A low range female voice falsetto would still be in audible range.
In Pipe Organ circles, they stop making pipes above a certain pitch, because those pitches when heard produce overtones that get mostly into the inaudible range. The whole theory of building (and playing) Pipe Organs rests on the addition of overtones into the sound mix to generate different tone colours. The highest pitches are heard as just increasingy just pure tones with no usuable overtones.
Similarly, with human voices, the upper pitches are mainly heard as fundamental pitches with no tone colour.
Also this theory applies to Drawbar Organs, and also to Electronic Generated Music (in earlier days was usually called "Music Concrete").