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Speaker as Microphone: How to

G5 Cyber Security

TL;DR

Yes, you can usually use a speaker as a microphone, but it won’t be great quality. It works because speakers and microphones are fundamentally similar – they both convert electrical signals into sound (and vice versa). You’ll need to enable loopback or listen-only mode on your computer.

How to Use a Speaker as a Microphone

  1. Understand the Basics: Speakers take an electrical signal and turn it into sound. Microphones do the opposite – they turn sound into an electrical signal. Both use transducers (coils of wire and magnets). This means, with the right setup, you can often reverse their roles.
    • Speakers are designed to *output* sound, so their sensitivity is lower than a dedicated microphone.
    • The quality will be significantly worse than using a proper microphone. Expect noise and distortion.
  2. Windows Setup (Loopback): Windows doesn’t natively allow you to use a speaker as a microphone without enabling loopback.
    1. Enable Stereo Mix: Right-click the sound icon in your system tray and select ‘Sounds’. Go to the ‘Recording’ tab.
    2. If ‘Stereo Mix’ isn’t visible, right-click in the empty space within the Recording tab and check ‘Show Disabled Devices’ and ‘Show Disconnected Devices’. It should then appear.
    3. Right-click ‘Stereo Mix’ and select ‘Properties’. Go to the ‘Listen’ tab.
    4. Check ‘Listen to this device’. Select your speaker from the ‘Playback through this device’ dropdown menu. Click ‘Apply’ and ‘OK’.
  3. macOS Setup (Soundflower or BlackHole): macOS requires a virtual audio driver.
    1. Install Soundflower or BlackHole: These are free, open-source drivers that create virtual audio devices. SoundFlower is older but still works for many. BlackHole is a more modern option.
    2. Configure Audio Input: Open ‘System Preferences’ > ‘Sound’. Go to the ‘Input’ tab.
    3. Select either Soundflower (2ch) or BlackHole from the list of input devices.
  4. Linux Setup (PulseAudio): Linux usually requires configuration through PulseAudio.
    1. Install pavucontrol: If not already installed, use your distribution’s package manager to install pavucontrol. For example, on Debian/Ubuntu: 
      sudo apt update
sudo apt install pavucontrol
    2. Configure Input Device: Open pavucontrol. Go to the ‘Input Devices’ tab.
    3. Select your speaker from the list of devices. Ensure it’s not muted and that its volume is turned up. You may need to experiment with different profiles. 
      pactl load-module module-loopback sink=your_speaker_sink source=your_speaker_source
  5. Testing:
    • Open a sound recording application (e.g., Audacity, Voice Recorder).
    • Select the newly enabled input device (‘Stereo Mix’ on Windows, Soundflower/BlackHole on macOS, or your speaker in PulseAudio) as your microphone source.
    • Speak into the speaker. You should hear sound being recorded.

Troubleshooting

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