Several suggestions have been made for an electronic tuning aid that displays beat information only, without any regard to an assumed tuning curve. Speaking as one who has written ETD software, I would like to address this issue. All major ETDs display beat information between a single note and an internally generated reference signal. Furthermore, all major ETDs display information on only one partial at a time. Steve Fairchild has suggested tuning while considering two or more partials at a time and has even constructed some experiements using several SATs at once (set to different partials). But the comparisons are always between a single note and an electronically synthesized reference. What is different about the present proposals is that the ETD not use any internal reference. Instead the technician would strike two keys at once, just as in aural interval tuning, and let the ETD "listen" to the beats between the two different notes and display the results in some manner. IMHO, this ETD would be significantly harder to make than the current ETDs. What you find fairly easy - picking out beats between two simultaneously sounding notes - actually relies on the incredibly complex pattern recognition capabilities on the ear-brain combination. There are amplitude fluctuations across the frequency spectrum. Yet to hear beats, you have to be able to pay attention to amplitude fluctuations at only one frequency, ignoring all the rest. There is a similar problem in radio communication with Morse code. Like beats, Morse code is made up of amplitude variations. Within the crowded amateur radio bands you may find a number of stations so close together in frequency that the radio is incapable of separating them. But a highly skilled amateur radio operator can pick out and understand a single transmission admidst all the interference. When computers came along, it was natural to try to make a computer read Morse code. This effort has been met with limited success. Computers can read Morse code, but only when it is fairly clear. Under the most difficult situations, the human listener still copies Morse code better than the computer. If an electronic device can detect beats, it would only be in situations where the beats were easy to hear anyway. As beats get harder to hear, the electronic device will fail sooner than the human ear. -Robert Scott Real-Time Specialties
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