Minimal audible field involves the subject sitting in a sound field and stimulus being presented via a loudspeaker.[2][14] The sound level is then measured at the position of the subjects head with the subject not in the sound field.[2] Minimal audible pressure involves presenting stimuli via headphones[2] or earphones[3][14] and measuring sound pressure in the subject's ear canal using a very small probe microphone.[2] The two different methods produce different thresholds[1][2] and minimal audible field thresholds are often 6 to 10 dB better than minimal audible pressure thresholds.[2] It is thought that this difference is due to: