MBP mid 2010 Has Distorted sound

Go step by step and test.

1. Reset PRAM. http://support.apple.com/kb/PH18761

2. Reset SMC.

Choose the method for “If the battery is non-removable”.

https://support.apple.com/en-us/HT201295

3. Finder > Applications > Utilities > Audio MIDI Setup > Built-in Output > Format

Default set is 2 ch 24 bit Integer 44.1 kHz

Click inside the box next to Format: and choose another value.

Then choose the default set value

4. https://support.apple.com/en-us/HT203186

Replace the speaker components internally. Make an appointment at the Apple Genius Bar for service. If you need to find an Apple Store - Find a Store - Apple.