Hi,
Have you verified that the speakers are the problem by connecting a set of headphones to the laptop and checking that the sound is clear when listening to them?
If so, replacement [https://id.aliexpress.com/i/32867983212.html?gatewayAdapt=glo2idn|speakers] (supplier example only), are available online. Search for ''Toshiba Satellite S55t-A5389 speakers'' to find suppliers that suit you best.
Here’s the Ifixit [[Topic:Toshiba Satellite S55t-A5389]] guide. This will help you to open the laptop to gain access so that the speakers can be replaced.