The speakers do not make any buzzing noises unless perhaps the volume is extremely loud. Other possibilities are bad speakers, or a grounding issue with the power adapter. Or maybe some debris got onto the speaker cones which can cause a static like sound. There may be some other possibilities as well.
Have Apple or an Apple Authorized Service Provider examine the laptop to provide you with a diagnosis & repair estimate.
Edit: A grounding issue could also be due to a connected device, so disconnect all external devices & disconnect the power adapter. If the static from the speakers only occurs with devices connected, then one of them is the source of the problem.
If you mute the audio or connect headphone/speakers, do you still hear the static sound? Do you hear it through the headphones/external speakers? Or do you hear it from the laptop....if the latter, then it may not be the speaker. It could be the fan bearing (can sound like static), or possibly even from the SSD chips which is usually more of a faint high pitch sound.