thermionic wrote on Tue, 12 September 2006 17:11 |
True and false... From what I understand, Neve discovered that one of the transformers in the chain wasn't terminated properly, and as such was creating a "ringing" spike around 56K However, anyone who's looked at a tone on an FFT plot will know that - unfiltered - you will observe overtones at various divisions, i.e. in the case of 56k: 112k, 28k, 14k and so on... Therefore, to my knowledge, it is generally accepted that Emerick picked up on the overtones that were within the 20k range. Justin |
"Dan Lavry" |
Listning to transients: It is a well accepted fact that even a very good ear does not hear much above 20KHz, that most mics do not pick up energy much above 20KHz, and that most speakers will not generate sound much above 20KHz. It is also well known that most of the energy generated by musical instruments is at frequencies not much higher then 20KHz. For some reason, many ear types seem to have bought into the notion that all that I have stated above is true for some of the music, and there is also another part of the signal which they refer to as “high frequency transients”. The concept of transient energy is well accepted by all EE’s (not just in audio) to differentiate between signals made of repetitive cycles and signals that have little or no repetition. EE's and math types make the distinction between steady state and transients (non steady state) because the math and analysis of steady state signals is simpler and easier. Non steady state analysis (transient analysis) requires much more complicated tools. However, the non repetitive audio signal behaviour (transients) does NOT contain frequencies higher than audio. Non-repetitive behaviour DOES NOT require, imply or call for high frequencies. The fast attack of sound, be it drum, bell or a muted trumpet may have some low energy at frequencies above human hearing. But if your system could pick 100KHz transient energy, it would certainly be able to pick up and react to 100KHz sine wave! Why bother with 100KHz energy? If you can not hear 30Khz sine wave, you can not hear 30khz transients. The whole concept of “high frequency transient” has been repeated over and over numerous times in the audio industry, in audio magazines, in marketing material and by people intend on finding "some sort of an explanation" for various fallacies they are trying to explain or promote. After so much repetition of that faulty concept, I would not be surprised if many ear types will simply refuse to hear what I am saying but I am stating the FACTS! Example – “multiple choice test question”: Which case yields the fastest voltage change you can archive with say a 22KHz bandwidth system (such as a 22KHz mic, ear or speaker)? I am talking about the steepest slop, thus the fastest changing signal. A. 100Hz 1V peak square wave B. 1KHz 1V peak square wave C. 5KHz 1V peak square wave D. 10KHz 1V peak square wave E. 22KHz 1V peak sine wave The 5 waves are plotted below: A. 100Hz 1V peak square wave is the red trace B. 1KHz 1V peak square wave is the blue trace C. 5KHz 1V peak square wave is the green trace D. 10KHz 1V peak square wave is the purple trace E. 22KHz 1V peak sine wave is the black trace The fastest signal slope you can ever get in a 22KHz bandwidth system is not a transient. It is the slope of a steady state tone sine wave at the edge of the bandwidth - it is a 22KHz sine wave. The fastest signal in a 30Khz bandwidth system is a 30KHz sine wave, and so on. It is faster then the fastest transient you can create within the given bandwidth! I know that many in audio “became attached” to that MISCONCEPTION about high frequency transients. Sorry to burst the bubble, but it is long overdue to have that nonsense cleared up. It is time to refocus on the activity to what happens WITHIN the audio band, and put an end to that fantasy about things that do not matter and things that do not exist. If you want to test your system or your ear for "the fastest signal it can handle", go for the highest sine wave frequency within the available bandwidth. That is true for ears as well as speakers, amps and everything else. There is no such a thing as high frequency transients extending beyond the audio bandwidth. A mic that can not capture a steady state signal above say 20KHz, can not capture transients above 20KHz. The same is true for the ear, speaker or anything else in the system. We can argue about how high an ear hears, and be sure it never gets higher then 30KHz. For most people it is well below 20KHz, be it steady state or transient energy. |
danlavry wrote on Tue, 12 September 2006 20:04 | ||
No one hears 56KHz. It is not uncommon to have some correction to some high frequency circuit also impact the audible frequencies. In fact there are some rather common mechanisms like that (aliasing, inter-modulation, beats between signals...) I doubt it that a high frequency ringing by itself will be heard, but the decay envelope may be heard, and that is NOT ALWAYS at high frequency... Regards Dan Lavry http://www.lavryengineering.com |
Jim Williams wrote on Fri, 15 September 2006 16:27 |
No one hears 56k hz, but one might sense it. I worked as a janitor in college and the classrooms had a motion sense burglar alarm running at 35k hz. I couldn't go into a room with that thing on, it drove me nuts. I always knew when it was on. The older guys couldn't sense it. |