See, the thing is: in the most recent issue of 'Batgirl' Barbara references 'tech' that she put in Cass' outfit (which apparently isn't waterproof as she implies that if Steph had washed the costume it wouldn't work... though Steph wearing Cass' sweating costume isn't the point here).
Since Cass was never really the technology and gadgetry kind of hero, prefering to use observations and restrained violence instead, might the technology have been there for Barbara's benefit instead.
Though that leads into when exactly did Barb install it, and if it was post-EvulCass did she really think that having something that makes an irritating noise in Cass' cowl would slow her down any?