goertzel算法c语言实现

Goertzel算法是一种快速的数字滤波器，用于计算特定频率的信号的幅度。下面是一个基于C语言的Goertzel算法实现：

#include <stdio.h>
#include <math.h>

#define PI 3.1415926535897932384626433832795

double goertzel(int numSamples, int TARGET_FREQUENCY, int SAMPLING_RATE, double* data)
{
    int k, i;
    double floatnumSamples;
    double omega, sine, cosine, coeff, q0, q1, q2, result, real, imag;

    floatnumSamples = (double) numSamples;
    k = (int) (0.5 + ((floatnumSamples * TARGET_FREQUENCY) / SAMPLING_RATE));
    omega = (2.0 * PI * k) / floatnumSamples;
    sine = sin(omega);
    cosine = cos(omega);
    coeff = 2.0 * cosine;
    q0 = 0;
    q1 = 0;
    q2 = 0;

    for (i = 0; i < numSamples; i++)
    {
        q0 = coeff * q1 - q2 + data[i];
        q2 = q1;
        q1 = q0;
    }

    real = (q1 - q2 * cosine);
    imag = (q2 * sine);
    result = sqrt(real*real + imag*imag);

    return result;
}

int main()
{
    int numSamples = 1000;
    int TARGET_FREQUENCY = 1000;
    int SAMPLING_RATE = 8000;
    double data[numSamples];
    double amplitude = 10000;

    // Generate sample data with a 1000 Hz sine wave
    for (int i = 0; i < numSamples; i++)
    {
        double t = (double)i / SAMPLING_RATE;
        data[i] = amplitude * sin(2.0 * PI * TARGET_FREQUENCY * t);
    }

    double result = goertzel(numSamples, TARGET_FREQUENCY, SAMPLING_RATE, data);
    printf("Amplitude at %d Hz: %f\n", TARGET_FREQUENCY, result);
    
    return 0;
}

在上面的示例中，我们生成了一个包含1000个采样点的1000 Hz正弦波，并使用Goertzel算法计算该信号在1000 Hz的幅度。函数`goertzel()`接受采样数据数组、目标频率、采样率和采样数作为输入参数，并返回计算结果。