The phrase "to upgrade the audio" means improving or making better the sound quality of something, like a music system or a movie theater. Full definition
Options include upgraded audio systems, ABS, side airbags, cruise control, leather seating and a sunroof. (edmunds.com)
However, it can be made more comfortable with six - way adjustable comfort seats, parking sensors, a reversing camera and a choice of upgraded audio systems. (evo.co.uk)
It packs the same video as the 2009 Blu - ray and a slightly upgraded audio track. (mediamikes.com)