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.

NOISE TEST:  Although our 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. 

So to setup our test, our shooter got in position and we chalk-outlined his footprints - to ensure he would maintain the same position and stance throughout the tests.  We then mounted our new SLM on a tri-pod and positioned the meter's microphone to the bow's left side, exactly 1 meter from the center of the test bow's riser.  The position of our shooter and the position of our meter remained constant throughout our test.  Also, the target was placed 40+ yards away, to ensure our peak dB readings were NOT that of the arrows impacting the target. 

Although ambient noise has an almost negligible effect on a peak dB measurement (particularly when the ambient noise is much lower than the sound being measured) we did measure the ambient noise in the room - which varied from only 40.5-40.9dB during the test.

Each test bow was setup for the same draw length, draw weight, and let-off.  On each bow we installed a NAP Quiktune 800 arrow rest and fork tamers on the rest prongs.  We shot all tests with the same set of arrows (Carbon Express 6075's w/4" Vanes).  Three tests were conducted:  1st - just as the bows came from the factory,  2nd - both with naked strings (no silencers), 3rd - both bows with a set of 4 Sims String Leeches installed (2 in string, 2 in buss cable).

Each noise was sampled 12 times and recorded (below).  The high and low readings were dropped, and the remaining 10 readings were averaged for a final dB rating.  Note that our readings indicate the PEAK sound made by the bow - even if it was only for an instant.  We did not test to see how long the sounds were present - only how loud.  Results are as follows........   

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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SCORECARD:

         
          ON TO ROUND #4
          RING THE BELL  -------_>