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Half Throttle Program

I was in a meeting in Highland Park, TX today about the Half Throttle Program.  The program is an effort to reduce the noise and distress residents are experiencing due to the use of gasoline powered blowers.  The program encourages residents and landscape contractors to voluntarily use gasoline powered blowers at half throttle within 150 feet (50 yards) of homes.  From the data they collected of battery powered blowers, they like to see levels at 64-67 dB at 75 feet away.  They recommend using half power of the Stihl gas-powered blower to achieve 78 dB at 75 feet.  That is very feasible.

We set our goal to 70 dB or less at 50 feet.  Timberline has been practicing low noise levels for quieter neighborhood and didn’t realize we have been exceeding the Half Throttle Program guidelines for some time.  We voluntarily implement the practice to reduce noise levels within 50 yards of homes, 7-9am on weekdays and all day on weekends.

https://timberlinelawnandlandscape.com/about-us/

 

What is the dB vs Perceived Volume?

Keep in mind that noise level and dB are not linear, meaning that 60 dB is not half the noise of 120 dB.  Actually, 3 dB is 50% reduction is SPL (Sound Pressure Level).  I believe this is the actual pressure on the ear.  But it feels (perceived) like 18.77% reduction in volume.  So, it only takes about 9-12 dB to get 50% reduction in volume.  See data from link below.  https://www.acousticalsurfaces.com/soundproofing_tips/noise_reduction.htm

 

Why don’t we use electric blowers?

Electric blowers do not have the same performance as gasoline powered leaf blowers. The limitation comes in the available power of batteries.  Another limitation is in the length of power cord.  And electric blowers aren’t always quieter.  They generate a very high-pitched scream, like a shop vacuum.  You can reduce the noise from the engine but the noise primarily comes from the movement of air.  The reason is that the motor must turn a multi-bladed fan very fast to move any reasonable amount of air and therefore it generates a siren type sound, which is very irritating.  Quiet gasoline powered blowers have a unique fan configuration that prevents this type of sound. There are some electric blowers that are louder, see attached link.

http://leafblowernoise.com/Electric%20blower%20sound.htm

 

What blower should we use?

I do not prefer one brand over the other.  But I have research and selected the Echo PB-760LNT for its low noise quality and performance.  It generates 535 CFM, 214 MPH, at 65 dB.  They claim it’s the most powerful low noise blower.  For good reasons, compare to the commercially popular Stihl BR430 which has 500 CFM, 219 MPH, at 76 dB.  They are both same size engine at 63.3 cc.  The Echo is 11 dB quieter which is about 50% noise volume reduction.  The price difference is about $120 more for the Echo.  Stihl does have a comparable model for low noise, the BR 500.  I don’t know what the price is on that one.  For comparison, the EGO electric leaf blower is rated at 64 dB and outputs 145 MPH.  It gives two ratings of 320 and 600 CFM depending on mode.

 

What is the difference between CFM and MPH?

CFM is used to measure how much volume of air the blower moves.  This is what ceiling fans are rated by.  Higher CFM is good because it can move more (volume).  MPH is use to rate how powerful the wind is, this is what hurricanes are rated by.  Higher MPH is useful because it can move heavier objects, for example wet leave or gravel.