BACKGROUND INFO: When you fire a compound bow, the violent explosion of energy causes vibrations in the bow, it's strings, and it's accessories. Those vibrations cause small air pressure changes in the air that our ears perceive as sound/noise. More importantly, game animals hear these noises too, but even more acutely than we do. So stealthy hunters demand their bows be relatively quiet, and bow manufacturers feverishly work to give hunters what they want.
But it's a tough task to accomplish. That's why there are literally hundreds of products on the market that you can ADD to your bow to make it quieter. Some work, some don't. But in the end, your best chance of having a quiet bowhunting rig is to start with a bow that's relatively quiet right out of the box. And in spite of all the industry's hype and harmonic hoopla, each bow seems to ultimately sing it's own unique tune. Some bow designs are quiet, some are not. So which of our test bows will have the softest voice? We're about to find out.
Sound intensity is generally measured in decibels (dB). The decibel scale is a little odd because it's a logarithmic scale rather than a linear scale (like weight or length). If you compare the smallest audible whisper of only 10dB to the roar of a jet engine at 130dB, the jet engine isn't 13 times more powerful, as the usual math might suggest. The jet engine is actually 1,000,000,000,000 times more powerful. That's because each jump of 10dB represents a 10X increase in sound intensity. If you'd like to know more about this topic, click here. But for the purposes of understanding our results, it's worth noting that an 83dB sound is approximately twice as intense at an 80dB sound. So a few decibels make a big difference.
Of course, a compound bow doesn't make a continuous noise, like the hum of a generator or whirling of a fan. The bow's sound will only occur for instant, so we had to use a decibel meter that could measure a PEAK decibel level with a very short sample time. After a bit of research and help from our friends at www.professionalequipment.com, we purchased a new Sound Level Meter for the job.
new Sound Meter is pre-calibrated and includes an NIST certificate,
we're not so concerned about obtaining dB readings as absolute
measurements. We're concerned with leveling the playing field and
accurately comparing the two bows. For the purposes of our test,
the actual dB numbers are essentially arbitrary.
ROUND RESULTS: Bowtech includes some rather snazzy string silencers with their 2004 bows. We found them to be quite effective - just shy of performing as well as the popular String Leeches by Sims Vibration Labs. This might have been a 10/8 round for the Liberty, but we were impressed that the Diablo quieted down nicely once we added the Sims String Leeches, losing out by only a fraction of a dB in our last test. But any way we measured it, the Liberty was the quieter bow. Liberty wins the round 10/9.
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