This invention relates to bit interleaver and de-interleaver apparatus, methods and processor control code for use in MIMO communications systems, in particular MIMO systems employing OFDM. One example method includes determining, by a computing device, that a notification is scheduled for output by the computing device during a first time period and that a pattern of audio detected during the first time period is indicative of human speech. The example apparatus also includes a sub-schedule generator configured to generate a first sub-schedule associated with a first time period. The ink supply conduits extend generally transversely from an upstream outer region towards a downstream inner region of the mounting surface.