Hz - and also no hearing aid is able to deal with sounds much below 400 Hz or so. The result is normal hearing ability across the frequency range. Note that this is an idealized situation. In the real world the curve of decreased sensitivity may not be so smooth and, particularly with 'analog' hearing aids, it may be difficult to to attain a perfect frequency-amplification curve. In the case of the ideal normal ear one would expect that the relationship between how loud a sound is and how loud it sounds is linear .
Low volume sounds sound very soft.
Very loud sounds are heard as being very loud. There is a lower threshold below which nothing is heard at all. At the threshold sounds are audible. As sounds become louder, they soon become annoying and then painful. Hard of hearing people have zero sensitivity to very soft sounds and are disproportionately sensitive to loud sounds.