The room I use for hearing tests has 14 inch thick walls and double glazing.
I therefore don't use a booth.
I was finding that people with HF loss often have VERY sensitive hearing at LF, so they can detect trucks etc despite the double glazing.
I have now had the room QUADRUPLE glazed ... so the external LF sounds are greatly reduced.
However ... this seems to have given me a new problem:
The room is now so quiet that WHEN external sounds DO get through (there are always some!) the person being tested is distracted by them, however faint!
I think I preferred the days when a steady burble of outside noise masked general activity around the building.
OK, the test results would be 10dB in error .. but at least the testing went smoothly!
My tests are now more accurcate .. but the testees moan about the smallest extraneous bump or click ... very wearing!
It looks like I'll now need to buy a booth as well .... madness!