Jacques Derrida’s argument against what can be heard is only sound
Simon Glendinning attributes an argument to Jacques Derrida, from Derrida’s essay ‘Différance’, according to which it is mistaken to think that what can be heard is only sound.
The argument is as follows: articulate meaningful speech can by definition be heard; in order for this to be possible, one needs to be able to hear the difference between different units of speech (the units are phonemes); the difference between two phonemes is not itself a sound or an audible something; therefore it must be possible to hear more than just sound.
The argument relies on Saussure’s idea that the identity of a phoneme is determined by its place within a system of differences, rather than purely by material qualities. Consider when a person with a high-pitched and unusual accent says ‘Ha,’ and says ‘He’, and when a person with a not so high-pitched or unusual accent does so. To hear the difference, one must adjust to the entire system of pronunciation for the relevant person. (My grasp of this idea is too limited to explain it further!)
Glendinning, S. 2000. Preface: Arguing with Derrida. Ratio 13: 299-306.