When measurements started to be used in reviews of consumer equipment in the late 1960s it became apparent that they did not always correlate with what was heard. In particular, the introduction of Dolby B noise-reduction on cassette recorders was found to make them sound a full 10dB less noisy, yet they did not measure 10dB better. Various new methods were then devised, including one which used a harsher weighting filter and a quasi-peak rectifier, defined as part of the German DIN45 500 ‘Hi Fi’ standard. This standard, no longer in use, attempted to lay down minimum performance requirements in all areas for ‘High Fidelity’ reproduction.