Due to high demand, expect some shipping delays at this time - orders may not ship for up to 2-3 business days.
0

Loud pop when recording with SPH0645
Moderators: adafruit_support_bill, adafruit

Forum rules
Talk about Adafruit Raspberry Pi® accessories! Please do not ask for Linux support, this is for Adafruit products only! For Raspberry Pi help please visit: http://www.raspberrypi.org/phpBB3/
Please be positive and constructive with your questions and comments.

Loud pop when recording with SPH0645

by hotfigs on Sat Jan 22, 2022 8:50 am

Hi,

I've got myself set up with a SPH0645 breakout board connected to a Raspberry Pi Zero 2 W. I followed the instructions from the "Adafruit I2S MEMS Microphone Breakout" guide and everything worked and I can record sound using arecord. However, when I do record, there is a loud pop at the start of the recording, which then settles down and the rest of the recording is ok. This pop is present whether I include the given ALSA config or without them.

Googling this, it sounds like there might be some issues with ALSA. In particular, the MAX98357 guide has a section on reducing pops when playing audio. That advice doesn't seem to apply exactly the same way to microphones, so i need to dig a bit deeper into alsa to figure out if you can do the same kind of thing (probably the next thing I will try).

I haven't seen much that mentions this specific issue with the SPH0645, so I'm wondering if anyone else has had this problem and if so, any suggestions on how to fix it?

(For extra details, I'm running bullseye and the kernel is 5.10.92-v7+) I've attached a screenshot of a recorded wav (amplified to 75 using alsa).

Thanks!
Attachments
Screenshot 2022-01-22 at 12.42.07.png
Screenshot 2022-01-22 at 12.42.07.png (100.24 KiB) Viewed 78 times

hotfigs
 
Posts: 1
Joined: Sat Jan 22, 2022 8:36 am

Re: Loud pop when recording with SPH0645

by mjaner on Wed Mar 16, 2022 4:30 am

Hi,
I found the same problem with Raspb pi 4 and the SPH0645.
My workaround was to implement a hi-pass filter with python. This removes the pop from the beginning and also de DC offset of the signal.

mjaner
 
Posts: 3
Joined: Wed Mar 16, 2022 4:26 am

Please be positive and constructive with your questions and comments.


cron