ITU G.729, are used in many telephone networks. G.729 in particular has a final data rate of 8 kbit/s with superb voice quality. G.723 achieves slightly worse quality at data rates of 5.3 and 6.4 kbit/s. Many voice vocoder systems use lower data rates, but below 5 kbit/s voice quality begins to drop rapidly. Several vocoder systems are used in NSA encryption systems: LPC-10, FIPS Pub 137, 2400 bit/s, which uses linear predictive coding Code-excited linear prediction (CELP), 2400 and 4800 bit/s, Federal Standard 1016, used in STU-III Continuously variable slope delta modulation (CVSD), 16 kbit/s, used in wide band encryptors such as the KY-57. Mixed-excitation linear prediction (MELP), MIL STD 3005, 2400 bit/s, used in the Future Narrowband Digital Terminal FNBDT, NSA's 21st century secure telephone. Adaptive Differential Pulse Code Modulation (ADPCM), former ITU-T G.721, 32 kbit/s used in STE secure telephone Modern vocoders that are used in communication equipment and in voice storage devices today are based on the following algorithms: Algebraic code-excited linear prediction (ACELP 4.7–24 kbit/s) Mixed-excitation linear prediction (MELPe 2400, 1200 and 600 bit/s) Multi-band excitation (AMBE 2000 bit/s – 9600 bit/s) Sinusoidal-Pulsed Representation (SPR 600 bit/s – 4800 bit/s) Robust Advanced Low-complexity Waveform Interpolation (RALCWI 2050, 2400 and 2750 bit/s) Tri-Wave Excited Linear Prediction (TWELP 600–9600 bit/s) Noise Robust Vocoder (NRV 300 and 800 bit/s) Vocoders are also currently used in developing psychophysics, linguistics, computational neuroscience and cochlear implant research. Linear prediction-based Since the late 1970s, most non-musical vocoders have been implemented using linear prediction, whereby the target signal's spectral envelope (formant) is estimated by an all-pole IIR filter. In linear prediction coding, the all-pole filter replaces the bandpass filter bank of its predecessor and is used at the encoder to whiten the signal (i.e., flatten the spectrum) and again at the decoder to re-apply the spectral shape of the target speech signal. One advantage of this type of filtering is that the location of the linear predictor's spectral peaks is entirely determined by the target signal, and can be as precise as allowed by the time period to be filtered. This is in contrast with vocoders realized using fixed-width filter banks, where spectral peaks can generally only be determined to be within the scope of a given frequency band. LP filtering also has disadvantages in that signals with a large number of constituent frequencies may exceed the number of frequencies that can be