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Therefore, moderation is the Order of the Day. This explains why telephones are limited to 3,000 Hz audio bandwidth, why Military microphones have an even more constrained frequency range, and why hams use just a 2700-3000 Hz audio and RF bandwidth for sideband communication.
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The really low frequencies between 1100 and 450 Hz consume the most speech energy, but contribute very little to intelligibility. Therefore, nearly half of speech intelligibility is contained in a mere 1000 to 4000 Hz frequency range, requiring minimal sound energy. In contrast, frequencies form 125 to 500 Hz contributes 55 % of sound energy but only 4 % to word intelligibility.Frequencies from 1000 to 4000 Hz contribute 48% of intelligibility but has only 4% of sound energy.Frequencies from 500 to 1000 Hz contributes 35% of word intelligibility and 35 % of sound energy.They contribute 83 % of word intelligibility. The frequencies important for speech intelligibility are the consonant sounds from 500 to 4000 Hz.Wider range input reduces intelligibility and wastes RF energy transmitting sound which is either not speech, or which does not enhance speech intelligibility, and may cause deleterious distortion in the desired frequency spectrum, explained more fully below.Īcoustic research presents interesting and important facts: Microphones intended for speech applications are limited to reproducing only 200 - 6000 Hz for good reasons. INTELLIGIBILITY TRUMPS AUDIO QUALITY EVERY TIME.
#Ham radio speech recorder full#
High grade, full spectrum studio quality microphones are simply not the best tool for the job because they cover a much wider frequency range than we need or want in ham radio.
#Ham radio speech recorder professional#
Professional grade microphones may be worse than using cheaper microphones specifically designed for the task! This is explained more fully in the LONGER answer, below: Computer speech recognition requires accurate speech audio input – but works better with less expensive, narrow range microphones specifically designed for articulate speech input. Instead, they specify narrow range microphones tailored for human speech reproduction, only, in noisy venues like Air Force jets and battlefields. This explains why the Military and the Air Force do not use “professional” studio grade microphones. This explains why Kenwood and other manufacturers put a lower cost, narrow range microphone in the box and in their other microphones. If qualified world class audio engineers at Shure thought an expensive professional studio grade cartridge would do better, they and transceiver manufacturers would specify that type of cartridge, instead. They were designed by ham operators employed by Shure Brothers, Inc., "with a frequency response tailored for optimum speech intelligibility." (Shure 444 User Manual.) They are used by hams and professional dispatchers because they provide clear, articulate speech reproduction, and no more, affirmatively excluding sound outside the human speech audio spectrum.
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We do not need, nor want, full spectrum audio on the air because it can degrade intelligibility.Ĭonsider the Shure Model 444 or Shure Model 522 communications microphones, which are legendary for providing accurate, effective communications input. Ham shacks are not recording studios, and transceivers are not professional grade recording tools. Studio grade microphones are expensive overkill with significant drawbacks in a ham shack. Different microphones are designed to serve different objectives. I agree it is NOT a matter of COST – it IS a matter of having the most appropriate frequency response curve. I did not miss your point WE SIMPLY DISAGREE ! BOB SAID: I think you missed the point Richard.