Normally, feedback can be connected to either an incorrect comfort tip size or a frequency setting that needs to be configured appropriately.
In hearing aids, when sound leaks from the receiver back to the microphone, the microphone will continuously re-amplify the sound. You can usually prevent this by making sure you use the proper size comfort tips that will snugly fit into your ear canal. So, either go up a size or down a size.
If you've already tried the different size comfort tips (unfortunately, for the HDs, we only have 4 sizes available), that Feedback may be connected to the bird chirp sound during the tuning process. What we usually advise our users is, if you're having a hard time hearing the bird chirp, do not increase the volume; Instead turn it down to the lowest setting, which is 1. This should prevent any unnecessary feedback being caused by that particular frequency.
If it's still the same, please give us a call so that you can talk to our professional support (in-house licensed audiologist) so that they can provide you with ample advice on what parts of the tuning process you can change to prevent it. Our Professional Support should be in at around 9am PST.
(844) 443-2744 / Press the appropriate number for Professional Support