Hearing experiments on guinea pigs

[Catherine]

Scientist did some hearing experiments by playing music to guinea pigs.
It seems recorded music comes in normal form and compressed form. The article explains it.
The music was a bit loud, but the guinea pigs listening to normal music did recover their hearing.
The guinea pigs who listened to compressed music had some damage.

https://www.musicradar.com/music-tech/sc...d-worrying

All I can think of is WHY?
Why would  you force guinea pigs to listen to music.
Why would you compress the music in the first place.

We already know loud music causes hearing damage.
Why are we experimenting with guinea pigs now. 

If compressed music is dangerous to hearing, why wasn't that tested when they first started compressing music.
Why subject guinea pigs to this now.
Guinea  pigs do not deserve this kind of treatment.