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E: N1 :: I P-41 E E
HIGH TECH MADE EASY
January 25, 2022
Natural State Concrete Supply
Attn: Brad Suen
3707 Jack Mann Road
Little Rock, AR. 72210
17200 Chenal Parkway Suite 300-351
Little Rock, AR 72223
501,258.1480
RE: Sound analysis of your concrete plant operation / sound containment at the new facility /
statement of work and results
Dear Mr. Suen
Based on our conversations, on -site visits and sound measurements at your current and future
facility, we are pleased to submit this statement of work and sound analysis. It is my
understanding that your request to rezone your property for a concrete plant has already been
approved by the City of Little Rock Planning commission and has Staffs approval.
I am very pleased that you plan to add even more sound containment and aesthetics that may
be necessary. To me, this shows that you have a great respect for the City of Little Rock Board
of Directors and neighboring property owners. I also understand that your new facility will have
new, state of the art equipment which is considerably quieter in operation than your present
equipment.
Your new plant operation contains approx. 20.71 acres of land. Your proposal to the City of
Little Rock is for only 7.44 acres of land to actually be used in your operation. This leaves
approx. 13.27 acres of land (ALMOST HALF) platted as a natural vegetation, sound and
greenspace buffer.
Special note: Upon examining your building site, I noticed NO other business in the park to
have ANY sound containment fence, panel or vegetation wall in place. The only fences I noticed
were chain link fences for security. Businesses such as:
AHTD (Arkansas Highway and Transportation Dept) Grounds maintenance division. Lots
of heavy equipment was noticed which will make considerable noise.
AR DOT (Arkansas Department of Transportation) District 6 Headquarters. Another
source of noise in the area.
RL Carriers Trucking Company. I observed the operation of this trucking company on
several site visits. A minimum of 20 Tractors (18 wheelers) and an average of 40 trailers
were observed at all times. I anticipate a minimum of 50 to 60 18 wheelers may be
docking and undocking trailers at peak times of operation in the morning and evening.
This operation will make considerable noise and the only fence in place was a chain link
fence for security.
Nick Ruffin Excavation. I have done business with this company in the past and know
firsthand that they operate dump trucks, 18 wheelers, bulldozers and backhoes. This
equipment loading and unloading from their site will make considerable noise.
SUMMARY OF RESULTS / OBSERVATIONS / FINDINGS RECOMMENDATUIONS:
A. Sound containment using Sound barrier walls.
I want to first give credit to the City of Little Rock Board of directors and especially to
Director B.J. Wyrick for her input and suggestions regarding Sound Barrier walls. On a
site visit, I noticed that the sound walls around the Fed Ex facility Director Wyrick
mentioned are only installed in the area between the adjacent residential area and
partially (I estimate 25%) around the back. It's with this success story and the laws of
physics, I make the following suggestion:
Move your material storage area to the south most internal building line instead of its
current location. This accomplishes two things. 1st, it moves the concrete wash area
which can produce more sound to another area of your property away from the current
residential area. 2nd, the back side of this storage area is constructed out of 2' x 2' x 4'
solid concrete blocks. I suggest the height of the outside walls of this storage area to be
a minimum of 8' in height, preferably 12' in height. A 12' high wall will provide 50%
more sound containment than an 8' high wall. The sound blocking factor of the fence
around FedEx's distribution center block an average of 15-20 decibels of sound. A 2'
thick solid concrete block wall will block almost 100% of any sound behind it. The only
sounds that can be transmitted through 2' thick concrete blocks are subharmonic
frequencies caused by things such as a locomotive, subway and an earthquake. This type
of sound containment fence has roughly 400% greater sound containment than the
fence found at the FedEx distribution center.
I suggest extending the concrete block fence (Starting from the SW corner of the
material storage area) at least 210' to the East and at least 175' to the North. I don't
suggest extending the fence more than is needed to block sound waves from entering
the residential area as it would produce diminishing returns and is very expensive.
suggest enhancing the natural vegetation buffer more if necessary. I do understand that
undue expenses to a new business like this can produce a financial hardship which may
not be overcome. I'm sure the City of Little Rock and your workforce does not need
another failed business due to start up costs being too high.
