What is a common cause of harmonic distortion in hearing aids?

Harmonic distortion in hearing aids often arises from mechanical stress. When components within the hearing aid, such as microphones or receivers, experience mechanical strain, they can fail to produce accurate audio signals, leading to distortion. This distortion manifests as additional unwanted frequencies that are multiples of the original signal, negatively impacting sound quality for the user. Mechanical stress can be caused by factors such as temperature changes, physical impact, or wear and tear over time, which can alter the response of the components and therefore create distortion. In contrast, the other options may not directly relate to harmonic distortion in the same way.