On 10/31/2020 6:15 AM, jimlux wrote:
This is a pretty standard technique these days - They use it for
calibrating radio telescope arrays, for instance.
Great tutorial, Jim! Two other important variables for earthbound
antenna measurements are 1) terrain and 2) soil conductivity. You can't
do this just anywhere. :) The N0AX/K7LXC test ranges were well chosen,
but they tell us nothing about vertical pattern.
More than thirty years ago, thanks to greater computer power, those of
us working in pro audio accomplished major advances in both acoustic
measurement and acoustic modeling. One of the most powerful tools, and
the earliest that got us all started, and the earliest, was Time Delay
Spectrometry, invented by Richard Heyser, an engineer who worked at JPL
on space communications. When he died early of cancer, he was President
Elect of the Audio Engineering Society.
Computing power led to 3D modeling of loudspeaker systems in models of
real acoustic spaces, taking into account the complex (mag, phase)
response of speakers and arrays of speakers, over nine octaves, and
computing responses over an audience. This required 3D measurement of
loudspeakers in 5 degree increments of azimuth and elevation, and of the
reflection/absorption properties of all of the surfaces in the acoustic
model. Modeling had to take into account variations in the acoustic
center of loudspeakers, and compute complex time response to every wall
surface, and over audience areas. Once the model was complete, the
response at any point could be convolved with a .WAV file of speech to
assess speech intelligibility. All of this was well developed by the
late '90s, and continued advancing thereafter.
Thanks to the broad frequency range of audio, and the extent to which
reflections from room surfaces must be considered and added to compute
both the responses and the room reverberant field, this modeling is
several orders of magnitude more complex than what we're doing with
antennas! Two of largest spaces I modeled at this degree of complexity
were the Staple Center and the Nokia Center (now known as the 7,000-seat
Microsoft Theater) nearby.
73, Jim K9YC
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