A sound is a vibration at a set frequency. For instance, a dog whistle is a sound that vibrates at such a high frequency that only animals can hear it. A subwoofer is a bass speaker that actually can produce sounds that the human ear cannot hear, but the human body can “feel” the vibrations in the air. Depending on the recording device, the ability to record and play back sound at these extreme frequencies varies depending on the type of recording media.

Audio recording occurs in two formats, analog and digital. While music purists may maintain that analog recordings have the most natural sound, digital recordings support a wider range of frequencies during the recording and playback process. This means that a digital recording can record more sound in the form of overall frequency range. A sound that is not recordable in analog format due to a very high or very low frequency could appear in a digital format.