Unfortunately, not everyone is lucky enough to have healthy ears and normal hearing. Some people's hearing is damaged due to certain trauma, some children are born deaf, and most people are hearing impaired due to the natural aging process of the ear or exposure to the noise. Science has managed to help people hear, after all. Imperfect, admittedly, but still enough to return the lost quality of life. Today it is possible to help hearing impaired people by using different hearing aids depending on the type of hearing loss. Hearing aids today, thanks to the technology of digital hearing aids, can help people to hear and understand better in almost all hearing situations, regardless of the direction of the sound source or the presence of noise. The rapid development of digital hearing aid technology allows precise tuning and adaptation to different hearing situations. Digital hearing aids determine their calculation of the required gain across the entire frequency range by choosing a fitting formula that calculates the amount of amplification required primarily on the hearing threshold of hearing aid users. Hearing aid fine-tuning allows you to change the gain in certain frequency areas - the hearing aid channels. It is possible to change the gain, separately for soft, medium and loudest sounds, as well as setting the maximum allowable gain so that the hearing aid does not become too loud and exceed the discomfort threshold or uncomfortable loudness level (UCL), but also so that the positive feedback does not cause the hearing aid to whistle unpleasantly. It is possible to adjust each hearing program separately, that is, the mode of operation in each hearing situation that the hearing aid can recognize automatically or the user can select it himself. Also, in this step, all algorithms are adjusted, i.e. possibilities of hearing aids such as microphone directionality, noise suppression, algorithms for enabling listening to higher frequency sounds using frequency lowering methods etc.