The top image is the air conditioner mounted near a back corner of my home. It is Carrier model 24AHA424A003. It has a scroll compressor, model ZP20K6E-PFV-130. I measured its output sound using my Android Smartphone. The condenser motor nominal speed is 800 RPM (13.3… Read more
Jet Aircraft Takeoff Acoustics from Ground Measurement
I made a video using my Android Smartphone of this aircraft taking off from SeaTac airport, headed northward. The image above was extracted from the video. The date was July 20, 11:50 AM. This was Delta flight 1172 headed to Fairbanks, Alaska, if my interpretation… Read more
MV Chetzemoka Ferry Acoustics
MV Chetzemoka Ferry Air Vent Pipes I recently rode on the MV Chetzemoka Ferry which was running between Tacoma’s Port Defiance and Vashon Island’s Tahlequah terminal. The ship is powered by a pair of EMD 12-710 diesel engines rated at 3000 hp each at 900… Read more
Matlab Butterworth High Pass Filter, 6th order
Matlab’s built-in function for Butterworth filtering has stability issues. The following code snippet yields an unstable filter. The cutoff frequency is 4 Hz. The sample rate is 20000 Hz. The filter is a high pass, sixth order. fh=4;sr=20000;order=6;Wn=fh/(sr/2);[bb,aa] = butter(order,Wn,’high’);flag = isstable(bb,aa);if(flag==1)fprintf(‘\n filter is stable… Read more
De Havilland Canada DHC-3 Seaplane Acoustics
The aircraft is a De Havilland Canada DHC-3 Otter, Single Engine, Seaplane. It is powered by a Pratt & Whitney R-1340 Wasp, 600 hp, air cooled, radial engine with a propeller hub speed of 2250 rpm (37.5 Hz). This aircraft is used for tours and… Read more
Spring-Action Teeter Totter Natural Frequency
Teeter-Totter, Playground along Riverview Blvd, Kent, Washington State I gave the teeter-totter an initial displacement, without human riders, and recorded the damped sine oscillation with my Android smartphone accelerometer app. The natural frequency was 2.1 Hz with 0.6% damping. The frequency would decrease with riders.… Read more
Duwamish River Wooden Footbridge, Tukwila, Washington State
This rustic bridge is popular with fishermen during the Salmon season from Summer through Fall. The Duwamish supports chinook, coho, chum and steelhead, as well as the more rare sockeye, sea-run cutthroat trout and bull trout. Pink salmon run in the millions every odd-numbered years… Read more
Goodtime III Sound & Vibration
My family and I recently took the Argosy Lock Cruise from Lake Union, through the Hiram M. Chittenden Locks, to the Seattle Waterfront, aboard the Goodtime III. The ship’s main engines are Caterpillar 3408’s coupled with Twin Disc MG514 reduction gears. Auxiliary power is supplied… Read more
2016 Toyota RAV4 Hybrid Natural Frequency
This is my current vehicle. With the car parked, I opened the hatch door and sat down on the cargo compartment floor facing outward with my feet on the ground. I then used my legs to move my gluteus maximus up-and-down a few times while… Read more
Life Fitness 9500HR Treadmill Footfall-Induced Vibration
I recently exercised on the treadmill at Rachel’s Body Shop Gym with an inclination of 3% and a speed of 3.6 mph. I measured the resulting vibration with my Android Smartphone which was mounted against the console screen. My footfall or step frequency was about… Read more