Help with class project

Other Hardware Audio
1

I'm trying to design an audio filter using passive components that could be used to remove unwanted frequencies above and below the human hearing bandwidth (20Hz - 20kHz).

I am looking for some design guidelines (since I have no experience with audio engineering).
Does anyone know (or know where I could find) parameters such as:
-What is good attenuation? Where ideally should the -3dB points be located?
-How high should the passband gain be compared to the stopbands?
-What should the ripple be? (if any)

Is there anyone with experience that could help get me good real-world design parameters?

2

Passive components bandpass filter tools
http://sim.okawa-denshi.jp/en/RLCbpkeisan.htm

3

Filters do not remove frequencies they attenuate them. That link will only deal with second order filters and depending on why you want to do this filtering might not be enough.
Higher order filters can be made by cascading second order filters and combining these can give a number of different transfer charastics. The simplest of which is called a Butterworth filter.
Note that inductors for low frequency filters get physically quite big, which is why active filters have been used over the last 50 years.