A method for generating computer generated speech from a natural language textual data stream, the method implemented by one or more processors and comprising: receiving a natural language textual data stream to be converted into computer generated speech for rendering to a user via one or more speakers of a computing device, wherein the natural language textual data stream includes a primary portion that is in a primary language assigned to the user, and a secondary language portion that is not in the primary language assigned to the user; determining whether the secondary language portion of the natural language textual data stream is in a secondary language that is not assigned as a familiar language for the user; processing the primary portion of the natural language textual data stream to determine a first set of phonemes that are assigned to the primary language and that correspond to the primary portion; processing the secondary language portion of the natural language textual data stream to determine a second set of phonemes in a universal phoneme set that corresponds to the secondary language portion, wherein the universal phoneme set includes at least phonemes common to a plurality of languages; in response to determining that the secondary language portion is in the secondary language that is not assigned as a familiar language for the user: mapping the one or more second phonemes, that correspond to the secondary language portion and that are not for the primary language, to one or more correlated phonemes in the primary language, wherein mapping the one or more second phonemes to the one or more correlated phonemes is based on defined mappings between phonemes in the universal phoneme set to primary language phonemes; generating a modified second set of phonemes by replacing the one or more second phonemes, in the second set of phonemes, with the correlated phonemes in the primary language; processing the first set of phonemes and the modified second set of phonemes to generate audio data that mimics a human speaker speaking the first set of phonemes and the modified second set of phonemes; and causing the audio data to be rendered via the one or more speakers of the computing device. receiving a natural language textual data stream to be converted into computer generated speech for rendering to a user via one or more speakers of a computing device, wherein the natural language textual data stream includes a primary portion that is in a primary language assigned to the user, and a secondary language portion that is not in the primary language assigned to the user; determining whether the secondary language portion of the natural language textual data stream is in a secondary language that is not assigned as a familiar language for the user; processing the primary portion of the natural language textual data stream to determine a first set of phonemes that are assigned to the primary language and that correspond to the primary portion; processing the secondary language portion of the natural language textual data stream to determine a second set of phonemes in a universal phoneme set that corresponds to the secondary language portion, wherein the universal phoneme set includes at least phonemes common to a plurality of languages; in response to determining that the secondary language portion is in the secondary language that is not assigned as a familiar language for the user: mapping the one or more second phonemes, that correspond to the secondary language portion and that are not for the primary language, to one or more correlated phonemes in the primary language, wherein mapping the one or more second phonemes to the one or more correlated phonemes is based on defined mappings between phonemes in the universal phoneme set to primary language phonemes; generating a modified second set of phonemes by replacing the one or more second phonemes, in the second set of phonemes, with the correlated phonemes in the primary language; processing the first set of phonemes and the modified second set of phonemes to generate audio data that mimics a human speaker speaking the first set of phonemes and the modified second set of phonemes; and causing the audio data to be rendered via the one or more speakers of the computing device. mapping the one or more second phonemes, that correspond to the secondary language portion and that are not for the primary language, to one or more correlated phonemes in the primary language, wherein mapping the one or more second phonemes to the one or more correlated phonemes is based on defined mappings between phonemes in the universal phoneme set to primary language phonemes; generating a modified second set of phonemes by replacing the one or more second phonemes, in the second set of phonemes, with the correlated phonemes in the primary language; processing the first set of phonemes and the modified second set of phonemes to generate audio data that mimics a human speaker speaking the first set of phonemes and the modified second set of phonemes; and causing the audio data to be rendered via the one or more speakers of the computing device.