People with reduced hearing find it particularly difficult to pick up and process voice or music signals when low acoustical noise frequencies are present, such as drumming or humming noises or passing cars. Low-frequency interference raises the perception threshold in the medium frequencies. Speech in particular, which is in that range, is heard less clearly or not at all.
This effect is very real: it is the basis of the well-known mp3 compression of music files. People with impaired hearing should therefore take particular care to have acoustically flawless surroundings.
