An effect caused when phase-shift in an audio device is not a linear function of frequency. In other words, different frequencies experience different time delays. This changes the waveform of the signal and is especially injurious to transients. Most transducers produce significant phase distortion. As low frequencies travel slightly faster than high frequencies and as air absorbs high frequencies more readily than low ones, the more delay there is between low frequencies and the higher harmonics of a sound, the sound becomes progressively more smeared and is perceived as more distant.