Opens in a new tab

AES E-Library

← Back to search

Journal Article

Optimum Use of Noise Reduction in FM Broadcasting

Authors: Dolby, Ray

Journal of the Audio Engineering Society · Volume 21 · Issue 5 · pp. 357–362 · June 1973

Abstract

A well-known problem in FM broadcasting is the excessive high-frequency preemphasis introduced by the 50- or 75-µs time constants now used. With modern program material the preemphasis results in possible overmodulation and the need for high-frequency limiting. If limiting is avoided in order to maintain signal integrity, then operation at an overall decreased level is required. The use of Dolby B-type compression during transmission provides an opportunity to reduce the preemphasis time constant to 25 µs, which permits the midband modulation level to be raised significantly with many types of program material. Listeners with conventional receivers are provided with a compatible signal but with the reception advantages of an increased modulation level. Listeners with 25-µs deemphasis time constants and B-type expanders have the dual advantages of increased level and lower noise.

Details

Publication
Journal of the Audio Engineering Society
Volume
21
Issue
5
Pages
357–362
Publication date
June 6, 1973
Affiliation
Dolby Laboratories, Inc., New York, NY and London (See document for exact affiliation information.)
Type
Journal Article