Bengali (বাংলা) has its own script, and FLORES-200 gives Bengali and Assamese the same script code. The 2011 Census counted 9,72,37,669 people with Bengali as their mother tongue, 8.03% of India and the second largest group. West Bengal had 7,86,98,852, Assam 90,24,324, Jharkhand 32,13,423 and Tripura 24,14,774. The Census counts people in India only; Bengali is spoken beyond India as well, which these figures do not cover.
If your staff mix English into Bengali sentences, or type Bengali in Roman letters, test both. AI4Bharat’s IndicLID identifies Bengali in native and romanised text, but no source here reports how well speech models transcribe mixed Bengali and English.
English spoken by people whose mother tongue is Bengali is its own test. In the Svarah paper, Whisper large scored 7.6% on their English, against 5.3% for native Hindi speakers.