Backends vary; a system can use loudspeakers in single, stereo, transaural (stereo with crosstalk cancelation), and array [Amano et al. 96] configurations. Headphones or nearphones are also widely used. Across these devices the amount of immersion or believable illusion differs drastically. Despite the fact that most people don't have an absolute tone hearing, the frequency spectra of the output device needs to be adjusted and considered. If a headphone cannot produce a rumbling sensation in the stomach, then the author who creates multimedia content for a broad range of platforms needs to consider that, and might program a different or additional acoustical event.