Do your audio recordings look like this (Note Air 2)?

[spessoa]

Hey guys, I bought recently a Note Air 2 and I noticed that the audios recorded (either using the Notes app or the Recorder app) with the device's built-in microphone present a sort of periodic noise/glitch. I tried using a USB microphone (external) and this glitch is not present. The audio samples are available on my Dropbox (see link) if you want to check them out. I contacted the seller and he sent me a new device, but to my surprise, the new device has the same issue (maybe the noise/glitch is a bit less audible in this new device). Can any Note Air 2 owner confirm if your devices have this issue as well?

Note: both devices were on firmware 2021-11-22_11-01_3.2_0ae74d7d5d when I recorded the audios.

[Renate]

They aren't actual MP3, are they?

[spessoa]

Originally Posted by Renate

They aren't actual MP3, are they?

Yes, the files I shared with you are MP3. I've recorded these using the device's Recorder app and sent them to my computer (share via bluetooth). They should be playable directly from the Dropbox web interface.

[Renate]

Was the USB connected when it made this noise?

It looks like MP4 to me:

\0\0\0 ftypmp42\0\0\0\0isommp42\0\0 xfree

[spessoa]

No, nothing was connected to the device's USB port when I recorded the audio with noise/glitch. The device was inserted into the sleep cover during this recording though.

You're right, it seems like the audio files are not encoded with MP3, but MP4 (despite the files being named with a .mp3 extension). If you're interested in the details of the file format/encoder, K-lite's MediaInfo reported this:

General
Complete name               : D:\DesktopSaulo\RecordedWithExternalMic-PerfectAudio(2021_11_22_11_34_36).mp3
Format                      : MPEG-4
Format profile              : Base Media / Version 2
Codec ID                    : mp42 (isom/mp42)
File size                   : 38.0 KiB
Duration                    : 19 s 460 ms
Overall bit rate mode       : Constant
Overall bit rate            : 16.0 kb/s
Encoded date                : UTC 2021-11-22 03:34:56
Tagged date                 : UTC 2021-11-22 03:34:56
com.android.version         : 11
FileExtension_Invalid       : mov mp4 m4v m4a m4b m4p 3ga 3gpa 3gpp 3gp 3gpp2 3g2 k3g jpm jpx mqv ismv isma ismt f4a f4b f4v

Audio
ID                          : 1
Format                      : AMR
Format/Info                 : Adaptive Multi-Rate
Format profile              : Narrow band
Codec ID                    : samr
Duration                    : 19 s 460 ms
Bit rate mode               : Constant
Bit rate                    : 12.8 kb/s
Channel(s)                  : 1 channel
Sampling rate               : 8 000 Hz
Bit depth                   : 13 bits
Stream size                 : 30.4 KiB (80%)
Title                       : SoundHandle
Writing library             :    
Language                    : English
Encoded date                : UTC 2021-11-22 03:34:56
Tagged date                 : UTC 2021-11-22 03:34:56

[Renate]

Maybe that strange noise is an encoding or decoding artefact?
An external USB mic may be coming in at a different sample rate?

[spessoa]

Do you mean the "Sampling rate" in the MediaInfo report? If yes, then both audio files were recorded using the same parameter/value (8 000 Hz). Next, you find the MediaInfo's report for the audio file recorded with the built-in mic (the report for the audio recorded with the USB mic is in my previous post):

General
Complete name : D:\DesktopSaulo\RecordedWithDevicesBuiltinMic-RepetetiveGlitches(2021_11_22_11_33_09).mp3
Format : MPEG-4
Format profile : Base Media / Version 2
Codec ID : mp42 (isom/mp42)
File size : 47.3 KiB
Duration : 24 s 740 ms
Overall bit rate mode : Constant
Overall bit rate : 15.7 kb/s
Encoded date : UTC 2021-11-22 03:33:34
Tagged date : UTC 2021-11-22 03:33:34
com.android.version : 11
FileExtension_Invalid : mov mp4 m4v m4a m4b m4p 3ga 3gpa 3gpp 3gp 3gpp2 3g2 k3g jpm jpx mqv ismv isma ismt f4a f4b f4v

Audio
ID : 1
Format : AMR
Format/Info : Adaptive Multi-Rate
Format profile : Narrow band
Codec ID : samr
Duration : 24 s 740 ms
Bit rate mode : Constant
Bit rate : 12.8 kb/s
Channel(s) : 1 channel
Sampling rate : 8 000 Hz
Bit depth : 13 bits
Stream size : 38.7 KiB (82%)
Title : SoundHandle
Writing library :
Language : English
Encoded date : UTC 2021-11-22 03:33:34
Tagged date : UTC 2021-11-22 03:33:34

Hey Renate, do you (or any other Forum's member) have a Boox device (preferably a Note Air 2 with update 2021-11-22_11-01_3.2_0ae74d7d5d) on which you can record audio using the device's built-in mic just to check that audios recorded with this mic do not present this noise/glitch?

I'd like to be sure that this is not a common issue with Boox's devices. As I said in my first post, I've already tried recording audios on two different devices and they both presented the same issue (or should I call it a "feature"?). This information will help me decide if I should request another replacement or not. This is very unlikely, but my guess is that I was unlucky enough to get two devices with the same defect (maybe devices from the same batch ).

[Renate]

I meant that the sample rate of the source before it gets sample rate conversion.

I checked a recording from May and just did another one with the Poke3 3.2 Except for the fact that it's muffled due to the case (I should drill a hole), it's fine. Both the old and the new one are MP4 wtih MP3 as the file extension. I can play them in VLC but not in Firefox or Audacity.

There's no setting for format or sample rate. You want to see some pathetic settings that you can't even get to normally?

$ am start -n com.simplemobiletools.voicerecorder/.activities.SettingsActivity