Do piano pedals change the sound?

Yes. Modern pianos have three pedals, from left to right, the soft pedal (or una corda), the sostenuto pedal (mainly found in American-made grands), and the sustaining pedal (or damper pedal). All of them change the instrument's sound in various ways, depending on the pedal and the piano.

The soft pedal, the one at the left, is designed to make the sound softer and lower the volume, but it also modifies timbre and color of the tone.

The middle pedal, the sostenuto pedal, is not so common, and it's the last pedal to be added to the modern grand. This pedal is made to sustain selected notes while other notes remain unaffected.

The pedal at the right, the sustaining pedal, raises all the dampers off the strings so that they can continue to vibrate and sound after a note on the keyboard has been released. It adds much expressivity to piano music, allowing notes to resonate, and certain harmonies and notes to be connected together. This is the most used pedal.