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I'm working on a project in which I need to record voice using a Raspberry Pi.

I'm using alsamixer and arecord, the problem is that when I'm recording it starts playing a weird whistle/whine/interference sound. it's like a beeeee and it doesn't matter even if there is not mic plugged in, it starts doing this sound. I have tried with a 7.1 channel sound card and a 3d sound card, but the result is the same. Any help is well received.

Pictures of my two sound cards:

USB sound card#1

USB sound card#2

I'm using this mic:

Microphone

I have also tried using some headphones as mic but the same happens.

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Question

record voice using Rpi alsamixer and arecord

problem weird whistle/whine/interference sound

Answer

Ah, that is usually called positive audio feedback oscillation, or Larsen Effect.

  1. Install latest driver.

  2. Try another USB sound card. Don't use cheapy or fancy cards like 3D, 7.1. I recommend just simple mono or stereo.

Positive audio feedback usually centres around the high frequency end. If you don't need very HiFi, you can get a sound card such a uGreen which enables you to select low frequency mode, that can reduce positive feedback triggering.

And when recording, try place microphone and speaker further apart, not facing each other, rearranging long cable, use shielded/grounded wires, turn down volume etc etc to change the physical positive feedback path.

If you are recording in a small room, or a narrow partition, it sometimes helps to place soft cloth curtains around you, or face loudspeaker towards an open window. The main idea is to change the main sound reflection path and phase angle, thus reduce the chance of triggering oscillation, ...

ugreen sound card

References

Audio feedback - Wikipedia

Audio feedback (also known as acoustic feedback, simply as feedback, or the Larsen effect) is a special kind of positive loop gain which occurs when a sound loop exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for example, a power amplified loudspeaker).

A typical case is that a signal received by the microphone is amplified and passed out of the loudspeaker. The sound from the loudspeaker can then be received by the microphone again, amplified further, and then passed out through the loudspeaker again.

For small PA systems the sound is readily recognized as a loud squeal or screech.

Full-duplex Intercom without Larsen Effect (audio feedback)

As both microphones and loudspeakers are always in operation, a special circuit is used to avoid that the loudspeaker output can be picked-up by the microphone enclosed in the same box, causing a very undesirable and loud "howl", i.e. the well known "Larsen effect".

The unusual feature of this design is the microphone amplifier Q1: its 180° phase-shifted audio output taken at the Collector and its in-phase output taken at the Emitter are mixed by the C3, C4, R7 and R8 network and R7 is trimmed until the two incoming signals almost cancel out. In this way, the loudspeaker will reproduce a very faint copy of the signals picked-up by the microphone.

Troubleshooting Rpi Larsen Effect Problem - answers.microsoft.com

Sound Audio Playback Echo on Windows 10 OT- unwanted sound echo

... I want to disable the strange echo/surround sound effect that I have, no matter what playback I disable or configure or whatever setting I change related to sound, this echo doesn't go away. I'm starting to get frustrated over this.

Sound problems can be caused by cables that aren't connected properly, damaged drivers, incompatible drivers, sound settings, missing updates, and problems with your sound card.

  1. uninstall the sound card drivers

  2. restart the computer.

  3. install the latest drivers and chcheck if that resolves the issue.

-- answers.microsoft.com

Ugreen USB 2.0 Multimode External Sound Card US$12

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Cmedia CM6533 chip set (with 5 band equalizer and AGC)

Built-in 8051, 256K Byte flash, 32k RAM, GPIO pins, I2C/SPI/UART DAC/ADC 8 ~ 96kHz sampling rate, 16/24 bits resolution Equalizer to compensate microphone and headphone frequency response

Top 10 Best Usb Sound Card Black Friday Deals 2018 - November 23, 2018 by Ami Way

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7) StarTech.com 7.1 with SPDIF Digital Audio

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10) Creative Sound Blaster Omni Surround 5.1 with headphone amp and Integrated beam forming microphone

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