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ACTIVE NOISE CANCELLATION

Category: Software
Product Number: ADAU1781
Software Version: Version 4.7. Build 0, Rev 1831 4/5/2022

Hi,

I am trying to do active noise cancellation. can i use ADAU1781 for ANC. please suggest best DSP for active noise cancellation.

Thank you

Parents
  • Hello harishsharma,

    The ADAU1787 will be the best choice for ANC . It is specifically designed for it . It has higher sample rate and low latency converters and so on. It is a fast DSP. So it would be the good choice for ANC. You can refer the datasheet of ADAU1787 for more info.

    Regards,

    Harish

  • Hello Harishgowtham,

    Please suggest any other with LFCSP package or any other that is not WLCSP package.

    Thank you

  • Hello Harishsharma,

    Yes, you can connect a microphone directly into the ADAU1787 since it has a PGA on the input with enough gain for most electret microphones. 

    Unfortunately, the ANC applications that these parts were all designed for are for very small headphones and earbuds so the parts are only available in a WLCSP package. The ADAU1772 can do ANC and is available in a LFCSP package but the latency is greater and the processing power is much less than the newer parts. 

    The ADAU1781 you first mentioned is obsolete and the latency is not good enough for high performance  ANC applications. 

    You also asked about the ADAU1467 for ANC. Again, the latency will be too great. The core can run at higher sample rates but the serial ports can only go as fast as 192kHz fs. You need latency from analog in to analog out of less than 10us for good ANC performance. Any DSP with no built in converters has to take the time to shift in the data and shift it out which adds to the latency.  At 192kHz it will take just over 5us to shift in the data. So double that because you have to shift it out. Then add the latency of the ADC and the DAC. Then count a few samples to resync the data and to process it through the core and you will limit how high of a frequency you can cancel. If you are getting rid of rumble or other low frequency noise then you may be able to do it. 

    Dave T

Reply
  • Hello Harishsharma,

    Yes, you can connect a microphone directly into the ADAU1787 since it has a PGA on the input with enough gain for most electret microphones. 

    Unfortunately, the ANC applications that these parts were all designed for are for very small headphones and earbuds so the parts are only available in a WLCSP package. The ADAU1772 can do ANC and is available in a LFCSP package but the latency is greater and the processing power is much less than the newer parts. 

    The ADAU1781 you first mentioned is obsolete and the latency is not good enough for high performance  ANC applications. 

    You also asked about the ADAU1467 for ANC. Again, the latency will be too great. The core can run at higher sample rates but the serial ports can only go as fast as 192kHz fs. You need latency from analog in to analog out of less than 10us for good ANC performance. Any DSP with no built in converters has to take the time to shift in the data and shift it out which adds to the latency.  At 192kHz it will take just over 5us to shift in the data. So double that because you have to shift it out. Then add the latency of the ADC and the DAC. Then count a few samples to resync the data and to process it through the core and you will limit how high of a frequency you can cancel. If you are getting rid of rumble or other low frequency noise then you may be able to do it. 

    Dave T

Children
  • Hello DaveThib,

    I am trying to cut particular frequency band from audio signal. i don't want to use DSP for this task. is there any programmable IC available from Analog Devices to do this task. low pass frequency 2000Hz can be changed in steps of 100Hz or less. specifically designed for audio signals.

    Thank You

  • Hello harishsharma,

    So now you are talking about a very different application, not ANC. If you just require a low pass filter with a certain step size, this is easy to do with pretty much all of our SigmaDSP products. They are all designed for audio. 

    How many steps? 

    What is the range of frequencies? ( This is related to number of steps)

    What is the sampling rate?

    How many channels?

    How steep of a cutoff for the filter?

    How do you need to control this corner frequency? Your user interface?

    Dave T