Sound problems - This is our side of the story

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Our first units were VERY noisey!  We admit!

Tank on at Larrys AFTER sound work!

As many close to me know, I'm a bit prolific (read: verbose) when it comes to the written word.  I tend to over-explain until peoples' eye's roll into the back of their heads!

Recently, we discovered the hard way that the safety and comfort of the users of our products are just as important as the quality of what we build.  What I'd like to discuss is our answer to rumors that our machine is too loud to use.

I think before I begin discussing how we resolved this issue - I want to take full responsibility for the problem in the first place! You see, I'm hearing impaired.  (And no, I didn't get this way from the tanks! LOL)  I've completely lost hearing in my right ear, and have 80% loss on the left.  Now, that is important because I hope you believe me when I say that had I known how loud our units were, I would have done something about it!

We've been testing our units in different places - garages, workshops, basements - all the while concerned about the function of the unit first and foremost.  There have been comments along the way - like 'Wow - that's loud' but it had always been as a secondary comment to 'Wow - that's amazing!'.  So there has been no measurements of the sound levels surrounding our tanks from the very beginning simply due to the fact I couldn't hear it, and no one complained loud enough! (Pun intended!)wink

Recently, one of our best supporters - Larry's Pro Shop inside Kingpins Portland - received their Sonic Revivify Series I.  We were excited and so were they!  After delivering and setting the unit up in the shop we left, giddy with excitement for them.  That feeling was short lived.  The very next day, I received an email from Larry himself saying 'can you please come take this unit out of here - it is too loud.'

Needless to say I was shocked; surprised as well.  I headed to the local tool store and bought a sensitive sound level measuring device called a decibel meter, then headed to Larry's to try and get a handle on what was going on.  When I arrived, the unit was turned off and unplugged.  Marilu was there and she described that the unit was actually painful and she couldn't handle working near the unit.

** To describe her work area is important here.  I believe it is like many or even most work areas in the pro shops I've seen - Full of machines and equipment, no empty surfaces really - and small.  I suspect it is about 9' x 15' in size.  Our tank, which ousted the Jayhawk "Detox" unit, was located about 12" off the floor in a metal rack near one corner of this space.  The doorway to the counter/display area was right next to this.  **

I asked Marilu if I could run the machine for some quick tests - and she agreed.  So I whipped out my decibel meter and stood about 2' away - and the unit clocked at a whopping 113dB!  The funny thing was that as everyone winced, I didn't hear a thing!  A quick aside, measuring the vacuum that Marilu uses we got a reading of 102dB and we all know how loud a vacuum sounds.

Now for some perspective - A normal environment is around 50-65dB.  This is like "talking in a room" or "cooking in your kitchen" sound levels, for example.  Another example for reference, an alarm clock going off is on average about 85dB. And for perspective, a rock concert is commonly measured at 120dB!  I will also add that there are health statements about how LONG a person should be exposed to noise safely as well.  The safe noise chart published here suggests that 85dB is safe for an 8 hour period.  At 112dB, you should limit exposure to 1 minute!  Oh my.

Let me also add some further information about sound - as not all sounds are the same, obviously.  Sounds come at us in many frequencies.  The sound of someone walking is like a bass drum, while the sound of an electric toothbrush is more like a cymbal of a drum set.  Regardless of the amplitude of the sound, the frequency of the sound is also a part of this picture.  Sound level (amplitude) is the volume of sound, measured in decibels.  And sound level is a measurement of all sound volume, regardless of the sounds' frequencies.

