AR - necessary constants for 166Khz sampling rate

16kHz might be a good compromise on small MCU's:
- GEQ will show frequencies up to ~6Khz
- FFT process may use up to 32millis (-> 100% CPU load). Try to stay below <60% so FreeRTOS can schedule all tasks properly.

- more CPU time is left for other WLED, so it maintains LED FPS and stays responsive on web UI.

usermods/audioreactive/audio_reactive.h

@@ -42,10 +42,12 @@
 constexpr i2s_port_t I2S_PORT = I2S_NUM_0;
 constexpr int BLOCK_SIZE = 128;
 constexpr SRate_t SAMPLE_RATE = 22050;          // Base sample rate in Hz - 22Khz is a standard rate. Physical sample time -> 23ms
+//constexpr SRate_t SAMPLE_RATE = 16000;        // 16kHz - use if FFTtask takes more than 20ms. Physical sample time -> 32ms
 //constexpr SRate_t SAMPLE_RATE = 20480;        // Base sample rate in Hz - 20Khz is experimental.    Physical sample time -> 25ms
 //constexpr SRate_t SAMPLE_RATE = 10240;        // Base sample rate in Hz - previous default.         Physical sample time -> 50ms
 
 #define FFT_MIN_CYCLE 21                      // minimum time before FFT task is repeated. Use with 22Khz sampling
+//#define FFT_MIN_CYCLE 30                      // Use with 16Khz sampling
 //#define FFT_MIN_CYCLE 23                      // minimum time before FFT task is repeated. Use with 20Khz sampling
 //#define FFT_MIN_CYCLE 46                      // minimum time before FFT task is repeated. Use with 10Khz sampling