Among the most frequent complaints voiced by hearing aid users are that noise is amplified too much and that certain sounds become too loud for the user to bear. Some modern hearing aids contain sensors that allow the hearing aid to detect sounds exceeding a certain loudness level, and then self-adjust to reduce the amplification (gain) for those sounds. Unfortunately, because noise is comprised of many of the same frequencies as speech, it is virtually impossible to "shut out" noise without also adversely affecting the quality of the speech signal.
The good news is that audiologists have learned to utilize modern technology to measure and control the maximum sound intensity reaching your ear. If sounds (speech or noise) exceed either the saturation level (maximum level the hearing aid can amplify without distortion) or your personal loudness discomfort level, distortion or discomfort will be the result. Modern hearing aids utilize technology that allows for adequate gain for soft sounds while minimally (or not at all) amplifying loud input signals. Concerning background noise, new techniques using multiple microphones within the same hearing aid aids are improving the listener's ability to function in noisy environments. With regard to clarity, even the most sophisticated hearing aids' ability to clarify speech is limited by the degree of inner ear and/or central auditory nervous system distortion.
Fortunately, as technology advances so does the ability of hearing aids to filter sounds and increase the quality of sound. Something to keep in mind is that hearing aids can only work to a point. If the physical anatomy of the ear is damaged or deteriorated, a hearing aid can only go so far. With the advent of cochlear devices and hearing implants, even those obstacles are being slowly overcome. When making the choice as to which hearing aid works best for you, make sure to take all of these factors into account to purchase the best hearing aid for you!