Single frequency lines in Spectrogram of generated wavs

Hi,
I traned a model for the Bandwidth expansion task using the code and VCTK dataset.
But I got bad generated wavs, which contain Single frequency lines in Spectrogram , as shown in the figure
![截屏2022-11-01 18 56 34](https://user-images.githubusercontent.com/16221172/199219252-fdb34e30-57e6-44d6-a883-be689398078f.png)




