Whistling taps?

[CJLees01]

The cold water tap in my bathroom has recently developed a habit of whistling quite loudly. (And it isn't even a good tune!). The volume gradually increases and decreases, but it can last for quite a while.

Turning the cold tap on stops the whistling.

We think (but aren't certain) that the problem might be somehow related to the toilet, because it seems to get worse whenever we flush the toilet.

Any ideas what might be the problem?

Thanks

Chris

 

[breezer]

new tap washer.

it changes when loo is flushed becuse of drop in water pressure