An odd sound I noticed over the weekend. Sitting still, applied brakes. Noticed an odd high pitch "howl" when applying brake lever. Howl might be an overstatement, but it is easy to hear. Let off it would stop, reapply and the sound would reappear. Cannot tell if noise is present at speed. Obviously something relating to ABS, probably pump? The only difference was that that outside temps fairly cool this weekend, I have only owned the bike since May so have not experienced colder weather with the bike. '03 with 40,000 miles. Normal or not?