B. Natural vegetation and greenspace buffer areas
I do not know what has been brought up previously regarding these areas as they relate
to sound containment, but much should be said. Technically speaking, the area of a
surface around a point sound source increases with the square of the distance from the
source. This means that the same sound energy from the source is distributed over a
larger area and the energy intensity reduces with the square of the distance from the
source. This is called the "Inverse Square Law". I will further explain:
For every doubling of distance from the source of the sound, the sound level decreases
by 6 decibels (which is significant). This also considers an area relatively flat and no
vegetation. Your vegetation buffer is fully wooded and contains natural evergreen and
deciduous trees along with native grasses to the area_ This vegetation will further block
sound to neighboring properties, Natural vegetation such as your existing trees, bamboo
and evergreen shrubs are highly desirable sound wall materials because they provide
excellent sound barriers and are much more pleasing to the eye than most traditional
man-made sound walls.
I recorded the sound frequency and levels of your existing operation. To include;
concrete truck loading, cleaning, loading of materials, mixing concrete and general
vehicle traffic onsite. Considerable time was spent at the new site playing back this
recording and measuring sound levels at your property line. The results are as follows:
(West property line)
This natural vegetation buffer is 570' in depth. This is almost twice the length of two
football fields!! We measured a sound drop of 39 decibels minimum during our tests
along this west property line. This is without any sound barrier walls in place. With a
sound barrier wall in place along the area where residential properties may be located,
the sound drop should be in excess of 60 decibels.
(North property line)
The North property line natural vegetation buffer is 120' in depth. There is also a 30'
utility access easement along the north property line. We measured a sound drop of 26
decibels minimum during our tests along this property line. According to the plans I
have and spending time on the property, I saw no residential areas along the north
property line.
(South property line)
The natural vegetation buffer is 75' deep along this portion of your property. This line is
heavily wooded and a 20 decibel drop in sound was measured. The 2' thick concrete
block sound wail will be constructed along the inside buffer line to the South. I suggest
installing the Silent Protector sound wall where needed to extend where residential
homes may be present.
(East property line)
The east property line also has a 120' natural vegetation buffer planned. There is also a
large emergency access route (per state fire code) platted along with ingress and egress
to the site. The east side of your operation includes quiet areas such as the sales and
administration office for your business. Only 1 residential home was noticed during our
tests. A minimum of 25 decibel sound drop was noted along this property line.
SOUND MEASUREMENTS AT YOUR CURRENT FACILITY:
Concrete plant at rest. Meaning no trucking or mixing activity. From my
observations, this is the state of the plant most of the time.
72.4 decibels
- Concrete truck at idle.
81.0 decibels
- Concrete truck, engine full speed.
86.2 decibels
- Blowing out (cleaning) of the concrete truck.
82.0 decibels
- Dump truck unloading gravel.
83.2 decibels
- Loading material (sand and rock) bins onto the conveyor belt
85.7 decibels
- Loading a truck with concrete at the mixing plant (highest level of
Sound in your entire operation)
90.3 decibels
TEST EQUIPMENT USED:
- Triplett PRO-3550 Sound pressure level (spl) meter. Professional series, meets ANSI 51.4
(type 2) and IE 651 (type 2) Industrial standards-
- Fender Passport P-250 Professional series PA/Sound system capable of re-creating
sound pressure levels in excess of 130dB.
- Olympus UN-7200 Digital recorder for accurate recording and reproduction.
- Audio Control DM-RTA1 Professional Spectrum Sound analyzer with HP Core i7
computer for engineering, evaluation and sound measuring.
SOUND ENGINEERING a DBA of UNLEASHED INNOVATIONS, INC. QUALIFICATIONS
- incorporated in Arkansas, December 1997
- Arkansas Better Business Bureau - A plus rating
- Licensed, # BL16768/2777
- Insured by State Farm Commercial
- Bonded by Western Surety Company
- Ownership has over 42 years' experience in Electronic / Audio Engineering, design,
testing and manufacturing.
- Owner is also an Arkansas Licensed Real Estate Broker. License # EB 00059035
Wayne "OZ" Richie, Chairman/CEO
Sound Engineering