Andy Birtwistle’s introduction to this special issue addresses the question "what is sonic materiality?" by examining how both "new" and "old" materialisms offer productive frameworks for conceptualizing sound's material dimensions. Drawing on work by Cox, Voegelin, and Cobussen, alongside critiques from Goh, Thompson, and Campbell, the article proposes understanding sound's materiality through texture, temporal flow, and spatiality. By engaging with Structural/Materialist film theory and creative sonic practices, Birtwistle discusses how materiality intersects with aesthetics, agency, and ethics in sound. The introduction argues that exploring sonic materiality opens new avenues for understanding sound across environmental soundscapes, artistic practices, and cultural contexts.