Audiophobe

One of my Friday lunch companions is reading a biography of Lord Kelvin (William Thomson), and mentioned that he had published a couple of papers on Fourier's work when he was 16.  As most of you know, I enjoy tracking down and reading historic papers. It took a bit of work to find them because the Cambridge Mathematical Journal was reprinted in a new collection that changed the volume and page numbers.  Kelvin published them under the pseudonym "P.Q.R." According to Wikipedia, Fourier's results had been attacked by the established British math community largely because he was French; Kelvin had made the decision to study and defend "continental mathematics." * Here are the two papers at archive.org: P.Q.R. "On Fourier's expansions of functions in trigonometric series". Cambridge Mathematical Journal. Vol 2: 258–262. (1841).   https://archive.org/details/sim_cambridge-and-dublin-mathematical-journal_1841-05_2_12/page/258/mode/2up P.Q.R. "N...

For the past several years, I've been interested in "correlation orthogonal" sequences, such as maximal length sequences (MLS, or M-sequences), Gold and Kasami sequences, Zadoff-Chu sequences, and so forth, for applications like measuring the impulse response of audio systems and room acoustics---what is broadly thought of as system identification .   M-sequences are generated by linear feedback shift registers (LFSR). Gold and Kasami sequences are generated by XOR'ing multiple M-sequences in various phases. Gold sequences are used in spread-spectrum radio applications such as GPS, where they are known as Gold Codes.  Because the transfer function (the frequency and phase response of a system, such as a loudspeaker) is the Fourier Transform of the impulse response, MLS became the dominant method for audio transfer function measurements starting in the late-80 [1].  In the early 00s, sine sweep methods were were rediscovered and popularized by Angelo Farina [2] and hav...