Log area ratio

Log area ratios (LAR) can be used to represent reflection coefficients (another form for linear prediction coefficients)^[1] for transmission over a channel.^[2] While not as efficient as line spectral pairs (LSPs), log area ratios are much simpler to compute. Let ${\displaystyle r_{k}}$ be the kth reflection coefficient of a filter, the kth LAR is:^[3]

${\displaystyle A_{k}=\log {1-r_{k} \over 1+r_{k}}}$

Use of Log Area Ratios have now been mostly replaced by Line Spectral Pairs, but older codecs, such as GSM-FR use LARs.