Every electronic device has system noise, whether it is a million dollar device or a ten dollar device. All recording devices introduce system noise into the audio being recorded. System noise can be a combination of clicks, pops, squeaks, creaks, crackle, sizzle, hum and white noise, each of which has varying rhythms and frequencies. All recording tape has inherent noise in the form of hiss, and perhaps clicks and pops. How extreme this is will depend on the quality of the tape.
All playback devices introduce extraneous noise into the sound produced during playback.
This noise is in the form of electronic system noise and mechanical noise and is in addition to the system noise introduced into the audio during recording. Recording environments are never silent, even when no one is present. There is always some sort of environmental sound, whether a refrigerator, wind, wall creaks, air conditioner or heating unit. Temporal masking by environmental sounds may also cause auditory illusions. Temporal masking occurs when one sound comes so close to another that the two seem as one, or the first masks the beginning articulation cue of the second making it sound like something other than what it is.