** Generally speaking, for cleaning purposes it is common to use one of three frequencies for ultrasonic transducers.  They are all above the range of human hearing - 25 kHz, 28 kHz, and 40 kHz.  These frequencies, while they can NOT be heard, can sometimes be felt! **

**A little science here, when a sound wave passes through a dense material, a 'sub-wave' form is generated called "a 3rd harmonic".  While this is a generalization, for the purposes of this writing it is enough. **

My hearing loss is severe, and frequencies above 5 kHz are outside of my hearing range.  Our tanks use a 28 kHz frequency for the ultrasonic transducers.  Regardless of the level or how loud a particular sound, I simply can't hear these frequencies nor can I hear the 3rd harmonic at 9 kHz!  My loss is abnormal, but more perspective here:  Young children can normally hear from 60 Hz to 24000 Hz. (we write that as "24 kHz").  This amazing hearing diminishes as children age to teens.  By then, MOST teens and young adults no longer hear above 18 kHz.  And as we age, this top-most frequency continues to decline. Such is the power of time.

Back to our problem now - so we had now established that our tank is unquestionably loud.  While I personally couldn't hear it, the sound decibel meter isn't lying, without a doubt it was loud!  So, the UBP field engineer - Fred Logue and I removed the unit and headed back to the lab.  We offered Larry his Detox unit back, but he didn't want it and said he believed we would get our product under control. 

I'll minimize the story a bit here, but over a period of 10-14 days, we acquired and tested 7 different sound DAMPENING materials.  Sound PROOFING is not possible in this case, but I digress.  Our sales engineer, Kevin Johnson, did a fantastic job with a material called Fortiflash.   (Click here for a posting on our website about it.) Each of the materials was applied or installed per the manufacturer's instructions.  We would cut the material and fit it into all the panels to give as much coverage as we could possible get.  All the while, we were taking measurements of the decibel lebels from each side, and the top of the unit.  Our results were excellent, but still not acceptable - our target was 85dB measured at 5 feet. 

** This target number was taken from the OSHA website for noise safety in a work environment. **

Products that were expensive and touted as being the best ended up being horrible for our needs!  Recall the earlier notes about frequencies - our tanks make noise at a VERY high frequency, which is further complicated by 'the 3rd harmonic'.  We knew we needed to reduce the overall decibel level, and in order to do so, we needed materials that targeted the high frequencies of our tank.  Owens Corning 703, for example, may be useful for room noise but for higher frequencies it was nearly useless.  What we DID learn was that fiberboard made the best impact! 
Further, we knew that ultrasonic transducers are in simple terms just speakers and speakers MAKE sound.  If you sat in front of a 600 watt speaker, obviously it would be loud!  Well, that's exactly what is going on here as our units utilize a whopping 600 watts of ultrasonic power!  (That is 6x the power of a Detox, by the way.  And for reference, in our competitive analysis work, the Detox measures at 92dB FYI).

I communicated with some physicists about sound and how to get this problem further under control. 
A review of the POWER being used was done, and we learned that there was a much better way to configure our array of 'speakers' so that we got a better cleaning but used less power!  (Less power = less sound level)  We were shown that the waveform interactions were more effective when using a much more precise and effective pattern, and that by having the transducers mounted offset from each other a specific distance, the waveforms would work together, instead of crossing through each other!  So one of the most effective steps we could take was to REDUCE the amount of transducers by 25% (to 450 watts) and implement this specific pattern - gaining an overall ultrasonic cleaning improvement of 45%!!!!  Science is so cool!

And we didn't stop there: 

    • We studied our lid design and made improvements to it. 
    • On the seal of the lid we added anti-vibration rubber.
    • We increased the lid thickness to hold sound dampening material. 
    • We added a sound dampening material to the tank walls, separately from the outer wall work we had done. 
    • We've replaced the air flow fan that cools our electronics with a ball bearing 'ultra-quiet' fan.  (This was adding to the overall din as well).
    • We've added rubber vibration gaskets to all panel and base mount points.

In the end, we successfully got our sound levels to 89dB when measured at 1 foot.  Since the normal worker is 5' or more away, sound levels drop to a safe level of 85dB at this point!  No hearing protection is needed!  Problem SOLVED.

Now, all units being manufactured at our factory are now being built with these sound dampening materials and improvements that meet our engineering specifications.  We have retrofit all units in stock and can now stand next to our units without discomfort and so can you!!! 

Thanks for reading.

Jim Shimota

Lead Engineer

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