It is well known that the speaker discriminative information is not equally distributed over the spectral domain. However, it is still not clear whether that distribution is altered when the speech is transmitted through telecommunication channels, which introduce different kinds of degradations. In this paper we address the analysis of different frequency sub-bands when the speech is distorted with different bandwidth filters and channel codecs, considering narrowband and wideband communications. Our i-vector experiments on different sub-bands with 782 speakers show that standard landline codecs perform generally better than wireless codecs due to their intrinsic coding algorithm, their performance being close to, but slightly worse than that of uncoded speech. Wideband signals offer significant benefits over narrowband for speaker verification. A smaller experiment with 21 speakers leads us to believe that the emerging super-wideband transmissions may provide even better results because it shows important speaker-specific content in the band 8-14kHz.