I think the statement you quoted is misleading. I'm pretty sure the Academy Curve is not designed to remove the crackling of playback or at least this is not the main purpose. This is an interesting queston though, and although I can't remember much from my lectures past The Jazz Singer, I thought I'd do some research and add a fuller answer anyway.
Academy Mono Optical Soudtrack
At the time when optical sound-on-film was developing, devices like the Movietone sound system were able to use the electrical signal from a microphone to modulate the width or height of a narrow band of light. This modulated light would be directly captured on the edge of a filmstrip, creating a soundtrack that is in-sync with the film. Due to the fact that this recording process used 'primitive' components and devices, quite a lot of noise was also present in the recording.
This optical recording process allowed advances in multitrack recording, and as a result, the noise present in each audio track would accumulate to a point where it would be significant in the final mix.
At the same time, sound systems in movie theatres were suffering from a problem with high frequency response. These problems along with others lead to the need for a process to attenuate the high and low frequency noise apparent during theatrical playback.
So a process of pre-emphasis and de-emphasis was developed. During the recording of each audio track, pre-emphasis was added to increase the level, particularly at higher frequencies. During playback, de-emphasis would be applied, restoring the original EQ to the sound track, and also removing the high and low frequencies that the theatre system had trouble reproducing. The EQ curve used in this de-emphasis process was known as the Academy Curve. This process of pre-emphasis and de-emphases was successful in bringing down the level of noise in the theatre, and removing any troublesome frequencies.
Sound Recording: The Electrica Era
Cinema Sound and EQ Curves
The Dolby Film Sound Revolution (Ioan Allen)
Academy Curve Info
Sound-On-Film: Analog sound-on-film recording
Pre-emphasis and De-emphasis(Dolby NR Example)