The S5A1903X01 implements the voice intelligibility processor (VIP). The VIP is a signal processing algorithm designed to increase the intelligibility of human speech in a high ambient noise environment. Unlike noise cancellation or adaptive speech filtering systems, VIP operates on the speech signal only and is totally independent of the noise. This approach makes speech clearer and easier to understand regardless of the characteristics of the noise source, and eliminates the need for processing of the noise signal. In addition to VIP, the S5A1903X01 includes voice equalizer. The equalizer is composed of four different frequency bands, and each band is controlled between +12dB and -12dB. Thus, it can be used to compensate of speaker characteristics. The Figure 1 shows how the S5A1903X01 interfaces to Vocoder and Codec in cellular phone.