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In the Forum: Playback Listening
In the Thread: Audio vs. Musical pitch
Post Subject: MicroPosted by Amir on: 5/4/2013
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 rowuk wrote:
Hi Amir,
your english is just fine.

I think that there is an additional factor that your formula needs. Sense of pitch is not determined acoustically by "Q" unless we are talking about pure sine waves. When we add the overtones found on real musical instruments, funny things happen. Depending on the note played, the first harmonic may not even be a perfect octave - as wind instruments for instance change their acoustical length based on frequency. A trumpet consists of a cylindrical and flared portion. The flare determines the acoustical length of the instrument. If you have a friend that plays trumpet, have him blow a few notes on his instrument and then do the same on a piece of garden hose. The garden hose cannot be used for anything "tonal" even although mathematically it represents a "best case" situation

When we hear a well played instrument, the sound is modelled by the player and the result is pleasing. In a speaker, we have "issues" in phase and relative loudness of each of the speaker drivers used. Also the directivity of the driver can cause a shift in how the sound is reproduced. Spatial distribution also separates the overtones from the fundemental, which requires a given listening distance to allow the sound wave to integrate.

I guess, what I am saying is that even if each driver behaved as a perfect piston and was perfectly integrated to another driver, we would still have issues that make the "cook" responsible for the end result - not the absolutely quality of each ingredient. In this respect, I believe that Audio like cooking is an art form rather than a science. Fast food is the science of eating: calories, salt and sugar, repeatability, profitability. Many audio dealers are very much like McDonalds in this respect. For this type of reproduction, I thing the math can become VERY accurate!



for a single sine wave (like 1khz) we have one unlinear transfer curve { like (output voltage)/(input voltage) curve}.
it's response depends level of input voltage.
for single frequency input signal the output signal is not single frequncy, it has harmonics that each harmonic has it's amplitude and phase. number of these harmonics and complexity of their phase and amplitude is dependent of taylor series order of transfer curve.

for audio band (all frequency from 20-20khz) for each frequency we have a special transfer curve.
at first look in audio measurement we use fourier transfer function (https://en.wikipedia.org/wiki/Fourier_transform) and transfer function says in each frequency what's the amplitude and phase. these two curves should be linear in ideal condition and fourier function model the system  if we think system is linear .

in real world because system is not linear we should not see fourier transfer function result and forget sub harmonics of unlinear curve.
i think we need to see coherence of curves (Vo/Vin for each frequency) from 20hz to 20 khz.
this means if at 100hz taylor series of transfer curve is A tand in 1khz taylor series of transfer curve is B , how much A and B are similar.
we should define a coherence function for audio band that analysing that curve help us.

stereophile measurement is not perfect but even in some curves we could see difference of micro and macro linearity.
Lamm , Audio Note , Hovland , Lavry seems to be better in micro linearity and boulder , Soulution , weiss are better in macro linearity.
90% parameters of audio reviewers in describing sound is focused on macro linearity and these shows they give golden  award to amplifiers like soulution.

in past lamm had an article about his view about linearity but now i could not find it on web?!!





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