multi-channel buffers

hello,I want to use multi-channel buffers to output 5.1 audio.But,when I  want to play on back- left sound is heard from front-left and vice-versa for the back-right.I have two questions about it:
1、From 《OpenAL Programming Guide》we know that "playing a buffer using the AL_FORMAT_51CHN16 format will require 6 free hardware voices".I really want to know what does"hardware voices"mean?
2、I have implemented code as below,does it has something wrong?


template<typename T>
T *load_data(const T *data, int size)
{
 size /= sizeof(T);


 T *data71 = new T[size*6];
 for(int i = 0;i < size;i++) {


    data71[i*6 + 0] = 0; // front-left
    data71[i*6 + 1] =0 ; // front-right
    data71[i*6 + 2] = 0; // front-center
    data71[i*6 + 3] = 0; // lfe (sub-woofer)
    data71[i*6 + 4] = data[i]; // back-left
    data71[i*6 + 5] = 0; // back-right
  }


 return data71;
}


thanks!

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