Advocate opinion on this proposal
The highlighted comment was created in this revision.
As the advocate to this Milestone, let me express my opinion on the proposal:
Although the microphone industry dates back to the origins of telephony, it was with the development of Radio Broadcasting, Radio Communication, and Public Address Systems at the beginning of 20th century that an increasing attention to the microphone design constraints came to be a key issue.
One of those constraint had to do with the microphone polar pattern, that indicates how sensitive a microphone is to sounds arriving at different angles about its central axis. That was, and still is, a very important issue in order to reduce unwanted background noise or ambient noise.
Before Shure Unidyne I, there were some other microphones or techniques that let the achievement of a not omnidirectional pattern. RCA 44 Style Ribbon Microphone, marketed in 1931, was a permanent magnet bi-directional microphone. Later on, RCA also developed the RCA 77 model, which was able to get an unidirectional pattern by combining to capsules or sensitive transducer elements: a pressure unit with a velocity unit. In the late 1930s, Western Electric also produced a switchable multi-pattern microphone, combining an omnidirectional unit with a bidirectional ribbon unit to get either an omnidirectional, bidirectional or unidirectional pattern. In addition, techniques based on an array of elements were very well known at that time in order to obtain a predetermined polar pattern.
All of those cases made use of more than one sensitive transducer element, so it was with the Shure Unidyne model I that a much simpler and more reliable directional microphone was achieved by using just a single element. Benjamin Bauer (Baumzweiger) found that by utilizing time delay networks on sounds arriving at openings at the back of the microphone, he was able to achieve controlled cancellation and produce a cardioid (unidirectional) pattern.
So, in my opinion, I find this proposal very appropriate to get an IEEE Milestone. Title and citation in the proposal are both also suitable for me.
Antonio Perez Yuste
I concur with Antonio's endorsement of this IEEE milestone proposal. It is technology and engineering that has stood the test of time. And, the proposal is enjoyable reading.