Project Summary This Administrative Supplement will support post-baccalaureate researcher Juan Londoño to receive research training through mentored leadership of a project characterizing the bilingual language input and production of children with hearing loss. The Supplement builds on parent R01 (DC018542) that gathers objective, longitudinal data to capture the vocal interactions of children with hearing loss (HL). Even with cochlear implantation, HL is a life-altering condition with high social costs. Inclusion of children with HL and typically hearing (TH) peers in preschool classrooms is a national standard, but it is not clear how early vocal interaction with peers and teachers contributes to the language development of children with HL and their TH peers. The parent R01 employs computational models of child location and orientation to indicate when children are in social contact with their peers and teachers. To supplement primary project analyses, the parent R01 characterizes classroom speech as English and Spanish by harnessing noise-robust automatic speech recognition tools but the reliability of these tools remains to be assessed. The goal of the Supplement is a) to conduct expert (manual) language annotation of R01 audio recordings to determine the language of children and teachers’ vocalizations (i.e., English and Spanish) speech and b) assess the reliability of automated language annotation tools when compared to expert annotation. Juan Londoño, the Supplement trainee will be the primary expert language identification annotator (English-Spanish). Language identification annotation will be performed on LENA-identified segments of Child Vocalization and Adult (Teacher) Vocalization to obtain separate estimates of the English and Spanish children hear from and produce with peers and teachers. Mr. Londoño’s training will be mentored in the selection of automated tools, the calculation of reliability measures, the interpretation and write-up of study statistical results, and the intersection of children’s bilingualism and hearing loss. As the Supplement research focuses on characterizing the bilingual experiences in preschool classrooms in which children speak English and or Spanish, Mr. Londoño’s bilingual language skills are critical for the successful completion of the project. The training afforded to him by the Supplement will help him accomplish his long-term objective of conducting independent research focused on improving language development outcomes in children with hearing loss and other at-risk populations. In support of this long-term objective, Mr. Londoño will pursue three Supplement goals: Expand his knowledge base in bilingual development and hearing loss (Goal 1); enhance his audio processing and quantitative analysis skills (Goal 2); and develop his leadership abilities in conducting research with diverse populations (Goal 3).