In the CD-I and CD-ROM XA compact disc formats, a method of recording audio that offers fidelity sufficient for speech but that is highly compressed compared with full-fidelity audio; level C uses 4-bit sampling at 18.9 khz for an effective bandwidth of 8.5 khz; level C mono requires 1 out of every 16 sectors on the disc, while stereo requires 1 in 8.