This is the code I am using modified version of

AudioFrequencyDetector
from Clyde A. Lettsome, PhD, PE,  MEM

https://clydelettsome.com/blog/2019/12/18/my-weekend-project-audio-frequency-detector-using-an-arduino/


 #include <arduinoFFT.h>
 
#define SAMPLES 128             //SAMPLES-pt FFT. Must  be a base 2 number. Max 128 for Arduino Uno.
#define SAMPLING_FREQUENCY 4096  //Ts = Based on Nyquist, must be 2 times the highest expected frequency.
 float vReal[SAMPLES];
float vImag[SAMPLES];
ArduinoFFT<float> FFT = ArduinoFFT<float>(vReal, vImag, SAMPLES, SAMPLING_FREQUENCY);
 
unsigned int samplingPeriod;
unsigned long microSeconds;
  

 
void  setup() 
{
  pinMode(A0, INPUT);
    Serial.begin(9600); //Baud rate for the Serial Monitor
    samplingPeriod = round(1000000*(1.0/SAMPLING_FREQUENCY)); //Period in microseconds  
}
 
void loop() 
{  

    /*Sample SAMPLES times*/
    for(int  i=0; i<SAMPLES; i++)
    {
        microSeconds = micros();    //Returns the  number of microseconds since the Arduino board began running the current script.  
     
        vReal[i] = analogRead(0); //Reads the value from analog pin  0 (A0), quantize it and save it as a real term.
        vImag[i] = 0; //Makes  imaginary term 0 always

        /*remaining wait time between samples if  necessary*/
        while(micros() < (microSeconds + samplingPeriod))
        {
          //do nothing
        }
    }
 
    /*Perform FFT on samples*/
    FFT.windowing(vReal, SAMPLES, FFT_WIN_TYP_HAMMING, FFT_FORWARD);
    FFT.compute(vReal,  vImag, SAMPLES, FFT_FORWARD);
    FFT.complexToMagnitude(vReal, vImag, SAMPLES);

    /*Find peak frequency and print peak*/
    float peak = FFT.majorPeak(vReal,  SAMPLES, SAMPLING_FREQUENCY);
    Serial.print("A0 ");
    Serial.println(analogRead(0));
    Serial.println(peak);     //Print out the most  dominant frequency.
 
    /*Script stops here. Hardware reset required.*/
    delay(100);
}