And by the way:
const unsigned char sample[] PROGMEM = {
126, 127, 128, 128, 128, 128, 128, 127, 128, 128, 128, 129, 129, 128, 127, 128, 128, 127, 126, 127, 128, 129, 128, 127, 126, 127, 128, 128, 126, 126, 127, 127, 127, 127, 127, 127, 126, 127, 129, 130, 129, 128, 126, 126, 126, 126, 127, 129, 130, 129, 127, 127, 127, 127, 128, 128, 128, 128, 127, 127, 127, 127, 127, 127, 128, 130, 131, 129, 127, 126, 126, 126, 127, 127, 128, 128, 128, 128, 127, 128, 128, 127, 127, 128, 128, 130, 130, 129, 126, 125, 127, 129, 130, 129, 128, 126, 125, 126, 129, 131, 131, 127, 123, 125, 129, 131, 130, 128, 129, 130, 130, 129, 127, 127, 128, 130, 129, 128, 126, 125, 126, 129, 131, 130, 128, 128, 128, 126, 125, 126, 128, 129, 128, 125, 125, 127, 129, 129, 129, 129, 127, 124, 123, 125, 128, 128, 126, 125, 125, 127, 129, 127, 126, 127, 128, 129, 129, 127, 124, 121, 123, 127, 130, 130, 128, 124, 122, 123, 127, 130, 131, 129, 125, 122, 122, 126, 128, 128, 128, 125, 123, 121, 118, 114, 111, 112, 113, 112, 109, 106, 107, 112, 117, 115, 111, 108, 109, 111, 112, 115, 116, 115, 112, 109, 107, 110, 114, 116, 115, 116, 117, 118, 118, 118, 117, 116, 115, 113, 110, 109, 111, 111, 111, 111, 114, 116, 115, 112, 110, 111, 113, 113, 110, 108, 110, 115, 117, 116, 114, 114, 114, 114, 113, 112, 113, 116, 116, 116, 116, 118, 119, 120, 121, 123, 124, 123, 119, 114, 112, 115, 118, 120, 122, 123, 123, 119, 116, 118, 124, 131, 130, 122, 116, 117, 123, 128, 132, 133, 131, 126, 121, 117, 117, 120, 124, 125, 123, 120, 118, 120, 125, 129, 128, 124, 120, 116, 115, 118, 123, 126, 125, 121, 117,
};
With the output set up correctly, this will sound more like a quiet hiss mixed with a quiet whatever it was supposed to be. The oscillation seems so weak that is maybe barely audible.
8-bit samples have a low "dynamic range"; making quiet sounds harder to listen, and the hiss ("white" noise) more apparent.