If one of the laptop speakers started making crackling noise, the first thing to do is test the laptop with headphones.
If both channels in headphones sound normal and crackling noise comes only from one of the laptop speakers, then you have to replace speaker as it is faulty speaker.
If you hear same crackling noise from one of the headphone channels, most likely there is a problem with the laptop sound card. In most laptops the sound card is integrated into the motherboard. If the sound card fails, you’ll have to replace the whole motherboard.