is the ratio between the peak amplitudes of the main and back lobes expressed in dB

Aspect ratio is the ratio of wingspan to chord (front to back of the wing).

Alternatively it can be found by (span x span)/ (wing area).

I have a 2004 cr85r withe a "15 in the front and a "47 in the back

the front should be wahever the back is. count them on the ring gear then count the pinoin and devide that and it will give you the gear ratio

Divide your rear sprocket into your front sprocket. Like 25x9. 25 divided by 9 = 2.77. so 2.77 to 1 is the drive ratio. If you go with a smaller sprocket like a 24 in the front but still a 9 in the back, you are lowering the gear ratio to 2.66 to 1. So your bike will be slower but easier to pedal.

If you go with a 25 in the front and a 10 in the back, you end up with a 2.5 to 1 ratio.

Don't confuse gear ratio with gear inches, that's a calculation including the wheel and sometimes the circumference of the tire.