This program is designed for testing the frequency response of a speaker
or any other audio equipment such as filters, amplifiers, etc.

It works by sending out (playing) sinus waves at one frequency at a time
and then meassure the input magnitude from for example a microphone for
each frequency. When it has tested a specified range it will stop and
draw a graph or diagram with deciBell versus frequency to let you see
and analyse the frequency response curve.

http://onyxsoft.se/speakerrangetester.html