We explore how discreet input can be provided using the tensor tympani -a small muscle in the middle ear that some people can voluntarily contract to induce a dull rumbling sound.We investigate the prevalence and ability to control the muscle through an online questionnaire (N=192) in which 43.2% of respondents reported the ability to ear rumble. Data collected from participants (N=16) shows how in-ear barometry can be used to detect voluntary tensor tympani contraction in the sealed ear canal. This data was used to train a classifer based on three simple ear rumble gestures which achieved 95% accuracy. Finally, we evaluate the use of ear rumbling for interaction, grounded in three manual, dual-task application scenarios (N=8). This highlights the applicability of EarRumble as a low-efort and discreet eyes-and hands-free interaction technique that users found magical and almost telepathic.