To beep, or not to beep, that is the question

Introduction

If your computer running Linux has the necessary hardware and is configured appropriately, applications and shell scripts can trigger a beep to signal an event such as an invalid keyboard entry, shutdown initiation, and so on. To check the current situation with your computer, enter the command shown below. Try it first in a Linux VT (virtual terminal) and then in a terminal window in X Windows. Do you hear a beep in each case?

user $ echo -e '\a'

The above command outputs the BEL character (ASCII code 007).

An alternative to the above command is:

user $ echo -e '\007'

Another command that should produce a beep is:

user $ tput bel

The tput utility is part of the ncurses package.

If you install the package app-misc/beep you can also use the ‘beep’ command (enter the command ‘man beep‘ to see its options):

user $ beep

Although you can enter the above-mentioned commands on the command line, they are intended to be used in shell scripts to notify the user about something.

There are thousands of posts on the Web regarding beeps in Linux, the majority of them concerned with disabling beeps because many people find them annoying. Historically, such beeps were emitted by the so-called ‘PC speaker‘. Note that the PC Speaker is not the same as the speakers connected to the sound card in your computer; the term refers to a small internal loudspeaker (moving-coil or piezoelectric) wired directly to the motherboard and intended solely to emit beeps to notify the user about something. Many modern computers, especially laptops, do not have a PC Speaker and either emulate one via the sound card or do nothing at all.

The reason people sometimes use the terms ‘bell’ and ‘ring’ instead of ‘beep’ is because old teletypwriters and teleprinters actually had an electromechanical bell which would ring when a certain dedicated character was received. I use the terms ‘beep’ and ‘bell’ interchangeably, although I prefer to use the term ‘beep’ when talking about audible notifications by computers.

I was motivated to write this post after helping a Gentoo Linux user to get his laptop to produce beeps (see the Gentoo Linux Forums thread ‘i want to beep [solved]‘). Producing a beep in Linux turns out to be more complicated than you would expect, and I’m not sure I fully understand the functional design of the applicable configuration options in the Kernel, nor their relevance (if any) to the X Windows server’s bell. Now, on the face of it the functionality of the applicable Kernel configuration options appears straightforward, but that is not the case in practice. Anyway, let’s look at how I believe a beep can be achieved (and disabled) in Linux…

PC Speaker drivers

Four Kernel options relate directly to a PC Speaker:

CONFIG_HAVE_PCSPKR_PLATFORM

If this is not set in the Kernel then CONFIG_PCSPKR_PLATFORM cannot be enabled.

CONFIG_PCSPKR_PLATFORM

Enable PC-Speaker support

This option allows to disable the internal PC-Speaker
support, saving some memory.

CONFIG_INPUT_PCSPKR

PC Speaker support

Say Y here if you want the standard PC Speaker to be used for
bells and whistles.

If unsure, say Y.

To compile this driver as a module, choose M here: the
module will be called pcspkr.

CONFIG_SND_PCSP

PC-Speaker support (READ HELP!)

If you don’t have a sound card in your computer, you can include a
driver for the PC speaker which allows it to act like a primitive
sound card.
This driver also replaces the pcspkr driver for beeps.

You can compile this as a module which will be called snd-pcsp.

WARNING: if you already have a soundcard, enabling this
driver may lead to a problem. Namely, it may get loaded
before the other sound driver of yours, making the
pc-speaker a default sound device. Which is likely not
what you want. To make this driver play nicely with other
sound driver, you can add this into your /etc/modprobe.conf:
options snd-pcsp index=2

You don’t need this driver if you only want your pc-speaker to beep.
You don’t need this driver if you have a tablet piezo beeper
in your PC instead of the real speaker.

Say N if you have a sound card.
Say M if you don’t.
Say Y only if you really know what you do.

If your computer does have a PC Speaker, you would use either CONFIG_INPUT_PCSPKR or CONFIG_SND_PCSP, but not both. When configuring the Kernel you can specify ‘M’ to build the driver as an external module, in which case you can decide in userspace whether or not to load it. Or you can specify ‘Y’ to build the driver into the Kernel (do not specify both as ‘Y’ simultaneously, though).

If your computer does have a PC Speaker, an advantage of using CONFIG_SND_PCSP instead of CONFIG_INPUT_PCSPKR is that the former adds a virtual sound card named ‘pcsp’ with a channel (without volume control) named ‘Beep’, and you should be able to mute it via ALSA Mixer.

