screen flicker openGL

I am trying to use openGL to create a music visualization program. To start with I am just using one VU bar, to test it.
The bar moves to the right position but flickers when it moves. This is the main part of the program:

void Analyse()
        bool quit = false;
	bool playing = true;
	bool *playingPtr = &playing;

	FMOD::Sound *sound;
	result = system01->createStream("/home/djameson/Music/Hurts-Like-Heaven-Cold-Play.mp3", FMOD_SOFTWARE, 0, &sound);

	FMOD::Channel *channel;
	result = system01->playSound(FMOD_CHANNEL_FREE, sound, false, &channel);

	result = channel->setVolume(0.5f);

		while(quit == false)

			result = system01->update();
			int sampleSize = 64;

			float *specLeft = new float[sampleSize];
			float *specRight = new float[sampleSize];

			channel->getSpectrum(specLeft, sampleSize, 0, FMOD_DSP_FFT_WINDOW_RECT);
			channel->getSpectrum(specRight, sampleSize, 1, FMOD_DSP_FFT_WINDOW_RECT);

			float *spec = new float[sampleSize];

			for (int i = 0; i < sampleSize; i++)
				spec[i] = (specLeft[i] + specRight[i]) / 2;

			float * maxIterator = max_element(&spec[0], &spec[sampleSize]);

			glClear( GL_COLOR_BUFFER_BIT );

				glMatrixMode( GL_MODELVIEW );

				glTranslatef( SCREEN_WIDTH / 2.f, SCREEN_HEIGHT , 0.f );

				glBegin( GL_QUADS );

				glVertex2f( -21.f, -spec[0] * 500);
				glVertex2f( 21.f, -spec[0]*500);
				glVertex2f( 21.f,  21.f);
				glVertex2f( -21.f, 21.f);


			if(*playingPtr == false)
				quit = true;

			delete [] spec;
			delete [] specLeft;
			delete [] specRight;


I initialize openGL and stuff in other functions, let me know if you need to see them and I will post them. The code obviously needs alot of improving but this is just a test thing. Thanks for your help!

I have v-sync enabled(i think) I did glxgears and got a fps rate of 60, I would post the thread in the fedora forum which I followed to check if I had v-sync enabled but It says there is a limit to the amount of URL’s in a new post.

I am using fedora 20

using freeglut

Are you using double buffering?