With all of the recent brouhaha over the "noise" of the proposed Palouse skatepark I'd like to provide some science that shows that the complaints are baseless.

So, close your eyes for a second and imagine that Metallica (circa 1985-95 when they were good) has decided to play a full-on arena style show at the Palouse skatepark amphitheater. Don't cheer to loudly, just imagine. We're going to calculate what the direct noise would be at the complainants front door…not even inside their house where it would be even quieter. Then we'll look at something a bit more realistic, but still a worst case scenario. Lets see what happens shall we…follow me to my science laboratory deep within the bowels of the Palouse hills! Buahahaha!!!

Ok! Everything here is out in the open, it's all based on a freely available interactive webpage who's calculations are based on ISO standards for industrial noise mitigation. (As an indication of how out in the open this is, I just changed the pictures and text to reflect that I screwed up and used feet instead of meters, but the tool uses meters…the correction ads some noise, but not as much as you'd think). You can play around with the numbers yourself and see how it works out for you. The only thing I won't do is post a google map, because I respect the privacy of those making the complaints. You'll have to trust me that the measurements I made go from the center of the amphitheater stage to the front door of the person who has complained that the noise would be too great to allow the skatepark amphitheater to be built.

The skatepark location will be along Whitman street in Palouse, with the amphitheater situated at the corner of Whitman and Hall streets. The back of the amphitheater abuts a dirt/grass cutbank that is ~105 feet from the front porch of the people who are objecting to the possible noise, beyond that cutback the hill slopes upward slightly more for an additional 423 feet. The whole horizontal distance is about 1 and 3/4 football fields. The distance upwards over this embankment and the rest of the gently sloping hill is 36.4 feet. Additionally, there is a two story house (lets say 20 feet, since we don't know how high the roof really is above this) in the direct line, several one story houses along the path as well, and two banks of trees that are taller than the houses, but I will leave the trees out of my calculations since they aren't a hard barrier.

So…Metallica is playing downtown. Grab your decibel meter and go rock out…just bring that meter back intact ok!! Turns out an accepted range for an arena concert is 135-145 dB, holy cr*p that's loud!! That's 10 BILLION times louder than absolute quiet and 10 Million times louder than a library at 40 dB!! So, how loud does it sound at the doorstep of the person who is worried about noise 1 and 3/4 football fields away and 36.4 feet up? Turns out we can figure this out!

We will use this interactive calculation tool to figure it out. The distance to the hill from the center of the bandstand is  about 105 feet in the direction of the front porch of our persons house, so we set our barrier 105 feet from the sound source. We'll assume the hill, plus the houses is one large barrier, which is fine since the front porch is lower than the top of the barrier anyway. So, 36.4 feet plus 20 feet for the two story house equals a barrier of 54.6 feet. The distance from the barrier to the reciever is 423 feet (assuming the majority of the barrier is at 105 feet (although changing this doesn't change much anyway we could move it closer to the house). The porch is at the top of the hill, so we set the receiver at 36.4 feet above the source. We set the ground effect on the "soft" setting since other than a sidewalk and a street the hill is grass or trees.

Now, we will use 20Hz for the sound frequency since low frequencies travel the furthest and have the most power, and because we know that heavy metal is so good when the bass is cranked and the drummer is using double kick drums! So this is a worst case scenario, except that it's actually a best case scenario because vintage Metallica rocks! Most of the sound of a band is well above this and would decay much faster with distance. So, what do we get?
Turns out that the direct sound from Metallica playing an arena show downtown is surprisingly low at their front door, 80.6 db, which is 1,00 times less than rocking out in front of the speakers and about the same noise level as a prop plane flying 1,000 feet overhead (can anybody say crop-dusters?). After 8 full hours this could cause hearing damage. Going indoors cuts that down 33 dB or so, which is a touch louder than being in a quiet suburb. Now…granted…nobody buys a house so they can have airplanes going over for three to four hours. So, if Metallica plays a show in Palouse I will definitely commiserate with them over the noise. But, until then, lets look at something more reasonable shall we?

The amphitheater supposedly seats around 80 people. You couldn't possibly put an arena speaker system there, or power one (sorry, I know you were clinging to that last hope that Metallica might come, sorry). But, manufacturers rate their systems based on the size of the audience they can project sound too. So, lets find a system that would work for an 80 seat amphitheater.

 This PA system, the Technomad iPA1, is quite a bit bigger than what is needed for a show this size, the manufacturer lists it as suitable for an audience of 200 plus. So, again, this is definitely a worst-case noise scenario…just not as soul-crushingly loud as Metallica would have been if they got back together, got younger, and shredded Eastern Washington. The manufacturer lists it's peak output at 116 dB, which is an overestimate of the total power since speakers can't run at their peak for long before they blow…but again this is supposed to be worst case. So, if we put noise level into the calculator as our sound source, keeping everything else the same as before, what do we get?
Hmmm…51.6 dB…10 Thousand times quieter than Metallica and 1000 times quieter than an overhead crop-duster…at least according to this noise comparison sheet published by Purdue University. That is equal to the sound of a quiet suburb, or a normal household conversation! If our subjects step inside, even if their walls are cheap, uninsulated 2X4 this would subtract 33dB, leaving them with the sound of rustling leaves! Remember, this is the worst case scenario in every respect.

So, if Metallica comes to play the proposed Palouse Skatepark amphitheater I will support the family who is worried about noise complaints…but only for as long as it takes me to pass their house on the way to the concert. And, if we take into account reflected sound these numbers will go up, but reflected sound is highly reduced in volume already. So…for any reasonable, wort-case scenario of how much noise they need to put up with if the skatepark is built and used for outdoor concerts…I'm sorry, but I have no sympathy for their concerns. The science of it just doesn't bear out that they will be harmed in any way no matter how many concerts might get held there each year, unless a trip to the library or to go birding is also something that hurts their ears.