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Going green


Contrary to your unpopular disbelief, consumers can and do make informed, environmentally conscious decisions every day. Your analogy: “that's like saying people buy cars based on how long they can go between oil changes,” in the June editorial is completely stupid. Of course people don't make decisions based upon oil changes, but they do make car-buying decisions based upon fuel efficiency, evidenced by the rise in the popularity of hybrid and E85 autos, and people dumping their gas-hogging SUVs for more fuel-efficient models. I would even speculate the last time the Dick household purchased a vehicle, fuel economy was at the forefront of the buying decision.

So what is so wrong with labeling more consumer devices with energy efficiency information? Refrigerator, freezer, washer and dryer, and other appliance manufacturers have published this information for years, and consumers do pay attention and make decisions based on this information.

You have my permission to print this in your magazine, although it's doubtful it will make it out of your recycling bin … you do recycle?
Lee McKenna

Audio peaks


I work for a TV and film production facility. We master on Panasonic DVCPRO HD and Sony Digital Betacam. Recently, clients have demanded louder levels, and our audio levels have been creeping up. I used to keep the peaks on the Digital Betacam meters at no more than -10dB (the reference tone being at -20dB). I thought this was some kind of standard. Now we are way up there, peaking at -4dB and compressing so as not to go over -4dB. It's pretty squashed.

Can you point me to any guidelines so I can explain why this is too much?
Joe Renna

Robert Fritts, audio mixer, Henninger Digital Audio, responds:

I'm not going to say that audio peaks above -10dBFS are a standard among all broadcast facilities, but it is a common practice throughout many broadcasters. Transient audio peaks must not exceed +10dB above reference tone when measured on an audio peak meter with the ballistics set to 0ms rise, 200ms fall. The NTSC reference tone should be set to -20dBFS. The problem with transient audio peaks reaching such high levels is that they may be clipped by the transmission limiters in the broadcasting facility.

For years, mixers have used the VU scale to give an indication of the average audio level, but this method of measurement does not accurately show the true transient audio peaks. So the true peak audio meter is used to measure and ensure the mixers that their audio peaks fit into the allotted space for transmission.

Every mixer has been in a situation where the producer asks for the mix to be louder. This is when the mixer needs to apply the right amount of compression and limiting to control such high levels. It is also important to keep a good sense of dynamic range for a good sounding mix.

A new method of audio measurement — called dial norm — is finding its way into mix rooms and broadcast facilities. Dial norm measures dialogue (human speech) and its overall volume over an entire program's length. Dolby developed such a product called the LM100. The device uses an algorithm to isolate human speech, measuring its volume over time and producing a dialogue level for a program.

The LM100 provides a true measurement of the overall loudness, but it does not determine whether a mix is good or even-balanced. VU and peak metering methods, along with the LM100, can give the mixer a better representation of the overall mix and how it best can fit into a safe range for broadcast transmission.

These tools are useful, but in the end, it's the critical listening of one's ear that determines the validity of a mix.

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