Noise from microphone with VS1063A

Writing software that inputs and/or outputs audio and performs DSP algorithms such as filters, new codecs or audio effects.
Jaehoon
Senior User
Posts: 39
Joined: Wed 2015-05-20 14:59

Noise from microphone with VS1063A

Postby Jaehoon » Fri 2016-03-11 9:59

Hello VLSI engineer.

I attached recording files from microphone (Sample1.m4a, Sample2.m4a). Our device use vs1053-vs1063-equalizer-130 patch.
The recording are marred by some noise.

These are setting in the VS1063A.

WriteSci(SCI_CLOCKF, 0x8BE8);
WriteSci(SCI_AICTRL0, 0xBB80);
WriteSci(SCI_AICTRL1, 0);
WriteSci(SCI_AICTRL2, 0);
WriteSci(SCI_AICTRL3, 0x4014);
WriteSci(SCI_MODE, SM_SDINEW | SM_RESET | SM_ENCODE);

Questions.

1. Could you analyze the recording noise?
2. How do I avoid the noise?

I attached microphone spec also.

Best regards,
Jaehoon.
Attachments
Sample2.m4a
(223.27 KiB) Downloaded 41 times
Sample1.m4a
(213.36 KiB) Downloaded 40 times
Mic_COB415L.pdf
(1.25 MiB) Downloaded 51 times

User avatar
Henrik
VLSI Staff
Posts: 1007
Joined: Tue 2010-06-22 14:10

Re: Noise from microphone with VS1063A

Postby Henrik » Mon 2016-03-14 15:55

Hello Jaehoon,

Jaehoon wrote:I attached recording files from microphone (Sample1.m4a, Sample2.m4a). Our device use vs1053-vs1063-equalizer-130 patch.
The recording are marred by some noise.

These are setting in the VS1063A.

WriteSci(SCI_CLOCKF, 0x8BE8);
WriteSci(SCI_AICTRL0, 0xBB80);
WriteSci(SCI_AICTRL1, 0);
WriteSci(SCI_AICTRL2, 0);
WriteSci(SCI_AICTRL3, 0x4014);
WriteSci(SCI_MODE, SM_SDINEW | SM_RESET | SM_ENCODE);


The settings don't really matter. When you start the Equalizer application, it takes over the VS1063a and reuses the registers SCI_AICTRL0 through SCI_AICTRL3 as explained in the document.

1. Could you analyze the recording noise?
2. How do I avoid the noise?


To my ear the noise sounds like normal background hiss. There are no tones or other "scratchy" elements, which is good. To improve, you could:
- Use a more directional microphone design (less amplification needed, so volume register can be set lower -> less noise).
- Attenuate higher frequencies. E.g. if you use the 7-channel equalizer designer, set 6250Hz at -6dB and 15600Hz at -12dB.
- Put an amplifier op-amp in front of the VS1063a and use line input instead.

Kind regards,
- Henrik
Good signatures never die. They just fade away.


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