May 1, 2002 12:00 PM
The new look for BE Radio premiered with the March issue, and your calls, letters and e-mails show that you like what you see. We have reprinted some of your comments here. Thank you to everyone who took the time to tell us what they thought of the new look and layout.
- Chriss Scherer
The magazine looks absolutely fabulous. BE Radio continues to be a leader.
Broadview Hts., OH
Nice new look for BE Radio. The larger type in the table of contents is nice, too. Same with the bold headers at the top of the pages. Makes it easy to flip through and find the section of interest.
director of engineering
Vermont Public Radio
Great new look for a great title. Congratulations. I always study BE Radio when it arrives, and there's not an issue where I don't learn�and learn�and learn.
Robert E. Richer
Crossed Field Antennas Ltd.
I like the new graphic look of BE Radio a lot. And unlike other mags that always claim their content will not change and then does, yours hasn't.
broadcast sales manager
Technet Systems Group
In Reader Feedback in the March 2002 issue, there is a photo of the KFBK Franklin tower. This is quite an unusual arrangement for feeding the uppersection of that tower. It is fed by open wire transmission line, suspended from the side of the tower. I know of no other installation like this and wonder if any other readers know of one.
The KYW/WKYC/WWWE (now WTAM) Franklin tower, built in Cleveland in 1956, was fed by hardline running up the inside of the tower.
I wanted to send a note to say thanks for your publication. It's good to know a magazine of your caliber still remembers those in the small markets.
Our little two-man operation services nearly 20 stations(maybe more) in Missouri-a radio network in the KC area and we also help service another network in Missouri that has a number of stations. Yep, we stay busy.
Anyhow, I enjoy BE Radio and look forward to the next issue. Keep up the good work. I appreciate the fact I don't have to work for Clear Channel, Infinity, or the other big boys to get a free subscription to your magazine.
Broadcast Communications Engineering
I enjoyed the article �Perceptual Audio Encoding� in the February 2002 issue of BE Radio, but I have a few questions about the content. First, while frequency masking and temporal masking are certainly important factors in MPEG encoding, why was sub-audible level masking not mentioned? In MPEG data reduction, one of the most efficient ways to reduce irrelevant data is to remove signals that are below the sensitivity of human hearing.
Second, I'm a bit surprised that 48kHz sampling was never once mentioned in the article. Instead, the article states, �The most common in broadcasting is the use of a 32kHz sampling rate as opposed to 44.1.� I'd like to know where this information comes from. In my experience, the most common codec sampling rate in broadcasting might be 16kHz, as used in the G.722 algorithm. Another choice might be 48kHz, as used in most professional stereo MPEG 2 applications. With 48kHz MPEG 2, especially as used in our enhanced compatible MUSICAM encoding, users benefit from a full 20kHz frequency response, as well as short delay. This mode of operation has been and remains the choice of golden ears worldwide.
Third, the article seems to suggest that 128kb/s transmission rates are the only option. It might be helpful to remind BE Radio readers that higher transmission rates are easily achievable with the right equipment. Then, let's try another listening test.
VP, business development
Corporate Computer Systems Inc., d/b/a MUSICAM USA
Doug Irwin replies:
Of course I did mention that perceptual audio encoding algoriths were in use in both radio broadcasting and production, but being a radio person myself I've become accustomed to not giving any thought to signals above 15kHz, except for 19kHz. A sampling rate of 32kHz is all that is necessary to handle anything transmitted in the FM band.
With the advent of IBOC, the 44.1kHz sampling rate will become commonplace, as will higher audio bandwidth. For over-the-air broadcast applications, 48kHz sampling will not be necessary, at least for the foreseeable future.
Thanks for reading the article and I'm glad you enjoyed it.
I read with interest the article �Perceptual Audio Coding� in the February 2002 issue of BE Radio. I commend Mr Irwin for such a clear and concise article about perceptual coding. With coded audio being used so extensively in the broadcasting world today, this is valuable information for your readers.
I would like to add the following that may also be of interest to readers of BE Radio.
In 1997, the MPEG-2 standard included AAC (Advanced Audio Coding) along with the existing Layer 1, Layer 2, and Layer 3 audio coding standards, adding to the palette of options available to implementers. This new standard truly represents the current state of the art & science of audio coding. It was developed through the combined efforts of a number of the top laboratories and developers in this area, including Fraunhofer, Dolby, Sony, and AT&T. In fact, a number of experts predict that major advancements beyond AAC, for general purpose codecs, are unlikely in the near future.
At this time, AAC codecs for the broadcast market are available from several manufacturers, including Telos Systems. AAC offers the first coding technology to achieve the ITU-R's criteria for �indistinguishable quality� at 128kb/s: To meet this requirement, no test item, out of a battery of difficult items, is permitted to score worse than the �Perceptible but not annoying� rating in controlled tests. AAC is the only codec to date to achieve this difficult criterion at 128kb/s stereo (12.5:1 compression ratio).
AAC's biggest advantage to broadcasters is that it offers them additional �coding headroom� in cases were perceptual coding must be used before, or after, the AAC link. It can also achieve fidelity equivalent to Layer 3 at 66 percent of the bit rate. AAC also offers reduced delay compared to Layer 3.
Speaking of delay, the latest MPEG standard (MPEG-4) adds an important AAC derivative; AAC-LD (Advanced Audio Coding Low Delay). This offers Layer 3 quality with greatly reduced delay. This technology is available now, and offers broadcasters the fidelity they want for live end-to-end interaction, without the uncomfortable difficulties of trying to converse with delay present.
Cleveland, OH 44114