The most important factor that affects hearing is the presence of noise. Noise is essentially the ambient sound environment that interferes with the perception of the sound of interest. Noise introduces hearing demands in that the user has to discriminate the sound of interest from a mixture of other sounds.

Spaces that introduce large amounts of reflection and reverberation of sound can cause problems with hearing. The sound becomes distorted and more difficult to discriminate from the background noise. This occurs in public spaces where announcements are important, such as train and underground stations, sports arenas and music halls. Increased reverberation affects people of all abilities, but affects those with reduced ability to a greater extent.

Hearing aids are least effective in noisy environments, as they amplify the background noise indiscriminately. Induction or T-coil loops transmit sound directly to a hearing aid, which can be set to only receive this signal, thereby eliminating the background noise entirely.