If you have a computer that has a sound card but does not have a PC Speaker (a laptop’s internal speakers are connected to a sound card, not a PC Speaker), the above two drivers do not really apply. I have always disabled them both in the Kernel, as my laptop does not have a PC Speaker.  Update (September 29, 2016): This is not always the case: if a computer uses a sound card to emulate a PC Speaker (typically laptops do this), then you do need to use one of these two drivers if you want to be able to hear event beeps in a VT — see my latest post Another look at beeps in Linux.

However, apparently for some laptops ALSA Mixer shows a channel named ‘Beep’ (with volume control) for the Intel HDA (High Definition Audio) sound card if CONFIG_INPUT_PCSPKR is set to ‘Y’ or ‘M’. I believe such laptops were designed to use their sound card to emulate a PC Speaker. I do not know whether or not the ‘digital beep’ Kernel options (see further on) are set in such cases, but Kernel bug report no. 13651 would appear to indicate that the design intention is for them to be set.

So, already things are confusing.

Of course, if your computer does have a PC Speaker and you don’t want it to emit beeps, set both CONFIG_INPUT_PCSPKR and CONFIG_INPUT_PCSP to ‘N’ in the Kernel. If either already exists as an external module and you do not wish to rebuild the Kernel, make sure the modules pcspkr and snd-pcsp are not loaded (blacklist them, for example).

Digital Beep

Now, there are two other Kernel options relating to event beeps. These are not for driving a PC Speaker, they are to enable the ALSA Intel HDA driver to emit event beeps in lieu of a PC Speaker: the so-called ‘digital beep’. In other words, these two options are intended to provide an alternative to using a PC Speaker. The two options are:

CONFIG_SND_HDA_INPUT_BEEP

Support digital beep via input layer

Say Y here to build a digital beep interface for HD-audio
driver. This interface is used to generate digital beeps.

CONFIG_SND_HDA_INPUT_BEEP_MODE

Digital beep registration mode (0=off, 1=on)

Set 0 to disable the digital beep interface for HD-audio by default.
Set 1 to always enable the digital beep interface for HD-audio by
default.

Note that the mode ‘2’ is no longer an option in newer Kernels.

So, if your installation uses the Intel HDA driver and you want your computer’s sound card to be able to emit beeps instead of a PC Speaker (which your computer may or may not have), set these two accordingly in the Kernel configuration:

user $ grep CONFIG_SND_HDA_INPUT_BEEP /usr/src/linux/.config
CONFIG_SND_HDA_INPUT_BEEP=y
CONFIG_SND_HDA_INPUT_BEEP_MODE=1

The functional design of these Kernel options is not clear, but Kernel bug report no. 13651 appears to indicate that the design intention is for CONFIG_SND_HDA_INPUT_BEEP and CONFIG_SND_HDA_INPUT_BEEP_MODE to be used in addition to either CONFIG_INPUT_PCSPKR or CONFIG_SND_PCSP, not instead of them. In other words, if your computer has a PC Speaker but you want beeps to be routed via its Intel HDA sound card instead then I believe you are expected to use either of the following two sets of options:

Option 1
CONFIG_HAVE_PCSPKR_PLATFORM=Y
CONFIG_PCSPKR_PLATFORM=Y
CONFIG_INPUT_PCSPKR=Y (or =M)
CONFIG_SND_HDA_INPUT_BEEP=Y
CONFIG_SND_HDA_INPUT_BEEP_MODE=1

Option 2
CONFIG_HAVE_PCSPKR_PLATFORM=Y
CONFIG_PCSPKR_PLATFORM=Y
CONFIG_SND_PCSP=Y (or =M)
CONFIG_SND_HDA_INPUT_BEEP=Y
CONFIG_SND_HDA_INPUT_BEEP_MODE=1

On the other hand, if your computer has a PC Speaker and your installation uses the Intel HDA driver for a sound card but you do want your computer to emit beeps from the PC Speaker, I think you would set the two options as follows in the Kernel configuration:

CONFIG_SND_HDA_INPUT_BEEP=N
CONFIG_SND_HDA_INPUT_BEEP_MODE=0

If you read the comment by ALSA developer Takashi Iwai quoted in Kernel bug report no. 13651 you’ll see that the functionality is not at all straightforward. For example, on some computers, especially laptops (which normally do not have a PC Speaker), the beep may be emitted via the sound card irrespective of whether or not you set CONFIG_SND_HDA_INPUT_BEEP.

