feedback loop. It shifts the frequency a little bit so that those tones do not lie on top of each other and multiply. Depending on the audiogram, you are going to see the DFC. It will not be off; it will either be set at medium or maximum. Medium is the phase inverter, or our previous default. Maximum is the phase inverter plus frequency shift. In the Genie Medical software, the medium or maximum setting depends on the bone conduction scores. You have no access to this in the Oticon software; everyone is on maximum. The reason we allow you to choose the setting is because people with perfect cochleae can perceive a frequency shift of about 7 Hz. If the patient’s bone thresholds are normal or near normal, the software will not apply the maximum setting, since the patient may be able to perceive changes at 9 Hz. If there is any type of mixed component or cochlear hearing loss, there is no risk that the listener will perceive this frequency shift, in which case, the setting will be placed at maximum.
Editor’s note: This Ask the Expert was adapted from the article Wireless Connectivity in our Daily Lives: Enhancing the Ponto Plus Experience. For more information about Oticon Medical and the Ponto System, visit www.oticonmedical.com or the Oticon Medical Expo Page on AudiologyOnline.
