/////////////////////////////////////////////////////////////// Elliptic                                                ////                                                         //// Elliptic implements cascaded IIR filters and a built-in //// elliptical filter design. It is capable of low-pass,    //// high-pass, or bandpass filtering with very steep        //// slopes.                                                 ////                                                         //// The atten determines how much of the signal is          //// attenuated outside the passband.                        ////                                                         //// Elliptic filters come with a trade-off for their steep  //// slopes: they have a certain amount of ripple outside    //// the passbands. A very small ripple (0.1 or 0.2 dB)      //// produces very little ringing, whereas a large ripple    //// (eg. 20 dB) produces a very strong harmonic ring.       ////                                                         //// The filter design algorithm sometimes can't fulfill the //// design criteria -- a particular combination of cutoff   //// frequencies, ripple, and attenuation. If that happens,  //// the user is warned that the filter is not initialized,  //// and the filter is bypassed. This may happen, for        //// instance, if you ask for a very steep attenuation with  //// very low ripple.                                        /////////////////////////////////////////////////////////////// // Settings//// atten (float): filter attenuation in dB. Default 90.0// ripple (float): filter ripple in dB. Default 0.2// bypass (int): switch bypass on or off. Default 0//// Before using the filter, you must initialize it as a// low-pass (lpf), high-pass (hpf), or band-pass filter and// designate the passband and stopband frequencies.//// lpf (passband Hz, stopband Hz): create a low-pass filter// hpf (stopband Hz, passband Hz): create a high-pass filter//// bpf (lower passband, upper passband, stopband)://   (usually these parameters are ascending values.)// Noise n => Elliptic ell => dac;0.1 => n.gain; 80 => ell.atten; // 80 dB attenuation10 => ell.ripple; // 10 dB ripple will cause ringing ell.bpf(500,600,650); // create band-pass filter which                      // passes the range 500-600 Hz                      // unattenuated, then slopes from                      // 600-650 Hz (and 450-500 Hz) true => ell.bypass; // bypass filter2::second => now; false => ell.bypass; // activate filterminute => now;