Monitoring the microphone level with a command line tool in Linux

Question

I am looking for a tool that will tell me, in less than half a second, if the microphone is picking up any sound above a certain threshold. (I plan to then mute the Master channel with another command line tool, like amixer.)

Answer 1

This solution will avoid writing repeatedly to disk, and even though it in worst case takes a second instead of the desired less than half a second, I found it to be fast enough after trying it. So, here are the two scripts I use:

./detect:

while true; do
    arecord -d 1 /dev/shm/tmp_rec.wav ; sox -t .wav /dev/shm/tmp_rec.wav -n stat 2>\
    &1 | grep "Maximum amplitude" | cut -d ':' -f 2 | ./check.py
    if [ $? -eq 0 ] ; then
         amixer set Master 0
    else
         amixer set Master 80
    fi
done

./check.py:

#!/usr/bin/env python
import sys

number = 0.0
thing="NO"

line = sys.stdin.readline()
thing = line.strip()
number = float(thing)

if number < 0.15:
    raise Exception,"Below threshold"

Hardly elegant, but it works.

Note: If you want a more gradual thing, add something like this:

   for i in `seq 0 80 | tac`; do
      amixer set Master $i
   done

for muting and

   for i in `seq 0 80`; do
      amixer set Master $i
   done

for unmuting.

Answer 2

Just version without python script and TALKING_PERIOD, that sets up how many seconds will sound be on DOWN_SOUND_PERC level, then goes to UP_SOUND_PERC level.

#!/bin/bash
    
TALKING_PERIOD=16
UP_SOUND_PERC=65
DOWN_SOUND_PERC=45
counter=0

while true; do
    echo "counter: " $counter
    if [ "$counter" -eq 0 ]; then
        nmb=$(arecord -d 1 /dev/shm/tmp_rec.wav ; sox -t .wav /dev/shm/tmp_rec.wav -n stat 2>&1 | grep "Maximum amplitude" | cut -d ':' -f 2)

        echo "nmb: " $nmb

        if (( $(echo "$nmb > 0.3" |bc -l) )); then
            echo "ticho"
            amixer -D pulse sset Master 45%
            counter=$TALKING_PERIOD
        else
            echo "hlasno"
            amixer -D pulse sset Master 65%
        fi
    fi

    if [[ $counter -gt 0 ]]; then
        ((counter--))
    fi

    sleep 1

done

Answer 3

There is a tool called pavumeter that lets you see the microphone level, Open capture interface of pavumeter,

Then adjust the capture sound level using pavucontrol, In pavucontrol, go to input devices, and adjust microphone sensitivity.

Edit: In the bash script by R4v0, done is inside code.

Edit2: I wanted to raise the volume each time there is noise, so i just edited more than to be less than and cancelled talking peroid

    if (( $(echo "$nmb < 0.3" |bc -l) )); then

Answer 4

I edited it to work with ffmpeg

sox and bc need to be installed.

Using -f "format" pulse seems too slow looping, so i used alsa

For -i "input" you can instead specify the stream

For more info: https://trac.ffmpeg.org/wiki/Capture/PulseAudio#Selectingtheinput

#!/bin/bash

ffmpeg -y -loglevel panic -f pulse -i default -t 0.5 /dev/shm/tmp_rec.wav ; sox -t .wav /dev/shm/tmp_rec.wav -n stat 2>&1 | grep "Maximum amplitude" | cut -d ':' -f 2