Morse - beeps not clear

Hello.

I am trying to create just a test app that would pretty much be morse translator but you also could beep your own message into it. Currently, it is set in a way that when you open the app and press space, it will beep. But there is strange... thing, sound. It is not clear. I am currently generating tone but I am thinking that I would use some mp3 of the beep instead if there will be a problem with sounds

The script is currently just attached to an empty game object.

This is totally my script and I totally did not copy and paste it and edit it just a little:

 [Range(870,990)]  //Creates a slider in the inspector
 public float frequency1;

 [Range(870,990)]  //Creates a slider in the inspector
 public float frequency2;

 public float sampleRate = 44100;
 public float waveLengthInSeconds = 2.0f;

 AudioSource audioSource;
 int timeIndex = 0;

 void Start()
 {
     audioSource = gameObject.AddComponent<AudioSource>();
     audioSource.playOnAwake = false;
     audioSource.spatialBlend = 0; //force 2D sound
     audioSource.Stop(); //avoids audiosource from starting to play automatically
 }

 void Update()
 {
     if(Input.GetKeyDown(KeyCode.Space))
     {
         timeIndex = 0;  //resets timer before playing sound
         audioSource.Play();
     }
     if(Input.GetKeyUp(KeyCode.Space))
     {
         audioSource.Stop();
     }
 }

 void OnAudioFilterRead(float[] data, int channels)
 {
     for(int i = 0; i < data.Length; i+= channels)
     {          
         data[i] = CreateSine(timeIndex, frequency1, sampleRate);

         if(channels == 2)
             data[i+1] = CreateSine(timeIndex, frequency2, sampleRate);

         timeIndex++;

         //if timeIndex gets too big, reset it to 0
         if(timeIndex >= (sampleRate * waveLengthInSeconds))
         {
             timeIndex = 0;
         }
     }
 }

 //Creates a sinewave
 public float CreateSine(int timeIndex, float frequency, float sampleRate)
 {
     return Mathf.Sin(2 * Mathf.PI * timeIndex * frequency / sampleRate);
 }