Active noise control on PXI

[radioactive28]

Hi all,

I'm currently trying to implement ANC for cancelling a standing wave using the vanilla LMS algorithm, with the following configuration:

- PXIe-1062Q chassis

- PXI-6733 AO module

- PXIe-4478 AI module

- Labview 8.6

- B&K microphone

- simple loudspeaker and amplifier

Both AO and AI modules are sampling at 10kHz, and I set DAQmx Read to return 250 samples per loop iteration. These 250 samples are then fed to the LMS controller where the filter size is 60 samples.

Basically, it's not working. I've already verified that the algorithm I'm using is correct, but just can't achieve cancellation. Usually, before the controller output "blows up," I hear low frequency pulses of sound (much lower than what I'm trying to cancel) and the output graph waveform shows the low frequency modulation as well.

I'm suspecting that the set-up is simply not processing fast enough for ANC, and the low frequency sound is related to my loop's high latency.

Can anyone comment?

[Nabeloabbasi]

hi i would be better to attach the VI, that will clear ur question

i have sililiar one

using LabVIEW and PXI

[johnsold]

Do the math.  Sample rate = 10000. Number of samples = 250. Minimum time between reads = 25 ms. Maximum possible update rate = 40 Hz.

Are your low frequency pulses at 40 Hz or less?

What is the bandwidth of the noise you are trying to cancel? How much latency can you tolerate?

Lynn

[ALI2020]

actually i have project to cancel noise ( active noise control using loudspeaker ) and my siganl processing is labview and am using labview 2011 
i want to aquire signal from speaker that is connected to signal generator and the paramters of this signal want to send it out to loudspeaker connected to the laptop so it can cancel eachother and no sound detected >>> i have used DAQ to eleminate the delay as i worked before without DAQ and there was delay  >>> now when the signal cames out to the cancelling speaker isnot match with the signal that is genertaed >>>>>i want to make the signal out of phase 180 so that it can cancel >>>>> i hope if u can help me i will apperciate this very very much 
thanks again 

[johnsold]

Duplicate thread.    Please keep the discussion in the linked thread rather than in this old one.

Lynn