Well they shouldn't.
Western Springs has been used for Speedway for 75 years. For 75 years you have known that living near there means you will hear speedway every Saturday night during the speedway season. If you don't like that don't complain: live somewhere else.
That is not very loud. I went to see HMS Pinafore at The Civic Theatre tonight (it was great) and the "noise level" was over 100 decibels there. How do I know? The person next to me is interested in theatre sound & had a meter. No sign of a council noise police shutting that down.
Stupid residents + Stupid Council = Stupid regulations