X Windows

A beep can be emitted in X Windows, and I have seen this beep referred to as the ‘X Windows server bell’ or the ‘X Windows keyboard bell’.

Given that X Windows can emit a beep via the sound card when neither the pcspkr module nor the snd-pcsp module is loaded and CONFIG_SND_HDA_INPUT_BEEP=N and CONFIG_SND_HDA_INPUT_BEEP_MODE=0, I assume X Windows emits beeps directly to the default sound card irrespective of the settings of those Kernel options. I could be wrong, but I have not found any explanation on the Web about the underlying mechanism; the X.Org Web site FAQ ‘How can I configure the Xserver bell (xkbbell) to use the sound subsystem of my computer? (ALSA, OSS, etc.)‘ simply states:

Answer (hopefully) goes here.. 🙂

*shrug*.

Below is a summary of the commands to disable, enable and configure the beep in X Windows.

To disable beeps in X Windows:

user $ xset b off

To enable beeps in X Windows:

user $ xset b on

To change the volume, pitch and duration of the beeps:

user $ xset b

For example, to set the beep volume to 25% without changing the pitch and duration:

user $ xset b 25

To return to the default settings:

user $ xset b

To view the current settings:

user $ xset q | grep bell

which displays the following (default) values in my case:

bell percent:  50        bell pitch:    400        bell duration:    100

To set the beep automatically each time X Windows starts, add the following line before the last one in the ~/.xinitrc file if you don’t use a Display Manager, otherwise use the Desktop Environment’s system settings GUI to run it at login:

xset b 20 400 20 &

PulseAudio

To confuse matters further, note that PulseAudio intercepts X11 beeps (see: PulseAudio Documentation – User Documentation – Modules – X Window system – module-x11-bell). Therefore, if your installation uses PulseAudio and you want the ability to emit event beeps in X Windows, you also need to configure PulseAudio so it does not ignore the beeps. This can either be done from the command line:

user $ pactl upload-sample /usr/share/sounds/freedesktop/stereo/bell.oga x11-bell
user $ pactl load-module module-x11-bell sample=x11-bell display=$DISPLAY

or you can edit /etc/pulse/default.pa and make sure the following lines are included in that file (they may already exist but are commented out):

load-sample-lazy x11-bell /usr/share/sounds/freedesktop/stereo/bell.oga
load-module module-x11-bell sample=x11-bell

On the other hand, if PulseAudio is installed and you want it to ignore event beeps in X Windows, delete or comment out the above-mentioned two lines in /etc/pulse/default.pa. You can achieve the same effect from the command line:

user $ pactl unload-module module-x11-bell

Configuring userspace to emit a ‘digital beep’

Installation of PulseAudio will have created the directory /usr/share/sounds/freedesktop/ and sub-directories containing various Ogg Vorbis audio files, including the ‘digital beep’ file bell.oga. If your installation does not have PulseAudio installed, you can obtain the same file /usr/share/sounds/freedesktop/stereo/bell.oga by installing the package x11-themes/sound-theme-freedesktop instead. You can configure your installation to use this file to emit a ‘digital beep’ in X Windows (but not in a VT) by using the XKB (X Windows keyboard extension) event daemon as explained in a post on the superuser Web site. That post relates to Ubuntu, but the basic principle applies whatever the Linux distribution.

Now, in my case I am using KDE Plasma 5 in Gentoo Linux, and I cannot hear any beep/bell in Konsole and Yakuake. I came across KDE bug report no. 177861 that has been outstanding since 2008, which indicated that KDE’s terminal applications will not emit beeps even if you do have a PC Speaker and your Kernel has been correctly configured to use it, or even if you have configured your installation to use a ‘digital beep’. You may have better luck with a different Desktop Environment but in KDE you will have to use a non-KDE X Windows terminal application if you want to hear beeps produced by shell scripts.

