How do I make microphone input mono?

I am using a USB-bluetooth microphone to do speech recognition with Google docs. The application says the sound is too soft but I have it turned up all the way. Is there any way in asoundrc to make the microphone register as mono rather than stereo? I think my sound is only coming in through one channel.

Someone told me this would do it but it looks like it affects outgoing as well as incoming.

pcm.makemono {

type route

slave.pcm "hw:2"

ttable {

    0.0 1    # in-channel 0, out-channel 0, 100% volume

    1.0 1    # in-channel 1, out-channel 0, 100% volume

}

}

Adding a pulseaudio filter

M=$(pacmd list-sources | grep -P "name:.*alsa.*input" | tail -n 1 | perl -pe 's/.*<//g;s/>.*//g')
pacmd load-module module-remap-source source_name=mono master=$M master_channel_map=front-left,front-right  channel_map=mono,mono

and selecting the new default in settings worked for me.