Take a look at this picture of the Sun - the red is the hottest part and the blue is coolest. Sound travels faster at the core of the Sun, the hottest part, and gets slower as it moves out into the cooler parts, towards the photosphere.

Don’t forget how important the speed of sound is in helioseismology!

A low speed means the temperature is low.

A high speed means the temperature is high.

Find out the different temperatures in the Sun by putting your cursor inside the white outlined area in the picture.