Acoustic interaction measurement

[lewisFeng]

I need measuring two buzzer working on 40Hz to verify the interaction to the circuit and SPL.
Below is my test schematic figure, I planed to use the free version of TrueRTA to measure the SPL, do any suggestion?
should I prepare rheostat or variometer or varicapacitance to measure the impedance or simply calculate it from the difference with theory output of SPL?

 

[Strong]

Lewis,
The setup should be OK for relative (uncalibrated) SPL measurements. Many internal sound cards have low frequency response roll-off starting about 100-Hz, but again for relative dB changes that should be OK with enough response at 40-Hz. If both speakes have same electrical sounrce, then I assume you are trying to measure constructive/destructive interference (phasing) with the two speakers. Note that 40-Hz is low frequency audio, and the sound wavelength in air is about 27-ft (8.2-m)! This would have a significant effect on the microphone and speaker spacings.

Walt

 

[lewisFeng]

Yes, I already have the mathematic inductive field interaction model. But the buzzer is outsourcing item, the electrical and mechanical parameter is very hard to calculate or simulate.I want to figure it out by relative test method.I thind it's no problem to view the microphone as a nearfield probe in 40Hz

 

[Strong]

Lewis,
You might want a more capable sound program to measure electrical and SPL properties. Take a look at ARTA along with application examples:

http://www.artalabs.hr/

Walt