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ADAU1467 - Suppression of Mechanical Noise and use of two microphones

Hi all,

I want to achieve the effect of active noise cancellation (ANC) for the recognition of the human voice with mechanical noise from machine tools and engines (according to the design of the post attached at the bottom). I use two microphones for the device where the 1st mic is dynamic (main microphone) and the 2nd mic is electret with preamplifier (reference microphone).
- voice transmission;
- suppression of noise received by the main microphone.

I conducted an experiment on EVAL-ADAU1467Z with the provided project and achieved probably some minimal result. Some effect was present but the noise in the vocal range was not suppressed, so the person's voice could not be heard clearly. What can you recommend to solve this situation?

The reference microphone is placed at a distance of 50 cm from the main microphone. Type of noise - mechanical (machine tools, engines, etc.).

Figure1 - Block diagram

Figure 2 - Approximate representation of the complete structure

Figure 3 - Photo (complete design unfortunately does not fit in the photo)

NLMS filter-DT-Edits.dspproj


Artem (Fox108).

  • Hello,

    I looked at your project, you are using an adaptive line enhancer (ALE) method, which works well for suppressing stationary narrowband interference (i.e. tones) from a broadband signal (i.e. speech). If the interference has a broadband component in the same range as the speech it will not be suppressed. You can observe this in the attached modified project, unwanted tones are suppressed but noise is not suppressed.

    NLMS filter-DT-Edits_modified.dspproj

  • I think a possible solution is shown in the attached figure. The noise is present at both the ref mic and main mic and will be removed from the main mic by the NLMS. Note when speech is present you need a voice activity detector (VAD) to freeze the NLMS. VAD can be very tricky, but in this case perhaps when energy level at main mic is above a threshold assume speech is present and freeze the NLMS. Also, this assumes the ref mic does not pick up the speech.

  • I aslo want to acheive ANC using 1467, I have two PDM mics, i want to ask how should I connect to eval kit, is it any GPIO or using 3.5 mm jack to INput

    If with gpio please suggest me which pins should i use for 2 PDM mics

  • Hello Rajbir,

    There won't be any jack here for a digital signal, well SPDIF is there but that's for an optical signal. For PDM mics you can use GPIO pins to bring the signal into the DSP. You can connect four PDM mics.

     Up to four PDM microphones can be connected as audio inputs. Each pair of microphones can share a single data line; therefore, using four PDM microphones requires two GPIO pins. Any multipurpose pin can be used as a microphone data input, with up to two microphones connected to each pin. This configuration is set up using the corresponding MPx_MODE and DMIC_CTRLx registers. A bit clock pin from one of the serial input clock domains (BCLK_INx) or one of the serial output clock domains (BCLK_ OUTx) must be a master clock source, and its output signal must be connected to the PDM microphones to provide them with a clock.

    For MPx and DMIC registers , Please refer the attached screenshots.

    In this SS , You can choose any two GPIO's for four mic (one GPIO for two mic data) and you can choose the master CLK from any of the serial input or output BCLKs .

    In this SS , Please enable the respective GPIO pins as a multipurpose by clicking the drop down menu that I circled .

    For more info, kindly refer page no 77 from the datasheet.

    Kindly reply if you need any clarification.



  • Thank yo so much to the help, but I have the new board and the datasheet is bit old for that, i can't able to find all the pins.

    Could you please send me the updated datasheet

  • I am not able to open the product page of ADAU1467

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    Reference #18.295b2d17.1648535398.25b38aab

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