Klas, you wrote,
>Have you ever put a medium class directional microphone on a rotating plate
>in front of a 10kHz speaker and looked at the linear voltage output for
>different degrees?? I guess not....
>
>Cause if you do, you will find so many peaks and gaps - 40 db and more!! -
>when turning the mic only a few degrees one or the other direction!
>And if you take another microphone of the same type, it will probably show
>a quite different "exact" polar pattern. I agree with what you say, but I
>think we must accept that polar patterns are very approximative and that,
>perhaps, the db scale is the most "readable".
Smoothing of both frequency response and polar pattern curves is
common, and is justifiable to a certain extent as being an average of
individual unit differences or variations over space. Smoothing is
helpful. But that has nothing to do with the scale.
>If one manuf uses db, everyone else has to do the same. But in this case it
>is not fraud, just an approximation.
My objection in the polar patterns is that a dB scale distorts the
-shape-, not the details. A linear polar plot of a cardoid mic, for
example, shows 1.0 on axis and 0.5 at 90 degrees. That corresponds to
the shape of the pattern in space, i.e., a source at five feet at 90
degrees will be as loud as the same source at ten feet on-axis. Being
able to visualize the pattern in space is very valuable. A dB scale
makes the pattern look much wider than it is.
-Dan Dugan
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