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Of course the rise/fall time and the intensity make differences, too.
Study Authors Year Published Min. Detectable FluctuationReisz 1928 ~1 dBDimmick & Olson 1941 JND = 1.5 dB to 3 dBAtal, et. al. 1962 ~ 1 dBJestaedt, et. al. 1977 JND @ 80 dB = 0.5 dB JND @ 5 dB = 1.5 dBToole and Olive 1988 .25 dB for a 5kHz resonance, Q = 1
I already provided you with a link providing evidence that differences as small as 3 millibels can be audible.
Good stuff. I remember hearing a lecturer in psychoacoustics describe how the precedence effect could be used to fool a listener into perceiving sound at the wrong loudspeaker of a pair. I don't recall the details, but it involved gradually shifting the signal from one side to the other without the listener noticing. So, I guess the JND could be unlimited if we are allowed to play some psychoacoustic tricks.
I don't want to take the Capacitors burn-in thread off topic, so I figured it's best to start a new thread. This is a great topic for The Lab because it addresses what types of changes can be heard, and what types are too small to worry about. Separating fact from fancy makes us more knowledgeable, and in turn smarter consumers.The conventional wisdom is that 1 dB is about the smallest change in level or frequency response that people can reliably identify. This is also known in science as the Just Noticeable Difference, or JND. However, the JND for level and response changes depends on the frequencies present, as well as their absolute volume level. At loud volumes the JND is smaller than at very soft levels. Likewise, JND is smaller at frequencies where our hearing is most sensitive. In other words, we can identify smaller level changes when the music is loud enough to hear clearly. So under ideal conditions - when listening at a decent level in a room with no damaging reflections, or when using earphones - it's possible to identify level and response differences smaller than 1 dB.The book, Introduction to the psychology of hearing by Brian C. J. Moore states that the smallest detectable volume change for broadband noise is between 0.5 and 1.0 dB. Section 19.2.1 of Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms by Floyd Toole shows that changes in frequency response as small as 1/3 dB can be heard under ideal circumstances. Both of these are scholarly works that refer to real research, versus the 0.03 dB JND claimed anecdotally with no further explanation by a hi-fi magazine writer linked in the other thread.However, when discussing changes in frequency response, versus volume level, two additional factors come into play. First, and perhaps too obvious, the frequencies being boosted or cut must be present in source. You could boost 50 Hz by 20 dB on a recorded flute solo, but that won't be noticed because flutes contain no content at such a low frequency. If such a boost is heard, it's surely due to other content in the recording, such as air conditioner rumble or other noises unrelated to the flute itself.Another factor is the bandwidth of the boost or cut. When dealing with broadband content such as a full music mix or pink noise, the JND for a boost or cut with a wide bandwidth (low Q) is smaller than when only a narrow range of frequencies is changed (high Q). This too makes sense, because more total energy is affected with a wide bandwidth. In Toole's book linked above, his JND of 1/3 dB is for a boost having Q of 1. When the Q is raised to 10 the JND rises to 3 dB before the response change can be noticed by listeners.
Toole provides good, useful information. However when it comes to low level frequency response changes, I see Toole only mentions two variables to address, that of sight and manufacturer. Since no other variables are addressed any low level results will be skewed.
an RC network has a bandwidth of many octaves. So any deviance is perceived at a much lower frequency response change than using even a low Q resonance circuit.
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