Hard of Hearing and Hearing Impaired

[Grushkin, Donald A]

Hello everyone, 
 
I'm preparing a couple of articles for publication, and would like some help if possible.  I am attempting to determine the origin or first usage of the terms "hard of hearing" and "hearing impaired".  I have been unable to locate any sources that point to when these terms first were used, or who originated them.  
 
For hard of hearing, I am making the assertion that this term likely began around the beginning of the 20th century, when modern electronic audiology made it possible to more precisely determine individuals' hearing ability.  Prior to this period, I have found references to "mutes", "semi-mutes", "only deaf" and "semi-deaf", but no "hard of hearing".  I do suspect, however, that "hard of hearing" might have been in folk usage prior to the 1900s to describe older persons who were beginning to lose their hearing.  
 
For hearing impaired, I have the general feeling that this term began around the 1970s to 1980s as a "politically correct" alternative to "deaf" or "hard of hearing".  Who started the term or exactly when, I do not know, but thinking back, I cannot recall seeing the use of 'hearing impaired" before this, but then again, I might have been too young then to really know or notice.  
 
So, can anyone provide me with sources supporting or refuting my perceptions?    My apologies here to those of you who are seeing this cross-posted.  
 
--Don Grushkin

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