added demo noise generator

util/demo_noise.h

@@ -0,0 +1,38 @@
+#pragma once
+#define _USE_MATH_DEFINES
+#include <math.h>
+#include <cstdlib>
+
+namespace trnr {
+template <typename t_sample>
+class demo_noise {
+public:
+    void set_samplerate(double _samplerate) {
+        samplerate = _samplerate;
+    }
+
+    void process_block(t_sample** samples, long sample_frames) {
+
+        for (int s = 0; s < sample_frames; s++) {
+            demo_counter++;
+
+            if (demo_counter == samplerate * 20) {
+                demo_counter = 0;
+            }
+            if (demo_counter > samplerate * 17) {
+                t_sample r1 = static_cast<t_sample>(rand()) / static_cast<t_sample>(RAND_MAX);
+                t_sample r2 = static_cast<t_sample>(rand()) / static_cast<t_sample>(RAND_MAX);
+
+                t_sample noise = static_cast<t_sample>(sqrt(-2.0 * log(r1)) * cos(2.0 * M_PI * r2));
+
+                samples[0][s] = noise / 10.0;
+                samples[1][s] = noise / 10.0;
+            }
+        }
+    }
+
+private:
+    double samplerate = 44100;
+    int demo_counter = 0;
+};
+}