A speech output device, a control method for a speech output device, a printer, and an interface board can improve the productivity of foreign language speaking workers in industries such as retailing and food services. A data communication unit 191 acquires print data. A data interpreter 193 analyzes and converts to text data at least part of the data acquired by the data communication unit 191. A language converter 194 converts the text data to one or more preset languages. A speech synthesizer 195 generates one or more units of synthesized speech data corresponding to the language-converted text data from the language converter 194. A speech data output unit 196 outputs the one or more units of synthesized speech data generated by the speech synthesizer 195 to a headphone 104.