NP | ZK translation: into the pitch of street noise

[Mike Jing]

P207.20-208.5   Here we are, all this and more, things that normally escape
the inquiring eye, a single searching look, so much to see, each of us
looking at both of us, and then we shake it all off and walk down four
flights into the pitch of street noise that tells us we’re back among the
others, in unsparing space.

In what sense is the word "pitch" used here?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://waste.org/pipermail/pynchon-l/attachments/20171110/485c7932/attachment.html>