Update (October 9, 2016): Regarding KDE’s terminal applications emitting beeps, I am currently using KDE Plasma 5.7.5 and have been able to configure Konsole and Yakuake to emit a ‘digital beep’ as follows:

• In Konsole, click on ‘Settings’ > ‘Configure Notifications…’, select ‘Bell in Visible Session’ and ensure ‘Play a sound’ is ticked and a file is specified there (I specify /usr/share/sounds/freedesktop/stereo/bell.oga). If you wish, do the same for ‘Bell in Non-Visible Session’.
• For Yakuake, press F12 to display the Yakuake window, click on the ‘Open Menu’ icon, select ‘Configure Notifications…’, select ‘Bell in Visible Session’ and ensure ‘Play a sound’ is ticked and a file is specified there (I specify /usr/share/sounds/freedesktop/stereo/bell.oga). If you wish, do the same for ‘Bell in Non-Visible Session’.

Below I explain how I implemented a ‘digital beep’ in KDE Plasma 5.

First I installed the XKB event daemon:

root # emerge xkbevd

The package vorbis-tools was already installed, otherwise I would have installed that too in order to install an audio player for Ogg Vorbis audio files:

root # emerge vorbis-tools

PulseAudio was also already installed, and hence an appropriate audio file for a beep already existed. Had I not previously installed PulseAudio I would have installed the following package to get an appropriate Ogg Vorbis audio file:

root # emerge sound-theme-freedesktop

I created the file /home/fitzcarraldo/.config/autostart/xkbevd.desktop containing the following:

[Desktop Entry]
Comment[en_GB]=Software terminal bell
Comment=Software terminal bell
Exec=xkbevd -bg
GenericName[en_GB]=XKB Event Daemon
GenericName=XKB Event Daemon
Icon=system-run
MimeType=
Name[en_GB]=XKB Event Daemon
Name=XKB Event Daemon
Path=
StartupNotify=true
Terminal=false
TerminalOptions=
Type=Application
X-DBUS-ServiceName=
X-DBUS-StartupType=none
X-KDE-SubstituteUID=false
X-KDE-Username=fitzcarraldo	

and I changed its permissions:

user $ chmod 755 /home/fitzcarraldo/.config/autostart/xkbevd.desktop

I created the file /home/fitzcarraldo/.xkb/xkbevd.cf containing the following:

soundDirectory="/usr/share/sounds/"
soundCmd="ogg123 -q"

Bell() "freedesktop/stereo/bell.oga"

If the file /usr/share/sounds/freedesktop/stereo/bell.oga does not exist in your installation then you can copy any suitable audio file of your choice into the directory /usr/share/sounds/ or use one of the existing audio files in that directory, and specify its filename in xkbevd.cf. For example:

soundDirectory="/usr/share/sounds/"
soundCmd="aplay -q"

Bell() "beep.wav"

Notice that the choice of audio player is up to you. In the first example of xkbevd.cf I specified the ogg123 player, whereas in the second example I specified the aplay player.

The aforementioned bug in KDE Konsole and Yakuake prevented me from testing the use of the XKB event daemon, so I installed a non-KDE X Windows terminal application to see if the ‘digital beep’ would work in that:

root # emerge xterm

The command echo -e '\a' generates a beep in xterm. So the ‘digital beep’ approach does work, albeit use of the XKB event daemon means you are limited to using it in X Windows. To reiterate, as the XKB event daemon is for X Windows, no ‘digital beep’ is generated if you enter a beep command outside of X Windows (e.g. in a VT).

By the way, I’m currently using Gentoo Stable Branch and hence Version 5.6.5 of KDE Plasma, and there is another KDE bug to complicate matters further: ‘System Settings’ > ‘Autostart’ > ‘Add Program…’ does not save all the entries I make via the GUI to the .desktop file, and does not set the file permissions correctly either. I don’t know if that is an upstream bug or a bug in the Gentoo implementation of Plasma 5.6.5. Anyway, that is why I manually created xkbevd.desktop and manually set the permissions, rather than using System Settings.

Instead of launching the XKB event daemon by using a .desktop file in ~/.config/autostart/, if you don’t use a Display Manager you could launch it by adding the command in the file ~/.xinitrc.

Summary

All the following factors govern whether or not your computer will issue a beep for the BEL character:

• the specific hardware and firmware in your computer;
• CONFIG_HAVE_PCSPKR_PLATFORM;
• CONFIG_PCSPKR_PLATFORM;
• CONFIG_INPUT_PCSPKR;
• CONFIG_SND_PCSP;
• CONFIG_SND_HDA_INPUT_BEEP;
• CONFIG_SND_HDA_INPUT_BEEP_MODE;
• X Windows settings;
• PulseAudio configuration (if installed);
• a bug in KDE’s terminal applications (if installed).

