Interact class with fft

Hi guys! well I have a beginner’s question. So I made an animated video interactive with sound. I get the interactivity and the sensitivity by fftSmooth.

for a example:

// update the sound playing system:

//grab the fft, and put in into a "smoothed" array
float * value = ofSoundGetSpectrum(bands);

//request 512 values for fft
for (int i = 0; i < bands; i++){
    fftSmooth[i] *= 0.99f;
    // take the max, either the smoothed or the incoming:
    if ( fftSmooth[i] < value[i]){
        fftSmooth[i] = value[i];

and the movement for a line is like that:

for (int i = 0; i < bands; i++) {
ofDrawLine(0, fftSmooth[i]*300, ofGetWidth(), fftSmooth[i]*300);

But I made a class with moving rectangles but I cant figure out how can I insert the fftSmooth for more interactive movement. I add on the class all the fftSmooth update but sometimes the program crushed.
This is the ccp file from my class:

ofBall::ofBall(float _x, float _y, int _w, int _h)
x = _x;
y = _y;
w = _w;
h = _h;

speedY = 0;
noiseSeed = ofRandom(100);


void ofBall::update(){

if(x > ofGetWidth() ){
    x = -20;

speedX = ofNoise(noiseSeed) *10;
noiseSeed = noiseSeed + 0.01;


void ofBall::draw(){


ofRect(x,y, w, h);


I want to add the ffSmooth into to speedX. for example speedX = ofNoise(noiseSeed) * (fftSmooth[i]*10)

Do anyone have any idea?

Thank you!!