I write from a US perspective. Don't know other countries problems
as we have enough local to keep me busy.
PZM is still a reg. trademark of Crown. Therefore, you should use a
different word such as Boundary Microphone.
The first reference to the concept that I could find in the US patent
data base is 7/1931, patent 1814357. Clearly expired.
The Crown SASS microphone was patented in 1987 and so IMHO it too has
expired and therefore it is now time to check it out and build and
sell like crazy.
For anyone who likes to build their own stuff it is gold to
understand your way around the US Patent Data base. If you have not
before, spend some time with it now and bookmark it.
see:
Rich Peet
--- In micbuilders@..., Indrek Rebane <indrek@b...> wrote:
Keith Nelsen wrote:
Think PZM (Pressure Zone Microphone) which eliminates sound from
other axis. Works great.
But if I recall correctly, making of PZM microphones has some
patent issues.
Indrek
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