A. If you are hearing event beeps but don’t want them:

• Preferably, set CONFIG_HAVE_PCSPKR_PLATFORM and CONFIG_PCSPKR_PLATFORM both to ‘N’.
• Either set both CONFIG_INPUT_PCSPKR and CONFIG_SND_PCSP to ‘N’ in your Kernel, or, if either driver exists as a module (pcspkr and snd-pcsp, respectively), blacklist it.
• Make sure CONFIG_SND_HDA_INPUT_BEEP is set to ‘N’.
• Make sure the X Windows bell is turned off.
• If you also have PulseAudio installed, make sure the PulseAudio module module-x11-bell is not loaded (also check /etc/pulse/default.pa to see if it has been enabled by default).

B. If you are not hearing event beeps but you do want to hear them:

1. If you are sure your computer has a PC Speaker:

• Make sure CONFIG_HAVE_PCSPKR_PLATFORM and CONFIG_PCSPKR_PLATFORM are set to ‘Y’.
• Either set CONFIG_INPUT_PCSPKR to ‘M’ and CONFIG_SND_PCSP to ‘N’ in your Kernel, or, if the module snd-pcsp already exists, blacklist it.
• Make sure the module pcspkr exists and is not blacklisted.
• Make sure the module pcspkr is loaded after the module snd-hda-intel.
• Make sure CONFIG_SND_HDA_INPUT_BEEP is set to ‘N’.
• Make sure the X Windows bell is turned on and the volume is turned up.
• If you have PulseAudio installed, make sure the PulseAudio module module-x11-bell is loaded (check /etc/pulse/default.pa to ensure it includes the applicable lines, or issue the two commands listed earlier).
• If you use KDE, use a non-KDE terminal application until KDE bug report no. 177861 is fixed.
• If, after doing all the above, you still do not hear a beep in X Windows, follow the procedure in the section above titled Configuring userspace to emit a ‘digital beep’.

Above I have recommended using pcspkr. However, an advantage of using snd-pcsp instead is that it adds a virtual sound card with a channel named ‘Beep’ and you should be able to mute that channel via ALSA Mixer as you wish. Therefore, if you do opt to use the module snd-pcsp instead of pcspkr then make sure you specify the module option (or Kernel Quirk if you built the driver into the Kernel) described in the Kernel Help text quoted earlier, so that pcsp does not become the default sound card instead of the Intel HDA sound card.

2. If your computer does not have a PC Speaker:

• Preferably, set CONFIG_HAVE_PCSPKR_PLATFORM and CONFIG_PCSPKR_PLATFORM both to ‘N’. *
• If you leave CONFIG_HAVE_PCSPKR_PLATFORM and CONFIG_PCSPKR_PLATFORM both set to ‘Y’, either set CONFIG_INPUT_PCSPKR and CONFIG_SND_PCSP both to ‘N’, or, if either module already exists, blacklist it. *
• Make sure CONFIG_SND_HDA_INPUT_BEEP is set to ‘Y’ and CONFIG_SND_HDA_INPUT_BEEP_MODE is set to ‘1’ (I’m not sure this step is required for all computers).
• Make sure the X Windows bell is turned on and its volume is turned up.
• If you have PulseAudio installed, make sure the PulseAudio module module-x11-bell is loaded.
• Use the XKB Event Daemon method to play an audio file (‘digital beep’) when the BEL character is detected in X Windows.
• If you use KDE, use a non-KDE terminal application until KDE bug report no. 177861 is fixed.
  Update (October 9, 2016): Regarding KDE’s terminal applications emitting beeps, I am currently using KDE Plasma 5.7.5 and have been able to configure Konsole and Yakuake to emit a ‘digital beep’ — see my update in the section titled Configuring userspace to emit a ‘digital beep’.
  
  * If your computer’s hardware and firmware have been designed to emulate a PC Speaker via a sound card, you may find that you can use the pcspkr (or snd-pcsp) driver to generate beeps in a VT. As the saying goes, your mileage may vary.

  And Finally

  If you know precisely how all these Kernel options are supposed to interact, do comment. Or if you know the relationship, if any, between the X Windows beep (a.k.a. ‘bell’) and these Kernel options, please also comment.

  Update (September 29, 2016): See my latest post Another look at beeps in Linux for the results of some experiments with these Kernel options on my laptop, giving more insight into how to configure them and how they work.