Hugh Hetherington Hearing Aid Museum
Hugh Hetherington Hearing Aid Museum

The Hearing Aid Museum

Hearing Aids of all types—Ear Trumpets, Carbon Hearing Aids, Vacuum Tube Hearing Aids, Transistor Hearing Aids, Body Hearing Aids, Eyeglass Hearing Aids and much more!

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Click on the "General Information" button (top button above) for an overview and general information on this category of hearing aid.

 

Hearing Testing Equipment

Maico Slide-rule Hearing Loss Percentage Calculator

 The Maico Percentage of Hearing Loss Calculator is a plastic cardboard slide rule device made to calculate percent hearing loss.  (In truth, hearing loss is measured in decibels (dB) on an open-ended logarithmic scale and thus cannot be expressed as a percentage.)

 In order to determine the "percentage" of hearing loss using the calculator, four cardboard sliders were moved to set arrows under the measured dB loss at 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz. The total "percentage" hearing loss is then read off on the bottom scale of the slide rule.

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There is also a scale on the reverse side to determine what was called the Social Adequacy Index. This was done by setting the hearing loss for speech (in decibels) computed from word discrimination tests using phonograph and voice.

 The only date on the slide is for one of the references cited and is 1948.

 

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The Maico Percentage Hearing Loss Calculator in its protective envelope.

 

 

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The Maico Percentage Hearing Loss Calculator with its protective envelope.

 

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The Maico Percentage Hearing Loss Calculator protective envelope with instructions for use.

 

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An insert that shows how to hold the Maico Percentage Hearing Loss Calculator when in use.

 


 

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