2006 V50 1.8 petrol Engine noise at 3500 revs

[jms700]

Hello,
I recently purchased a 2006, 1.8 V50 with 40k miles on it.

In every gear, between 3500 and 3600 revs the engine noise is noticeably different and sounds similar to a VTEC engine as it engages however with no change in power.

The garage i purchased it from claims it is normal resonance in the engine and is to be expected in all V50's.
can any one confirm this or advise me on what to do ?

Thanks