The MobileCinema i55 has a built-in speaker(s). Most of the other battery powered projectors that were released around the same time as this data projector also have a built-in speaker(s).
We think you might also be interested in some of the alternative projectors with a built-in speaker(s) currently available including the Aiptek MobileCinema A50P (£175.37), or the Philips PPX2330 (£189) which both of have better reviews.
We compared all the other multimedia projectors which also have a built-in speaker(s) to this projector and we think the Philips PPX3407 (£169) is also worth considering.
What is a built-in speaker(s)?