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Field Report: iZotope ANR-B
I once heard a radio personality say, "You can judge a person's intelligence in opposite proportion to his or her tolerance of noise." This quote stuck with me. As engineers we obsess over noise. It's our job to eliminate it. To parallel the quote above, engineers could say the following: "Allowing noise in a broadcast air chain proportionately insults the intelligence of the listener." Bold statement? Probably, but realistically an engineer should continually strive to keep their audio plants working in pristine sonic condition. When audio chains are left unmaintained we assume our audience to be lazy listeners. We can even drive people away, especially the audiophiles in the audience. In addition, sonically shaping and fine-tuning audio is difficult when a chronic noise floor exists. Some noise however is unavoidable. Various programming material or live feeds can be inherently noisy, or have a constant noise floor. Or worse, HVAC noise is sometimes unavoidable. That's where ANR-B from iZotope comes into play. It's an adaptive realtime noise suppression system and it makes handling noise much easier.
iZotope is a familiar name in software applications for audio professionals. ANR-B however lives in a 1RU space with analog and AES XLR outputs. It is designed for placement in an audio chain that suffers from steady-state and slowly changing noises of all types. 60Hz hum, buzzes and hisses are popular problems. But what happens when a news feed comes in with unbelievable noise from a nearby generator or engine? I recently put ANR-B through a relentless field test. Let's start with the easy stuff.
|Performance at a glance|
Eliminates steady-state noise
Stores several user profiles
AES or analog I/O
Minimal buttons and switches for easy use
Working with the King
I have some digital recordings of Elvis classics. The 1960s tape noise is miserably apparent, especially on "Love Me Tender." I was curious to see how ANR-B handled this situation. Keep in mind that this unit is a noise suppression system, not a noise elimination system. Frankly, the suppression can be cranked up to 100 (on a scale of 0 to 100), and the tape hiss will disappear. However, a tradeoff between no noise and digital artifacting must be considered and ANR-B makes the tradeoff easy to manage. Concerning the Elvis material, the hiss was at least 50 percent suppressed without considerable (if any) degradation to The King's unmistakable voice and guitar. Keep in mind, this was done in real time.
Standing in my basement about 12' from an air-handling unit, I opened a handheld mic and interviewed Hershey, my chocolate lab. In normal circumstances, the air handler would have been a distraction during a news interview. However with marginal use of ANR-B suppression, the air handler virtually disappeared without compromising my voice material. It samples and removes steady-state noises, and if any added hiss or rumble develops over time, it will be dealt with accordingly.
I asked our production director to talk on a handheld mic in a room with servers, HVAC fans, and a rack full of noisy equipment. With ANR-B in line, the noise was effectively eliminated. He even situated himself next to the air conditioner output. What had been unusable audio became perfectly suitable in a live interview situation, for example.
Outside the radio station, I popped the hood on my truck and started it. I again asked our production director for some help. He took the mic and actually stuck his head down near the engine and began talking. I regret not having metered the loudness of the engine, but I can attest that the engine noise was considerable. ANR-B was most impressive during this test. The suppression level was manually raised to 80 and the tradeoff between noise reduction and artifacting was superb. Virtually no artifacting and the truck engine was nearly gone.
In each of these tests, a trial-and-error method was used to test the adapt and train modes on each audio channel. Adapt mode is optimized for speech. ANR-B continually diagnoses the noise and speech characteristics and recognizes the difference between the two. This allows for noise attenuation without compromising the dialog. Adapt mode also adjusts for changes to steady-state noise sources over time. If HVAC rumble gets louder and quieter, ANR-B will adjust.
Pressing the train button quickly takes a snapshot of the actual noise. This feature is best used in manual mode (adapt mode off) and it defines the noise for ANR-B to reduce. Training and adapting can be done simultaneously and can be done independently on each input channel.
-- continued on page 2
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