GitLab

Summary:
follow up to https://github.com/pytorch/audio/issues/2823
- move bark spectrogram to prototype
- decrease autograd test tolerance (passing on circle ci)
- add diagram for bark fbanks

cc jdariasl

Pull Request resolved: https://github.com/pytorch/audio/pull/2843

Reviewed By: nateanl

Differential Revision: D41199522

Pulled By: carolineechen

fbshipit-source-id: 8e6c2e20fb7b14f39477683b3c6ed8356359a213