In what way does the theme of surveillance appear within Chapter 18, in relation to the bond between R and the narrator?

While the theme of surveillance is most often portrayed as a negative one within the novel, in Chapter 18, a different perspective is demonstrated when the narrator secretly listens to R's movements as he bathes by holding her end of their communication device up to her ear. The scene has sensual qualities, rather than sinister ones, but the scene itself is still inextricably linked with many of the novel's motifs, including surveillance, sound, and secrecy.