Bathroom kitchen tap making gurgling sound after shower installation

[Longshanks]

Hi

We had a shower tray and new shower installed this week. (To replace bath/shower combo)

Everything good, except… when bathroom tap drains, there is a distinct gurgling sound from area of waste pipe. The fitter installed separate discharge pipe for shower, so not sure how/why this could have happened.

Guy is coming next week to take a look but wanted to reach out to garner views on what might be happening.

Definitely something that wasn’t happening before the shower fit,

Thanks