Long loud Noise after flushing the toilet

[Sedgy40]

was at a friends house in Wiltshire the weekend,3story house toilet on each floor flushed the loo there middle floor and it made a very long loud noise.
Is that pressure too high on cold main as it fills cistern?
Thanks in advance

 

[moonlight]

Washer in the float valve most likely needs replacing.

 

[Sedgy40]

Washer in the float valve most likely needs replacing.

New fill valve then?
When flushed and noise is there,if a cold tap is opened it gets quieter.

 

[moonlight]

You can just change the diaphragm washer inside the fill valve.
That

The noise is because the washer is vibrating with flow of water. Reducing the flow with the tap will lessen the sound.

 

[Sedgy40]

You can just change the diaphragm washer inside the fill valve.
That

The noise is because the washer is vibrating with flow of water. Reducing the flow with the tap will lessen the sound.

Thanks I will pass on the info.