During last week’s group meeting, Pradheep Shanmugalingam, one of the lab’s PhD students, mentioned that he was working on an experiment which involved the use of sine wave speech. This is speech which has been treated so that its essential features, the formants which allow us to distinguish sounds, are replicated using synthetic sine waves. The result is a musical R2-D2 warbling which on first hearing is hardly recognisable as speech.
The paradigm that Pradheep is using relies on this fact; that unless people are told they are listening to speech, they don’t hear any speech content in the sounds. Once they are told, however, a process of ‘tuning in’ takes place: a recognition of the speech as speech, which also transfers to novel sine wave sentences they have never heard.
You can try out a related process for yourself at this web page by Matt Davis at the Cambridge Cognition and Brain Sciences Unit. Listen to the sine wave speech first, then the unencoded message, and then return to the sine waves. When you hear them a second time, the speech ‘pops out’.
This reminded me, in a roundabout way, of Alvin Lucier’s I am Sitting in a Room. In this minimalist composition from 1969, Lucier set up a feedback loop, reciting a text – which is also a description of what he is about to do – in a room, recording the result, and then replaying the tape in the same room whilst recording this second performance. As the iterations continue, in Lucier’s words, “the resonant frequencies of the room reinforce themselves so that any semblance of my speech, with perhaps the exception of rhythm, is destroyed.”
What emerges instead, as Lucier puts it, are “the natural resonant frequencies of the room articulated by speech.” And yet, knowing this is speech, and with Lucier’s pacing and characteristic stammer resonating in our ears, the sense of it persists through its degradation, even as the sounds turn into deep bottle tones and high glass rubbings. Eventually though, sense vanishes, and you’re left just with a whistle and throb that sounds like water in the pipes, as Lucier’s formants disappear into the room’s. There’s an original recording of the piece here on Ubuweb.