Dynamic Noise Limiter
DNL (Dynamic Noise Limiter) is a noise suppression system for audio recordings introduced by Philips in the 1970s , which, unlike the well-known Dolby method, reduces the impression of noise even in the case of non-specially coded recordings during playback. To achieve this effect, the high frequencies of the signal are attenuated depending on the audio signal strength - the quieter the signal, the higher the attenuation of high frequencies. This procedure means that the noise is only attenuated in quiet passages, since it is largely masked by the useful signal in loud passages.
The DNL method can be found e.g. B. in the 8000 series of cassette recorders from BASF , which were sold in the 1970s. National Semiconductor has further developed the process and offers it in the form of the IC LM1894.
literature
- Gustav Büscher, Alfred Wiegelmann: Little ABC of electroacoustics (= Radio-Praktiker-Bücherei. Vol. 29 / 30a). 6th, completely revised and expanded edition. Franzis, Munich 1972, ISBN 3-7723-0296-3 .
- Helmut Röder, Heinz Ruckriegel, Heinz Häberle: Communication electronics . Radio and television electronics (= electronics. Vol. 3). 5th edition. Verlag Europa-Lehrmittel, Wuppertal 1980, ISBN 3-8085-3225-4 .