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BEC Preview: Guidelines for Loudness in Internet Radio

John Kean is a consultant with Cavell Mertz & Associates. He recently participated in a Q&A to preview his upcoming BEC session.

John Kean is a consultant with Cavell Mertz & Associates. He has previously served as senior technologist for NPR Labs. He is a past president of the IEEE Broadcast Symposium and the Washington DC Section of the AES, is a contributing author to the NAB Engineering Handbook, editions 7, 8 and 9, and a recipient of the Association of Public Radio Engineers’ Engineering Achievement Award.

He recently participated in an emailed Q&A to preview his upcoming Broadcast Engineering Conference session.

Radio: Your presentation is titled, �The AES Loudness Guidelines for Internet Audio and What they Mean for Producers, Distributors and Listeners.� Briefly, can you summarize the subject matter of your overall presentation for those who may not be able to see it?

John Kean:The AES Loudness Guidelines represent a major step forward in measuring the audio levels for production and distribution of audio content to consumers over the Internet. The AES Technical Committee was formed early last year to fill a need for audio metrics for Internet audio services. �Despite the extensive development of the Internet to deliver audio by music program services, radio stations and others, no industry guidelines existed to define at what levels, and range of levels, audio should be encoded for listeners. As a result, listeners might change program services in their car, on their smart phone or computer, and hear an entirely different audio level. This has been reported by consumers as an annoyance, and some studies have shown that unexpected shifts in level may lead to listener turn-off-something that programmers want to avoid!

Radio: What are the new AES recommendations regarding the overall technical guidelines for Internet-based audio services?

Kean: In addition to live streams, the guidelines apply to podcasts and progressive file transfer applications, which employ recorded content. Although this involves literally thousands of different audio services, experience has shown that a common measurement of loudness, as perceived by listeners, is practical. The Technical Committee used standards for measurement that were developed in the past decade by the International Telecommunications Union, and where possible, relied on procedures that were developed by the European Broadcasting Union’s PLOUD Committee. We had great confidence in adapting this technology to the Internet because these organizations have successfully tackled audio metrics to deliver content to their listeners via radio and television.�

Radio: Also regarding AES work, can you give us a sneak peek into what type of new �second generation� audio solutions the body is looking into for consumer playback devices? What are the current issues in this subject that need addressing?

Kean:The present guidelines address metrics and policies for encoding digital audio before it is streamed or recorded for distribution over the Internet. This might be thought of as a “single-ended” solution that addresses the average loudness delivered to listeners as well as possible. However, the needs and desires of listeners vary, and certainly their listening environments vary, as well. For example, the same listener in his/her quiet living room might want a very different loudness range (the variation in loudness around the long-term average) than listening in the kitchen, or riding light rail transport. Addressing the average loudness is a step forward, but the next work of the committee will be to employ technology at the listener’s device. Modern playback devices have considerable data processing capability that can be harnessed to optimize the listening experience.

Radio: Drawing from your expertise, what is the future of Internet-based audio services?

Kean:The future of Internet-based audio is bright! It is an all-digital medium with the capacity to deliver audio with enormous high quality and excitement. Developments in improvements in the digital audio codecs, which encode and decode the audio at each end of a link, continue to improve in efficiency and quality. The committee is looking at harnessing the metadata payload of digital audio to add audio metrics at the point of encoding. This could allow the playback devices to know the audio content being sent to intelligently manage loudness range according to their needs and tastes. Then, the audio in a single stream can be optimized for listeners in their quiet listening room, in the car, or on the train-all at the same time! This is Internet audio services in the near future.�

Radio: What do you anticipate will be the most significant technology trend at the 2016 NAB Show?

Kean:If you’ll excuse my bias toward audio services, I think the technology trend will be increased use of digital audio to deliver programming to listeners. This has been going on for more than a decade in radio, and will continue to progress. Internet audio services started more recently but have advanced at an even greater rate in North America. With advances in the encoding and intelligent loudness management, I predict listeners are in for great experience in the next couple of years.