Ambient noise sampled by a mobile device from a local environment is used to automatically trigger actions associated with content currently playing on the mobile device. In some implementations, subtitles or closed captions associated with the currently playing content are automatically invoked and displayed on a user interface based on a level of ambient noise. In some implementations, audio associated with the currently playing content is adjusted or muted. Actions can be automatically triggered based on a comparison of the sampled ambient noise, or an audio fingerprint of the sampled ambient noise, with reference data, such as a reference volume level or a reference audio fingerprint. In some implementations, a reference volume level can be learned on the mobile device based on ambient noise samples.