Theres a vacuum in space, so how do we know if the Sun makes a noise?
The Sun is full of all sorts of sound waves travelling through the interior. Some of them resonate because they are particular frequencies. However, you cannot hear the Sun using a microphone. Instead, we see the sound waves because of the effect they have on the Sun. These sound waves are reflected at the surface, although it is not solid. However, there is an abrupt change in density, which allows the reflection to happen. As they reflect at the surface, the sound waves cause a change in brightness and push up some material too. With the kind of instruments as carried on board SOHO, we can measure the changes in brightness and the velocity changes at the surface. From those measurements, we can work out the sound of the Sun.
