Understanding speech in noise is a fundamental challenge for speech comprehension. This perceptual demand is amplified in a second language: It is a common experience in bars, train stations, and other noisy environments that degraded signal quality severely compromises second language comprehension. Through a novel design, paired with a carefully selected participant profile, we independently assessed signal-driven and knowledge-driven contributions to the brain bases of first versus second language processing. We were able to dissociate the neural processes driven by the speech signal from the processes that come from speakers' knowledge of their first versus second languages. The neurophysiological data show that, in combination with impaired access to top–down linguistic information in the second language, the locus of bilinguals' difficulty in understanding second language speech in noisy conditions arises from a failure to successfully perform a basic, low-level process: cortical entrainment to speech signals above the syllabic level.

在噪音中理解语音是语音理解的一项基本挑战。这种感知需求在第二语言中被放大：在酒吧、火车站和其他嘈杂环境中，信号质量下降严重影响第二语言理解是一种常见的体验。通过新颖的设计，搭配精心挑选的参与者资料，我们独立评估了信号驱动和知识驱动对第一语言和第二语言处理的大脑基础的贡献。我们能够将语音信号驱动的神经过程与来自说话者的第一语言和第二语言知识的过程分离。神经生理学数据表明，与第二语言自上而下的语言信息的获取能力受损相结合，双语者的