Audio Engineering Society

Chicago Section

Meeting Review, February 28, 2005


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2/28/05 Meeting Highlights
by Jeff Segota

The February 28th meeting of the Chicago Section featured a presentation on the Fundamentals of Broadcast Audio Processing by A.J. Bautista. This was the first of a two-meeting series on current and future practices in broadcast audio, covering the basics in the science and art of processing, primarily for FM. Mr. Bautista holds a B.S. in Electrical Engineering and a B.A. in Communications Studies from University of Iowa, he is a SBE-certified Senior Radio Engineer and has many years experience with several major-market radio stations. About forty people were in attendance, of which about half were members. The presentation generated a great deal of discussion.

 

 

 

The main goal of audio processing for broadcast is to reduce the dynamic range of the program material so can it be heard in environments where the background noise level is high, such as in cars. Also, the competition for listeners has led many stations to make their signal as loud as possible without exceeding the allotted bandwidth. The other purposes of audio processing are to add pre-emphasis for noise reduction, and to generate the baseband composite signal, either mono, stereo, or stereo with subcarriers.

 

All these functions can be performed using a single piece of commercially available equipment, and the block diagram of a well-known processor was shown in order to explain how such a device works. Two stages in particular, the phase scrambler and the FM smart clipper, were noted for their unique affect on the sound. The author brought two commonly used models to see, and one of them was used to process samples of pop and classical music using typical parameter settings for each. This led to discussion of how the program material dictates the Engineer's choice of processing parameters, or "sound" of the broadcast.