Today’s work teams often consist of people speaking different languages. This can pose challenges as individuals may find themselves engaged in tasks in one language while being exposed to irrelevant speech in another. Previous research on bilingual language production has revealed that simultaneous processing of two languages – one relevant to the task and the other not – leads to cross-language interference. This project investigates the effects of exposure to irrelevant speech in one language on serial recall task performance in another language, and on the subsequent access and use of the language, which was present in the auditory background. To this end, the study initially assesses the language proficiency of German-English bilingual participants in their second language (L2; English). Participants are then asked to perform a visually presented serial recall task in their first language (L1; German) while being exposed to irrelevant speech in either L1 or L2. Following this, participants' proficiency in L2 is measured once again. The project aims to examine two key factors: (a) participants’ performance in serial recall when exposed to irrelevant speech in L1 versus L2, and (b) shifts in L2 proficiency before and after exposure to irrelevant speech in L2. The resulting data will enable testing for differences between L1 und L2 background speech, thus potentially refining the theoretical foundations of the irrelevant speech effect. Additionally, it will shed light on the processes through which bilingual speakers dynamically adapt their language balance within a given context.