Purpose:Demonstrate the frequency just noticeable difference and, in general, to demonstrate a large number of hearing tests as performed by clinical audiologists.
Description:This device can be used for over 66 different audio demonstrations and tests as described in an accompanying manual.
The setup shown above is used to illustrate the just noticeable difference (JND) in frequency. Two built-in oscillators are set to very closely-spaced frequencies, and the device then produces a series of alternating tones of the two frequencies, each lasing about one-half second. As the two frequencies are separated the listener is asked to say when he or she actually can hear the difference - the frequency JND. The JND is typically about one-half percent in frequency, but becomes larger at low frequencies.
See manual for a large number of other experiments. Note that due to aging of the equipment and the loss of the frequency counter, some experiments may not be functional.