Transmissions and transitions: a study of two common assumptions in multi-band ASR

Is multi-band automatic speech recognition (ASR) inherently inferior to a full-band approach because phonetic information is lost due to the division of the frequency space into sub-bands? Do the phonetic transitions in sub-bands occur at different times? The first statement is a common objection of the critics of multi-band ASR, and the second, a common assumption by multi-band researchers. This paper is dedicated to finding answers to both these questions. To study the first point, we calculate phonetic feature transmission for sub-bands. Not only do we fail to substantiate the above objection, but we observe the contrary. We confirm the second hypothesis by analyzing the phonetic transition lags in each sub-band. These results reinforce our view that multi-band speech analysis provides useful information for ASR, particularly when band merging takes place at the end state for a phonetic or syllabic model, allowing sub-bands to be independently time-aligned within the model