The cracked metal buzzing sound (F3) of the upright piano when we press down it's key.

[maxim_tuner]

https://youtu.be/6id3CD5jau0

• One of the double strings in the choir (3) (F3) and( F#3) there broke. That's why we hear it. How to fix this?
  It is necessary to call the technician tuner to replace this string. You can make a temporary plug from rubber or plastic there too.