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RE: Measurements are not equivalent to perception

Posted by KlausR. (A) on October 23, 2010 at 23:00:32

In Reply to: Measurements are not equivalent to perception posted by Tony Lauck on October 22, 2010 at 17:31:45:

>>Meyer shows frequency response measured at different locations in the hall for celli and first and second violins. Takatsu shows IACC (interaural cross-correlation coefficient) at various location in the hall.<<


>These kinds of measurements do not relate to timbre, etc. <

“Timbre is that attribute of auditory sensation in terms of which a listener can judge that two sounds similarly presented and having the same loudness and pitch are dissimilar” (American National Standards Association, New York, 1960).

The response curves at the different locations show differences of up to 5 dB, if you had two loudspeakers having two of these different curves as on-axis response you would not doubt for a second that they will sound different.

IACC relates to spaciousness, hence to soundstage.


>It [human hearing system ] correctly perceives timbre so that the type of object creating a sound can be accurately recognized under a wide variety of acoustic conditions.<

My daughter has a new flute, and I still have mine which is about 40 years old. You’d immediately recognize each of the two as flute, you’d also note immediately that they sound different. In the above mentioned paper Meyer addresses different seating arrangements: “ So the sound of the first violins is brilliant and very vigorous, while the sound of the second violins is a little dark and poor.” “The difference in timbre between the first and second violins (in the European seating arrangement) may be advantageous in passages where the same phrase must be be played by both groups alternatively.” No doubt you recognize both groups as violins, yet they sound different.

Meyer further elaborates: “ The greatest difference between the two groups (first and second violins) is measured by the microphone near the first violins, because the masking of the second violins by the musicians of the first violins is strongest here. The first violins are relatively loud here, especially in the lower frequency range, where they have no directivity. The higher-frequency sound does not reach this place in the angular range of preferred sound radiation, nor by a reflection from the ceiling, so the spectrum at this place has quite a different character than at other places in the hall.”


>Reproduced sound will not sound different if the recording/playback is tonally flat and undistorted and the correct acoustic environment presented.<

It must and will sound different because many musical instruments radiate different portions of their operating range into different directions, whereas loudspeakers don’t make such directional distinction, and because human hearing is directional, meaning that it makes a spectral difference whether the same frequencies come from the front, or from the sides, above or from behind. Searchers at French IRCAM (Institute for research and coordination of acoustics and music) have found that there is a perceptual difference between an instrument and its reproduction via loudspeakers and that when the directivity of the instrument is simulated by a dodecahedron loudspeaker arrangement, the perceptual gap is closed. This is the reason why directivity behaviour of instruments is analyzed, as to include the correct behaviour in acoustic modeling of performance venues (auralization).


>If all one wants to do is babel about how it is impossible to reproduce the live concert experience, than none of this effort is needed. Success will never be achieved by looking at a bunch of measurements. Measurements are useful only when equipment is on a design bench or repair shop.<

Without science and measurements you would not be able to hear a single note of your favorite music in your home, unless of course you were rich and had Karajan and Wiener Philharmonics come to your home and perform. If you reject science and measurements you should do that also when you GP uses both for diagnosis when you’re seriously ill, or when your audiologist wants to install the hearing aid with frequency response tailored to your particular impairment. If you think live concerts are useful as sonic reference for judging audio gear, be my guest. I no longer do.

Klaus

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