add reference

examples/gno.land/p/demo/audio/biquad/biquad.gno

@@ -12,14 +12,19 @@ type Filter struct {
 	x1_f, x2_f, y1_f, y2_f float64
 }
 
-// New provides a new biquad
+// New provides a new biquad according to the equation for a first-order
+// biquad. The algorithm follows the equations in this: https://www.ti.com/lit/pdf/slaa447
 // Inputs:
-// fc: filter cutoff
-// fs: sample rate
-// q: resonance coefficient
-// db: shelf decibels (strength)
-// filterType: string that specifies the type of filter (currently only 'highpass' or 'lowpass')
-// Outputs: a filter object
+//
+//	fc: filter cutoff
+//	fs: sample rate
+//	q: resonance coefficient
+//	db: shelf decibels (strength)
+//	filterType: string that specifies the type of filter (currently only 'highpass' or 'lowpass')
+//
+// Outputs:
+//
+//	a filter object
 func New(fc float64, fs float64, q float64, db float64, filterType string) *Filter {
 	w0 := 2 * math.Pi * (fc / fs)
 	cosW := math.Cos(w0)