I'll never understand why doctors switch people to bi-weekly injections. Most studies agree that the half-life of testosterone cypionate and ethanate are at best, 8 days. Some studies suggest it can be more like 5 days. I personally felt like ->-bleeped-<- by day 10 when I was on bi weekly shots(I switched to weekly after the first few months).
Anyways, yes, my voice does get higher sometimes, particularly right before it drops again, but also randomly. I've been on T for almost a year, and there's been periods where I thought it wasn't dropping more or I'd be speaking higher again and had problems with resonance. Things get reedy and nasal sometimes. Overall though, it's still dropping, although recordings are the only way to tell with all the ups and downs. Until your vocal cords adjust and stabilize, you can expect some variation in pitch one way or the other, it's normal.
I doubt it has much to do with the shot cycles, although there's some evidence that changes may happen faster with weekly shots, since T levels are more frequently in the male range.
