What caused sound waves in the early universe? (In the CMB etc.))

Factual Questions
1

The map of Cosmic Microwave Background fluctuations shows the variations in temperature in the ancient CMB.

What originally caused these sound waves? I dont really get it, was it the fluctuations themselves?

here’s that map yo:

http://www.google.com/imgres?um=1&hl=en&safe=off&sa=N&authuser=0&biw=1436&bih=806&tbm=isch&tbnid=6vxC6ZbWd3JIsM:&imgrefurl=http://www.astro.virginia.edu/~jh8h/Foundations/chapter14/chapter14.html&docid=u8X3-HFEf2VDHM&imgurl=http://www.astro.virginia.edu/~jh8h/Foundations/chapter14/cobe3.gif&w=658&h=340&ei=eoWYT-_jM8zcggejlLSBBw&zoom=1&iact=hc&vpx=157&vpy=169&dur=1004&hovh=161&hovw=313&tx=176&ty=86&sig=109790455819136706236&page=1&tbnh=97&tbnw=187&start=0&ndsp=28&ved=1t:429,r:0,s:0,i:70