PulseAudio: Mono-Sink Audio

| Created October 25, 2018 | Modified December 18, 2025

Just in case your 10,000+ employee corporation doesn’t plug in the microphone jack correctly and no one is allowed to ask questions (presentation-only).

Creating a Mono Audio Sink with PulseAudio

To force stereo audio output into a single mono channel, you can use the PulseAudio module module-remap-sink. This is often useful for presentations or when hardware is misconfigured (e.g., a microphone is plugged into an unbalanced stereo input, but only one channel is picked up).

Steps to Set Up a Mono Sink

Find the name of your default audio sink by running:
```
pacmd list-sinks | grep name:
```
Load the module-remap-sink to create a new mono sink.

Replace <name_of_audio_sink_given_by_previous_command> with the actual sink name found in step 1 (e.g., <alsa_output.pci-0000_00_1b.0.analog-stereo>). The channels=2 argument tells PulseAudio to treat the input as stereo, and channel_map=mono,mono maps both input channels to a single mono output, effectively mixing them.
```
pacmd load-module module-remap-sink sink_name=mono master=<name_of_audio_sink_given_by_previous_command> channels=2 channel_map=mono,mono
```
Alternatively, you can use a single command to automatically detect the sink name:
```
pacmd load-module module-remap-sink sink_name=mono master=$(pacmd list-sinks | grep -m 1 -oP 'name:\s<\K.*(?=>)') channels=2 channel_map=mono,mono
```
Select the “Mono” Output: In your Sound Preferences (or system audio settings), choose the newly created “Mono” sink as the output device.

Important Note on Volume: Since two audio channels are being mixed into one, the resulting audio signal will be doubled in amplitude, potentially causing distortion. You must reduce the volume by half in your system settings to avoid clipping.

Testing and Persistence

To test the audio output, run:
```
speaker-test -c 2 -t sine
```
To have the mono sink run at startup, add the pacmd load-module command (without the leading pacmd) to the configuration file at /etc/pulse/default.pa.

Removing the Mono Sink

To remove the temporary mono channel, use the unload-module command:

pacmd unload-module module-remap-sink

Source: https://askubuntu.com/questions/17791/can-i-downmix-stereo-audio-to-mono

Thanks to ondrejch!