added some notes

wip/dsp-notes.md

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+# digital signal processing 
+
+A boring lecture about signals and systems, and its digital implementation in DSP.  
+Borderline 'song' less 'poetic'.  
+
+The actual material (text that is read out by a vocal synthesiser) is in Japanese.  
+
+## Simple notes  
+ 
+For things that are not easily pronounced (e.g. formulae, expressions, symbols), inclusive either:  
+- Mark how the thing should be pronounced in a pair of adjacent parentheses  
+  - e.g. H(ω) (エッチオメガ)  
+- (inclusive) Or don't embed these elements too deep into the flow of sentences; use common, laymen's language instead  
+  - e.g. not `Fs/2（サンプリング周波数の半分）までの帯域を忠実に再構成できる` but `サンプリング周波数の半分までの帯域を忠実に再構成できる`