Dynamic Noise Limiter

DNL ( Dynamic Noise Limiter) is a well-established in the 1970s by Philips noise reduction system for audio recordings, which unlike the famous Dolby method also reduces the noise impression when not specially encoded programs only during playback. To achieve this effect, the high frequencies are attenuated depending on the signal strength of the audio signal - the quieter signal, the higher the attenuation of high frequencies. This procedure means that only in quiet passages, the noise is muted, since it is largely masked in loud passages from the useful signal.

The DNL method can be found eg in the 8000 tape recorder series from BASF, which were sold in the 1970s. National Semiconductor has developed the technique and provide it in the form of IC LM1894.