When swinging my racquets around, I noticed that my Tour 90 makes a lower frequency sound (?) than my Yonex RD Ti-50 racquet. Infact the Yonex makes a very high pitched sound. The weird thing is, the Yonex weighs more (I added lots of tape too) than the Tour 90. It is also more head heavy. Racquet head speed is definitely not an issue- no matter how slow or fast, Yonex always makes a higher pitched noise than the Tour 90. What could be causing this difference? Is it material the racquets are made up of? On a side note, the sounds that the Tour 90 make when it rips through the air is much more convincing than the Yonex (toy-like in comparison)! So, anyone else notice anything similar??