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Creating 8 different waves with phase lag

Hi,

I am trying to generate 8 different sound waves to 8 loudspeakers from the attached VI. These loudspeakers are located around an annular tube. What I am trying to do is, add a phase lag to each loudspeaker and try to spin the soundwaves. So, I send a sine wave to the first loudspeaker. Then I add a phase lag to the sine wave of the second loudspeaker and keep increasing this phase lag for subsequent loudspeakers. Hence, I'll need 8 different signals.

However, my problem is, I only have 4 AO channels on my DAQ device (PCI 6229) therefore I can't generate 8 different signals. I could split these 4 signals using the hardware and also invert them, but I don't know how I could generate the waves such that they have a phase lag I need. Is there any way to do this?

Thanks.
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Hi Imperial-Aero,

What you are trying to do is going to be quite tricky because you need to have an array size of waveforms equal to the number of physical channels which you are emitting on. therefore, without more AO channels, you cannot do what you require in software.

However, there is one possibility: If you have the speakers connected by 2 to each channel, you could please a low pass filter on one of the speaker connections and hence induce a phase delay in the hardware.

How does this sound?

Rob
Rob L

NI Applications Engineer

UK & Ireland


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